trans-[Ru(NO)(NH3)P(O-)(OEt)2]2+: A new and robust NO/ HNO-donor

This study describes the synthesis and reactivity in aqueous media of a new potential NO/HNO-donor: trans-[Ru(NO)(NH3)(4)P(O-)(OEt)(2)](PF6)(2). This compound exhibits a remarkable robustness over a wide range of pH relative to other similar ruthenium phosphorus nitrosyl complexes. At pH 3.0 and 25 degrees C, trans-[Ru(NO)(NH3)(4)P(O-)(OEt)(2)](PF6)(2) decays, yielding free diethyl phosphite with a half-life of 9 days (k = 8.9 x 10 (7) s (1)). At pH 7.5 and 25 degrees C, this complex is competitively consumed by diethyl phosphite dissociation (k = 5.15 x 10 (5) s (1)) and nucleophilic attack at the nitrosyl group (k = 7.25 x 10 (5) s (1)). Nevertheless, the trans-[Ru(NO)(NH3)(4)P(O-)(OEt)(2)](PF6)(2) exhibits a half-life of 1.5 h (pH 7.5 and 25 degrees C) for delivering NO/HNO by electrochemical activation at potentials of -0.50 and -0.80 V versus SCE. The NO liberation from trans-[Ru(NO)(NH3)(4)P(O-)(OEt)(2)](+) ion occurs with k(-NO) = 0.24 +/- 0.01 s (1), and electrochemical data indicate that k(-HNO) >> k(-NO). (C) 2014 Elsevier B.V. All rights reserved.