DONOR COMPLEXES OF SILYLENE, GERMYLENE, AND STANNYLENE

The complexes of various donor molecules, AH(3) (A = N, P, As, Sb, Bi) and AH(2) (A = O, S, Se, Te) with silylene, germylene, and stannylene ((1)A(1) ground state) were studied by means of quantum chemical inve stigations at ab initio level utilizing all valence electron basis set s and relativistic corrected effective core potential methods. Accordi ngly, the donor molecules are weakly bound, the association energies a re in the range of 15-30 kcal per mole. The exothermic energies for ad duct formation, i.e., the resulting binding energies for the donor com plexes, decrease in the order silylene > germylene > stannylene. The p opulation analysis indicates for NH3 and BiH3 only a weak bonding towa rds the XH2 fragment (X = Si, Ge, Sn) while the higher homologues (A = P, As, Sb) form ylide structures, 1.2-dipolaric in nature. The additi on of two donor molecules has been studied for silylene and is much le ss favourable than donor mono-addition. For the donor mono-addition a dual parameter relationship between (a) the HOMO energies of the donor (n-orbital of the AH(3) unit, n, p-orbitals for AH(2)) and (b) the co valent bond energies (from the literature) versus the binding energies of the donor-acceptor compounds was examined. This dual parameter equ ation describes satisfactorily the essential features of the stabiliti es of the donor-acceptor structures.