Ligand Bridged Bisstyryl Ruthenium Complexes

Author : David Peter Klein
Publisher :
ISBN 13 :
Total Pages : 194 pages
Book Rating : 4.:/5 (6 download)

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Download or read book Chemistry of Ruthenium Complexes Incorporating the Doubly-linked Bis(dimethylsilylcyclopentadienyl) Ligand written by David Peter Klein and published by . This book was released on 2004 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes three investigations of the dinuclear ruthenium complex, [([eta]5-C5H3)2(SiMe2)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 [([eta]5-C5H3)2(SiMe2)2]Ru2(CO)3[P(OR)3]HBF4− (R= Me, Ph). A fundamentally new mechanism for alkyne hydroamination catalyzed by the ruthenium complex, [([eta]5-C5H3)2(SiMe2)2]Ru2(CO)3(C2H4)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, [([eta]5-C5H3)2(SiMe2)2]2Ru4(CO)3H4, and the square planar cluster, [([eta]5-C5H3)2(SiMe2)2]2Ru4(CO)4H4, have been isolated from the photochemical reaction of H2 with the doubly-linked dicyclopentadienyl complex, [([eta]5-C5H3)2(SiMe2)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, [([eta]5-C5H3)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] + k2[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.