Experimental and Theoretical Studies of Ni,( C2H4)m. Synthesis, Vibrational and Electronic Spectra, and Generalized Valence Bond-Configuration Interaction Studies. The Metal Atom Chemistry and a Localized Bonding Model for Ethylene Chemisorbed on Bulk Nickel

Using cryochemical manipulation of Ni atom reactions with ethylene-argon mixtures at 15-25 K and from examination of the vibrational and electronic spectra, we have identified N i ~ ( c 2 H 4 ) ~ (where rn = 1,2) in the presence of Ni(CZH4), (where m = I , 2, 3). These results suggest strongly that the ethylene moiety is complexed to the chemical site in a r-complexed manner, probably i n association with only one of the Ni atoms. Some evidence for the formation of Nix(C2Hd)L with x 2 3 is presented. To further characterize the Ni2(ClH4) complex, we carried out generalized valence bond (GVB) and configuration interaction (CI) calculations on Ni(C2H4) and Ni2(C2H4) in the r-coordinate geometry. For both complexes the ethylene geometry is found to be only weakly perturbed, with R(CC) = l .32 A and R(hiC) = 2.07 A. The CH bonds are found to bend only 2’ out of the ethylene molecular plane. There is a n increase in ethylene-Ni binding energy upon coordination of the second Ni atom, from 14.2 kcal for Ni(C2H4) to 27.2 kcal for Ni*(CzHd). The experimental and theoretical results are discussed with reference to the problem of chemisorption of ethylene on bulk nickel.