13C, 1H and 31P dynamic NMR studies of tetraalkyldiphosphanes: Barrier to internal rotation about the P?P Bond in tetraisopropyldiphosphane |
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Authors: | J P Albrand A Cogne C Taieb |
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Abstract: | The 1H, 31P and 13C NMR spectra of tetramethyldiphosphane (1), tetraethyldiphosphane (2) and tetraisopropyldiphosphane (3) have been studied in the temperature range 30 to ?150°C and at magnetic induction up to 5.87 T. In the range ?100 to ?135 °C, the 1H and 13C spectra of 3 show important changes which can be attributed to freezing the interconversion between two equivalent non-trans conformations. The line shape analysis of the 13C signals leads to ΔG≠ = 29.4 kJ mol?1 at ?113 °C for the dynamic process involved. The spin coupling parameters 1J(PP) and N(PC) = 1J(PC) + 2J(PC) observed for 1 in the temperature range 30 to ?120 °C show variations which could be due to a preference for the trans conformation in this diphosphane. |
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