New ruthenium(II) thiolato complexes: Synthesis, reactivity, spectral, structural and DFT studies

Ruthenium complexes [Ru(mpy)2(DMSO)2] (1) and [Ru(mbtz)2(DMSO)2] (2) containing 2-mercaptopyridine (mpy) and 2-mercaptobenzothiazole (mbtz) have been synthesized. Reactivity of 1 have been examined with 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), EPh3 (E = P, As) and 1,2-bis(diphenylphosphino)-methane (dppm). It reacted with bipy or phen in DMF to afford [Ru(mpy)2(bipy)] (3) and [Ru(mpy)2(phen)] (4) while, its reaction with EPh3 or dppm in common organic solvents failed to afford products containing EPh3 or dppm. Complexes under investigation have been characterized by elemental analyses, spectral, electrochemical studies and structures of 1–4 have been determined crystallographically. Density functional theory calculations have been performed on 1–4 and the model complex [Ru(mpy)(PMe3)2] (5) using exchange correlation functionals BP86. Optimized bond length and angles are in good agreement with the structural data. The Ru–N and Ru–S bond distances in [Ru(mpy)2]-moiety of 1 are relatively shorter than 5, indicating higher stability of 1 in comparison to 5. The WBI values of Ru–N1, Ru–N2, Ru–S1 and Ru–S2 bonds indicate Ru–mpy bonding trend as 3 > 4 > 1 > 5. There is an overall charge flow in the direction L → [Ru(mpy)2] (L = DMSO, bipy, phen and PMe3). Due to greater ionic character and Pauli repulsive interactions for Ru–PMe3 bond in comparison to Ru–DMSO, the DMSO ligands in 1 may not be substituted by phosphine ligands experimentally.