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Insertion of ethylene into the Ti]methyl bond in TiH CHq is 2 3 chosen as a model reaction for investigating the performance of a range of contemporary quantum chemical models in polymerization studies. Basis set effects are investigated at the self-consistent-field level, covering Hartree]Fock, pure DFT, and hybrid DFT. In agreement with findings in part I of this study, the basis set sensitivity of ethylene is shown to introduce a bias in computed energetics, amounting to 2]3 kcalrmol when DZP bases are used to compute the overall heat of monomer insertion. The geometry of stationary points relevant to the insertion reaction is determined using hybrid density functional theory. Based on these structures, the energy profile of the insertion reaction is computed using a range of popular quantum chemical approximations. The Ž . methods include Hartree]Fock and Møller]Plesset MP perturbation theory up through the fourth order in spin-restricted, spin-unrestricted, and spin-projected formalisms. Furthermore, configuration-interaction-based methods are included, of which the top level method is singly and doubly excited coupled clusters with a perturbative estimate of the contribution from triply excited w Ž .x configurations added CCSD T . The performance of the methods just mentioned, as well as three pure density functional and three hybrid density functional methods, are compared with respect to ‘‘best’’ relative energies, Ž . defined through extrapolation of CCSD T correlation energies according to the PCI scheme of Siegbahn and coworkers. Even though the MP series show poor Correspondence to: K. J. Børve Contractrgrant sponsor: Norwegian Academy of Science and Letters and Statoil, through the VISTA program ( ) Journal of Computational Chemistry, Vol. 19, No. 8, 947]96

An investigation of the quantum chemical description of the ethylenic double bond in reactions: II. Insertion of ethylene into a titanium-carbon bond