RESUMEN
Theoretical energy-based conformational analysis of bis(2-phenethyl)vinylphosphine and related phosphine oxide, sulfide and selenide synthesized from available secondary phosphine chalcogenides and vinyl sulfoxides is performed at the MP2/6-311G** level to study stereochemical behavior of their (31)P-(1)H spin-spin coupling constants measured experimentally and calculated at different levels of theory. All four title compounds are shown to exist in the equilibrium mixture of two conformers: major planar s-cis and minor orthogonal ones, while (31)P-(1) H spin-spin coupling constants under study are found to demonstrate marked stereochemical dependences with respect to the geometry of the coupling pathways, and to the internal rotation of the vinyl group around the P(X)-C bonds (X = LP, O, S and Se), opening a new guide in the conformational studies of unsaturated phosphines and phosphine chalcogenides.
Asunto(s)
Calcógenos/química , Fosfinas/química , Compuestos de Vinilo/análisis , Simulación por Computador , Espectroscopía de Resonancia Magnética , Modelos Químicos , Conformación Molecular , Óxidos/síntesis química , Óxidos/química , Fosfinas/análisis , Isótopos de Fósforo , Protones , Estándares de Referencia , Compuestos de Selenio/síntesis química , Compuestos de Selenio/química , Estereoisomerismo , Sulfuros/síntesis química , Sulfuros/químicaRESUMEN
Theoretical energy-based conformational analysis of divinyl selenide performed at the MP2/6-311G** level is substantiated by the second-order polarization propagator approach (SOPPA) calculations and experimental measurements of its (77)Se-(1)H spin-spin coupling constants, demonstrating marked stereochemical behavior in respect of the internal rotation of both vinyl groups around the Se-C bonds. Based on these data, divinyl selenide is shown to exist in an equilibrium mixture of three nonplanar conformers: one the preferred syn-s-cis-s-trans and two minor anti-s-trans-s-trans and syn-s-trans-s-trans forms.
Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Espectroscopía de Resonancia Magnética/normas , Compuestos de Organoselenio/química , Selenio/química , Simulación por Computador , Isótopos , Modelos Químicos , Conformación Molecular , Estructura Molecular , Compuestos de Organoselenio/síntesis química , Protones , Estándares de Referencia , Sensibilidad y Especificidad , EstereoisomerismoRESUMEN
One-bond carbon-carbon coupling constants were calculated in a series of nine aliphatic and alicyclic oximes at the SOPPA (second-order polarization propagator approach) level in good agreement with the available experimental data, and several unknown couplings were predicted with high reliability. The experimental difference between J(C,C) of the corresponding carbon-carbon bonds in cis and trans orientations to the nitrogen lone pair is very well reproduced at the SOPPA level, and this provides an additional tool in the configurational assignment at the C=N bond in oximes and related systems.