The solution conformation and rotational dynamics of tetramesityldiphosphane studied by 2-D NMRspectroscopy

Abstract

Detailed proton and ¹³C dynamic NMR and 2-D EXSY studies of tetramesityldiphosphane at a field of 11.8 T over the temperature range 193–313 K showed that rotations about the P–P bond and two types of P–C_ipso bond are associated with three different barriers. This supports a gauche conformation of this molecule in solution at low temperature rather than trans as found in the solid state, and is consistent with the pattern of coupling constants observed in the low temperature proton and ¹³C spectra. It can be attributed to favoured electron lone pair/lone pair interactions allied to a propeller twist of the mesityl groups which minimises their effective steric requirements.