Search

A wide variety of substrates, including carboranes, metallocarboranes, and boron hydrides, were found to undergo catalytic isotopic exchange of terminal hydrogen with deuterium gas in the presence of various transition metal complexes. A mechanism is postulated which rationalizes the varied results and which involves oxidative addition of boron-hydrogen bonds to catalytic species.

A number of B-sigma-carboranyl iridium complexes have been prepared by both intra- and intermolecular oxidative addition of terminal boron-hydrogen bonds to iridium(I) species. The products from reactions between 1,2-, 1,7-, or 1,12-C2B10H12 and L2IrCl (L = PPh3 or AsPh3) are trigonal bipyramidal complexes of iridium(III) with axial hydride and chloride ligands, two equatorial L ligands and an equatorial carboranyl ligand sigma-bonded to the metal through one of the boron atoms closest to the carbon atoms. The preparation, characterization and structures of these complexes are discussed, as well as their significance as model intermediates for transition metal catalyzed deuterium exchange at terminal boron-hydrogen bonds.

A number of B-sigma-metallocarboranes have been prepared by oxidative addition of carboranyl boron-hydrogen bonds to an iridium complex. The complexes are models for intermediates in the transition metal catalyzed exchange of deuterium gas for hydrogen at terminal B-H bonds, and do themselves actively catalyze such exchange. Spectra are reported for 3-((PPh3)2Ir HCl)-1,2-C2B10H11.

A number of Group VIII hydrogenation catalysts have been found to effect the exchange of deuterium gas with terminal B-H bonds in a wide variety of carboranes, metallocarboranes and other boron compounds. (Author)