FLASH VACUUM THERMOLYSIS - FIRST GAS-PHASE GENERATION OF UNHINDERED SILYLIDENEPHOSPHANES AND CHARACTERIZATION BY PHOTOELECTRON-SPECTROSCOPY

The flash vacuum thermolysis of cyclodisilaphosphanes, cyclotrisilapho sphanes, and a phosphasilacyclobutane, potential precursors of unhinde red silylidenephosphanes (R2Si=PR'), has been investigated by NMR as w ell as by coupling with HRMS and, particularly, photoelectron spectros copy. This last technique led us to characterize for the first time, i n the gas phase, two very reactive species of this series, the P-tert- butyl- and P-phenyl(dimethysilylidene)phosphanes (Me2Si=P-t-Bu and Me2 Si=PPh). The first ionization potentials at weaker energy are associat ed with the ejection of an electron from the pi(Si=P) bond. The ioniza tions of the lone pair on phosphorus are observed at higher energy.