COMPARATIVE TIME-RESOLVED IR AND UV SPECTROSCOPIC STUDY OF MONOPHOSPHINE AND DIPHOSPHINE PLATINUM(II) AZIDO COMPLEXES

Solutions of cis-diazido-bis(triphenylphosphine)platinum(II) (cis-[Pt- II(PPh3)(2)(N-3)(2)]) and zido-1,3-bis(diphenylphosphino)propaneplatin um(II) ([Pt-II(dppp)(N-3)(2)]) were Studied by time-resolved LR and UV -Vis absorption spectroscopy after excitation by 308 nm laser pulses. Photoinduced electron transfer reduces [Pt-II(dppp)(N-3)(2)] to [Pt-I( dppp)N-3] (IR maximum 2045 cm(-1)) which delays in several solvents at room temperature (half-life similar to 0.3 ms) via intramolecular ele ctron transfer to coordinatively unsaturated [Pt-0(dppp)]. With cis-[P t-II(PPh3)(2)(N-3)(2)], photoisomerization to trans-[Pt-II(PPh3)(2)(N- 3)(2)] (IR maximum 2050 cm(-1)) and photoreduction compete as primary photoreactions, whereas the decay of [Pt-I(PPh3)(2)N-3] is analogous t o that of [Pt-I(dppp)N-3]. Oxygen scavenges [Pt-I(PPh3)(2)N-3] and [Pt -I(dppp)N-3] with rate constants k(ox) = (1.3-2.8) x 10(7) M-1 s(-1). The photochemistry of cis-[Pt-II(PPh3)(2)(N-3)(2)] and [Pt-II(dppp)(N- 3)(2)] in the absence and presence of O-2 is discussed. (C) 1998 Elsev ier Science S.A.