DINUCLEAR DIHYDRIDE COMPLEXES OF IRIDIUM - A STUDY OF STRUCTURE AND DYNAMICS

Reaction of the neutral dihydride complexes (eta-C(5)R(5))Ir(L)H-2 (L = P(OPh)(3), CO; R = H, Me) with triflic acid (HO3SCF3) at ambient tem perature or above affords hydrogen and the dimeric hydride bridged spe cies {[(eta-C(5)R(5))Ir(L)H](2)(mu-H)}O3SCF3. Deprotonation of the cat ionic complexes gives the neutral dimers of the form [(eta-C(5)R(5))Ir (L)H](2). Spectroscopic data are consistent with the presence of only terminal hydride ligands in these complexes. Variable temperature H-1 and P-31 NMR studies indicate that a rapid dynamic process exchanges t he two terminal hydride ligands and that the complexes exist as unequa l mixtures of the racemic and meso diastereomers. Synthesis of a lower symmetry derivative, [(eta-C(5)Me(4)Et)Ir(CO)H](2), reveals that a ra pid epimerization process occurs that interconverts the two diastereom ers. Thermolysis of the carbonyl complex [(eta-C(5)Me(5))Ir(CO)H](2) a ffords [(eta-C(5)Me(5))Ir(CO)](2) and dihydrogen.