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)4P(OEt)3NO]X3(X=PF6-andCF3COO-) are presented. The X-ray structure of trans-[Ru(NH3)4P(OEt)3NO](CF3COO)3 · 3CF3COOH indicates coordination of the nitrosyl as NO with a Ru–N–O angle of 175.1(8)° and a Ru–NO bond length of 1.774(8) Å. Loss of NO2- from trans-[Ru(NH3)4P(OEt)3NO]3+ is pH dependent with kobs (s−1) = (k0Ka + k1[H+])/([H+] + Ka)], where k0 = 2 × 10−5 s−1, k1 = 0.40 ± 0.03 s−1, and pKa = 8.6 ± 0.3. The nitrosyl complex undergoes a one-electron reduction (E0 = 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 °C and pH 5.0).

The trans-lablilizing ligand, P(OEt)3 facilitates dissociation of NO2- from trans-[(NO)P(OEt)3(NH3)4Ru]3+ and NO from the one-electron reduced complex. This compound’s biological effect on increasing neuronal firing in hippocampal slices appears to be related to its ability to generate NO.Figure optionsDownload as PowerPoint slide