Photoinduced One-Pot Synthesis of a Chromium Germylyne Complex and Its Formation Mechanism

A chromium germylyne (or germylidyne)
complex having a CrGe
triple bond, [Cp*(OC)2CrGeTsi] (1)
(Tsi = C(SiMe3)3), was directly synthesized
by the photochemical reaction of a methyl chromium complex [Cp*Cr(CO)3Me] and a trihydrogermane (TsiGeH3). Detailed monitoring
the reaction by NMR revealed the initial formation of hydrido (hydrogermylene)
complex [Cp*(OC)2(H)CrGe(H)Tsi] (2) as an intermediate and its facile release of dihydrogen to afford 1 under UV–vis light irradiation. The intermediate 2 was isolated from another experiment under blue LED light
irradiation. The structures of 1 and 2 were
confirmed by X-ray crystallography. Based on the analysis of absorption
bands of intermediate 2 using TD-DFT calculations, we
suggest possible mechanisms for releasing dihydrogen from 2 to afford 1, which includes a process forming a metallogermylene
by weakening the Cr–Ge multiple bond.