Synthesis and structural studies of rhenium(I) tricarbonyl complexes with thione containing chelators

Sodium dihydrobis(2-mercaptothiazolyl)borate, Na[H2B(tiaz)2], reacts with (NEt4)2[Re(CO)3Br3] in water to afford fac-[Re{κ3-H(μ-H)B(tiaz)2}(CO)3] (1). In a similar manner, treatment of the same Re(I) starting material with bis(2-mercaptoimidazolyl)methane, H2C(timMe)2, yields fac-[ReBr{κ2-H2C(timMe)2}(CO)3] (2). The organometallic complexes 1 and 2 have been characterized by IR, 1H and 13C NMR spectroscopy, and also by X-ray crystallographic analysis. X-ray diffraction analysis revealed the presence of a short B–H⋯Re interaction in the case of 1, and the absence of C–H⋯Re interactions in the crystal structure of 2. For both compounds the rhenium atom adopts a slightly distorted octahedral coordination with a facial arrangement of the carbonyl ligands. The three remaining coordination positions are occupied by the two thione sulfur atoms from the anchor ligands, and by an agostic hydride (1) or a bromide ligand (2). Compound 1 is highly stable either in the solid state or in solution. In particular, its B–H⋯Re interaction is retained in solution, even in coordinating solvents, namely acetonitrile, dimethylsulfoxide and tetrahydrofuran. Unlike 1, compound 2 is only moderately stable in acetonitrile, undergoing a slow release of the bis(2-mercaptoimidazolyl)methane.