Alkyne-Carbaborane Coupling at a Molybdenum Centre: Crystal Structure of 2-C(H)=C(H)SiMe3>-3,1,2-MoC2B9H10>

DOI: 10.1039/DT9930003551

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 3551 - 3558 (1993)

Update date:2022-08-02

Topics:

Authors:

Dossett, Stephen J.

Li, Sihai

Mullica, Donald F.

Sappenfield, Eric L.

Stone, F. Gordon A.

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Article abstract of DOI:10.1039/DT9930003551

In CH2Cl2 the complex decomposed to yield a mixture of and 2-C(Ph)=C(H)Ph>-3,1,2-MoC2B9H8>.Protonation (HBF4*Et2O) of , in CH2Cl2 at -78 deg C, in the presence of an excess of Me3SiCCSiMe3, afforded a chromatographically seperable mixture of and 2-C(H)=C(H)SiMe3>-3,1,2-MoC2B9H10>.The latter complex forms via the intermediacy of Me3SiCCH, generated by HF cleavage of Me3SiCCSiMe3, and its structure was established by X-ray diffraction.The molibdenum atom is ligated on one side by three CO groups, and on the other by the open pentagonal face of the nido-1,2-C2B9 cage framework.The boron atom located in the β site with respect to the two carbons carries a vinyl substituent C(H)=C(H)SiMe3, and this exopolyhedral group is η² co-ordinated to the molybdenum atom .Treatment of and Me3SiCCH with HBF4*Et2O gives initially the complex , which subsequently rearranges to 2-C(H)=C(H)SiMe3>-3,1,2-MoC2B9H8>.Use of Me3SiCCD in the synthesis, combined with NMR studies, suggests that insertion of the alkyne into the cage B-H bond proceedds via the intermediacy of a molybdenum vinylidene species.The NMR data (1H, 13C-<1H>, 11B-<1H>, and 31P-<1H>) for the new compounds are reported and discussed in relation to the structures proposed.