title: Photochemical E-Z isomerization of meta-terphenyl-protected phosphaalkenes and structural characterizations.
abstract: 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.
authors.affiliation: Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106-7708, USA.
authors.forename: Vittal B
authors.initials: VB
authors.lastname: Gudimetla
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold
authors.forename: John L
authors.initials: JL
authors.lastname: Payton
authors.forename: Huo-Lei
authors.initials: HL
authors.lastname: Peng
authors.forename: M Cather
authors.initials: MC
authors.lastname: Simpson
authors.forename: John D
authors.initials: JD
authors.lastname: Protasiewicz
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007536:Isomerism; D008958:Models, Molecular; D015394:Molecular Structure; D010758:Phosphorus / Q000737:chemistry*; D010777:Photochemistry; D013057:Spectrum Analysis; D013730:Terphenyl Compounds / Q000737:chemistry*
chemical_list: D000475:Alkenes; D013730:Terphenyl Compounds; D010758:Phosphorus