2,3,5-Metallotriazoles: Amphoteric Mesoionic Chelates from Nitrosoguanidines.

Soluble nitrosoguanidine- and -methylnitrosoguanidine-based metallotriazole complexes of ruthenium(II) monocarbonyls have been prepared and characterized. Both nitrosoguanidines prove to be strong chelates with the formally π-accepting nitroso nitrogen binding to carbon monoxide and a π-donating amide to the CO. The resulting ensemble consists of ruthenium examples of 1-metallo-2,3,5-triazoles.

Nitric Oxide Catalysis of Diazene E/Z Isomerization.

Nitric oxide is an efficient catalyst for the cis-trans (E/Z) isomerization of diazenes. We compare the effect of room temperature solutions bearing low concentrations of nitric oxide, nitrogen dioxide, or oxygen on the rate of cis-trans isomerization, CTI, of the alkene bond in stilbene and on the azo double bond in azobenzene, as well as in four azo derivatives as measured by UV-vis spectroscopy. These rate enhancements can be as large as 3 orders of magnitude for azobenzene in solution.

E/Z oxime isomerism in PhC(NOH)CN.

The reaction of nitric oxide with benzyl cyanide in the presence of potassium methoxide at low temperature gave the dipotassium salt of a bis-diazeniumdiolate 2 in excellent yield. Two new stereospecific syntheses of E or Z 2-(hydroxyimino)-2-phenylacetonitrile from 2 have been found. The thermodynamics of the E/Z isomerization has been investigated spectroscopically in solution, in the solid state by differential scanning calorimetry (DSC), and theoretically in the gas phase.