Manganese germylene hydride complexes: reactivity with carbon dioxide, benzophenone, and diisopropylcarbodiimide.

Reactions of bis(hydrocarbyl)germylene manganese(I) hydride complexes [(dmpe)2MnH(GeR2)] (1a: R = Ph, 1b: R = Et) with carbon dioxide yielded the previously reported carbonyl formate complex [(dmpe)2Mn(κ1-O2CH)(CO)] (3) via the unstable κ2-formatogermyl intermediates [(dmpe)2Mn{κ2-GeR2(OCHO)}] (5a: R = Ph, 5b: R = Et). By contrast, addition of CO2 to [(dmpe)2MnH(GenBuH)] (2a), which contains a terminal GeH substitutent, resulted in the sequential formation of (i) the formatogermylene hydride complex [(dmpe)2MnH{GenBu(κ1-O2CH)}] (6), (ii) the isolable metallacyclic κ2-formatogermyl complex [(dmpe)2Mn{κ2-GenBu(κ1-O2CH)(OCHO)}] (7), and with heating(III) complex 3. Exposure of 2a to benzophenone also afforded a new germylene hydride complex, [(dmpe)2MnH{GenBu(OCHPh2)}] (8). Reactions of 1a-b and 2a with C(NiPr)2 afforded a family of stable metallacyclic κ2-amidinylgermyl complexes [(dmpe)2Mn{κ2-GeRR'(NiPrCHNiPr)}] (9a: R = R' = Ph, 9b: R = R' = Et, 10: R = nBu and R' = H). Addition of carbon dioxide to 10 yielded [(dmpe)2Mn{κ2-GenBu(κ1-O2CH)(NiPrCHNiPr)}] (11), and reaction of CO2 with the κ2-amidinylsilyl derivative [(dmpe)2Mn{κ2-SiPhH(NiPrCHNiPr)}] afforded [(dmpe)2Mn{κ2-SiPh(κ1-O2CH)(NiPrCHNiPr)}] (12). Complexes 6, 7, 8, 9a, 11, and 12 were crystallographically characterized, and DFT calculations were conducted to probe the effect that different substituents on Ge have on Mn-Ge bonding in κ2-formatogermyl, κ2-amidinylgermyl, and germylene complexes.