Transition-Metal-Containing Polymers by ADMET: Polymerization of cis-Mo(CO)4(Ph2P(CH2)3CH═CH2)2

Abstract

Polymerization of the cis-Mo(CO)4(Ph2P(CH2)3CH═CH2)2 complex using acyclic diene metathesis (ADMET) polymerization is reported. Ideally, ADMET polymerization is performed in bulk monomer to maximize monomer concentration and favor formation of polymer. The monomer in this case is a solid with a melting temperature of 128 °C, which is well above room temperature and above the range of catalyst stability. The polymerization was carried out therefore in a concentrated solution of toluene. The complex underwent polymerization when catalyzed with Grubbs’ second-generation catalyst; neither Grubbs’ first-generation catalyst nor Schrock’s catalyst was active. Homopolymerization resulted in oligomers of Mn = 2060 (n ≈ 3, GPC relative to polystyrene). At elevated temperatures the coordination core of the polymerized cis-Mo(CO)4(Ph2P(CH2)3CH═CH2)2 complex isomerized to the trans geometry. Copolymerization with 1,9-decadiene was also carried out and resulted in an oligomer of slightly higher molecular weight, Mn = 5800. It is suggested that ADMET is not an effective method for obtaining high molecular weight polymers in this case because the monomer is neither a liquid nor a low-melting solid, and therefore a high monomer concentration could not be achieved.