Polymerization of 1-alkynes initiated by μ-alkylidene complexes of tungsten, 2. Kinetics and mechanism of the initiation reaction

The existence of two successive and quite different stages in the polymerization of monosubstituted 1-alkynes (1-heptyne), initiated by a homo dinuclear μ-alkylidene derivative of tungsten, is demonstrated. The first step leads to a mixture of species, the stability of which increases with the number of inserted monomeric units until inactivation. In order to explain the reactivation of these species in the second step, the loss of one carbonyl ligand is postulated, although no experimental evidence of that exists. The second step leads to high molecular weight polymer.