Photochemistry of some alkoxycarbonylplatinum(II) complexes

Abstract

Alkoxycarbonylplatinum(II) complexes trans-Pt(CO 2CH 2R)Cl(PPh 3) 2, where R = H, Me and Ph, were synthesized in two steps and were characterized by infrared and ultraviolet absorption, proton and phosphorus-31 nuclear magnetic resonance, and mass spectral techniques, and by elemental analysis. Irradiation of the complexes in the solid state or in fluid solution with 254 nm light causes a steady decrease in the intensities of the infrared absorptions in the 1650 and 1070 cm −1 regions, which is interpreted as signifying labilization of the alkoxycarbonyl ligand. In dichloromethane solution, irradiation causes dissociation of the alkoxycarbonyl ligand, which then decomposes into carbon monoxide and an alkoxide ion. The carbon monoxide is thought to re-coordinate to afford the stable product trans-PtCl(CO)(PPh 3) 2 +. In the presence of oxygen, triphenylphosphine which dissociates from the metal, is photooxidized to form triphenylphosphine oxide in a parallel photoreaction. Disappearance quantum yields for the alkoxycarbonyl complexes are quite small, Φ ∼ 10 −4−10 −3 mol/einstein, and follow the trend H > Me > Ph.