The design and synthesis of mixed-metal coordination cages, which can act as hosts to encapsule guest molecules, is a subject of intensive research, and the utilization of metalloligand is an effective method to construct a designed heterometallic architecture. Herein, a series of heterometallic cages with half-sandwich Rh, Ir and Ru fragments using Cu^II-metalloligand as a building block by a stepwise approach is reported. The cavity sizes of the cages could be controlled easily by the lengths of the organic ligands. Because the metalloligands in the oxalate-based cage are somewhat distorted and concave, there are weak Cu⋅⋅⋅O interactions in the molecules, forming a binuclear copper unit. By increasing the height of the cages using longer ligands, 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (H₂CA), the organometallic boxes display interesting host–guest behavior, which are made large enough to accommodate some large molecules, such as pyrene and [Pt(acac)₂]. Interestingly, the heterometallic cage with larger cavity size can transfer into a homometallic hexanuclear prism in the presence of pyrazine.

By carefully selecting an existing synthetic strategy and suitable coordination subunits, constructing desired coordination geometries is no longer that difficult to accomplish. Herein, a new strategy to construct a series of unprecedented structures by using conjugated Cp*Rh-based complex BN-OTf (Cp*=η⁵-C₅Me₅) as the building block is proposed. DFT calculations revealed extensive delocalized π bonds in the subunit. With BN-OTf, rectangular macrocycles TN-bpy and TN-bpe were controllably synthesized. Single-crystal XRD studies confirmed one-dimensional stacking channels for the tetranuclear structure. Notably, the starting ligand imidazole-4,5-dicarboxylate was found to act not only as a tetradentate but also as a hexadentate ligand that can coordinate to further metal ions. Subsequently, [4 Rh+1 M] heterometallic complexes HMZ (M=Cu and Zn) were accessed by chelating borderline hard/soft Lewis acids. With TN-Linker or HMZ, two routes resulted in the [8 Rh+2 M] heterometallic cages HMC (M=Cu and Zn) with excellent crystallinity and stability. Surprisingly, when BN-OTf bonded to rhodium itself, triangular prisms TP-Linker were obtained with high solubility after being linked by bipyridine linkers. Both the X-ray structure and ¹H NMR spectrum confirmed the novel isomerization of the triangular structures. All of the compounds were obtained in high yields and were fully characterized by ¹H NMR spectroscopy, elemental analysis, IR spectroscopy, and in most cases single-crystal X-ray structure determination.

In contrast to conventional stepwise synthesis of molecular Borromean rings, a self-assembly synthetic method which proceeds without the aid of a template has been developed. In the formation of molecular rectangles, by adjustment of the long-arm length of the rectangles, a series of size-dependent Borromean-link frameworks were constructed. Both the shortest length of two arms and the relative proportion of the length of the long arm to that of the short arm play a key role in the formation of Borromean rings. DFT calculations were used to provide theoretical support for the formation of discrete interlocked frameworks.

In contrast to conventional stepwise synthesis of molecular Borromean rings, a self-assembly synthetic method which proceeds without the aid of a template has been developed. In the formation of molecular rectangles, by adjustment of the long-arm length of the rectangles, a series of size-dependent Borromean-link frameworks were constructed. Both the shortest length of two arms and the relative proportion of the length of the long arm to that of the short arm play a key role in the formation of Borromean rings. DFT calculations were used to provide theoretical support for the formation of discrete interlocked frameworks.

A series of microporous lanthanide coordination polymers containing p-dicarboxylate carborane ligand (1–8) have been synthesized from the reactions of 1,12-dihydroxycarbonyl-1,12-dicarba-closo-dodecaborane (p-CDCH₂) with rare earth metals. Based on the well-known effect of lanthanide contraction, three distinct structure types were isolated: Structure type I crystallizes in the triclinic space group P with formula {[Ln₂(p-CDC)₃S₆]⋅χS}_n (S=solvent molecules, such as H₂O, MeOH, and DMF), Ln=Yb³⁺ (1), Y³⁺ (2), Tb³⁺ (3), Gd³⁺ (4), Sm³⁺ (6) and structure type II also crystallizes in the triclinic space group P with formula {[Eu₂(p-CDC)₃(MeOH)₂(H₂O)₄]⋅[Eu₂(p-CDC)₃(H₂O)₄(DMF)₂]⋅2DMF}_n (5). Nevertheless, structure type III crystallizes in the monoclinic space group P21/n with formula {[Ln₂(p-CDC)₃(MeOH)₄(DMF)₂]⋅2 MeOH}_n, Ln=Ce³⁺ (7) and La³⁺ (8). The structures of type I polymers consist of four-connected 2D lamellar networks, but type II and type III polymers are composed of six-connected 3D structures. Gas sorption property of compound 1’ was studied, which showed selective CO₂ capture over CH₄ and N₂.

A series of iridium- and rhodium-based hexanuclear organometallic cages containing 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone, 9,10-dihydroxy-1,4-anthraquinone, and 6,11-dihydroxynaphthacene-5,12-dione ligands were synthesized from the self-assembly of the corresponding molecular “clips” and 2,4,6-tri(4-pyridyl)-1,3,5-triazine ligands in good yields. These organometallic cages can form inclusion systems with a wide variety of π-donor substrates, including coronene, pyrene, [Pt(acac)₂], and hexamethoxytriphenylene. The 1:1 complexation of the resulting supramolecular assemblies was confirmed by ¹H NMR spectroscopy. Large complexation shifts (Δδ>1 ppm) were observed in the ¹H NMR spectra of guests in the presence of cage [Cp*₆M₆(μ-DHNA)₃(tpt)₂](OTf)₆ (6a; M=Ir, tpt=2,4,6-tri(4-pyridyl)-1,3,5-triazine). The formation of discrete 1:1 donor–acceptor complexes, pyrene⊂6 b (M=Rh), coronene⊂6 a, coronene⊂6 b, and [Pt(acac)₂]⊂6 a was confirmed by their single-crystal X-ray analyses. In these systems, the most important driving force for the formation of guest–host complexes is clearly the donor–acceptor π⋅⋅⋅π stacking interaction, including charge-transfer interactions between the electron-donating and electron-accepting aromatic components. These structures provide compelling evidence for the existence of strong attractive forces between the electron-deficient triazine core and electron-rich guest. The results presented here may provide useful guidance for designing artificial receptors for functional biomolecules.

Synthesis, structure, and reactivity of carboranylamidinate-based half-sandwich iridium and rhodium complexes are reported for the first time. Treatment of dimeric metal complexes [{Cp*M(μ-Cl)Cl}₂] (M=Ir, Rh; Cp*=η⁵-C₅Me₅) with a solution of one equivalent of nBuLi and a carboranylamidine produces 18-electron complexes [Cp*IrCl(Cab^N-DIC)] (1 a; Cab^N-DIC=[iPrNC(closo-1,2-C₂B₁₀H₁₀)(NHiPr)]), [Cp*RhCl(Cab^N-DIC)] (1 b), and [Cp*RhCl(Cab^N-DCC)] (1 c; Cab^N-DCC=[CyNC(closo-1,2-C₂B₁₀H₁₀)(NHCy)]). A series of 16-electron half-sandwich Ir and Rh complexes [Cp*Ir(Cab^N′-DIC)] (2 a; Cab^N′-DIC=[iPrNC(closo-1,2-C₂B₁₀H₁₀)(NiPr)]), [Cp*Ir(Cab^N′-DCC)] (2 b, Cab^N′-DCC=[CyNC(closo-1,2-C₂B₁₀H₁₀)(NCy)]), and [Cp*Rh(Cab^N′-DIC)] (2 c) is also obtained when an excess of nBuLi is used. The unexpected products [Cp*M(Cab^N,S-DIC)], [Cp*M(Cab^N,S-DCC)] (M=Ir 3 a, 3 b; Rh 3 c, 3 d), formed through BH activation, are obtained by reaction of [{Cp*MCl₂}₂] with carboranylamidinate sulfides [RNC(closo-1,2-C₂B₁₀H₁₀)(NHR)]S⁻ (R=iPr, Cy), which can be prepared by inserting sulfur into the CLi bond of lithium carboranylamidinates. Iridium complex 1 a shows catalytic activities of up to 2.69×10⁶ g_PNB  h⁻¹ for the polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst. Catalytic activities and the molecular weight of polynorbornene (PNB) were investigated under various reaction conditions. All complexes were fully characterized by elemental analysis and IR and NMR spectroscopy; the structures of 1 a–c, 2 a, b; and 3 a, b, d were further confirmed by single crystal X-ray diffraction.

The synthesis of Group IV metal complexes that contain a tetradentate dianionic [OSSO]-carborane ligand [(HOC₆H₂tBu₂-4,6)₂(CH₂)₂S₂C₂(B₁₀H₁₀)] (1 a) is described. Reactions of TiCl₄ and Ti(OiPr)₄ with the [OSSO]-type ligand 1 a afford six-coordinated titanium complex [Ti(OC₆H₂tBu₂-4,6)₂(CH₂)₂S₂C₂(B₁₀H₁₀)Cl₂] (2 a) and four-coordinated titanium complex [Ti(OC₆H₂tBu₂-4,6)₂(CH₂)₂S₂C₂(B₁₀H₁₀)(OiPr)₂] (2 b), respectively. ZrCl₄ and HfCl₄ were treated with 1 a to give six-coordinated zirconium complex [Zr(OC₆H₂tBu₂-4,6)₂(CH₂)₂S₂C₂(B₁₀H₁₀)Cl₂(thf)₂] (2 c) and six-coordinated hafnium complex [Hf(OC₆H₂tBu₂-4,6)₂(CH₂)₂S₂C₂(B₁₀H₁₀)Cl₂] (2 d). All the complexes were fully characterized by IR, NMR spectroscopy, and elemental analysis. In addition, X-ray structure analyses were performed on complexes 2 a and 2 b and reveal the expected different coordination geometry due to steric hindrance effects. Extended X-ray absorption fine structure (EXAFS) spectroscopy was performed on complexes 2 c and 2 d to describe the coordination chemistry of this ligand around Zr and Hf. Six-coordinated titanium complex 2 a showed good activity toward ethylene polymerization as well as toward copolymerization of ethylene with 1-hexene in the presence of methylaluminoxane (MAO) as cocatalyst (up to 1060 kg [mol (Ti)]⁻¹ h⁻¹ in the case of 10 atm of ethylene pressure).

A series of half-sandwich rhodium-based metallamacrocycles with tetra- and hexanuclearities have been synthesized. They are assembled by linking the deprotonated 2,4-diacetyl-5-hydroxy-5-methyl-3-(3-pyridinyl)cyclohexanone (HL) ligand in the presence of counteranions. When the counteranion was the tetrahedral BF₄⁻ ion, tetranuclear metallamacrocycle [(Cp*RhL)₄][BF₄]₄ (1 d) was formed. However, the larger OTf⁻, PF₆⁻, and SbF₆⁻ counterions favored the formation of hexanuclear metallamacrocycles [(Cp*RhL)₆⊃2OTf][OTf]₄ (1 a), [(Cp*RhL)₆⊃2PF₆][PF₆]₄ (1 b), and [(Cp*RhL)₆⊃2SbF₆][SbF₆]₄⋅6CH₃CN (1 c) when the reactions were performed under the same conditions. Single-crystal X-ray analysis indicated that, in the solid state, two counteranions were encapsulated in each belt-like host molecule of hexanuclear metallamacrocycles 1 a, b, and c. Based on the results of ¹H NMR analysis in methanol, the nuclearities of 1 a–c and the two encapsulated anions in each molecular cavity were maintained in solution. In addition, tetranuclear metallamacrocycle 1 d was converted into the hexanuclear metallamacrocycles 1 a′, b, and c after addition of the appropriate anion as its [NBu₄]⁺ salt. The compound 1 a′ was characterized by single-crystal X-ray diffraction to have the formula [(Cp*RhL)₆⊃2OTf][BF₄]₄⋅2MeOH⋅2H₂O. From the interconversion of the hexanuclear metallamacrocycles, we have concluded that the hexanuclear belt-like host in 1 a–c has an clear selectivity for larger anions, in the sequence SbF₆⁻≈PF₆⁻>OTf⁻>BF₄⁻>Cl⁻.

A series of binuclear complexes [{Cp*Ir(OOCCH₂COO)}₂(pyrazine)] (1 b), [{Cp*Ir(OOCCH₂COO)}₂(bpy)] (2 b; bpy=4,4′-bipyridine), [{Cp*Ir(OOCCH₂COO)}₂(bpe)] (3 b; bpe=trans-1,2-bis(4-pyridyl)ethylene) and tetranuclear metallamacrocycles [{(Cp*Ir)₂(OOC-CC-COO)(pyrazine)}₂] (1 c), [{(Cp*Ir)₂(OOC-CC-COO)(bpy)}₂] (2 c), [{(Cp*Ir)₂(OOC-CC-COO)(bpe)}₂] (3 c), and [{(Cp*Ir)₂[OOC(H₃C₆)-NN-(C₆H₃)COO](pyrazine)}₂] (1 d), [{(Cp*Ir)₂[OOC(H₃C₆)-NN-(C₆H₃)COO](bpy)}₂] (2 d), [{(Cp*Ir)₂[OOC(H₃C₆)-NN-(C₆H₃)COO](bpe)}₂] (3 d) were formed by reactions of 1 a–3 a {[(Cp*Ir)₂(pyrazine)Cl₂] (1 a), [(Cp*Ir)₂(bpy)Cl₂] (2 a), and [(Cp*Ir)₂(bpe)Cl₂] (3 a)} with malonic acid, fumaric acid, or H₂ADB (azobenzene-4,4′-chcarboxylic acid), respectively, under mild conditions. The metallamacrocycles were directly self-assembled by activation of CH bonds from dicarboxylic acids. Interestingly, after exposure to UV/Vis light, 3 c was converted to [2+2] cycloaddition complex 4. The molecular structures of 2 b, 1 c, 1 d, and 4 were characterized by single-crystal x-ray crystallography. Nanosized tubular channels, which may play important roles for their stability, were also observed in 1 c, 1 d, and 4. All complexes were well characterized by ¹H NMR and IR spectroscopy, as well as elemental analysis.

Monophosphine-o-carborane has four competitive coordination modes when it coordinates to metal centers. To explore the structural transitions driven by these competitive coordination modes, a series of monophosphine-o-carborane Ir,Rh complexes were synthesized and characterized. [Cp*M(Cl)₂{1-(PPh₂)-1,2-C₂B₁₀H₁₁}] (M=Ir (1 a), Rh (1 b); Cp*=η⁵-C₅Me₅), [Cp*Ir(H){7-(PPh₂)-7,8-C₂B₉H₁₁}] (2 a), and [1-(PPh₂)-3-(η⁵-Cp*)-3,1,2-MC₂B₉H₁₀] (M=Ir (3 a), Rh (3 b)) can be all prepared directly by the reaction of 1-(PPh₂)-1,2-C₂B₁₀H₁₁ with dimeric complexes [(Cp*MCl₂)₂] (M=Ir, Rh) under different conditions. Compound 3 b was treated with AgOTf (OTf=CF₃SO₃⁻) to afford the tetranuclear metallacarborane [Ag₂(thf)₂(OTf)₂{1-(PPh₂)-3-(η⁵-Cp*)-3,1,2-RhC₂B₉H₁₀}₂] (4 b). The arylphosphine group in 3 a and 3 b was functionalized by elemental sulfur (1 equiv) in the presence of Et₃N to afford [1-{(S)PPh₂}-3-(η⁵-Cp*)-3,1,2-MC₂B₉H₁₀] (M=Ir (5 a), Rh (5 b)). Additionally, the 1-(PPh₂)-1,2-C₂B₁₀H₁₁ ligand was functionalized by elemental sulfur (2 equiv) and then treated with [(Cp*IrCl₂)₂], thus resulting in two 16-electron complexes [Cp*Ir(7-{(S)PPh₂}-8-S-7,8-C₂B₉H₉)] (6 a) and [Cp*Ir(7-{(S)PPh₂}-8-S-9-OCH₃-7,8-C₂B₉H₉)] (7 a). Compound 6 a further reacted with nBuPPh₂, thereby leading to 18-electron complex [Cp*Ir(nBuPPh₂)(7-{(S)PPh₂}-8-S-7,8-C₂B₉H₁₀)] (8 a). The influences of other factors on structural transitions or the formation of targeted compounds, including reaction temperature and solvent, were also explored.

The organochalcogen ligands (S, Se) derived from 3-methylimidazole-2-thione/selone groups mbit (2a), mbis (2b), ebit (2c), and ebis (2d) [mbit = 1,1′-methylenebis(1,3-dihydro-3-methyl-2H-imidazole-2-thione), mbis = 1,1′-methylenebis(1,3-dihydro-3-methyl-2H-imidazole-2-selone), ebit = 1,1′-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H-imidazole-2-thione), ebis = 1,1′-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H-imidazole-2-selone)] were synthesized and characterized. Mononuclear Ni^II complexes NiBr₂mbit (3a), NiBr₂mbis (3b), NiBr₂ebit (3c), and NiBr₂ebis (3d) were obtained by the reactions of Ni(PPh₃)₂Br₂ with 2a, 2b, 2c, and 2d, respectively. However, when the corresponding ligands 2a, 2b, 2c, and 2d were treated with CoCl₂ in thf solution Co^II 1D coordination polymers (CoCl₂mbit)_n (4a), (CoCl₂mbis)_n (4b), (CoCl₂ebit)_n (4c), and (CoCl₂ebis)_n (4d) were obtained. All compounds were fully characterized by IR spectroscopy and elemental analysis. The crystal structures of 2c, 3a, 3b, 3c, 4a, 4b, and 4c were determined by X-ray crystallography. The local geometry around the nickel atom in complexes 3a–c was distorted tetrahedron with coordinated S(Se) and two Br atoms, and the organochalcogen ligands form an eight- or a nine-membered ring with the nickel atom included. The cobalt atom coordination polymers 4a and 4b coexist as left-handed and right-handed helical chains, but 4c formed a zigzag chain with a CH₃CN solvent molecule taken up in the channel structure. After activation with methylaluminoxane (MAO), the nickel complexes exhibited high activities for addition polymerization of norbornene (1.42 × 10⁸ g PNBmol^–1 Nih^–1 for 3a). The effects of the Al/Ni ratio, reaction temperature, and reaction time to norbornene polymerization were also investigated.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A series of new indanimine ligands [ArNCC₂H₃(CH₃)C₆H₂(R)OH] (Ar = Ph, R = Me (1), R = H (2), and R = Cl (3); Ar = 2,6-i-Pr₂C₆H₃, R = Me (4), R = H (5), and R = Cl (6)) were synthesized and characterized. Reaction of indanimines with Ni(OAc)₂·4H₂O results in the formation of the trinuclear hexa(indaniminato)tri (nickel(II)) complexes Ni₃[ArN = CC₂H₃(CH₃)C₆H₂(R)O]₆ (Ar = Ph, R = Me (7), R = H (8), and R = Cl (9)) and the mononuclear bis(indaniminato)nickel (II) complexes Ni[ArNCC₂H₃(CH₃)C₆H₂(R)O]₂ (Ar = 2,6-i-Pr₂C₆H₃, R = Me (10), R = H (11), and R = Cl (12)). All nickel complexes were characterized by their IR, NMR spectra, and elemental analyses. In addition, X-ray structure analyses were performed for complexes 7, 10, 11, and 12. After being activated with methylaluminoxane (MAO), these nickel(II) complexes can polymerize norbornene to produce addition-type polynorbornene (PNB) with high molecular weight M_v (10⁶ g mol⁻¹), highly catalytic activities up to 2.18 × 10⁷ gPNB mol⁻¹ Ni h⁻¹. Catalytic activities and the molecular weight of PNB have been investigated for various reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 489–500, 2008