Vinylsilanes CH2CHSiR3 (R=Me, NMe2, OMe, OTMS) copolymerize with ethylene rapidly in the presence of catalytic amounts of [Cp2ZrMe][MeB(C6F5)(3)] (Cp=(5)-C5Me5) (I) to give high molecular weight silyl-functionalized polyethylene. The molecular weight of the polymer can be controlled by varying the comonomer concentration as well as the reaction temperature. Relatively low molecular weight polymer was produced at a higher silyl monomer concentration and a higher polymerization temperature. The incorporation of silyl monomer in the polymer is in the range of 0.1- 6.0%. On the other hands, catalysts [Cp2ZrMe][MeB(C6F5)(3)] (Cp=(5)-C5H5) (II) and [Cp2ZrMe][MeB(C6F5)(3)] (Cp=(5)-1,2-C5Me2H3) (III) show much lower activity. With the use of more coordinatively unsaturated constrained geometry catalysts (CGC), Me2Si((5)-C5Me4)((NBu)-Bu-t)MMe][MeB(C6F5)(3)] (IV, M=Zr; V, M=Ti), the silyl monomer incorporation in the polymer was increased to 40%. The Ti catalyst is more active and produces polymer with a higher molecular weight with a higher silyl monomer incorporation at 23 degrees C. The copolymerization of vinyltrimethylsilane with propylene was also investigated with these catalysts, yielding high silyl-functionalized propylene copolymer/oligmer. The microstructure of the copolymers/oligomers has been thoroughly investigated by 1D and 2D NMR techniques (H-1, C-13, NOE, DEPT, HETCOR, and FLOCK). The results show that the backbone of the copolymers/oligomers is essentially random. Several termination pathways have been identified. In particular, two unsaturated silyl terminations, cis and/or trans-TMSCHCH, were identified with the constrained geometry catalysts. Their formation was rationalized based on transition state models. It was found that occasional 1,2-insertion of either propylene or vinyltrimethylsilane into the chain propagation process has a high probability serving as the trigger for polymer chain termination via -H elimination. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1308-1321