Reactions of Manganese Silyl and Silylene Complexes with CO2 and C(NiPr)2: Synthesis of Mn(I) Formate and Amidinylsilyl Complexes

Reactions of the disilyl hydride complexes [(dmpe)(2)MnH(SiH2R)(2)] (1(Ph): R = Ph, 1(Bu): R = n(Bu)) or the silylene hydride complexes [(dmpe)(2)MnH(-SiR2)] (2(Ph2): R = Ph, 2(Et2): R = Et) with the heterocumulenes carbon dioxide (CO2) and diisopropylcarbodiimide {C(NiPr)(2)} were investigated. With CO2, these reactions yielded the manganese(I) formate complex trans-[(dmpe)(2)Mn(CO)(kappa(1)-O2CH)] (3), with polysiloxane byproducts. Compound 3 was found to undergo reversible CO2 elimination at room temperature, and was only stable under an atmosphere of CO2. By contrast, reactions with C(NiPr)(2) afforded manganese(I) amidinylsilyl complexes [(dmpe)(2)Mn{kappa(2)-SiRR'(NiPrCHNiPr)}] {5(Ph,H): R = Ph, R' = H, 5(Bu,H): R = n(Bu,R)' = H, 5(Ph2): R = R' = Ph, 5(Et2): R = R' = Et}. Complexes 3, 5(Ph,H), and 5(Ph2) were crystallographically characterized. DFT calculations and analysis of XRD bond metrics suggest that the structure of 5 involves a contribution from a resonance structure featuring a neutral base-stabilized silylene and an anionic amido donor on manganese.