An Infrared and Solid-State 31P NMR Study of the Adsorption of P(CH3)Cl2 and P(CH3)Cl2/PCl3 Mixtures on Silica

Abstract

The adsorption of PMeCl 2 and of mixtures of PMeCl 2 and PCl 3 on silica have been studied using infrared spectroscopy and 31 P solid-state NMR. PMeCl 2 gives a single phosphorus containing product (A) as a result of a reaction with surface SiOH groups, SiOP=O(H,Me) ; HCl and surface SiCl are byproducts of the reaction. A reaction mechanism has been devised. The rate of reaction is slow and high pressures of reactant (10 to 80 Torr) are required. Commercially available PMeC1 2 samples are usually contaminated with PCl 3 at the 2 to 5 mol % level. At the pressures needed to effect chemisorption of PMeCl 2 , the contaminant PCl 3 has a significant influence on the course of the reaction. The major feature with such low levels of PCl 3 as an impurity is the conversion of A to a second species B, (SiO) 2 P=O(H), with minor amounts of SiOP=O(H,OH). A plausible sequence of reaction steps leading to this product has been elaborated, but the chemistry is complex.