The kinetics of propylene polymerization in toluene solution by bis(2-phenylindenyl)zirconium dichloride/methylaluminoxane at 20 °C were investigated. As the structure and properties of elastomeric polypropylenes produced by these catalysts depend sensitively on the reaction conditions, a detailed study of the kinetics was carried out to evaluate the influence of these parameters on the polymerization behavior. Studies of the solubilities and mass-transfer rates reveal that dissolved atactic polypropylene has little effect on propylene solubility but influences the mass-transfer rate of propylene into solution. The rates of propylene polymerization reach a maximum after 10−20 min and then decrease. The decrease in rate over time is faster at higher monomer concentrations. Catalyst activity was negligible at [Al]/[Zr] = 1000 but constant from [Al]/[Zr] = 2500 to [Al]/[Zr] = 10 000. Analysis of molecular weights as a function of monomer concentration reveal β-hydride elimination to be the primary chain-transfer mechanism. Narrow molecular weight distributions (M w/M n = 2.0−2.6) were obtained. The increase of the isotactic dyads and pentads ([m] and [mmmm]) with increasing monomer concentration reveals an additional kinetic event which competes with the stereodifferentiating olefin insertion step. Modeling studies are more consistent with a mechanism involving interconversion of the catalyst between isospecific and aspecific states than a mechanism involving epimerization of the stereogenic centers of the growing polymer chain.

A new synthesis of unbridged mixed ring zirconocenes was developed and a series of mixed ligand zirconocenes with substituted 2-arylindenyl and 1-methyl-2-arylindenyl ligands have been prepared. When activated with methylaluminoxane, the mixed ligand complexes catalyze the polymerization of propylene to give elastomeric polypropylene. The propylene polymerization behavior of the mixed ligand catalysts was compared to that of their bis(indenyl) analogues to determine the relative contribution of each ligand to the activity and stereospecificity of the catalyst. The effects of 2-arylindenyl and 1-methyl-2-arylindenyl ligands on the stereospecificity of the catalysts are essentially additive; the stereospecificity of the mixed ring complex is intermediate to that of the bis(2-arylindene) analogues. However, the effect of 1-methyl substitution on catalyst productivity is not additive; the productivities exhibited by bis(2-arylindenyl)ZrCl2/MAO and (1-methyl-2-arylindenyl)(2-arylindenyl)ZrCl2/MAO derived catalysts are similar and substantially higher than those of the bis(1-methyl-2-phenylindenyl)ZrCl2/MAO catalysts.

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The thermally induced reductive elimination of biphenyl from Cp*Ru(NO)Ph2 (1) has been reinvestigated. Careful monitoring of the reaction in aromatic solvents by 1H NMR spectroscopy has revealed the presence of intermediate Cp*Ru(NO)(η2-arene) complexes (4a, arene = benzene; 4b, arene = toluene). Complexes 4 were independently prepared from Cp*Ru(NO)(Me)(OTf) (5) and LiHBEt3 in benzene with loss of CH4 and LiOTf. At 25 °C added naphthalene displaced the bound arene to generate Cp*Ru(NO)(η2-naphthalene) (6). The crystal structure of complex 6 has been determined; it crystallizes in triclinic space group P1̄, with a = 8.6333(16) Å, b = 9.8642(10) Å, c = 11.2055(13) Å, β = 80.551(13)°, V = 870.6(2) Å3, and Z = 2. The ligand substitution and oxidative addition reactions of 6 with several organic substrates have been investigated. A kinetic study has shown that the reactions of 6 with phosphines, triphenylsilane, and dimethyl disulfide require initial naphthalene dissociation. The oxidative addition of diaryl disulfides also occurs, but the mechanism is more complicated. We suggest that the reaction of 6 with diaryl disulfide (aryl = Ph, p-tolyl) is catalyzed by a small concentration of a secondary product.

The synthesis, characterization, chemical vapor deposition, and mechanistic investigation of the thermal decomposition in aromatic solvents of cis-bis(η2,η1-pent-4-en-1-yl)platinum (1) are described. Complex 1 has a unique chelated structure, giving rise to enhanced volatility, and has proved useful for the chemical vapor deposition of thin platinum films under mild conditions. Films deposited on a glass slide in a hot walled glass tube at 175 °C have an elemental composition of 82% Pt and 18% C. Kinetic, deuterium labeling, and chemical trapping experiments indicate that the decomposition of 1 in aromatic solvents proceeds by reversible β-hydride elimination followed by reversible dissociation of 1,4-pentadiene to give a 3-coordinate platinum hydride intermediate (9). Reductive elimination of 1-pentene from 9 deposits metallic platinum. The rate of decomposition exhibits a significant β-deuterium isotope effect of k H/k D = 3.8 ± 0.3. Added olefins are rapidly isomerized during the decomposition of 1; trapping experiments with diphenylacetylene indicate that intermediate 9 is the highly active catalyst that is responsible for the alkene isomerization.

The complex (7?5-C5H5XCO)2FeC^CC^CH was prepared by sequential treatment of LiC=CC^=C-SHCH3)3 with (775-C5H5XCO)2FeCI and tetrabutylammonium fluoride. The monometallic complexes (?75-C5H5)(CO)-LFeC=CC=CH (L = CO, PPh3) were deprotonated with sec-BuLi, and the resulting anions were trapped with (j75-C5H5)M(CO)"CI to form (7?5-C5H5XCO)LFeC=cC=CM-(CO)"foe-