Regioselective partial hydrogenation of tricyclopentadiene (TCPD) was achieved with a high turnover number of 10000 by catalysis with it N-heterocyclic carbene-palladium complex. Copolymerization of ethylene and the partially hydrogenated product, dihydrotricyclopentadiene (HTCPD), wits realized using a catalytic system of [8-(eta(5)-C5Me4)-2-Me(C9H8N)-kappa N]TiMe2 (C9H10NH = 1,2,3,4-tetrahydroquinoline) activated with (Ph3C)(+)[B(C6F5)(4)](-). The copolymer was unambiguously characterized through the analysis of one- and two-dimensional NMR spectra. The monomer reactivity ratios, r(ethylene) and determined through the Fineman-Ross plot, were 2.8 and 0.025, respectively, indicating negligible successive insertion of two HTCPD. A nearly alternating copolymer with a HTCPD content of 45 mol % was obtained with it satisfactory activity (4.7 x 10(6) g/(mol Ti h)), of which T-g was 177 degrees C, significantly higher than that of norbornene/ethylene copolymer at the same cycloolefin content. Tensile stress-strain curves indicated that the brittleness observed for a high-T-g norbornene/ethylene copolymer was relieved to show some ductile property for the HTCPD/ethylene copolymer of the same level of high Tg.