Photochemical E-Z isomerization of meta-terphenyl-protected phosphaalkenes and structural characterizations.
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.
Gudimetla
Vittal B
VB
Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106-7708, USA.
Rheingold
Arnold L
AL
Payton
John L
JL
Peng
Huo-Lei
HL
Simpson
M Cather
MC
Protasiewicz
John D
JD
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*
D000475:Alkenes; D013730:Terphenyl Compounds; D010758:Phosphorus