Comparative studies on the contribution of NHS hydrogen bonds in tungsten and molybdenum benzenedithiolate complexes.

A series of monooxotungsten(iv) and dioxotungsten(vi) benzenedithiolates, (NEt4)2[WIVO(1,2-S2-3-RCONHC6H3)2] (1-W; R = CH3 (a), t-Bu (b), or CF3 (c)) and (NEt4)2[WVIO2(1,2-S2-3-RCONHC6H3)2] (2-W), were synthesized and compared with the corresponding molybdenum analogues. Single crystals of trans-1b-W were successfully obtained, and the crystal structure was determined by X-ray analysis although 1b-Mo could not be crystallized. The NHS hydrogen bonds shifted the potential of the W(iv/v) redox couple to more positive values, and the strength of the hydrogen bond and the positive shift value were strongly correlated. The hydrogen bonds in both 1-W and 2-W were weaker than those in the corresponding molybdenum analogues; however, the effect of the hydrogen bonds on the redox potential was greater in 1-W.