Coordination chemistry of a kinetically stabilized germabenzene: Syntheses and properties of stable eta(6)-germabenzene complexes coordinated to transition metals

摘要

The first stable eta(6)-germabenzene complexes, that is, [M(CO)(3) (eta(6)-C(5)H(5)GeTbt)] {M = Cr (2), Mo (3), and W (4); Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}, have been synthesized by ligand-exchange reactions between [M(CO)(3)(CH3CN)(3)] (M = Cr, Mo, and W) and the kinetically stabilized germabenzene 1 and characterized by H-1 and C-13 NMR, IR, and UV/Vis spectroscopy. In the H-1 and C-13 NMR spectra of 2-4, all of the signals for the germabenzene rings were shifted upfield relative to their counterparts in the free germabenzene 1. X-ray crystallographic analysis of 2 and 4 revealed that the germabenzene ligand was nearly planar and was coordinated to the M(CO)(3) group (M Cr, W) in an eta(6) fashion. The formation of complexes 2-4 from germabenzene I should be noted as the application of germaaromatics as 6 pi-electron ligands toward complexation with Group 6 metals. On the other hand, treatment of 1 with [(RuCp*Cl)(4)] (Cp* = C5Me5) in THF afforded a novel eta(5)-germacy-clohexadienido complex of ruthenium-[RuCp*(eta(5)-C(5)H(5)GeTbt(Cl))] (9)-instead of the expected eta(6)-germa-benzene-ruthenium cationic complex [RuCp*{eta(6)-C(5)H(5)GeTbt}]Cl (10). Crystallographic structural analysis of 9 showed that the five carbon atoms of the germacyclohexadienido ligand of 9 were coordinated to the Ru center in an eta(5) fashion.