Reactivity of trans-[Ru(NH3)4P(OEt)3NO]X3 (X = PF6-, CF3COO-):: modulation of the release of NO by the trans-effect

The synthesis, characterization and reactivity of trans-[Ru(NH3)(4)P(OEt)(3)NO]X-3 (X = PF6- and CF3COO-) are presented. The X-ray structure of trans-[Ru(NH3)(4)P(OEt)(3)NO](CF3COO)(3) center dot 3CF(3)COOH indicates coordination of the nitrosyl as NO. with a Ru-N-O angle of 175.1(8)degrees and a Ru-NO bond length of 1.774(8) angstrom. Loss of NO2- from trans-[Ru(NH3),P(OEt)(3)NO](3)(+) is pH dependent with k(obs) (S-1) = (k(0)K(a) + k(1)[H+])/([H+] + K-a)], where k(0) = 2 x 10(-5) s(-1), k(1) = 0.40 +/- 0.03 s(-1), and pK(a), = 8.6 +/- 0.3. The nitrosyl complex undergoes a one-electron reduction (E-0 = 0.14 V versus NHE) involving the coordinated nitrosyl group followed by dissociation of NO, which is facilitated by the phosphito ligand (k(-NO) = 0.97 s(-1) at 25 degrees C and pH 5.0). (c) 2004 Published by Elsevier B.V.