Light-Induced Metastable Linkage Isomers of Transition Metal Nitrosyls

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Abstract
Previously observed long-lived light-induced metastable states of transition metal nitrosyl complexes were identified as η2 nitrosyl and isonitrosyl linkage isomers. A novel technique combining low temperature X-ray crystallography and photochemistry was used to determine the geometry of the new species. Light-induced side-bound nitrosyl ligands were observed in complexes with the electronic configurations {MNO}6 and {MNO}10, using the nomenclature introduced by Enemark and Feltham. The isonitrosyl binding mode was observed only in the {MNO}6 complexes. The influence of the trans ligand, with respect to NO, on thermal stability of the isonitrosyls was studied in a series of complexes of Ru (II). In general, the isonitrosyl species were found to be more stable in complexes with the weak π-donor ligand in the trans position. Results of theoretical calculations based on density functional theory indicate that the new linkage isomers correspond to local minima on the electronic ground state potential energy surface.