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)

摘要

The sigma-type charge-transfer (CT) interaction between [M(RrR'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(H_2timdt)_2],and on the adducts [M(H_2timdt)_2]-I_2 (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]I_2,which was also characterised by single-crystal X-ray diffraction.In addition,the strength of the donor-acceptor interaction has been evaluated through thecalculated 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(Et_2timdt)_2]_2I_2 (M = Ni,Pd,Pt).The ZPE- and CP BSSE-corrected binding energy for [Ni(H_2timdt)_2]-I_2 has been evaluated as -11 kcal/mol.