Stabilization of dichalcogenide ligands in the coordination sphere of a ruthenium system

Abstract

The synthesis, structure and electronic properties of tetraruthenium dichalcogenide complexes displaying the exclusive coordination mode of dichalcogenide ligands have been discussed. The reactions of Li[BH₂E₃] (E = S or Se) with [ClRu(μ-Cl)(p-cymene)]₂ (p-cymene = η⁶-{p-C₆H₄(ⁱPr)Me}) at room temperature yielded tetrametallic dichalcogenide complexes [{Ru₂Cl₂(p-cymene)₂}₂(μ₄,η²-E₂)], 1–2 (E = S (1) and Se (2)). The solid-state X-ray structure of 1 shows that two {(p-cymene)RuCl}₂ moieties are bridged by a S–S bond. In addition to 2, the reaction of Li[BH₂Se₃] with [ClRu(μ-Cl)(p-cymene)]₂ also yielded a mononuclear tris-homocubane analogue [Ru(p-cymene){Se₇(BH)₃}] (3) which is an analogue of 1,3,3-tris-homocubane and possesses D₃ symmetry. In order to isolate the Cp* analogue of 1, the reaction of [Cp*Ru(μ-Cl)Cl]₂ with Li[BH₂S₃] was carried out, which led to the formation of bis/tris-homocubane derivatives [(Cp*Ru)₂{μ-S_n(BH)₂}] (n = 7 (4) and 6 (5)) along with the formation of ruthenium disulfide complexes [(RuCp*)₂(μ,η²:η²-S₂)(μ,η¹:η¹-S₂)] and [(RuCp*)₂(μ-SBHS-κ¹B:κ²S:κ²S)(μ,η¹:η¹-S₂)]. Complexes 1–5 have been characterized by multi-nuclear NMR, IR, UV-vis spectroscopy, and mass spectrometry and their molecular formulations (except 2) have been determined by single crystal X-ray crystallography. Furthermore, DFT calculations were performed that rationalize the stabilization of the dichalcogenide units (E₂²⁻) by the tetrametallic systems in 1–2.