Structure of triphenylphosphoranylideneketen

Abstract

A three-dimensional X-ray diffraction analysis of the structure of triphenylphosphoranylideneketen (C₆H₅)₃PCCO, has been completed. The crystals are monoclinic, space group P2₁/n, with a= 14·527, b= 10·299, c= 10·794 Å, β= 94° 10′. The structure was solved by direct methods. All fifteen hydrogen atoms were located from a difference synthesis. The final R factor for 2106 reflexions collected with a Hilger and Watts diffractometer is 9·2%. The bond lengths in the cumulene chain are remarkably short, and the chain is bent to an angle of 145·5° at the carbon atom nearest the phosphorus. A d_π–ππ type of interaction is postulated to account for the molecular geometry.