METAL RARE GAS INTERACTION - NEW BOND

The interaction between the pentacarbonyls M(CO)5 (M = Cr and Mo) and a rare-gas atom X (X = Ar, Kr, Xe) has been studied through ab initio calculations both at the SCF level and at the level of the dispersion energy. The SCF calculations were carried out with two different basis sets, the largest one being of double- quality. The interaction at the SCF level was attractive with the small basis set but repulsive with the large one. This repulsive character of the interaction at the SCF level has been discussed in terms of (1) the donor ability of the rare gas; (2) the existence of a destabilizing TT interaction together with a stabilizing a interaction; (3) the steric requirements of the rare gas. The dispersion energy in Mo(CO)5Kr has been estimated on the basis of a perturbation treatment for MoKr. This produces for the stabilization energy of Mo(CO)5Kr a value of 2.5 kcal/mol; however, this result is certainly underestimated and the exact value may be as high as 8-10 kcal/mol. Copyright © 1979, American Chemical Society. All rights reserved.