Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent.
ABSTRACT: The tris-N-heterocycle germanide (tmim)Ge- (1) (tmimH3 = tris(3-methylindol-2-yl)methane) was synthesized by nucleophilic substitution for the tmim3- trianion on GeCl2·dioxane. In combination with the previously reported (tmim)Si- and (tmim)P analogues, it provides a convenient model for investigating the influence of the central atom on the properties of isoelectronic ligands. Complexation of the germanide (tmim)Ge- to CuCl resulted in the dimeric chloro cuprate [(tmim)GeCu(?-Cl)]2 2-, which is prone to dissociation in MeCN to form the neutral, solvated germylcopper (tmim)GeCu(NCMe)3. The reaction of 1 with Fe2(CO)9 afforded the germyl iron tetracarbonyl [(tmim)GeFe(CO)4]-. Analysis of the ??(CO) infrared absorption bands in this complex indicates that the combined electron donating and accepting properties of 1 are found in between those of (tmim)P and (tmim)Si-. In contrast to (tmim)Si-, (tmim)Ge- is reluctant to coordinate to FeCl2, likely because of its softer Lewis base character. Key structural features of the ligands and complexes reflect changes in their electronic properties. In particular, the N-Ge-N angles increase upon coordination to a metal fragment, suggesting increasing hybridization of the Ge s- and p-orbitals. These findings will be useful in further understanding low-valent heavier group 14 complexes in organometallic chemistry.
PROVIDER: S-EPMC6354728 | BioStudies |