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

Abstract

AbstractRuthenium‐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(S‐C5H4N)2] (1) obtained from reaction of Ru3(CO)12, Me3NO2H2O, and 2‐mercaptopyridine in THF. 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 σ‐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).