| This dissertation describes three investigations of the dinuclear ruthenium complex, {(eta5-C5H3)2(SiMe 2)2)Ru2(CO)4: (1) its use as a catalyst for the hydroamination of alkynes by a new mechanism, (2) its reactions with H2 to give new ruthenium clusters containing bridging hydride ligands, and (3) the determination of thermodynamic and kinetic acidities of two related complexes, {(eta5-C5H 3)2(SiMe2)2}Ru2(CO) 3{P(OR)3}H+BF4- (R= Me, Ph).;A fundamentally new mechanism for alkyne hydroamination catalyzed by the ruthenium complex, {(eta5-C5H3) 2(SiMe2)2}Ru2(CO)3(C 2H4)H+BF4-, has been proposed. Many of the intermediates in the catalytic cycle have been isolated and/or characterized spectroscopically and found to react according to the proposed mechanism. The catalyst activity is terminated as a result of the isomerization of a bridging alkyne ligand in a key intermediate in the catalytic cycle.;The butterfly cluster, {(eta5-C5H3) 2(SiMe2)2}2Ru4(CO) 3H4, and the square planar cluster, {(eta5-C 5H3)2(SiMe2)2}2Ru 4(CO)4H4, have been isolated from the photochemical reaction of H2 with the doubly-linked dicyclopentadienyl complex, {(eta5-C5H3)2(SiMe 2)2}Ru2(CO)4, in benzene. Wavelength-dependent photolysis studies suggest that the first step in the reaction of {(eta 5-C5H3)2(SiMe2)2 )Ru2(CO)4 with H2 involves metal-metal bond cleavage.;The reaction of the protonated phosphite complexes, {(eta5-C 5H3)2(SiMe2)2}Ru2(CO) 3{P(OR)3}H+BF4- (R= Me, Ph), with tertiary amines (DABCO, 4-methylmorpholine, NEt3, N(n-Bu)3) results in clean deprotonation of the metal-metal bond by the amine. Equilibrium measurements show that the P(OPh) 3 complex is more acidic than the P(OMe)3 complex. The rates of deprotonation of the phosphite complexes have been determined, and follow the rate law: Rate = k1[complex] + k 2[amine][complex]. Comparisons of the k2 rate constants reveal that the reactions are much more sensitive to the steric properties of the amine and metal complex than to electronic factors. |
