Group 4 ansa-cyclopentadienylamido (CpA) complexes [Me2Si(Cp＇)(NR)]MCl2 (R = alkyl, M = Ti, Zr) efficiently copolymerize ethylene with a variety of alpha-olefins. Ethylene/norbornene copolymerization reactivity ratios mere determined at 40 degrees C for CpA catalysts [Me2Si(Cp＇)((NBu)-Bu-t)]TiCl2 (Cp＇ = Me4Cp, 2,4-Me2Cp, 3-(BuCp)-Bu-t, Ind), and the resulting values are low (r(1) = 2.0-5.1, r(2) --> 0), suggesting a tendency toward alternating comonomer insertion at high norbornene/ethylene feed ratios. As reaction temperature is increased and norbornene concentration is decreased, productivity increases and norbornene incorporation decreases. No more than 46 mol % norbornene is incorporated into the copolymer using these CpA catalysts even at low feed ratios (EM greater than or equal to 0.02), and norbornene homopolymerizations with [Me2Si(Me4Cp)((NBu)-Bu-t)]TiCl2 proceed to very low conversion (<1%). C-13 NMR spectroscopy of CpA-derived poly(ethylene-co-norbornene)s shows the copolymers contain virtually no consecutive norbornene sequences, and the microstructure of the resulting ethylene norbornene copolymers is dependent on catalyst geometry.