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ABSTRACT:The perfluoro and perprotiopentaphenyl boroles 1 and 2 react with dihydrogen to effect H-H bond cleavage and formation of boracyclopentene products. The mechanism of this reaction has been studied experimentally through evaluation of the kinetic properties of the slower reaction between 2 and H2. The reaction is first order in both . A minimal kinetic isotope effect of 1.10(5) was observed, suggesting rate limiting binding of H2 to the boron center of the borole. To explain the stereochemistry of the observed products, a ring-opening/ring-closing mechanism is proposed and supported by the separate synthesis of a proposed intermediate and its observed conversion to product. Furthermore, extensive DFT mapping of the reaction mechanism supports the plausibility of this proposal. The study illustrates a new mechanism for the activation of H2 by a strong main group Lewis acid in the absence of an external base, a process driven in part by the antiaromaticity of the borole rings in 1 and 2.

Experimental and computational data shows that a new perfluorinated boraindene reacts reversibly with H2 to form a reactive hydroborane that can be trapped with an olefin.

B(C(6)F(5))(3)-catalyzed bis(hydrosilylation) of alpha-diketones can give high diastereomeric excess of either meso/anti (small silanes and disilane reagents) or dl/syn (bulky silanes) silyl-protected 1,2-diols. This easily tuned diastereoselectivity is rationalized based on the classic Felkin-Anh model applied to a mechanism relying on Si-H abstraction by the electrophilic borane reagent.