A theoretical investigation of the donor ability of [M(R,R'timdt)2] dithiolene complexes towards molecular diiodine (M = Ni, Pd, Pt; R,R'timdt = formally monoreduced disubstituted imidazolidine-2,4,5-trithione).

The σ-type charge-transfer (CT) interaction between [M(R,R'timdt)2] donors (M = Ni, Pd, Pt; R,R'timdt = formally monoreduced disubstituted imidazolidine-2,4,5-trithione) and I2 was thoroughly studied by a large set of theor. calcns. at different levels of theory (HF, pure and hybrid-DFT with different functionals and basis sets) on I2 (and for the sake of comparison on IBr and Br2), on the model donor dithiolene complexes [M(H2timdt)2], and on [M(H2timdt)2]·I2 (M = Ni, Pd, Pt). The computations have accounted for the ability of adducts to assume different stoichiometries and to make up polymeric networks based on S-I contacts, as in the case of [Ni(Me,CHMe2-timdt)2]·I2, which was also characterized by single-crystal x-ray diffraction. The strength of the donor-acceptor interaction was evaluated through the calcd. vibrational features of the model adducts, compared with the exptl. FT-Raman spectra recorded on the adducts between [M(Et2timdt)2] and [M(Me,CHMe2-timdt)2] (M = Ni, Pd, Pt) and I2. The frontier-orbital compn., the NBO-charge distribution and bond orders indicate a medium-weak donor ability for the dithiolene donors, which depends only slightly on the nature of the central metal ion, and decreases on passing from M = Ni to M = Pd and Pt, in agreement with the values of the exptl. frequencies of the FT-Raman-active I-I stretching vibrations in [M(Et2timdt)2]·2I2 (M = Ni, Pd, Pt). The ZPE- and CP BSSE-cor. binding energy for [Ni(H2timdt)2]·I2 was evaluated as -11 kcal/mol. [on SciFinder(R)]