The reaction of L2(H2O)Rh2+ (L2 = meso-hexamethylcyclam) with nitrous acid in acidic aqueous solutions follows mixed second order kinetics and generates the intermediate L2(H2O)Rh(HNO2)2+.  L2(H2O)Rh(HNO2)2+ is formally a rhodium(II) complex of HNO2, and is analogous to the early iron and copper intermediates in the reduction of nitrite by nitrite reductase and deoxyhemoglobin.  The lifetime of the intermediate in the presence of excess L2(H2O)Rh2+ is about one minute; in contrast, its lifetime in the presence of excess nitrite is on the millisecond timescale.  The latter reaction proceeds by nitrite-catalyzed disproportionation to yield L2(H2O)RhNO2+ and L2Rh(NO2)2+; the mechanism of this reaction will be discussed in the context of the disproportionation of L2(H2O)Rh2+ in the presence of excess chloride.  In addition, we have independently synthesized L2Rh(NO2)2+ by the reaction of L2(H2O)RhH2+ with excess HNO2 at room temperature.  X-ray crystallography reveals L2Rh(NO2)2+ to be a trans bis(nitro) complex with structural parameters consistent with those in similar bis(nitro) complexes of Rh.

Formation and disproportionation of a rhodium(II) complex of nitrous acid

244th National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.