Complexes of germanium chlorides (RnGeCl4-n, n=0-3; R=Me, Ph) with redox active N-hetero­aromatic ligands: an electrochemical study

Abstract

Methyl and phenyl germanium chlorides (RnGeCl4-n, n=1, 2, 3), just like GeCl4, form complexes with electroactive bidentate (2,2'-bipyridine) and monodentate (imidazole, pyrimidine and 2,6-dichloro-pyridine) ligands, RnGeCl4-n‧Lx (x=1 or 2 for bi- and monodentate Ls, respectively), which were studied by cyclic voltammetry and electron paramagnetic resonance (EPR) spectroscopy supported by density functional theory (DFT) calculations. Dative interactions of lone pair of N of these heteroaromatic ligands towards Ge lower the reduction potential Ep of such complexes by about 1 V compared to own reduction potential Eo of L. Electron transfer to these complexes is reversible, resulting in corresponding anion radicals. Elimination of Cl- anion from these species leads to L-coordinated radicals whose one-electron reduction is also reversible. Real-time, time-dependent EPR spectro­electrochemistry of electrogenerated anion radicals of complexes with 2,2'-bipyridine (bipy) has shown that spin in these species is delocalized on the bipy moiety; nitrogen hfc constants suggest that two N atoms are non-equivalent and occupy different positions in the Ge environment. These findings are supported by DFT calculations.