Reactions of [(dmpe)2MnH(C2H4)] with hydrogermanes to form germylene, germyl, hydrogermane, and germanide complexes

Abstract

Reactions of the ethylene hydride complex trans-[(dmpe)₂MnH(C₂H₄)] (1) with secondary hydrogermanes H₂GeR₂ at 55–60 °C afforded the base-free terminal germylene hydride complexes trans-[(dmpe)₂MnH(GeR₂)] (R = Ph; 2a, R = Et; 2b). Room temperature reactions of 2a or 2b with an excess of the primary hydrogermanes H₃GeR′ (R′ = Ph or ⁿBu) afforded trans-[(dmpe)₂MnH(GeHR′)] (R′ = Ph; 3a, R′ = ⁿBu; 3b) in rapid equilibrium with small amounts of 2a/b, as well as the digermyl hydride complex mer-[(dmpe)₂MnH(GeH₂R′)₂] {R′ = Ph (4a) or ⁿBu (4b)} and the trans-hydrogermane germyl complex trans-[(dmpe)₂Mn(GeH₂R′)(HGeH₂R′)] {R′ = Ph (5a) or ⁿBu (5b)}. Pure 3b was isolated from the reaction of 2b with H₃GeⁿBu, whereas 3a decomposed readily in solution in the absence of free H₃GePh, and a pure bulk sample was not obtained. Reactions of 1 with H₃GeR′ (R′ = Ph or ⁿBu) also proceeded at 55–60 °C to afford mixtures of 3a/b, 4a/b and 5a/b, accompanied by remaining 1. However, upon continued heating to consume 1, various unidentified manganese-containing intermediates were formed, ultimately affording the germanide complex [{(dmpe)₂MnH}₂(μ-Ge)] (6) in 17–49% spectroscopic yield. Pure trans,trans-6 was isolated in 27% yield from the reaction of 1 with H₃GeⁿBu, and it is notable that this reaction involves stripping of all four substituents from the hydrogermane. Complexes 2a, 3a, and 6 were crystallographically characterized, and the nature of the MnGe bonding in these species (as well as in 2b and 3b) was probed computationally.