Metal thiolate complexes binding molecular nitrogen under mild conditions: [μ-N 2{Ru(P iPr 3)(N 2Me 2S 2)} 2], the first dinuclear example

Abstract

Binding N 2 to the metal sulfur cofactors of nitrogenase is considered the first step of biological N 2 fixation. In quest of low-molecular weight complexes modeling this step [μ-N 2{Ru(P iPr 3)(N 2Me 2S 2)} 2] ( 3) was synthesized and completely characterized. Complex 3 was obtained from [Ru(N 2)(P iPr 3)(N 2Me 2S 2)] ( 1) that dissociates N 2 under reduced partial pressure of N 2. Complex 1, in turn, forms from [Ru(CH 3CN)(P iPr 3)(N 2Me 2S 2)] ( 2) and N 2 at standard conditions (20 °C, 1 bar) such that the formation of 3 corresponds with a binding of molecular nitrogen to metal thiolate complex fragments under mild conditions, not requiring abiologically strong reductants. Complex 3 forms as racemate of ( R, R)- 3 and ( S, S)- 3 enantiomers which spontaneously separate upon crystallization and could both be characterized by X-ray crystallography. Complex 3 exhibits short bonds trans to the N 2 ligand, a ν(N 2) frequency (2042 cm −1) low in comparison with that of 1 (2113 cm −1) and a non-linear [RuNNRu] entity. The thiolate donors of 3 represent Broensted-basic sites for reversible protonations so that 3 becomes a complex suited for investigations aiming at the reduction of N 2 by nitrogenase-like coupled [2H +/2e −] transfer steps.