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 diiodine has been thoroughly investigated by a large set of theoretical calculations 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 the adducts [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 sulfur−iodine contacts, as in the case of [Ni(Me,iPr‐timdt)2]·I2, which was also characterised by single‐crystal X‐ray diffraction. In addition, the strength of the donor−acceptor interaction has been evaluated through the calculated vibrational features of the model adducts, compared with the experimental FT‐Raman spectra recorded on the adducts between [M(Et2timdt)2] and [M(Me,iPr‐timdt)2] (M = Ni, Pd, Pt) and diiodine. The frontier‐orbital composition, 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 experimental frequencies of the FT‐Raman‐active I−I stretching vibrations in the adducts [M(Et2timdt)2]·2I2 (M = Ni, Pd, Pt). The ZPE‐ and CP BSSE‐corrected binding energy for [Ni(H2timdt)2]·I2 has been evaluated as −11 kcal/mol. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)