The crystal and molecular structure of triphenylphosphoranylidenethioketen

Abstract

The structure of triphenylphosphoranylidenethioketen, Ph₃PCCS, has been determined by single-crystal X-ray diffraction methods. The crystals are monoclinic, space-group P2₁/c with a= 8·722, b= 10·819, c= 17·664 Å, β= 98° 8′. The structure was solved by direct methods. The R factor is 0·072 for 1388 planes whose intensities were measured on a linear diffractometer. The hydrogen atoms were located from a difference synthesis and their co-ordinates were refined. The bond lengths in the cumulene chain are short and the chain is bent to an angle of 168° at the carbon atom attached to phosphorus. It is suggested that the d orbitals of the sulphur atom act as an electron sink thereby reducing the d_π–π_π interaction postulated to account for the shape of the Ph₃PCCO molecule.