Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent

Abstract

The tris-N-heterocycle germanide (tmim)Ge - (1) (tmimH 3 = tris(3-methylindol-2-yl)methane) was synthesized by nucleophilic substitution for the tmim 3- trianion on GeCl 2 ·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(μ-Cl)] 22- , which is prone to dissociation in MeCN to form the neutral, solvated germylcopper (tmim)GeCu(NCMe) 3 . The reaction of 1 with Fe 2 (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 FeCl 2 , 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.