Preparative and structural studies on ruthenium(II)-thiolate cyanocarbonyls:: Comparison to the [Fe(CO)x(CN)y(SR)z]n- coordination modes of active sites of hydrogenases

Ruthenium-thiolate cyanocarbonyl compounds [Na(.)2THF][Ru(CO)(CN)(S-C5H4N)(2)] (2), and [PPN] [Ru(CO)(CN)(S-C5H4N)(2)] (3) were prepared from reactions of [Na][N(SiMe3)(2)] and cis-[Ru(CO)(2)(SC5H4N)(2)] (1) obtained from reaction of Ru-3(CO)(12), Me(3)NO(.)2H(2)O, and 2-mercaptopyridine in THE Complexes 1, 2 and 3 were characterized by IR and single-crystal X-ray diffraction. The IR spectrum of complex 2 in the aprotic solvent THF reveals two weak absorption bands for the CN- ligands at 2098 w and 2086 w cm(-1) and one strong absorption band 1931 s cm(-1) assigned to the carbonyl stretching frequency that support the dimeric architecture with two [Ru(CO)(CN)(S-C5H4N)(2)] units connected through CN-Na+-NC interactions, as observed in the single-crystal X-ray structure. Ethylation of complex 3 by electrophile [Et3O][BF4] occurring initially at the more accessible, delicately balanced nucleophilic site to yield the charge-controlled, collision product 4 (Scheme II), and subsequently isomerizing to neutral [Ru(CO)(CNEt)(S-C5H4N)(2)] (5) demonstrated the enhanced nucleophilicity toward electrophiles with replacement of carbonyl ligand with cyanide ligand in complex 1, indicative of the strong a-donor role of the cyanide vs CO ligand. In comparison with displaying a reversible redox process of complex [Fe(Co)(CN)(S-C4H3N2)(2)](-), the electrochemistry of complex 3 reveals an irreversible oxidation at 0.29 V (vs Ag/AgNO3).