Manganese Silylene Hydride Complexes: Synthesis and Reactivity with Ethylene to Afford Silene Hydride Complexes

Reaction of the ethylene hydride complex trans[(dmpe)(2)MnH(C2H4)] (1) with Et2SiH2 at 20 degrees C afforded the silylene hydride [(dmpe)(2)MnH(=SiEt2)] (2a) as the transisomer. By contrast, reaction of 1 with Ph2SiH2 at 60 degrees C afforded [(dmpe)(2)MnH(=SiPh2)] (2b) as a mixture of the cis (major) and trans (minor) isomers, featuring a Mn-H-Si interaction in the former. The reaction to form 2b also yielded [(dmpe)(2)MnH2(SiHPh2)] (3b); [(dmpe)(2)MnH2(SiHR2)] (R= Et (3a) and Ph (3b)) were accessed cleanly by reaction of 2a and 2b with H-2, and the analogous reactions with D-2 afforded [(dmpe)(2)MnD2(SiHR2)] exclusively. Both 2a and 2b engaged in unique reactivity with ethylene, generating the silene hydride complexes cis-[(dmpe)(2)MnH(R2Si= CHMe)] (R= Et (4a), Ph (4b)). Compounds trans-2a, cis-2b, 3b, and 4b were crystallographically characterized, and bonding in 2a, 2b, 4a, and 4b was probed computationally.