The versatility of the 1,4-dithiane ligand towards the coordination chemistry of ruthenium-phosphine complexes

Abstract: The trans-[RuCl2(dppb)(1,4-dt)], mer-[RuCl3(dppb)(1,4-dt)] and [{RuCl3(dppb)}2(μ-(1,4-dt))] complexes were synthesized and characterized by spectroscopic and electrochemical techniques. Despite the favorable energy for the C 2h conformation, the crystallographic data point for the 1,4-dithiane (1,4-dt) D2 conformer in the trans-[RuCl2(dppb)(1,4-dt)] complex, where it acts as a bidentate ligand. The E 1/2 value of this complex is higher than those found for some related pyridine derivative compounds showing that with this thio-ligand, the Ru(II) atom presents a relatively strong π back-bonding interaction. Apart from the phosphine intraligand transitions, the UV/Vis spectrum of the trans-[RuCl2(dppb)(1,4-dt)] complex shows only one band at 457nm assigned to the MLCT transition. The bands observed in the spectra of the mer-[RuCl3(dppb)(1,4-dt)] and [{RuCl3(dppb)}2(μ-(1,4-dt))] complexes, at 530, 420 and 347nm were attributed to the contribution of the (RuIII)←(Cl,S) LMCT transitions. The EPR spectrum of the mer-[RuCl3(dppb)(1,4-dt)] complex shows three g-values in 2.87, 2.15 and 1.73, suggesting that the 1,4-dt is coordinated in a monodentate mode. The NMR, EPR, FTIR and crystallographic data point for the ruthenium-phosphine species as the first example of metallic system that form complexes with the 1,4-dithiane acting as bidentate, monodentate and bridged ligand. [Copyright &y& Elsevier]