Liang Deng

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Name: 邓亮; Liang Deng

Organization: Chinese Academy of Sciences , China

Department: Shanghai Institute of Organic Chemistry

Title: Researcher/Professor(PhD)

TOPICS

Inorganic Chemistry

Organic Chemistry

Chemicals
References

An Iron(II) Ylide Complex as a Masked Open-Shell Iron Alkylidene Species in Its Alkylidene-Transfer Reactions with Alkenes

Co-reporter:Jian Liu, Lianrui Hu, Lei Wang, Hui Chen, and Liang Deng

Journal of the American Chemical Society March 15, 2017 Volume 139(Issue 10) pp:3876-3876

Publication Date(Web):February 21, 2017

DOI:10.1021/jacs.7b00484

Transition-metal alkylidenes are important reactive organometallic intermediates, and our current knowledge on them has been mainly restricted to those with closed-shell electronic configurations. In this study, we present an exploration on open-shell iron alkylidenes with a weak-field tripodal amido-phosphine-amido ligand. We found that a high-spin (amido-phosphine-amido)iron(II) complex can react with (p-tolyl)2CN2 to afford a high-spin (amido-ylide-amido)iron(II) complex, 2, which could transfer its alkylidene moiety to a variety of alkenes, either the electron-rich or electron-deficient ones, to form cyclopropane derivatives. The reaction of 2 with cis-β-deuterio-styrene gave deuterated cyclopropane derivatives with partial loss of the stereochemical integrity with respect to the cis-styrene. Kinetic study on the cyclopropanation reaction of 2 with 4-fluoro-styrene disclosed the activation parameters of ΔH⧧ = 23 ± 1 kcal/mol and ΔS⧧ = −20 ± 3 cal/mol/K, which are comparable to those of the cyclopropanation reactions involving transition-metal alkylidenes. However, the cyclopropanation of para-substituted styrenes by 2 shows a nonlinear Hammett plot of log(kX/kH) vs σp. By introduction of a radical parameter, a linear plot of log(kX/kH) vs 0.59σp + 0.55σc• was obtained, which suggests the “nucleophilic” radical nature of the transition state of the cyclopropanation step. In corroboration with the experimental observations, density functional theory calculation on the reaction of 2 with styrene suggests the involvement of an open-shell (amido-phosphine-amido)iron alkylidene intermediate that is higher in energy than its (amido-ylide-amido)iron(II) precursor and an “outer-sphere” radical-type mechanism for the cyclopropanation step. The negative charge distribution on the alkylidene carbon atoms of the open-shell states (S = 2 and 1) explains the high activity of the cyclopropanation reaction toward electron-deficient alkenes. The study demonstrates the unique activity of open-shell iron alkylidene species beyond its closed-shell analogues, thus pointing out their potential synthetic usage in catalysis.

Synthesis, Structure, and Reactivity of Low-Spin Cobalt(II) Imido Complexes [(Me3P)3Co(NAr)]

Co-reporter:Yang Liu, Jingzhen Du, and Liang Deng

Inorganic Chemistry July 17, 2017 Volume 56(Issue 14) pp:8278-8278

Publication Date(Web):June 29, 2017

DOI:10.1021/acs.inorgchem.7b00941

The reactions of [Co(PMe3)4] with the bulky organic azides, DippN3 and DmpN3 [Dipp, 2,6-diisopropylphenyl; Dmp, 2,6-di(2′,4′,6′-trimethylphenyl)phenyl], afforded the cobalt(II) terminal imido complexes [(Me3P)3Co(NAr)] (Ar = Dipp, 1; Dmp, 2). The cobalt imido complexes in their solid states show trigonal pyramidal coordination geometry and long Co–N(imido) separations (ca. 1.71 Å). Spectroscopic characterization and theoretical studies indicated their low-spin cobalt(II) nature. Reactivity studies on 1 revealed its nitrene-transfer reactions with PMe3 and CO, the imido/oxo and imido/sulfido exchange reactions with PhCHO and CS2, and the single-electron oxidation reaction by ferrocenium cation to form cobalt(III) imide.

Mode of Activation of Cobalt(II) Amides for Catalytic Hydrosilylation of Alkenes with Tertiary Silanes

Co-reporter:Yang Liu and Liang Deng

Journal of the American Chemical Society 2017 Volume 139(Issue 5) pp:1798-1801

Publication Date(Web):January 25, 2017

DOI:10.1021/jacs.6b12938

Cobalt(II) complexes capable of catalyzing alkene hydrosilylation in the absence of external activators are rarely known, and their activation mode has remained poorly understood. We present here that cobalt(II) amide complexes, [Co(N(SiMe3)2)2] and its NHC adducts [(NHC)Co(N(SiMe3)2)2] (NHC = N-heterocyclic carbene), are effective catalysts for the hydrosilylation of alkenes with tertiary silanes. Mechanistic studies revealed that cobalt(II) amides can react with hydrosilane to form cobalt(I) species, silylamide, and hydrogen, which serves as the entry to the genuine catalytically active species, presumably cobalt(I) species, for the cobalt-catalyzed hydrosilylation reaction.

An NHC–Silyl–NHC Pincer Ligand for the Oxidative Addition of C−H, N−H, and O−H Bonds to Cobalt(I) Complexes

Co-reporter:Jian Sun;Lun Luo; Dr. Yi Luo; Dr. Liang Deng

Angewandte Chemie 2017 Volume 129(Issue 10) pp:2764-2768

Publication Date(Web):2017/03/01

DOI:10.1002/ange.201611162

AbstractN-Heterocyclic carbene based pincer ligands bearing a central silyl donor, [CSiC]−, have been envisioned as a class of strongly σ-donating ligands that can be used for synthesizing electron-rich transition-metal complexes for the activation of inert bonds. However, this type of pincer ligand and complexes thereof have remained elusive owing to their challenging synthesis. We herein describe the first synthesis of a CSiC pincer ligand scaffold through the coupling of a silyl–NHC chelate with a benzyl–NHC chelate induced by one-electron oxidation in the coordination sphere of a cobalt complex. The monoanionic CSiC ligand stabilizes the CoI dinitrogen complex [(CSiC)Co(N2)] with an unusual coordination geometry and enables the challenging oxidative addition of E−H bonds (E=C, N, O) to CoI to form CoIII complexes. The structure and reactivity of the cobalt(I) complex are ascribed to the unique electronic properties of the CSiC pincer ligand, which provides a strong trans effect and pronounced σ-donation.

A square planar iron(II) biphenyl-2,2′-diyl complex with NHC ligation: Synthesis, characterization, and its reactivity toward unsaturated organic substrates

Co-reporter:Lijun Wang, Jun Cheng, Liang Deng

Inorganica Chimica Acta 2017 Volume 460(Volume 460) pp:

Publication Date(Web):24 April 2017

DOI:10.1016/j.ica.2016.08.028

•A square planar iron(II) biphenyl complex bearing N-heterocyclic carbene ligands is prepared.•Characterization data established its S = 1 ground spin-state.•The iron(II) biphenyl complex reacts with alkyne and nitrile to form substituted phenanthrene and phenanthridine.•The iron(II) biphenyl complex reacts with CO and ButNC to form six-coordinate low-spin iron(II) biphenyl complexes.The synthesis, characterization, and reactivity study of a square planar iron(II) biphenyl-2,2′-diyl complex [(IPr2Me2)2Fe(But2Bip)] (1, IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, But2Bip = 4,4′-di(tert-butyl)biphenyl-2,2′-diyl) has been performed. Complex 1 was prepared by the salt elimination reaction of (IPr2Me2)2FeCl2 with 2,2′-dilithium-4,4′-di(tert-butyl)biphenyl. Characterization data obtained from NMR spectroscopy, X-ray crystal structure determination, solution magnetic susceptibility measurement, 57Fe Mössbauer spectroscopy, in combination with DFT calculations, suggest the intermediate-spin ferrous nature of the iron biphenyl-2,2′-diyl complex. Complex 1 reacts with PhCCPh, EtCCEt and PhCN to form 2,7-di(tert-butyl)-9,10-diphenylphenanthrene (2), 2,7-di-tert-butyl-9,10-diethylphenanthrene (3), and 3,8-di(tert-butyl)-6-phenylphenanthridine (4), respectively, whereas, its interaction with AdNC and CO lead to the formation of the six-coordinate iron(II) biphenyl-2,2′-diyl complexes [(IPr2Me2)2Fe(But2Bip)L2] (L = AdNC, 5; CO, 6). The attainment of 2–4 supports the proposed mechanisms that involve ferroles as key intermediates in iron-catalyzed cycloaddition reactions.A square planar iron(II) biphenyl-2,2′-diyl complex bearing N-heterocyclic carbene ligand react with alkyne and nitrile to form substituted phenanthrene and phenanthridine.Download high-res image (63KB)Download full-size image

Open-shell iron hydrocarbyls

Co-reporter:Zhenbo Mo, Liang Deng

Coordination Chemistry Reviews 2017 Volume 350(Volume 350) pp:

Publication Date(Web):1 November 2017

DOI:10.1016/j.ccr.2017.07.007

•Known categories of open-shell iron hydrocarbyls are summarized.•Preparation methods and structural features are summarized.•Spectroscopic features of open-shell iron hydrocarbyls are summarized.•The diversified reactivities of open-shell iron hydrocarbyls are summarized.Open-shell iron hydrocarbyl species attract great interests in the recent years for their relevance to the key intermediates of many iron-catalyzed organic transformations, and also their rich electronic structures that might lead to unique physical properties. While a plenty of studies on open-shell iron hydrocarbyls are scattered in literature, pertinent review on the chemistry of this type of intriguing complexes is lacking. In this article, we summarize the synthetic methods, structure and spectroscopic features, as well as the established reactivity of open-shell iron hydrocarbyl complexes, particularly those with the coordination numbers less than five. As we shall see, while the preparation methods of open-shell iron hydrocarbyls parallel with those of their closed-shell analogs, the open-shell nature of this type of organo-iron species could endow them unique spectroscopic features and also reactivity.Download high-res image (83KB)Download full-size image

Two-Coordinate Co(II) Imido Complexes as Outstanding Single-Molecule Magnets

Co-reporter:Xiao-Nan Yao, Jing-Zhen Du, Yi-Quan Zhang, Xue-Bing Leng, Mu-Wen Yang, Shang-Da JiangZhen-Xing Wang, Zhong-Wen Ouyang, Liang Deng, Bing-Wu Wang, Song Gao

Journal of the American Chemical Society 2016 Volume 139(Issue 1) pp:373-380

Publication Date(Web):December 12, 2016

DOI:10.1021/jacs.6b11043

The pursuit of single-molecule magnets (SMMs) with better performance urges new molecular design that can endow SMMs larger magnetic anisotropy. Here we report that two-coordinate cobalt imido complexes featuring highly covalent Co═N cores exhibit slow relaxation of magnetization under zero direct-current field with a high effective relaxation barrier up to 413 cm–1, a new record for transition metal based SMMs. Two theoretical models were carried out to investigate the anisotropy of these complexes: single-ion model and Co–N coupling model. The former indicates that the pseudo linear ligand field helps to preserve the first-order orbital momentum, while the latter suggests that the strong ferromagnetic interaction between Co and N makes the [CoN]+ fragment a pseudo single paramagnetic ion, and that the excellent performance of these cobalt imido SMMs is attributed to the inherent large magnetic anisotropy of the [CoN]+ core with |MJ = ± 7/2⟩ ground Kramers doublet.

Cobalt Complex-Catalyzed Hydrosilylation of Alkenes and Alkynes

Co-reporter:Jian Sun and Liang Deng

ACS Catalysis 2016 Volume 6(Issue 1) pp:290

Publication Date(Web):November 30, 2015

DOI:10.1021/acscatal.5b02308

The demand for economical and environmentally benign catalysts for important chemical transformations has recently initiated great efforts on nonprecious metal-catalyzed hydrosilylation reactions. The special chemical properties of cobalt enable the development of diverse cobalt complex-based catalysts for hydrosilylation reactions. This paper reviews the significant advances of cobalt complex-catalyzed hydrosilylation of alkenes and alkynes from the early studies in the 1960s until now, with the objective of providing readers with the status of the field and the underlying late 3d metal chemistry that is meaningful for new nonprecious metal catalyst design. Progress, problems, and perspectives in this vibrant field are discussed.Keywords: alkene; alkyne; cobalt; hydrosilylation; selectivity

Three- and Four-Coordinate Homoleptic Iron(I)–NHC Complexes: Synthesis and Characterization

Co-reporter:Zhenwu Ouyang, Yinshan Meng, Jun Cheng, Jie Xiao, Song Gao, and Liang Deng

Organometallics 2016 Volume 35(Issue 10) pp:1361-1367

Publication Date(Web):March 2, 2016

DOI:10.1021/acs.organomet.6b00047

The use of the monodentate N-heterocyclic carbene (NHC) 1,3,4,5-tetramethylimidazol-2-ylidene (IMe2Me2) and its N,N-diethyl and N,N-diisopropyl analogues IEt2Me2 and IPr2Me2 enabled the preparation of the four-coordinate homoleptic iron(I)–NHC complexes [(NHC)4Fe][BPh4] (NHC = IMe2Me2, 1; IEt2Me2, 2; IPr2Me2, 3) and the first three-coordinate homoleptic iron(I)–NHC complex, [(IPr2Me2)3Fe][BPh4] (5). X-ray crystallographic studies revealed the tetrahedral coordination geometries of the cations in 1 and 2, the square-planar geometry in 3, and the trigonal-planar geometry in 5. 57Fe Mössbauer spectroscopy and magnetic susceptibility measurements suggested that 1, 2, and 5 are high-spin (S = 3/2) iron(I) species and that 3 is a low-spin (S = 1/2) complex. 1H NMR and UV–vis–NIR spectroscopies revealed the existence of tetrahedral–square-planar isomerization (for 2 and 3) and NHC dissociation (for 3) in solutions of 2 and 3.

Converting carbon dioxide into alkanes via alkane reverse combustion reaction

Co-reporter:Yafei Gao

Science Bulletin 2016 Volume 61( Issue 15) pp:1160-1162

Publication Date(Web):2016/08/01

DOI:10.1007/s11434-016-1137-4

Selective Double Carbomagnesiation of Internal Alkynes Catalyzed by Iron-N-Heterocyclic Carbene Complexes: A Convenient Method to Highly Substituted 1,3-Dienyl Magnesium Reagents

Co-reporter:Yuesheng Liu; Lijun Wang

Journal of the American Chemical Society 2015 Volume 138(Issue 1) pp:112-115

Publication Date(Web):December 29, 2015

DOI:10.1021/jacs.5b12522

Controlled multicarbometalation of alkynes has been envisaged as an efficient synthetic method for dienyl and polyenyl metal reagents, but an effective catalyst enabling the transformation has remained elusive. Herein, we report that an iron(II)-N-heterocyclic carbene (NHC) complex (IEt2Me2)2FeCl2 (IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) can serve as a precatalyst for the double carbometalation of internal unsymmetrical alkynes with alkyl Grignard reagents, producing highly substituted 1,3-dienyl magnesium reagents with high regio- and stereoselectivity. Mechanistic studies suggest the involvement of low-coordinate organoiron(II)-NHC species as the in-cycle intermediates. The strong σ-donating nature of IEt2Me2 and its appropriate steric property are thought the key factors endowing the iron-NHC catalyst fine performance.

Three-Coordinate Iron(IV) Bisimido Complexes with Aminocarbene Ligation: Synthesis, Structure, and Reactivity

Co-reporter:Lei Wang; Lianrui Hu; Hezhong Zhang; Hui Chen

Journal of the American Chemical Society 2015 Volume 137(Issue 44) pp:14196-14207

Publication Date(Web):October 27, 2015

DOI:10.1021/jacs.5b09579

High-valent iron imido species are implicated as reactive intermediates in many iron-catalyzed transformations. However, isolable complexes of this type are rare, and their reactivity is poorly understood. Herein, we report the synthesis, characterization, and reactivity studies on novel three-coordinate iron(IV) bisimido complexes with aminocarbene ligation. Using our recently reported synthetic method for [LFe(NDipp)2] (L = IMes, 1; Me2-cAAC, 2), four new iron(IV) imido complexes, [(IPr)Fe(NDipp)2] (3) and [(Me2-cAAC)Fe(NR)2] (R = Mes, 4; Ad, 5; CMe2CH2Ph, 6), were prepared from the reactions of three-coordinate iron(0) compounds with organic azides. Characterization data acquired from 1H and 13C NMR spectroscopy, 57Fe Mössbauer spectroscopy, and X-ray diffraction studies suggest a low-spin singlet ground state for these iron(IV) complexes and the multiple-bond character of their Fe–N bonds. A reactivity study taking the reactions of 1 as representative revealed an intramolecular alkane dehydrogenation of 1 to produce the iron(II) complex [(IMes)Fe(NHDipp)(NHC6H3-2-Pri-6-CMe═CH2)] (7), a Si–H bond activation reaction of 1 with PhSiH3 to produce the iron(II) complex [(IMes)Fe(NHDipp)(NDippSiPhH2)] (8), and a [2+2]-addition reaction of 1 with PhNCNPh and p-PriC6H4NCO to form the corresponding open-shell formal iron(IV) monoimido complexes [(IMes)Fe(NDipp)(N(Dipp)C(NPh)(═NPh))] (9) and [(IMes)Fe(NDipp)(N(Dipp)C(O)N(p-PriC6H4))] (10), as well as [NDipp]-group-transfer reactions with CO and ButNC. Density functional theory calculations suggested that the alkane chain dehydrogenation reaction starts with a hydrogen atom abstraction mechanism, whereas the Si–H activation reaction proceeds in a [2π+2σ]-addition manner. Both reactions have the pathways at the triplet potential energy surfaces being energetically preferred, and have formal iron(IV) hydride and iron(IV) silyl species as intermediates, respectively. The low-coordinate nature and low d-electron count (d4) of iron(IV) imido complexes are thought to be the key features endowing their unique reactivity.

Observation of the single-ion magnet behavior of d8 ions on two-coordinate Co(I)–NHC complexes

Co-reporter:Yin-Shan Meng, Zhenbo Mo, Bing-Wu Wang, Yi-Quan Zhang, Liang Deng and Song Gao

Chemical Science 2015 vol. 6(Issue 12) pp:7156-7162

Publication Date(Web):10 Sep 2015

DOI:10.1039/C5SC02611C

The slow magnetic relaxation typical for single-ion magnets has been known for certain low-coordinate 3d metal complexes with d6, d7, and d9 electronic configurations, but never for d8 complexes. Herein, we report a study on two-coordinate d8 cobalt(I)–N-heterocyclic carbene complexes, for which slow magnetic relaxation behavior was observed for [Co(IMes)2][BPh4] (IMes: 1,3-dimesitylimidazol-2-ylidene) under an applied dc field. The system represents the first d8 single-ion magnet, and features a fitted energy barrier of Ueff = 21.3 cm−1 and pre-exponential factor of τ0 = 6.6 × 10−6 s. The analog two-coordinate cobalt(I) complexes with different NHC ligands, [Co(sIMes)2][BPh4] (sIMes: 1,3-dimesitylimidazolin-2-ylidene) and [Co(IAd)2][BArF4] (IAd: 1,3-dimesitylimidazol-2-ylidene; BArF4: tetra(3,5-ditrifluoromethylphenyl)borate), do not show such single-ion magnet behaviour. Ab initio calculations imply that the dihedral angle between the two NHC planes and the degree of unsaturation of the NHC ligands can dramatically alter the D value of the two-coordinate cobalt(I)–NHC ions, possibly via changing of the Co–NHC π-interactions, and hence affect the spin–orbit coupling splitting.

Linear and T-Shaped Iron(I) Complexes Supported by N-Heterocyclic Carbene Ligands: Synthesis and Structure Characterization

Co-reporter:Zhenwu Ouyang; Jingzhen Du; Lei Wang; Jared L. Kneebone; Michael L. Neidig

Inorganic Chemistry 2015 Volume 54(Issue 17) pp:8808-8816

Publication Date(Web):August 14, 2015

DOI:10.1021/acs.inorgchem.5b01522

The use of the N-heterocyclic carbene (NHC) ligands 1,3-bis(2′,6′-diethylphenyl)-4,5-(CH2)4-imidazol-2-ylidene (cyIDep), 1,3-bis(2′,6′-diethylphenyl)-imidazolin-2-ylidene (sIDep), and its N-mesityl analogue sIMes enables the preparation of the two-coordinate homoleptic iron(I)-NHC complexes [(cyIDep)2Fe][BArF4] (3, ArF denoted for 3,5-di(trifluoromethyl)phenyl) and [(sIDep)2Fe][BArF4] (4) and the T-shaped iron(I)-NHC complex [(sIMes)2Fe(THF)][BPh4] (5, THF = tetrahydrofuran). Complexes 3–5 were prepared via the sequential protocol of control reduction of iron(II) dihalides by KC8 in the presence of the corresponding NHC ligands followed by halide-abstraction with NaBAr4. Spectroscopic characterization, including single-crystal X-ray diffraction studies and 57Fe Mössbauer spectroscopy, in combination with density functional theory calculations, suggest their high-spin nature. Solution property study (absorption spectroscopy and cyclic voltammetry) indicates that 3 and 5 keep their corresponding two- and three-coordinate nature in THF solution, and 4 might reversibly coordinate a THF molecule to form, presumably, the T-shaped species [(sIDep)2Fe(THF)][BArF4]. The isolation of 3 and 4 demonstrates the accessibility of homoleptic two-coordinate iron(I)-NHC complexes.

Four-Coordinate Iron(II) Diaryl Compounds with Monodentate N-Heterocyclic Carbene Ligation: Synthesis, Characterization, and Their Tetrahedral-Square Planar Isomerization in Solution

Co-reporter:Yuesheng Liu, Lun Luo, Jie Xiao, Lei Wang, You Song, Jingping Qu, Yi Luo, and Liang Deng

Inorganic Chemistry 2015 Volume 54(Issue 10) pp:4752-4760

Publication Date(Web):March 30, 2015

DOI:10.1021/acs.inorgchem.5b00138

The salt elimination reactions of (IPr2Me2)2FeCl2 (IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with the corresponding aryl Grignard reagents afford [(IPr2Me2)2FeAr2] (Ar = Ph, 3; C6H4-p-Me, 4; C6H4-p-tBu, 5; C6H3-3,5-(CF3)2, 6) in good yields. X-ray crystallographic studies revealed the presence of both tetrahedral and trans square planar isomers for 3 and 6 and the tetrahedral structures for 4 and 5. Magnetic susceptibility and 57Fe Mössbauer spectrum measurements on the solid samples indicated the high-spin (S = 2) and intermediate-spin (S = 1) nature of the tetrahedral and square planar structures, respectively. Solution property studies, including solution magnetic susceptibility measurement, variable-temperature 1H and 19F NMR, and absorption spectroscopy, on 3–6, as well as an 57Fe Mössbauer spectrum study on a frozen tetrahydrofuran solution of tetrahedral [(IPr2Me2)257FePh2] suggest the coexistence of tetrahedral and trans square planar structures in solution phase. Density functional theory calculations on (IPr2Me2)2FePh2 disclosed that the tetrahedral and trans square planar isomers are close in energy and that the geometry isomerization can occur by spin-change-coupled geometric transformation on four-coordinate iron(II) center.

Three-Coordinate Iron(II) Dialkenyl Compound with NHC Ligation: Synthesis, Structure, and Reactivity

Co-reporter:Yuesheng Liu, Lei Wang, and Liang Deng

Organometallics 2015 Volume 34(Issue 17) pp:4401-4407

Publication Date(Web):August 27, 2015

DOI:10.1021/acs.organomet.5b00632

The reaction of [(IPr2Me2)2FePh2] with PhC≡CPh furnished a three-coordinate iron(II) dialkenyl complex, [(IPr2Me2)Fe(σ-CPh═CPh2)2] (1, IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), that represents a rare example of isolable low-coordinate iron alkenyl complexes with a high-spin ground state. Complex 1 was characterized by 1H NMR spectroscopy, solution magnetic susceptibility measurement, Mössbauer spectroscopy, single-crystal X-ray diffraction study, and elemental analyses. A reactivity study revealed the reactions of 1 with PhCH2Cl to produce cross-coupling product Ph2C═CPhCH2Ph (2), with [Cp2Fe][BArF4] to yield Ph2C═CPh–CPh═CPh2 (3), and with CO, 2,6-dimethylphenyl isocyanide, and phenyl azide to produce novel iron(0) and iron(II) complexes 4–6 bearing triphenylvinyl-derived ligands. These transformations demonstrated the high reactivity of the low-coordinate iron alkenyl complex.

A Two-Coordinate Cobalt(II) Imido Complex with NHC Ligation: Synthesis, Structure, and Reactivity

Co-reporter:Jingzhen Du;Linbo Wang;Dr. Meihua Xie;Dr. Liang Deng

Angewandte Chemie 2015 Volume 127( Issue 43) pp:12831-12835

Publication Date(Web):

DOI:10.1002/ange.201505937

Abstract

The synthesis, structural characterization, and reactivity of the first two-coordinate cobalt complex featuring a metal–element multiple bond [(IPr)Co(NDmp)] (4; IPr=1,3-bis(2′,6′-diisopropylphenyl)imidazole-2-ylidene; Dmp=2,6-dimesitylphenyl) is reported. Complex 4 was prepared from the reaction of [(IPr)Co(η²-vtms)₂] (vtms=vinyltrimethylsilane) with DmpN₃. An X-ray diffraction study revealed its linear CCoN core and a short CoN distance (1.691(6) Å). Spectroscopic characterization and calculation studies indicated the high-spin nature of 4 and the multiple-bond character of the CoN bond. Complex 4 effected group-transfer reactions to CO and ethylene to form isocyanide and imine, respectively. It also facilitated EH (E=C, Si) σ-bond activation of terminal alkyne and hydrosilanes to produce the corresponding cobalt(II) alkynyl and cobalt(II) hydride complexes as 1,2-addition products.

High-Spin Iron(II) Alkynyl Complexes with N-Heterocyclic Carbene Ligation: Synthesis, Characterization, and Reactivity Study

Co-reporter:Xiaojie Wang, Jia Zhang, Lei Wang, and Liang Deng

Organometallics 2015 Volume 34(Issue 12) pp:2775-2782

Publication Date(Web):June 2, 2015

DOI:10.1021/acs.organomet.5b00028

High-spin iron(II) alkynyl complexes [(IPr2Me2)2Fe(C≡CBut)2] (1) and [(IPr2Me2)2Fe(C≡CR)(NHMes)] (R = But 2, SiMe3 3) bearing a monodentate N-heterocyclic carbene ligand IPr2Me2 (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) have been prepared by salt metathesis and/or amine elimination methods and characterized by various spectroscopic methods. Complex 1 reacts with PMe3 (4 equiv) and ButNC (4 equiv) to form trans-[(PMe3)4Fe(C≡CBut)2] (4) and [η3-{(ButC≡C)(But)CC(IPr2Me2)C(NBut)}Fe(NCBut)3] (5), respectively. In contrast, the reactions of 1 with 4-Pri-C6H4NCO and PriNCNPri lead to the formation of the zwitterionic salts 4-Pri-C6H4NC(O)(IPr2Me2) and (PriN)2C(IPr2Me2), respectively. The interaction of 1 with I2 gives ButC≡CC≡CBut and (IPr2Me2)2FeI2. The C(sp)–C(sp3) cross-coupling products n-C8H17C≡CBut and c-C6H11C≡CBut are formed in high yields when 1 is treated with the corresponding alkyl halides n-C8H17X and c-C6H11X (X = Br, Cl). The formation of the ring-opening product 7,7-dimethyloct-1-en-5-yne in the reaction of 1 with cyclopropylmethyl bromide supports the radical character of the cross-coupling reaction.

Silane-Functionalized N-Heterocyclic Carbene–Cobalt Complexes Containing a Five-Coordinate Silicon with a Covalent Co–Si Bond

Co-reporter:Jian Sun, Chong Ou, Chao Wang, Masanobu Uchiyama, and Liang Deng

Organometallics 2015 Volume 34(Issue 8) pp:1546-1551

Publication Date(Web):April 8, 2015

DOI:10.1021/acs.organomet.5b00114

Novel cobalt complexes featuring five-coordinate silicon centers with a covalent Co–Si bond, i.e., [(SiN2C)Co(OPy)] complexes (SiN2C = tetradentate silane-anchored bis(pyridine)-N-heterocyclic carbene (NHC) ligand, OPy = 2-pyridonato), were prepared by reaction of bidentate hydrosilyl-NHC-supported cobalt(II) complexes with 2-pyridone and characterized by 1H, 13C, and 29Si NMR, single-crystal X-ray diffraction, and elemental analyses. Theoretical calculations support a covalent nature of the Co–Si interaction, in contrast to the metal→Si dative bonds in metallasilatranes.

Carbon–Carbon Bond Formation Reactivity of a Four-Coordinate NHC-Supported Iron(II) Phenyl Compound

Co-reporter:Yuesheng Liu, Jie Xiao, Lei Wang, You Song, and Liang Deng

Organometallics 2015 Volume 34(Issue 3) pp:599-605

Publication Date(Web):January 23, 2015

DOI:10.1021/om501061b

The preparation and characterization of a NHC-coordinated (NHC = N-heterocyclic carbene) ferrous phenyl complex [(IPr2Me2)2FePh2] (1; IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) as well as its C–C bond formation reactivity have been studied. The four-coordinate iron(II) phenyl complex was prepared from the reaction of ferrous chloride with PhMgBr and IPr2Me2. It reacts with nonactivated primary and secondary alkyl bromides and chlorides to furnish cross-coupling products and the iron(II) monophenyl species (IPr2Me2)2FePhX (X = Br (2), Cl). When it is treated with cyclooctatetraene (cot) or [Cp2Fe][BArF4] in the presence of PMe3, it undergoes coordination or one-electron oxidation induced reductive elimination of biphenyl to form the corresponding iron(0) or iron(I) species [(IPr2Me2)2Fe(η4-cot)] (3) or [(IPr2Me2)2Fe(PMe3)2][BArF4] (4). All of these iron-containing products have been fully characterized by various spectroscopic methods. Complex 1 and (IPr2Me2)2FeCl2 catalyze the reaction of n-C8H17Br with (p-tolyl)MgBr to afford the cross-coupling product in moderate yields (49% and 47%), whereas the reactions employing 4 and 1/PMe3 as catalysts give the cross-coupling product in very low yields. The results reflect the complexity of the reaction mechanism of iron-catalyzed coupling reactions.

A Two-Coordinate Cobalt(II) Imido Complex with NHC Ligation: Synthesis, Structure, and Reactivity

Co-reporter:Jingzhen Du;Linbo Wang;Dr. Meihua Xie;Dr. Liang Deng

Angewandte Chemie International Edition 2015 Volume 54( Issue 43) pp:12640-12644

Publication Date(Web):

DOI:10.1002/anie.201505937

Abstract

Regio- and Stereoselective Hydrosilylation of Alkynes Catalyzed by Three-Coordinate Cobalt(I) Alkyl and Silyl Complexes

Co-reporter:Zhenbo Mo ; Jie Xiao ; Yafei Gao

Journal of the American Chemical Society 2014 Volume 136(Issue 50) pp:17414-17417

Publication Date(Web):November 26, 2014

DOI:10.1021/ja510924v

A three-coordinate cobalt(I) complex exhibits high catalytic efficiency and selectivity as well as good functional group compatibility in alkyne hydrosilylation. [Co(IAd)(PPh3)(CH2TMS)] (1) (IAd = 1,3-diadamantylimidazol-2-ylidene) facilitates regio- and stereoselective hydrosilylation of terminal, symmetrical internal, and trimethylsilyl-substituted unsymmetrical internal alkynes to produce single hydrosilylation products in the forms of β-(E)-silylalkenes, (E)-silylalkenes, and (Z)-α,α-disilylalkenes, respectively, in high yields. The comparable catalytic efficiency and selectivity of the Co(I) silyl complex [Co(IAd)(PPh3)(SiHPh2)] that was prepared from the reaction of 1 with H2SiPh2, and the isolation of an alkyne Co(I) complex [Co(IAd)(η2-PhC≡CPh)(CH2TMS)] from the reaction of 1 with the acetylene, point out a modified Chalk–Harrod catalytic cycle for these hydrosilylation reactions. The high selectivity is thought to be governed by steric factors.

Three-Coordinate Cobalt(IV) and Cobalt(V) Imido Complexes with N-Heterocyclic Carbene Ligation: Synthesis, Structure, and Their Distinct Reactivity in C–H Bond Amination

Co-reporter:Long Zhang ; Yuesheng Liu

Journal of the American Chemical Society 2014 Volume 136(Issue 44) pp:15525-15528

Publication Date(Web):October 20, 2014

DOI:10.1021/ja509731z

The reaction of the cobalt(0) alkene complex [(IMes)Co(η2:η2-dvtms)] (1) (IMes = 1,3-bis(1′,3′,5′-trimethylphenyl)imidazol-2-ylidene, dvtms = divinyltetramethyldisiloxane) with 2 equiv of DippN3 (Dipp = 2,6-diisopropylphenyl) afforded the cobalt(IV) imido complex [(IMes)Co(NDipp)2] (2), which could be oxidized by [Cp2Fe][BArF4] (ArF = 3,5-di(trifluoromethyl)phenyl) to give the cobalt(V) imido species [(IMes)Co(NDipp)2][BArF4] (3). The molecular structures of all these complexes were established by single-crystal X-ray diffraction studies. Characterization data and theoretical calculations suggest ground spin states of S = 1/2 and S = 0 for the cobalt(IV) and cobalt(V) species, respectively. When heated, the cobalt(IV) imido species was converted to a cobalt(II) diamido complex via an intramolecular C–H bond amination reaction, but the cobalt(V) species was stable under similar conditions. The different outcomes suggest that a high oxidation state does not guarantee C–H bond activation reactivity of late-transition-metal imido species.

(Aminocarbene)(Divinyltetramethyldisiloxane)Iron(0) Compounds: A Class of Low-Coordinate Iron(0) Reagents

Co-reporter:Hezhong Zhang;Zhenwu Ouyang;Yuesheng Liu;Qiang Zhang;Lei Wang ;Dr. Liang Deng

Angewandte Chemie 2014 Volume 126( Issue 32) pp:8572-8576

Publication Date(Web):

DOI:10.1002/ange.201404677

Abstract

The combined use of aminocarbene and divinyltetramethyldisiloxane (dvtms) as supporting ligands enables the access of unprecedented low-coordinate iron(0) alkene compounds [L_nFe(η²:η²-dvtms)] (L=N-heterocyclic carbene (NHC) or cyclic (alkyl)(amino)carbene (CAAC), n=1 or 2) from the reactions of FeCl₂ with alkali-metal reducing agents, free aminocarbene ligands, and dvtms. The iron(0) species deliver their {L_nFe⁰} fragments to perform redox reactions with Ph₂SiH₂, S₈, Se, and DippN₃, furnishing novel aminocarbene-supported iron(IV) silylene, all-ferrous iron–sulfur/selenium cubanes, and bis(imido)iron(IV) compounds. These conversions demonstrate the potential synthetic utility of the carbene-supported iron(0) complexes as a valuable class of low-coordinate iron(0) reagents.

Iron(II) Dihydrocarbyls Supported by a Biphenyl-Linked Bis(benzimidazol-2-ylidene) Ligand: Syntheses and Characterization

Co-reporter:Yang Liu, Min Shi, and Liang Deng

Organometallics 2014 Volume 33(Issue 20) pp:5660-5669

Publication Date(Web):April 1, 2014

DOI:10.1021/om5000612

The use of a biphenyl-linked bis(benzimidazol-2-ylidene) ligand enables the access of dialkyl-, diaryl-, and diallyliron(II) species with bis(NHC) ligation. Deprotonation of the biphenyl-linked bis(benzimidazolium) salt (1) with 2 equiv of KH affords the biphenyl-linked dibenzotetraazafulvalene 2 in high yield. Treatment of 2 with 0.5 equiv of [(TMEDA)FeCl2]2 leads to the formation of the biphenyl-linked bis(benzimidazol-2-ylidene)iron(II) dichloride 3. Further salt elimination reactions between 3 and 2 equiv of TMSCH2Li, C6H5CH2K, PhMgBr, 3,5-(CF3)2C6H3MgBr, C3H5MgCl, and 2-Me-C3H4MgCl yield the corresponding biphenyl-linked bis(benzimidazol-2-ylidene)iron(II) dihydrocarbyls, denoted as [bis(NHC)FeR2] (R = CH2TMS (4), CH2Ph (5), Ph (6), C6H3-3,5-(CF3)2 (7), η3-CH2CHCH2 (8), η3-CH2C(Me)CH2 (9)). Compounds 2–9 have been fully characterized by NMR spectroscopy, absorption spectroscopy, solution magnetic susceptibility measurements, elemental analysis, and X-ray crystallography, revealing that 3–7 are four-coordinate high-spin iron(II) compounds with a formal 14-electron count and 8 and 9 are diamagnetic bis(η3-allyl)iron(II) species with 18 valence electrons. Attempts to prepare the bis(hydrocarbyl)iron(II) complexes of bulky allyls lead to the isolation of mono(η1-allyl)iron(II) chloride, denoted as [bis(NHC)FeCl(η1-TMSCHCHCHTMS)] (10), in low yield, whose structure has also been established by an single-crystal X-ray diffraction study. The achievement of the syntheses of these bis(hydrocarbyl)iron(II) compounds proves the unique electronic and steric features of the biphenyl-linked bis(benzimidazol-2-ylidene).

(Aminocarbene)(Divinyltetramethyldisiloxane)Iron(0) Compounds: A Class of Low-Coordinate Iron(0) Reagents

Co-reporter:Hezhong Zhang;Zhenwu Ouyang;Yuesheng Liu;Qiang Zhang;Lei Wang ;Dr. Liang Deng

Angewandte Chemie International Edition 2014 Volume 53( Issue 32) pp:8432-8436

Publication Date(Web):

DOI:10.1002/anie.201404677

Abstract

Reactivity of a Bis(amidinato)iron(II) Complex [Fe(MesC(NPri)2)2] toward Some Oxidizing Reagents

Co-reporter:Long Zhang, Li Xiang, Yihua Yu, and Liang Deng

Inorganic Chemistry 2013 Volume 52(Issue 10) pp:5906-5913

Publication Date(Web):May 8, 2013

DOI:10.1021/ic400053g

A diversified reactivity of the mononuclear bis(amidinato)iron(II) complex [Fe(MesC(NPri)2)2] (1) toward oxidizing reagents has been disclosed. The bis(amidinato)iron(II) complex was synthesized from the reaction of [Fe(Mes)2]2 with 4 equiv of diisopropyl carbodiimide in good yield. Treatment of 1 with 1 equiv of benzyl chloride gives the high-spin ferric complex [FeCl(MesC(NPri)2)2] (2), with 0.25 equiv of S8 affords the sulfur-insertion product [Fe(MesC(NPri)(NPriS))2] (3), with 1 equiv of 3,5-dimethylphenyl azide or phenyl azide yields nitrene-insertion product [Fe(MesC(NPri)2)(PriNC(Mes)N(Pri)NAr)] (Ar = 3,5-dimethylphenyl, 4a; phenyl, 4b), and with 1 equiv of oxo-transfer reagent, trimethylamine oxide or 2,6-dichloropyridine oxide, generates the oxo-bridged diferric complex [(MesC(NPri)2)2FeOFe(MesC(NPri)2)2] (5). Complexes 1–3, 4a, and 5 have been characterized by 1H NMR, UV–vis, IR, elemental analysis, and single-crystal X-ray diffraction studies. The formations of these unusual sulfur- and nitrene-insertion products 3, 4a, and 4b, can be explained by the sequential redox reaction between 1 and the oxidants, followed by migratory insertion steps.

Monomeric Bis(anilido)iron(II) Complexes with N-Heterocyclic Carbene Ligation: Synthesis, Characterization, and Redox Reactivity toward Aryl Halides

Co-reporter:Xiaojie Wang ; Zhenbo Mo ; Jie Xiao

Inorganic Chemistry 2013 Volume 52(Issue 1) pp:59-65

Publication Date(Web):December 18, 2012

DOI:10.1021/ic301894e

Using monodentate N-heterocyclic carbenes as the ancillary ligands, seven monomeric bis(anilido)iron(II) complexes [(IPr2Me2)2Fe(NHAr)2] (IPr2Me2 = 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene; Ar = Ph, C6H4-2-Pri, Mes, C6H3-2,6-Cl2, Dipp) and [(IPr)Fe(NHAr)2] (IPr = 2,5-di(2,6-diisopropylphenyl)imidazol-1-ylidene; Ar = C6H3-2,6-Cl2, Dipp) have been prepared by the one-pot reactions of [Fe(Mes)2]2 with the corresponding N-heterocyclic carbenes, and anilines. These high-spin diamido complexes have been fully characterized by 1H NMR, solution magnetic susceptibility, UV–vis, IR, X-ray diffraction, cyclic voltammetry, as well as elemental analysis. The strong affinity of the N-heterocyclic carbene ligands toward ferrous centers, and the steric protection exerted by the NHC ligands are the key factors to stabilize these bis(anilido)iron complexes in a monomeric manner. Reactivity studies revealed the four-coordinate complex [(IPr2Me2)2Fe(NHMes)2] can react with 1 equiv of 1-iodo-3,5-dimethylbenzene or 1-bromo-3,5-dimethylbenzene in C6D6 and THF-d8 to furnish 1-C6D5-3,5-Me2C6H3, and 5-D-1,3-Me2C6H3, respectively. Under similar conditions, the three-coordinate compound [(IPr)Fe(NHDipp)2] is inert toward these halides.

Iron-mediated C–H bond amination by organic azides on a tripodal bis(anilido)iminophosphorane platform

Co-reporter:Jie Xiao and Liang Deng

Dalton Transactions 2013 vol. 42(Issue 16) pp:5607-5610

Publication Date(Web):26 Feb 2013

DOI:10.1039/C3DT50518A

The bis(anilido)iminophosphorane complex, abbreviated as [(MesN2NAd)Fe(THF)], can react with alkyl azides to yield ligand-based C–H bond amination products suggesting the high reactivity of iron(IV)–imido species supported by the tripodal bis(anilido)iminophosphorane ligand platform [MesN2NAd]2−.

Square Planar Nickel(II) Complexes with Halogenated o-Diiminobenzosemiquinonato Ligation: Synthesis, Characterization, and Redox Property

Co-reporter:Wansheng Zuo;Long Zhang;Meihua Xie

Chinese Journal of Chemistry 2013 Volume 31( Issue 12) pp:1473-1482

Publication Date(Web):

DOI:10.1002/cjoc.201300664

Abstract

Seven square planar bis(o-diiminobenzosemiquinonato)nickel(II) complexes, [Ni(o-C₆H₄(NH)(NAr))₂] (Ar=Mes, 1; p-F-C₆H₄, 2; p-Cl-C₆H₄, 3), [Ni(o-4,5-F₂-C₆H₂(NH)(NPh))₂] (4), and [Ni(o-4,5-Cl₂-C₆H₂(NH)(NAr))₂] (Ar=Ph, 5; 2,6-F₂-C₆H₃, 6; 2,6-Cl₂-C₆H₃, 7), have been synthesized and characterized by ¹H NMR, ¹³C NMR, ¹⁹F NMR, IR, UV-Vis-NIR, elemental analyses, HRMS, as well as single-crystal X-ray diffraction studies (1 and 7). The cyclic voltammograms of these complexes exhibit two reversible redox processes of [NiL₂]^0/1− and [NiL₂]^1−/2−, and one irreversible process of [NiL₂]^0/2+. Substituent effects on the redox properties of these complexes, in addition with those of the known complexes [Ni(o-C₆H₄(NH)(NPh))₂] (8) and [Ni(o-3,5-Bu^t₂-C₆H₂(NH)₂)₂] (9), are identified by comparing the half-wave potentials of the reduction waves, as 1≈9<8≈2<3<4<5<7<6, reflecting the ease of reduction of [NiL₂] parallels the electron-donating and -withdrawing ability of the substituent group. Reduction of 1 with one or two equivalents of sodium metal in THF has led to the isolation of [Na(THF)₃][1] and [Na(THF)₃]₂[1]. The structure data of these two complexes revealed by low-temperature X-ray crystallography suggest their corresponding electronic structures of [Ni^II(¹L^·1−)(¹L²⁻)]¹⁻ and [Ni^II(¹L²⁻)²]²⁻, which are in line with those of [9]ⁿ (n=1−, 2−) suggested by spectroelectrochemical study.

Anchoring of Silyl Donors on a N-Heterocyclic Carbene through the Cobalt-Mediated Silylation of Benzylic CH Bonds

Co-reporter:Zhenbo Mo;Yang Liu ;Dr. Liang Deng

Angewandte Chemie International Edition 2013 Volume 52( Issue 41) pp:10845-10849

Publication Date(Web):

DOI:10.1002/anie.201304596

Anchoring of Silyl Donors on a N-Heterocyclic Carbene through the Cobalt-Mediated Silylation of Benzylic CH Bonds

Co-reporter:Zhenbo Mo;Yang Liu ;Dr. Liang Deng

Angewandte Chemie 2013 Volume 125( Issue 41) pp:11045-11049

Publication Date(Web):

DOI:10.1002/ange.201304596

Iron(II) Complexes Featuring Bidentate N-Heterocyclic Carbene–Silyl Ligands: Synthesis and Characterization

Co-reporter:Zhenwu Ouyang and Liang Deng

Organometallics 2013 Volume 32(Issue 24) pp:7268-7271

Publication Date(Web):December 11, 2013

DOI:10.1021/om4010274

Two silyl donor containing N-heterocyclic carbene iron(II) complexes, [(CSi)Fe(IMes′)] (CSi = bidentate silyl donor containing N-heterocyclic carbene ligand, IMes′ = cyclometalated IMes ligand, IMes = 1,3-dimesitylimidazol-2-ylidene) have been synthesized by sequential iron-mediated benzylic C–H bond activation and silylation reactions starting from [(IMes)2FeCl2]. Single-crystal X-ray diffraction studies revealed that the [(CSi)Fe(IMes′)] complexes have seesaw-type FeSiC3 cores. Solution magnetic susceptibility measurements, UV–vis–near-IR spectra, and bond distance data from X-ray diffraction studies corroborate an intermediate spin state, S = 1, for these unique iron(II) complexes. DFT calculations revealed that the bidentate CSi chelates are essentially σ-donating ligands in the iron(II) compounds.

Intramolecular C(sp3)–H Bond Activation Reactions of Low-Valent Cobalt Complexes with Coordination Unsaturation

Co-reporter:Zhenbo Mo, Dake Chen, Xuebin Leng, and Liang Deng

Organometallics 2012 Volume 31(Issue 20) pp:7040-7043

Publication Date(Web):October 9, 2012

DOI:10.1021/om300804a

Intramolecular C(sp3)–H bond activation reactions mediated by low-valent cobalt, both Co(I) and Co(0), have been observed in the reactions of the three-coordinate cobalt complex [Co(IMes)2Cl] (IMes = 1,3-dimesitylimidazol-2-ylidene) with alkylation reagents and sodium amalgam. The reactions with alkylation reagents gave [Co(IMes)(IMes′)(N2)], featuring a metalated IMes′ anion, whereas the one-electron-reduction reaction afforded [Co(IMes′)2]. The Co(II) complex can react with CO, isocyanide, and a diazo compound to furnish interesting cobalt complexes bearing functionalized N-heterocyclic carbene ligands. The establishment of these conversions demonstrates the capability of low-valent cobalt with coordination unsaturation to mediate C(sp3)–H bond activation and functionalization.

Dinuclear Iron Complex-Catalyzed Cross-Coupling of Primary Alkyl Fluorides with Aryl Grignard Reagents

Co-reporter:Zhenbo Mo, Qiang Zhang, and Liang Deng

Organometallics 2012 Volume 31(Issue 18) pp:6518-6521

Publication Date(Web):August 31, 2012

DOI:10.1021/om300722g

Iron-catalyzed cross-coupling of nonactivated primary alkyl fluorides with aryl Grignard reagents has been achieved by using the low-coordinate dinuclear iron complex [(IPr2Me2)Fe(μ2-NDipp)2Fe(IPr2Me2)] as the catalyst. This iron-catalyzed C(sp3)–F bond arylation reaction is applicable to a variety of aryl Grignard reagents and primary alkyl fluorides. The product pattern suggests the involvement of a radical-type mechanism for its C–F bond scission step.

Dinuclear Iron–Imido Complexes with N-Heterocyclic Carbene Ligation: Synthesis, Structure, and Redox Reactivity

Co-reporter:Qiang Zhang, Li Xiang, and Liang Deng

Organometallics 2012 Volume 31(Issue 12) pp:4537-4543

Publication Date(Web):June 1, 2012

DOI:10.1021/om300319n

The introduction of an N-heterocyclic carbene ligand (NHC) to iron–imido chemistry has led to the successful preparation of a series of iron–imido complexes featuring rhombic [Fe(μ2-NDipp)2Fe]n (n = 0, 1+, 2+) cores. The dimeric iron(II)–imido complex [(IPr2Me2)Fe(μ2-NDipp)2Fe(IPr2Me2)] (1) was prepared by protonolysis of the ferrous precursor [(IPr2Me2)Fe(Mes)2] with the aniline derivative DippNH2. Complex 1 has a rhombic [Fe(μ2-NDipp)2Fe] core in which the iron sites adopt trigonal-planar geometry and have a formal Fe(II) oxidation state. Oxidation of 1 with 1 or 2 equiv of [Cp2Fe][BF4] resulted in the formation of the dinuclear iron(III) complex [F(IPr2Me2)Fe(μ2-NDipp)2Fe(IPr2Me2)F] (2) or [F(IPr2Me2)Fe(μ2-NDipp)2Fe(IPr2Me2)(BF4)] (3), respectively. However, the reaction of 1 with benzyl chloride could give either the diferric complex [Cl(IPr2Me2)Fe(μ2-NDipp)2Fe(IPr2Me2)Cl] (4) or the mixed-valent complex [(IPr2Me2)Fe(μ2-NDipp)2Fe(IPr2Me2)Cl] (5), depending on the reaction stoichiometry. Complex 5 is also accessible upon the reaction of 1 with 4. Complexes 1–5 have been fully characterized by 1H NMR, UV–vis spectroscopy, single-crystal X-ray diffraction studies, and elemental analysis. The successful preparation of these complexes revealed the potential of the iron–imido rhomb for mediating electron transfer.

Synthesis, Structure, and Reactivity Study of Iron(II) Complexes with Bulky Bis(anilido)thioether Ligation

Co-reporter:Jie Xiao and Liang Deng

Organometallics 2012 Volume 31(Issue 1) pp:428-434

Publication Date(Web):December 15, 2011

DOI:10.1021/om201010a

The synthesis, molecular structure, and ligand substitution reactivity of iron(II) complexes bearing the bulky N,N′-dimesityl-2,2′-diamidophenyl sulfide ligand have been studied. The ligand H2(mesNSN) (1) was synthesized by a Pd-mediated Buchwald–Hartwig amination method. An amine elimination reaction between 1 and [Fe(NTMS2)2]2 afforded the high-spin complex [(mesNSN)Fe(THF)] (2), displaying a distorted trigonal-monopyramidal geometry. Interaction of 2 with PMe3 and 2,5-di-tert-butylimidazol-1-ylidene (IBut) gave the ligand substitution products [(mesNSN)Fe(PMe3)] (3) and [(mesNSN)Fe(IBut)] (4), respectively. Both 3 and 4 are high spin and display molecular geometry similar to that of 2. The reaction of 2 with 3 equiv of isocyanide gave the low-spin complexes [(mesNSN)Fe(CNR)3] (R = But (5), Ph-2,6-Me2 (6)). Recrystallization of 6 has led to the isolation of the carbon–sulfur bond cleavage product [(mesNS)Fe(CNPh-2,6-Me2)3] (7). Quite unexpectedly, the interaction of 2 with 3-hexyne and deuterated benzene could induce Fe–N(amido) bond cleavage, giving [(mesHNSN)2Fe(THF)] (8) and [(mesHNSN)2Fe] (9), respectively. The formation of 7–9 suggests the lability of the [(mesNSN)Fe] fragment, which could suffer from degradation in the presence of bulky strong field ligands.

C-H bond amination by iron-imido/nitrene species

Co-reporter:Long Zhang

Science Bulletin 2012 Volume 57( Issue 19) pp:2352-2360

Publication Date(Web):2012 July

DOI:10.1007/s11434-012-5151-x

C-H amination by iron-imido/nitrene species has attracted increasing research interest in recent years because of its potential use in economical and environmentally benign syntheses of amino compounds. With the aim of providing a comprehensive overview of this field, which is of interest to both the synthetic organic and inorganic communities, this paper reviews the status quo of C-H amination chemistry by iron-imido/nitrene intermediates, as well as by well-defined iron-imido/nitrene compounds, with special emphasis on their structure/reactivity correlations. Achievements, problems, and perspectives in this growing field are discussed.

Square-Planar Cobalt Complexes with Monodentate N-Heterocyclic Carbene Ligation: Synthesis, Structure, and Catalytic Application

Co-reporter:Zhenbo Mo, Yuxue Li, Hung Kay Lee, and Liang Deng

Organometallics 2011 Volume 30(Issue 17) pp:4687-4694

Publication Date(Web):August 18, 2011

DOI:10.1021/om200527y

The unique cobalt(I)-NHC complex [Co(IEt)4][BPh4] (1) (IEt = 1,3-diethyl-4,5-dimethylimidazole-2-ylidene) and its analogues employing other carbene ligands were prepared by the reactions of [Co(PPh3)3Cl] with free carbene ligands followed by anion exchange. X-ray diffraction revealed 1 features a homoleptic cation [Co(IEt)4]+ with square-planar geometry. Electrochemical studies showed the square-planar complexes support the redox series [Co(IEt)4]+/2+/3+, of which the divalent cation has been synthesized and structurally characterized as in [Co(IEt)4][BF4]2 (2). Both EPR and DFT studies indicated 2 has a low-spin Co(II) center. 1 can efficiently catalyze the oxidative homocoupling reactions of aryl Grignard reagents. Investigations on the stoichiometric reactions of 1 with organic halides and 2 with aryl Grignard reagents established an interesting radical mechanism involving the [Co(IEt)4]+/2+ redox shuttle for these cobalt-NHC complex catalyzed homocoupling reactions.

Synthesis, Structure, and Reactivity of Organo-Iron(II) Complexes with N-Heterocyclic Carbene Ligation

Co-reporter:Li Xiang, Jie Xiao, and Liang Deng

Organometallics 2011 Volume 30(Issue 7) pp:2018-2025

Publication Date(Web):March 14, 2011

DOI:10.1021/om2000663

The synthesis, structure, and reactivity of some organo-iron complexes with monodentate N-heterocyclic carbene (NHC) ligation were studied. Mononuclear ferrous complexes [(IEt)2FeR2] (IEt = 2,5-diethyl-3,4-dimethylimidazol-1-ylidene, R = Me (2a), CH2TMS (2b)) and [(IPr)FeMes2] (3, IPr = 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene) were prepared in good yields via salt elimination reactions of [(NHC)2FeCl2] (1) with alkylation reagents. The interaction of 1 with PhLi gave a mixture of dinuclear complexes [Cl(IEt)Fe(IEt′)2Fe(IEt)Cl] (4a) and [Ph(IEt)Fe(IEt′)2Fe(IEt)Ph] (4b) (IEt′ = 3-Et-4,5-Me2-2-ylideneimidazolyl anion), in which N−C(ethyl) bond cleavage of the NHC ligand was involved. Complexes 2a−4b were characterized by 1H NMR, elemental analyses, and single-crystal X-ray diffraction studies. Solution magnetism measurement by Evan’s method revealed the high-spin electronic configuration for the mononuclear organo-iron(II) complexes 2a, 2b, and 3. Reactivity studies showed the tetrahedral complex 2a was inert toward many unsaturated organic substrates, whereas the trigonal-planar complex 3 could react with CO and carbodiimide PriN═C═NPri to yield dimesityl ketone and [(IPr)Fe(Mes)(η2-PriNC(Mes)NPri)] (5), respectively. Relevant to iron-catalyzed Kumada couplings, both complexes 2b and 3 were found reactive with PhI to yield the corresponding carbon−carbon bond formation products Ph−CH2TMS and Ph−Mes.

Converting carbon dioxide into alkanes via alkane reverse combustion reaction

Co-reporter:Yafei Gao, Liang Deng

Science Bulletin (August 2016) Volume 61(Issue 15) pp:1160-1162

Publication Date(Web):1 August 2016

DOI:10.1007/s11434-016-1137-4

Observation of the single-ion magnet behavior of d8 ions on two-coordinate Co(I)–NHC complexes

Co-reporter:Yin-Shan Meng, Zhenbo Mo, Bing-Wu Wang, Yi-Quan Zhang, Liang Deng and Song Gao

Chemical Science (2010-Present) 2015 - vol. 6(Issue 12) pp:NaN7162-7162

Publication Date(Web):2015/09/10

DOI:10.1039/C5SC02611C

Iron-mediated C–H bond amination by organic azides on a tripodal bis(anilido)iminophosphorane platform

Co-reporter:Jie Xiao and Liang Deng