Comparative time-resolved IR and UV spectroscopic study of monophosphine and diphosphine platinum(II) azido complexes

Abstract

Solution of cis-diazido-bis(triphenylphosphine)platinum(II) cis-[Pt 11(PPh 3) 2(N 3) 2] and diazido-1,3-(diphenylphosphino)-propaneplatinum(II) ([Pt 11(dppp)(N 3) 2] were studies by time-resolved IR and UV-Vis absorption spectroscopy after excitation by 308 nm laser pulses. Photoinduced electron transfer reduces [Pt 11(dppp)(N 3) 2] to [Pt 1(dppp)N 3] (IR maximum 2045 cm −1) which decays in several solvents at room temperature (half-life ∼ 0.3 ms) via intramolecular electron transfer to coordinatively unsaturated [Pt 0(dppp)]. With cis-[Pt II(PPh 3) 2(N 3) 2]. photoisomerization to rans-[Pt II(PPh 3) 2(N 3) 2] (IR maximum 2050 cm −) and photoreduction compete as primary photoreactions, whereas the decay of [Pt I(PPh 3) 2N 3] is analogous to that of [Pt I(PPh 3) 2(N 3) 2]. Oxygen scavenges [Pt I(PPh 3) 2N 3] and [Pt I(dppp)N 3] with rate constant k 0=(1.3–2.8) × 10 7M −1. The photochemistry of cis-[Pt II(PPh 3) 2] and [Pt II(dppp)(N 3) 2] in the absence adn presence of O 2 is dicussed.