Synthesis, structure and characterization of dimolybdaheteroboranes

Abstract

Chalcogen-stabilized dimolybdaboranes 3–5 (3: [(Cp∗Mo)₂B₄H₅Se(Ph)], 4: [(Cp∗Mo)₂B₄H₃Se₂(SeCH₂Ph)] and 5: [(Cp∗Mo)₂B₃H₆(BSR)(μ-η¹-SR)] (R = 2,6-(tBu)₂-C₆H₂OH)) have been isolated from the mild pyrolysis of dichalcogenide ligands, RE-E‘R (R = Ph: E = S, E‘ = Se; R = CH₂Ph, [2,6-(tBu)₂-C₆H₂OH]: E = E‘ = Se, S) and [(Cp∗Mo)₂B₄H₈], 2, an intermediate generated from the reaction of [Cp∗MoCl₄] (1) (Cp∗ = η⁵-C₅Me₅), with [LiBH₄.thf]. The geometry of [(Cp∗Mo)₂B₄H₅Se(Ph)] is similar to that of [(Cp∗Mo)₂B₅H₉], in which one BH₃ unit on the open face is replaced by a triple bridged selenium atom. All the compounds have been characterized in solution by ¹H, ¹¹B, ¹³C NMR and IR spectroscopy and elemental analysis. The structural types were unequivocally established by X-ray crystallographic analysis of compounds 3–5.