Jj. Novoa et al., ON THE BONDING NATURE OF THE M-CENTER-DOT-CENTER-DOT-CENTER-DOT-M INTERACTIONS IN DIMERS OF SQUARE-PLANAR PT(II) AND RH(I) COMPLEXES, Journal of the American Chemical Society, 117(27), 1995, pp. 7169-7171
A qualitative and semiquantitative study of the weakly bonding nature
of M ... M contacts between square-planar d(8)-ML(4) molecules is pres
ented. The results of ab initio calculations on the model dimers cis-[
PiCl(2)(CO)(2)](2) (in two different conformations), [PtCl2{HNCH(OH)}2
], and [RhCl(CO)(3)](2) are reported. These are predicted to be stable
toward dissociation into two monomers, with bonding energies in exces
s of 3 kcal/mol and M ... M distances well in the range of the experim
ental values for dimers and chains. The effect of adding axial groups
to the ML(4) dimers on the strength of the M ... M interaction has bee
n explored by means of ab initio calculations on several adducts of [P
tCl2(CO)(2)] as well as by extended Huckel calculations on the model a
dducts [Cl4YRh ... RhZCl(4)](n-) (Y, Z = Cl-, CO, H+, or AuCl). A qual
itative ordering for the M ... M bond strengths is proposed, which is
consistent with the available experimental data.