The exploration of co-complexation reactions between alkai-metal reagents and ZnEt2 with bidentate aminopyrrolyl ligands afforded a series of alkali-metal (Li, Na, K) alkyl zincates with a variety of intriguing structures, ranging from molecular complexes to more coordination polymers. All aforementioned complexes have been characterized by X-ray crystallography, NMR, IR and UV-vis spectroscopy.

Lithium complex stabilised by 2-amino-functionalized benzoylpyrrole was synthesized, and its structural features were provided. The molecular structure shows a novel tetrameric cage structure, which includes a eight-membered (LiN)4 ring and a eight-membered (LiO)4 ring with the coordinating pyrrolyl ligands. It was proved to an efficient catalyst for the cyclotrimerisation of isocyanates in good to excellent yields under mild conditions.Lithium complex stabilised by 2-amino-functionalized benzoylpyrrole was synthesized, and its structural features were provided. The molecular structure shows a novel tetrameric cage structure, which includes a eight-membered (LiN)4 ring and a eight-membered (LiO)4 ring with the coordinating pyrrolyl ligands. It was proved to an efficient catalyst for the cyclotrimerisation of isocyanates in good to excellent yields under mild conditions.Download high-res image (50KB)Download full-size image

•Insertion of CO2 into the Li–N bond of amidinolithium compound has been studied.•Two amidinolithium compounds were characterized by NMR, elemental analysis and X-ray study.•They show a novel cage structure and a “wheel” cage structure, respectively.Insertion of CO2 into the Li–N bond of two amidinolithium compounds [{LiN(2,6-Me2C6H3)C(H)N(2,6- Me2C6H3)}2(THF)3] and [{LiN(4-CH3C6H4)C(H)N(4-CH3C6H4)}2(THF)3] have been studied, and two lithium carbamate compounds [Li{O2C(N(2,6-Me2C6H3)C(H)N(2,6-Me2C6H3))}·THF]4 (1) and [Li{O2C(N(4-CH3C6H4)C(H)N(4-CH3C6H4))}·THF]6 (2) were obtained. The molecular structure of 1 shows a novel cage structure containing four eight-membered (LiOCOLiOCO) rings and two four-membered (LiOLiO) rings with the [Li4(CO2)4]4+ cluster in central. And an unusual and novel structure of 2 was obtained with a “wheel” cage structure including six six-membered (LiOLiOCO) rings surrounding the [Li6(CO2)6]6+ cluster. Both of 1 and 2 were fully characterized by elemental analysis, NMR spectroscopy, and X-ray structural determinations.

•A series of aluminum complexes of β-hydroxy-imino ligands were synthesized.•Their structures were characterized by NMR, elemental analysis and X-ray study.•Those compounds as catalysts for Tishchenko reaction have been investigated.Four aluminum alkoxide complexes containing β-hydroxy-imino ligands, [(2,6-Me2C6H3)NCPhCH2CPh2O]2AlMe (3a), [(2,6-iPr2C6H3)NCPhCH2CPh2O]2AlMe (3b), [(2,6-Me2C6H3)NCPhCH2C(C12H8)OAlMe2]2 (3c) and [(2,6-iPr2C6H3)NCPhCH2C(C12H8)OAlMe2]2 (3d) were synthesized in high yields, and their structural features were provided. The catalytic behavior of those four complexes about the Tishchenko reaction with a range of aromatic aldehydes as substrates were assessed, and it present a synthetically useful protocol to the solvent-free Tishchenko reaction under mild conditions.

A direct transition-metal-free synthesis of 2-benzoylpyrrole derivatives from free (N–H) pyrroles and benzaldehyde has been developed. The benzoylation reaction at the 2 or 5-position of pyrrole proceeded well under the alkali metalation system and with 2,6-dimethylaniline as the additive in moderate to good yields. This strategy offers a simple, efficient approach to synthesis of the 2-benzoylpyrrole derivatives.A direct transition-metal-free synthesis of 2-benzoylpyrrole derivatives from free (N–H) pyrroles and benzaldehyde has been developed. This strategy offers a simple, efficient approach to synthesis of the 2-benzoylpyrrole derivatives.

•A simple and efficient catalytic system for Tishchenko reaction is presented.•The redox reaction between aminopyrrolyl lithium and aldehyde was reported firstly.•The initiated intermediate was characterized by NMR, elemental analysis and X-ray study.The dimerization of aldehydes to the analogous carboxylic esters (Tischenko reaction) has been achieved in impressive yields using the dilithium compounds containing bidentate di-anionic pyrrolyl ligands as initiators. The initiated intermediate {[2-(tBuNCH)C4H3NLi][PhCH2OLi(TMEDA)]}2 was isolated and characterized by satisfactory C, H and N microanalysis, 1H, 13C{1H} and 7Li NMR spectra in pyridine-d5 at ambient temperature, and single crystal X-ray structural data. The processes involve a redox reaction of 2-aminopyrrolyl dilithium compound with aldehyde.The dimerization of aldehydes (Tischenko reaction) has been achieved in impressive yields using 2-aminopyrrolyl dilithium compounds as initiators. The initiated intermediate {[2-(tBuNCH)C4H3NLi][PhCH2OLi(TMEDA)]}2 was isolated and characterized by microanalysis, NMR spectra and single crystal X-ray structural data. The processes involve a redox reaction of 2-aminopyrrolyl dilithium compound with aldehyde.

•A series of tridentate pyrrolylzinc compounds were synthesized.•Their structures were characterized by NMR, elemental analysis and X-ray study.•Those compounds as catalysts for cyclotrimerization of isocyanates have been investigated.The reactions of ZnEt2 with NNN-tridentate pincer type pyrrolyl ligands, 2,5-bis((dimethylamino)methylene)-1H-pyrrole (HL1), 2,5-bis((pyrrolidin-1-yl)methylene)-1H-pyrrole (HL2) and 2,5-bis((piperidino)methylene)-1H-pyrrole (HL3), afford zinc ethyl compounds [C4H2N(2,5-CH2NMe2)2]ZnC2H5 (1), [C4H2N(2,5-CH2N(CH2)4)2]ZnC2H5 (2), and [C4H2N(2,5-CH2N(CH2)5)2]ZnC2H5 (3) in high yield. Subjecting 1, 2, 3 with one equivalent of tert-butylphenol in THF generated {[C4H2N(2,5-CH2NMe2)2]Zn(O–C6H4-4-tBu)}2 (4), {[C4H2N(2,5-CH2N(CH2)4)2]Zn(O–C6H4-4-tBu)}2 (5), {[C4H2N(2,5-CH2N(CH2)5)2]Zn(O–C6H4-4-tBu)}2 (6), respectively. Each has been characterized by satisfactory C, H and N microanalysis, NMR spectroscopy at ambient temperature, and single crystal X-ray structural analysis. The compounds Et6Zn6O2[C4H2N(2,5-CH2N(CH2)4)2]2 (7) and Et6Zn6O2[C4H2N(2,5-CH2N(CH2)5)2]2 (8) obtained accidentally from zinc ethyl compounds with traces of water. Each of compound 1–6 has been used as initiator for cyclotrimerization of isocyanate, and the organozinc compound 3 shows moderate reactivity toward the cyclotrimerization of isocyanate in Et2O solvent under mild conditions.A series of zinc complexes containing monoanionic tridentate pyrrolyl ligands have been prepared in good yield and characterized by microanalysis, multinuclear NMR ambient temperature solution spectra and X-ray molecular structures. Each of the complexes exhibited moderate to good catalytic activity for cyclotrimerization of isocyanates under mild condition.

The exploration of co-complexation reactions between alkai-metal reagents and ZnEt2 with bidentate aminopyrrolyl ligands afforded a series of alkali-metal (Li, Na, K) alkyl zincates with a variety of intriguing structures, ranging from molecular complexes to more coordination polymers. All aforementioned complexes have been characterized by X-ray crystallography, NMR, IR and UV-vis spectroscopy.