Photolysis of (tripod)IrX3 (tripod  = 1,1,1-tris(diphenylphosphinomethyl)ethane and X = Cl, Br) yields an insoluble product. The proposed photochemical process is dissociation of an arm of the tripod ligand followed by coordination to another Ir center to give insoluble tripod-bridged structures. DFT (Density Functional Theory) calculation of the lowest energy triplet support phosphine arm dissociation. Furthermore, DFT investigation of (PNN)IrCl3 (PNN = 2-(di-t-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine) and (PNP)IrCl3 (PNP = 2,6-bis(di-t-butylphosphinomethyl)pyridine) predicts dissociation of a halide from the iridium center in the triplet excited state. However, no photochemical activity has been observed experimentally. Under photolytic conditions (PNN)IrCl3 is inactive and (PNP)IrCl3 undergoes very slow (days), likely thermal, ?-hydrogen elimination to form the iridacycle [2-[[[6-[[bis(1,1-dimethylethyl)phosphino-?P]methyl]-2-pyridinyl-?N]methyl](1,1-dimethylethyl)phosphino-?P]-2-methylpropyl-?C]dichloro iridium. Furthermore the photochemistry of [PtBr6]2- in dichloromethane was investigated. Photolysis in the presents of L resulted in heterolytic dissociation of bromide to form [PtBr5L]� complex (L = THF, DMSO and alkenes). The DMSO complex was characterized by standard 195Pt-NMR spectroscopy and single crystal X-ray diffraction.

Photochemistry of platinum and iridium complexes

246th National Meeting (2013)

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