Hydrostannylation of carbon dioxide by a hydridostannylene molybdenum complex

Abstract

Reaction of the aryltin(II) hydrides {Ar^iPr₄Sn(μ-H)}₂ or {Ar^iPr₆Sn(μ-H)}₂ (Ar^iPr₄ = –C₆H₃-2,6-(C₆H₃-2,6-ⁱPr₂)₂, Ar^iPr₆ = –C₆H₃-2,6-(C₆H₂-2,4,6-ⁱPr₃)₂) with two equivalents of the molybdenum carbonyl [Mo(CO)₅(THF)] afforded the divalent tin hydride transition metal complexes, Mo(CO)₅{Sn(Ar^iPr₆)H}, (1), or Mo(CO)₅{Sn(Ar^iPr₄)(THF)H} (2), respectively. Complex 1 effects the facile hydrostannylation of carbon dioxide, to yield Mo(CO)₅{Sn(Ar^iPr₆)(κ²-O,O′-O₂CH)}, (3), which features a bidentate formate ligand coordinating the tin atom. Reaction of 3 with the pinacolborane, HBpin (pin = pinacolato) in benzene regenerated 1 in quantitative yield. All complexes were characterized by X-ray crystallography, as well as UV-visible, IR, and multinuclear NMR spectroscopies. The isolation of 1 and 2 is consistent with the existence of monomeric forms of {Ar^iPr₄Sn(μ-H)}₂ and {Ar^iPr₆Sn(μ-H)}₂ in solution. Regeneration of 1 from 3via reaction with pinacolborane as the hydrogen source shows the catalytic potential of 1 in the hydrogenation of CO₂.