Hydrostannylation of carbon dioxide by a hydridostannylene molybdenum complex.

Reaction of the aryltin(II) hydrides {AriPr4Sn(µ-H)}2 or {AriPr6Sn(µ-H)}2 (AriPr4 = -C6H3-2,6-(C6H3-2,6-iPr2)2, AriPr6 = -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(AriPr6)H}, (1), or Mo(CO)5{Sn(AriPr4)(THF)H} (2), respectively. Complex 1 effects the facile hydrostannylation of carbon dioxide, to yield Mo(CO)5{Sn(AriPr6)(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 {AriPr4Sn(µ-H)}2 and {AriPr6Sn(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.