文摘
The 蟽,蟺-cyclooctenyl iridium(III) pincer compounds [Ir(魏3-pydc-X)(1-魏-4,5-畏-C8H13)] (X = H (1), Cl, Br) have been prepared from [Ir(渭-OMe)(cod)]2 and the corresponding 4-substituted pyridine-2,6-dicarboxylic acids (H2pydc-X) or, alternatively, from their lithium salts (X = H) and [Ir(cod)(CH3CN)2]PF6. Deuterium labeling studies in combination with theoretical calculations have shown that formation of 1 involves a metal-mediated proton transfer in the reactive intermediate [Ir(魏2-Hpydc)(cod)], through the solvent-stabilized hydrido complex [IrH(魏3-pydc)(cod)(CH3OH)], followed by olefin insertion. The formation of this hydrido intermediate results from solvent-assisted proton transfer through a hydrogen-bonding network, forming an eight-membered metallacycle. In contrast, reaction of [Ir(渭-OMe)(cod)]2 with iminodiacetic acid derivatives, RN(CH2COOH)2, gave the stable iridium(I) mononuclear [Ir{魏2-MeN(CH2COOH)(CH2COO)}(cod)] (R = Me) complex having a free carboxymethyl group and the tetranuclear complex [Ir4{魏4-PhN(CH2COO)2}2(cod)4] (R = Ph) with doubly deprotonated ligands. The molecular structure of the related cyclooctene complex [Ir4{魏4-PhN(CH2COO)2}2(coe)8] has been determined by X-ray analysis. Reaction of 1 with monodentate N- and P-donor ligands gave the compounds [Ir(魏3-pydc)(1-魏-4,5-畏-C8H13)(L)] (L = py, BnNH2, PPh3, PMe3). Reaction of 1 with the short-bite bis(diphenylphosphino)methane (dppm) afforded the mononuclear 1-dppm, with an uncoordinated P-donor atom, or the dinuclear complex 12-dppm as a function of the molar ratio used. Similarly, the dinuclear complexes 12-dppe and 12-dppp have been prepared using 1,2-bis(diphenylphosphino)ethane (dppe) and 1,3-bis(diphenylphosphino)propane (dppp) as bridging ligands. The diphosphine-bridged dinuclear assemblies have been obtained as two diastereoisomers in a 1:1 ratio due to the chirality of the mononuclear building block. The single-crystal X-ray structures of 1-py and 1-dppm are reported.