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

Reaction of the ethylene hydride complex trans-[(dmpe)₂ MnH(C₂ H₄ )] (1) with Et₂ SiH₂ at 20 °C afforded the silylene hydride [(dmpe)₂ MnH(=SiEt₂ )] (2 a) as the trans-isomer. By contrast, reaction of 1 with Ph₂ SiH₂ at 60 °C afforded [(dmpe)₂ MnH(=SiPh₂ )] (2 b) as a mixture of the cis (major) and trans (minor) isomers, featuring a Mn-H-Si interaction in the former. The reaction to form 2 b also yielded [(dmpe)₂ MnH₂ (SiHPh₂ )] (3 b); [(dmpe)₂ MnH₂ (SiHR₂ )] (R=Et (3 a) and Ph (3 b)) were accessed cleanly by reaction of 2 a and 2 b with H₂ , and the analogous reactions with D₂ afforded [(dmpe)₂ MnD₂ (SiHR₂ )] exclusively. Both 2 a and 2 b engaged in unique reactivity with ethylene, generating the silene hydride complexes cis-[(dmpe)₂ MnH(R₂ Si=CHMe)] (R=Et (4 a), Ph (4 b)). Compounds trans-2 a, cis-2 b, 3 b, and 4 b were crystallographically characterized, and bonding in 2 a, 2 b, 4 a, and 4 b was probed computationally.