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) <i>via</i> the unstable κ²-formatogermyl intermediates [(dmpe)₂Mn{κ²-GeR₂(OCHO)}] (5a: R = Ph, 5b: R = Et). By contrast, addition of CO₂ to [(dmpe)₂MnH(Ge^<i>n</i>BuH)] (2a), which contains a terminal GeH substitutent, resulted in the sequential formation of (i) the formatogermylene hydride complex [(dmpe)₂MnH{Ge^<i>n</i>Bu(κ¹-O₂CH)}] (6), (ii) the isolable metallacyclic κ²-formatogermyl complex [(dmpe)₂Mn{κ²-Ge^<i>n</i>Bu(κ¹-O₂CH)(OCHO)}] (7), and with heating(III) complex 3. Exposure of 2a to benzophenone also afforded a new germylene hydride complex, [(dmpe)₂MnH{Ge^<i>n</i>Bu(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 = ^<i>n</i>Bu and R' = H). Addition of carbon dioxide to 10 yielded [(dmpe)₂Mn{κ²-Ge^<i>n</i>Bu(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.