A dipyrromethane-based diphosphane–germylene as precursor to tetrahedral copper(i) and T-shaped silver(i) and gold(i) PGeP pincer complexes

Abstract

A six-membered ring N-heterocyclic germylene flanked by two CH₂PⁱPr₂ groups, Ge(pyrmPⁱPr₂)₂CMe₂ (1; (HpyrmPⁱPr₂)₂CMe₂ = 5,5-dimethyl-1,9-bis(di-isopropylphosphanylmethyl)dipyrromethane), has been prepared in high yield. Upon treatment with group 11 metal precursors of the type [MCl(PPh₃)]_n (M = Cu (n = 4), Ag (n = 4), Au (n = 1)), germylene 1 easily forms a PGeP chloridogermyl ligand that is able to stabilize tetrahedral copper(I) and unusual T-shaped silver(I) and gold(I) PGeP pincer complexes, as has been demonstrated by the isolation of [Cu{κ³P,Ge,P-GeCl(pyrmPⁱPr₂)₂CMe₂}(PPh₃)] (2) and [M{κ³P,Ge,P-GeCl(pyrmPⁱPr₂)₂CMe₂}] (M = Ag (3), Au (4)). Theoretical calculations have shown that the Ge–M bonds of these complexes are weak and that their strength decreases in the series 2 > 3 > 4.