Dihydrido Olefin and Solvento Complexes of Iridium and the Mechanisms of Olefin Hydrogenation and Alkane Dehydrogenation

Article abstract of DOI:10.1021/ja00389a018

Tests for homogeneity are applied to the catalysts L2>A/CH2Cl2/H2 (cod-1,5-cyclooctadiene; A = BF4; L=PPh3, PMePh2) and their possible generality is discussed. L2>A (L=PPh3) reacts with H2 and S (S=solvent) to give the isolable complexes <IrH2S2L2>A (1) in which the displacement order of the M-S groups is H2O ca.THF2L2>A (ol = C2H4, C3H8) and L2>A (ol = PhCH=CH2, C5H8, t-BuCH=CH2).Their role in hydrogenation is discussed in the light of stepwise catalytic 1H NMR studies at -80 to +25 deg C, in which they appear to be intermediates in catalysis.A catalytic cycle is proposed.Selectivity in competitive experiments is discussed.The rhodium analogues do no exhibit similar properties.