Isocyanide as a ligand on ruthenium(II) ammines

Article abstract of DOI:10.1021/ic00141a024

A pentaammine-isocyanide complex of Ru(II) is readily prepared by the reaction of Ru(NH₃)₅H₂O²⁺ with the ligand, but if the contact time is long, a trans-bis(isocyanide) complex results. Measurement of the rate of aquation of the benzyl isocyanide complex Ru(NH₃)₅C₇H₇NC²⁺ compared with earlier measurements for Ru(NH₃)6²⁺ shows that C₇H₇NC (as compared to ammonia) labilizes a trans ammonia by a factor of 40. A similar comparison between Ru(NH₃)₄(H₂O)C₇H₇NC ²⁺, now following the replacement of H₂O by isn (isonicotinamide), shows that the trans isocyanide (compared to trans ammonia) is slightly delabilizing. The rate of aquation of isn in a trans position is enormously enhanced by isocyanide as compared to ammonia, and the affinity of Ru(II) for isn is much reduced. As determined by cyclic voltammetry, the values of E_f for the couples Ru(NH₃)₅C₇H₇NC^3+/2+, Ru(NH₃)₄(H₂O)C₇H₇NC ^3+/2+, trans-Ru(NH₃)₄(C₇H₇NC) ₂^3+/2+, and trans-Ru(NH₃)₄(C-HxNC)₂^3+/2+ are 0.79, 0.92, 0.99, and 0.93 V vs. NHE at 25°C.