MATRIX PHOTOCHEMISTRY OF CPRU(CO)2(NO2) - ISOMERIZATION, CO LOSS, AND OXYGEN-TRANSFER

Matrix isolation at 13 K combined with Fourier transform infrared spectroscopy (FTIR) has been used to study the photochemical reactions of CpRu(CO)2(NO2), Cp = eta-5-C5H5. UV photolysis of CpRu(CO)2(NO2) at relatively long wavelengths (lambda > 350 nm) results in the reversible formation of two photoproducts A and B, which are assigned as exo-CpRu(CO)2(ONO) and endo-CpRu(CO)2(ONO), respectively. The use of slightly shorter photolysis wavelengths (lambda = 314 or 280 nm) results additionally in the formation of C, which is a CO loss product. The yield of this is low, but there are indications that two such products are formed. These form no N2 adducts, indicating that they are coordinatively saturated, suggesting that further NO2- group isomerization has occurred. One of the CO loss species is thought to contain NO2- in an (N,O)-bridging form, analogous to eta-2-CO2 coordination. Photolysis at short wavelengths (lambda = 254 and 229 nm) results in the formation of CpRu(CO)(NO) and CO2, via an oxygen-transfer reaction. This type of reaction has been widely studied in the past, but relatively little mechanistic information has been gained. In this study we demonstrate that the photoreaction is not intermolecular and that A is the precursor to the oxygen transfer in this reaction.