Transition-metal-promoted reactions of boron hydrides. 17. Titanium-catalyzed decaborane-olefin hydroborations

The titanium-catalyzed hydroboration reactions of decaborane with a variety of terminal olefins have been found to result in the exclusive, high-yield formation of monosubstituted decaborane 6-R-B10H13 products, arising from anti-Markovnikov addition of the cage B6-H to the olefin. The titanium-catalyzed reactions arc slow. often less than one turnover per hour; however, their high selectivities and yields coupled with the fact that they are simple, one-pot reactions give them significant advantages over the previously reported routes to 6-R-B10H13 compounds. The catalyst also has extended activity with reactions carried out for as long as 13 days, showing little decrease in reactivity, thereby allowing for the production of large amounts of 6-R-B10H13. The titanium-catalyzed reactions of decaborane with the nonconjugated diolefins, 1.5-hexadiene and diallylsilane. were found to give, depending upon reaction conditions and stoichiometries, high yields of either alkenyl-substituted 6-(CH2=CH(CH2)(4))-B10H13 (4) and 6-(CH2=CHCH2SiMe2(CH2)(3))-B10H13 (5) or linked-cage 6,6'-(CH2)(6)-(B10H13)(2) (6) and Me2Si(6-(CH2)(3)-B10H13)(2) (7) compounds, respectively. The unique tetra-cage product, Si(6-(CH2)(3)-B10H13)(4) (8), was obtained by the catalyzed reaction of 4 equiv of decaborane with tetraallylsilane. Sequential use of the titanium catalyst and previously reported platinum catalysts (PtBr2 or H2PtCl6. 6H(2)O with an initiator) provides an efficient pathway to asymmetrically substituted 6-R-9-R'-B10H12 species. The structures of compounds 5, 6, and 8, as well as a platinum derivative, (PSH+)(2)-commo-Pt-[nido-7-Pt-8-(n-C8H17)B10H11](2)(2-), of 6-(n-octyl)decaborane have been established by single-crystal crystallographic determinations.