| Abstract: | The reaction of norbornene (NBE) and norbornadiene (NBD) in the presence of seven-coordinate tungsten(II) and molybdenum(II) complexes of the [(CO)4M(μ-Cl)3M(SnCl3)(CO)3] and [MCl(M′Cl3)(CO)3(NCMe)2] (M=W, Mo; M′=Sn, Ge) types leads to ring-opening metathesis polymerization (ROMP) and to the formation of high molecular weight polymers. The geometric structure of these polymers was determined by means of 1H- and 13C-NMR spectroscopy. The monitoring of the reaction between cyclic olefins and the metal complex by means of 1H-NMR spectroscopy allowed us to observe the coordination of NBD to metal atoms in the initiation step of the polymerization process. Compounds of the [MCl(SnCl3)(CO)3(η4-NBD)] type prepared directly from [(CO)4M(μ-Cl)3M(SnCl3)(CO)3] or [MCl(M′Cl3)(CO)3(NCMe)2] (M=W, Mo) in the presence of an excess of NBD initiate the ROMP reaction immediately. The detection of the first-formed products in the reaction between the metal complex and cyclic olefins provides valuable information concerning the nature of the initiating species. |
