Ring-opening polymerization of norbornene by eta-cycloheptatrienyl molybdenum and tungsten complexes

The eta-cycloheptatrienyl complexes [M(eta-C7H7)LI2] (M = Mo, W; L -MeCN, P Ph3), activated with Me3SiCH2MgCl catalyze the ring-opening polymerization of norbornene to give high molecular weight, poly(1,3-cyclopentylenevinylen e) in high yield. By using the molybdenum complexes essentially all of the double bonds in the resulting polymers are in the trans-configuration as re vealed by C-13 NMR spectrometry. The tungsten catalyst [W(eta-C7H7)(MeCN)I- 2]exhibits higher reactivity toward this ring-opening polymerization but:lo wer stereoselectivity in comparison with the molybdenum analogs. (C) 1999 E lsevier Science S.A. All rights reserved.