Nature of M-(η2-H-SiR2) bonds in chromium, molybdenum and tungsten complexes [(η5-C5H5)(dmpe)M(η2-H-SiR2)] and [(η5-C5H5)(CO)2M(η2-H-SiMe2)]: A theoretical study

σ-Silane, disilanyl, and [W(μ-H)Si(μ-H)W] bridging silylene complexes via the reactions of W(PMe3)4(η2-CH2PMe2)H with phenylsilanes

W(PMe3)4(η(2)-CH2PMe2)H reacts with PhSiH3 to give the first examples of diphenyldisilanyl compounds, W(PMe3)4(SiH2SiHPh2)H3 and W(PMe3)3(SiH2Ph)(SiH2SiHPh2)H4, via a mechanism that is proposed to involve migration of a SiHPh2 group to a silylene ligand. In addition to the formation of the aforementioned mononuclear compounds, the reaction of W(PMe3)4(η(2)-CH2PMe2)H with PhSiH3 also yields a novel dinuclear compound, [W(PMe3)2(SiHPh2)H2](μ-Si,P-SiHPhCH2PMe2)(μ-SiH2)[W(PMe3)3H2], which features a bridging silylene ligand that participates in 3-center-2-electron interactions with both tungsten centers. The bonding within the [W(μ-H)Si(μ-H)W] core can be described by a variety of resonance structures, some of which possess multiple bond character between tungsten and silicon. In this regard, [W(PMe3)2(SiHPh2)H2](μ-Si,P-SiHPhCH2PMe2)(μ-SiH2)[W(PMe3)3H2] possesses the shortest W-Si bond length reported. The corresponding reaction of W(PMe3)4(η(2)-CH2PMe2)H with Ph2SiH2 yields the σ-silane compound, W(PMe3)3(σ-HSiHPh2)H4.