Preparation and Characterization of (1-Me-indenyl)Ni(PR3)(CC−Ph) (R = Cy, Ph) and Alkyne Polymerization Catalysis

The complexes (1-Me-Ind)(PR3)Ni−CC−Ph (R = Ph and Cy) have been prepared and characterized spectroscopically and by means of single-crystal structural analyses. These compounds are inert toward the insertion of alkynes, but when combined with methylaluminoxane (MAO), they form active catalysts for the homogeneous polymerization of phenylacetylene. cis-Poly(Ph−CC−H) is thus obtained with M w values in the range of 104 and relatively narrow polydispersities. The combination of the corresponding Ni−Cl complexes with MAO gives similar results with Ph−CC−H and also polymerizes 1-hexyne and 3-hexyne, but the degree of polymerization is much lower. Optimization studies have shown that the polymerization reactions give the best results with THF as solvent and a 1:10 ratio of Ni to MAO. Evidence is presented for the involvement in the catalytic cycle of bimetallic species with a Ni(μ-X)(μ-Me)Al core.