Coordination polymerization Schrock

Cycloalkenes undergo ring-opening polymerization in the presence of coordination initiators based on transition metals to yield polymers containing a double bond, for instance, cyclo-pentene yields polypentenamer [IUPAC poly(pent-l-ene-l,5-diyl)] [Amass, 1989 Cazalis et al., 2000, 2002a,b Claverie and Soula, 2003 Doherty et al., 1986 Ivin, 1984, 1987 Ivin and Mol, 1997 Ofstead, 1988 Schrock, 1990, 1994 Tmka and Gmbbs, 2001], The... 

Klaus H. Theopold was born in Berlin, studied at the Universitat Hamburg for his Vordiplom in 1977, and at UC Berkeley, where he obtained his PhD in 1982 under the direction of Professor R. G. Bergman. After spending a year as postdoctoral fellow in the laboratory of Professor R. R. Schrock at MIT, he began his independent career in 1983 as an Assistant Professor at Cornell University. In 1990 he moved to the University of Delaware, where he is currently Professor of Chemistry. His scientific interests encompass synthetic and mechanistic studies of transition metal compounds, in particular paramagnetic organometal-lics, polymerization catalysis, and coordination compounds relevant to the activation of O2. 

ADMET polymerization has also been applied to 1,5-hexadiene, and polybutadiene (PBD) exclusively in the 1,4 mode was obtained [49]. Unlike PBD produced by ROMP, this ADMET polymer has a trans content of 75% [52]. With [W]l and [Mo]2,theAfn of these polymers was approximately 8.0 X lO gmol , witha poly-dispersity near 2.0. Attempts to polymerize 1,5-hexadiene with [Ru]l, however, resulted in oligomers of approximately 1.0 x lO gmoD, in addition to cyclics and unreacted monomer, even after extended reaction times [53]. This decrease in activity was attributed to stable intramolecular ii-complexation of the distal olefin of the 4-penten-l-ylidene complex to the metal center. Such coordination could obstruct bimolecular coordination of another diene to the metal, and thereby prevent further polymerization. The absence of this effect with Schrock s catalysts was explained in part by the steric congestion around the metal center of those catalysts and the lack of a labile ligand. A number of hydrocarbon dienes have been utilized in ADMET polymerizations [54, 55]. 

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