Substitution kinetics of the aqua ligand in [Re(NO)(H2O)(CN)4]2- by the monodentate nucleophiles SCN-, N3- and thiourea and the X-ray crystal structure of (AsPh4)2[Re(NO)(SC(NH2)2)(CN) 4]

Article abstract of DOI:10.1016/0277-5387(95)00308-8

The substitution reactions between [Re(NO)(H₂O)(CN)₄]^2- and the nucleophiles SCN^-, N₃^- and thiourea revealed that both the aqua and the hydroxo ligands are substituted with respective rate constants of 3.6(1) × 10^-3 and 1.57(5) × 10^-3 M^-1 s^-1 at 40°C in the case of SCN^-. The pK_a1 was spectrophotometrically determined as 9.90(2) at 25°C and kinetically as 9.50(4) at 40°C with NCS^- as the incoming nucleophile. The (AsPh₄)₂[Re(NO)(SC(NH₂)₂)(CN) ₄] complex was isolated as the product for the reaction between [Re(NO)(H₂O)(CN)₄]^2- and thiourea and its X-ray crystal structure determined. The Re - NO and N - O bond lengths are 1.736(11) and 1.146(13) A, respectively, while the Re - S bond distance is 2.503(4) A. The thiourea is bonded cis with respect to the nitrosyl group.