Reactivity of Monomeric N→Ge Coordinated Germanium(II) Hydrides

Abstract

Monomeric organogermanium(II) hydrides {(LGeH)M(CO)5} (M = Cr (1), W (2), L = [2‐(CH2NEt2)‐4,6‐tBu2‐C6H2]–) were treated with ortho‐quinones and terminal alkyne HC≡CCO2Me to give {[(LH)Ge(κ2‐O2‐3,5‐tBu2C6H2)]M(CO)5} (M = Cr (3), W (4)), {[(LH)Ge(κ2‐O2‐3,4,5,6‐Cl4C6)]M(CO)5} (M = Cr (5), W (6)) and {[LGeCH=CH(COOMe)]Cr(CO)5} (11). These reactions proceeded as catalyst‐free reductions of C=O and C≡C bonds. Experimental data demonstrated zwitterionic character of Ge(II) complexes 3–6, where the 1,3,2‐benzodioxagermylenolato anion involving the GeO2C2 five membered ring coordinates the M(CO)5 fragment. This anionic part is compensated by the NHEt2 counter cation that is part of ligand L. Reactions of 1 and 2 differ mutually in the case of reduction of HC≡CCO2Me. The experimental and theoretical data suggest that compound 1 reacts with HC≡CCO2Me to give vinyl germylene 11 as the product of the anti‐Markovnikov cis‐1,2‐addition, while complex 2 is inactive. These results thus suggest that the reactivity of the terminal GeH bond may be tuned by its coordination to various transition metals.