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Trivinylphosphine and trivinylphosphine chalcogenides: stereochemical trends of 31P1H spin–spin coupling constants

A combined theoretical and experimental study of the stereochemical behavior of 31P1H spin–spin coupling constants has been performed in the series of trivinylphosphine and related trivinylphosphine oxide, sulfide and selenide. Theoretical energy‐based conformational analysis of the title compounds performed at the MP2/6‐311G** level reveals that each of the four compounds of this series exists in the equilibrium mixture of five true‐minimum conformers, namely s‐cis‐s‐cis‐s‐cis, s‐cis‐s‐cis‐gauche, syn‐s‐cis‐gauche‐gauche, anti‐s‐cis‐gauche‐gauche and gauche‐gauche‐gauche, which were taken into account in the conformational averaging of 31P1H spin–spin couplings calculated at the second‐order polarization propagator approach/aug‐cc‐pVTZ‐J level of theory. All 31P1H spin–spin coupling constants involving phosphorus and either of the vinyl protons are found to demonstrate a marked stereochemical dependences with respect to the geometry of the coupling pathway and internal rotation of the vinyl group around the PC bond which is of major importance in the stereochemical studies of the unsaturated phosphines and phosphine chalcogenides. Copyright © 2010 John Wiley & Sons, Ltd.