Abstract
The oxidative addition reaction of ditellurides R₂Te₂ [R = ⁿBu, Ph, Th (2-thienyl, C4H3S)] to [Pt(η²-nb)(dppn)] (nb = norbornene, dppn = 1,2-bis(diphenylphosphano)naphthalene) was found to afford [Pt(TeR)₂(dppn)] [R = ⁿBu (1), Ph (2), Th (3)] and [Pt(TeR)(R)(dppn)] [R = Ph (4), Th (5)] as a result of the cleavage of the Te-Te or C-Te bond, respectively. The reactions and the product distributions were monitored by 31P{1H} NMR spectroscopy. The spectral interpretation was assisted by the high-yield preparation of [Pt(TePh)₂(dppn)] (2) and [Pt(TeTh)₂(dppn)] (3) by ligand exchange reactions from [PtCl₂(dppn)], and by the crystal structure determinations and spectral characterizations of 2 and 3. Two series of reactions were carried out both at room temperature and at −80 °C. One involved the addition of the toluene solution of R₂Te₂ to that of [Pt(η²-nb)(dppn)], and the other the addition of [Pt(η²-nb)(dppn)] solution to the R₂Te₂ solution. The oxidative addition of ⁿBu₂Te₂ to [Pt(η²-nb)(dppn)] yielded solely [Pt(TenBu)₂(dppn)]. In case of Ph₂Te₂ and Th₂Te₂, the reaction of equimolar amounts of ditelluride and [Pt(η²-nb)(dppn)] afforded only [Pt(TeR)(R)(dppn)] (R = Ph, Th), but when an excess of R₂Te₂ was used, the addition of [Pt(η²-nb)(dppn)] to the ditelluride resulted in the formation of a mixture of [Pt(TeR)₂(dppn)] and [Pt(TeR)(R)(dppn)] with the latter the main component. An excess of R₂Te₂ and the lowering of the temperature favoured the formation of [Pt(TeR)₂(dppn)]. The reaction energetics in toluene was calculated at revPBE/def2-TZVP(-f) level of theory. The increase of the electron withdrawing nature of the organic substituent rendered [Pt(TeR)(R)(dppn)] increasingly stable with respect to [Pt(TeR)₂(dppn)]. The computation of the energy profiles of the likely pathways of the oxidative addition indicated that concurrent formation of [Pt(TeR)₂(dppn)] and [Pt(TeR)(R)(dppn)] (R = Ph, Th) may be more likely than the formation of the latter due to the decomposition of the former. This was verified experimentally by stirring pure [Pt(TeR)₂(dppn)] in toluene for a prolonged time at room temperature. No decomposition was observed
