Transition metal complexes containing the 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligand: crystal structures of [4-MeC5H4NMe]2[Pd(S2C2B10H10)I2], [NEt3H][Mo(η5-C5H5)(NO)(S2C2B10H10)I], [NBu4][Re(O)(S2C2B10H10)2] and [4-MeC5H4NMe]2[{Mo(O)(µ-O)(S2C2B10H10)}2]

Abstract

The dithiol ligand 1,2-dicarbaborane-1,2-dithiol, 1,2-(HS)₂-1,2-C₂B₁₀H₁₀ (H₂cbdt), reacted with anhydrous PdI₂ to form [Pd(cbdt)I₂]^2–, isolated as its [4-MeC₅H₄NMe]⁺ salt 1 and with [{Mo(η⁵-C₅H₅)(NO)I₂}₂] in the presence of NEt₃ to afford the mononuclear complex [NEt₃H][Mo(η⁵-C₅H₅)(NO)(cbdt)I] 2. Complete halide substitution occurred with [NBu₄][Re(O)Cl₄] to give [NBu₄][Re(O)(cbdt)₂] 3 and the reaction with MoCl₅ in tetrahydrofuran afforded the oxo-bridged molybdenum(V) dimer [4-MeC₅H₄NMe]₂[Mo(O)(µ-O)(cbdt)}₂] 4 which is diamagnetic. The salts 1–4 have been characterised by single crystal X-ray diffraction studies. In all cases only very limited conjugation appears to occur between the sulfur atoms and the carbon atoms of the carbaborane cage, C–S bond lengths averaging 1.785 Å, slightly shorter than the pure single bond value. The electrochemical properties of the new complexes were investigated but no simple reversible electron transfer processes were observed.