Gudimetla Vittal B, Rheingold Arnold L, Payton John L, Peng Huo-Lei, Simpson M Cather, Protasiewicz John D
Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106-7708, USA.
Inorg Chem. 2006 Jun 26;45(13):4895-901. doi: 10.1021/ic0520521.
A series of phosphaalkenes, E-ArP=C(H)Ar' (Ar = 2,6-Mes2C6H3, Ar' = Ph (1a); Ar = 2,6-Mes2C6H3, Ar' = p-C6H4Br (2a); Ar = 4-Br-2,6-Mes2C6H2, Ar' = Ph (3a); Ar = 4-Br-2,6-Mes2C6H2, Ar' = p-C6H4Br (4a)) have been prepared by phospha-Wittig reactions and characterized. Exposure of these materials either to room light over an extended period of time (days) or to UV light (hours) produced equilibrium mixtures of the E and Z isomers (1b-4b) as indicated by 1H and 31P NMR spectroscopy. The structures of compounds 4a and 4b were determined by single-crystal X-ray diffraction methods. Variable-temperature (1)H NMR studies of 4b indicate hindered rotation about the P-CAr bond, with DeltaH(double dagger) = 13.8 kcal/mol and DeltaS(double dagger) = 1.3 eu. The electronic structures of E- and Z-PhP=C(H)Ph have been examined using density functional theory.
