No abstract

A family of ruthenium alkylidene complexes, (H 2 IMes)RuCl 2 (dCHR)(3-bromopyridine) 2 , where R ) Me, Et, nPr, as well as the corresponding PCy 3 complexes, (H 2 IMes)RuCl 2 (dCHR)(PCy 3 ), have been prepared. The PCy 3 alkylidene complexes exhibit much higher stoichiometric reactivity than does the analogous benzylidene complex, reflecting faster dissociation of PCy 3 from the alkylidene complexes.

The second-generation Grubbs analogues (H2IMes)RuCl2(CHPh)(PR3) (R = Me, Bu) were essentially metathesis-inactive and air-stable at room temperature but exhibited first-order metathesis with ethyl vinyl ether at elevated temperature. The PMe3 complex underwent second-order ligand exchange with PBu3, indicating different coordination mechanisms (dissociative vs associative) in the two reactions.

Electrical conductance data for Ni(NCS)2 in DMSO and Cu(C104)2 in MeOH at 25°are reported. They indicate the two electrolytes to be associated in the two solvents with association constants X'níncS'1' = 989 ^' ® DMSO and J^cuClO + = 193 M~' in MeOH. Pressure-jump relaxation kinetic data are reported for Ni(NCS)2 in DMSO at 20, 25, 30, and 35°. ^The analysis of the data reveals the mechanism to be interchange dissociative (Id) with the rate constant of ligand penetration in the first coordination sphere of Ni2+ to be of the same order of magnitude as the pseudo-first-order rate constant for solvent exchange. The activation enthalpy confirms the above. Ultrasonic relaxation data of Cu(C104)2 in MeOH at 25°also indicate the mechanism to be Id with k23 = /rexch. Previous findings in MeOH and DMSO indicating slower rates of substitution are suggested to be due to the structure of the ligand, specifically to the multidenticity of it in the case of previous studies in DMSO. The general validity of the Eigen interchange dissociative mechanism for monodentate ligands is reaffirmed.

Two olefin metathesis methods have been developed for the preparation of metal‐incorporated polyacetylene (MIPA) with high levels of covalently attached ruthenium complex. Treatment of freshly prepared, porous polyacetylene (PA) formed by polymerization of acetylene by the metathesis catalyst (H2IMes)RuCl2(CHPh)(3‐bromopyridine)2 (G2B) with additional G2B resulted in the incorporation of the ruthenium complex into the solid polymer in levels up to 75% by mass, giving two‐step MIPA (MIPA2). Alternatively, single‐step MIPA (MIPA1) samples with similar levels (up to 79% by mass) of ruthenium incorporation were obtained by polymerization of acetylene with highly concentrated solutions of G2B, and the resulting materials formed fine suspensions in CH2Cl2. A variety of experiments confirmed that both the methods give materials with ruthenium covalently attached to PA chains. Shiny, tough MIPA films were obtained by pressing the black powders obtained by either method. Some MIPA properties were dependent on the amount of metal incorporation, but even samples with high incorporation levels mimicked untreated PA in many respects. MIPA1, but not MIPA2, was made electrically conductive by doping with iodine. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1061–1072, 2009