Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The interactions of tungsten chlorides and oxychlorides with methyl 10-undecenoate, methyl palmitate and methyl acetate, respectively, have been investigated by UV-VIS, IR and EPR spectroscopic methods. The primary complex formed by coordination of the carbonyl group to WCl₆ is converted successively to an analogical, very stable complex WOCl₄.ester under the simultaneous formation of acyl chloride and methyl chloride. In the case of methyl undecenoate, the coordination reaction is accompanied by a partial reduction of WCl₆ to WCl₅. The latter reacts with the ester in excess to give a complex characterized by a broad EPR single line at g = 1.767 (ΔH = 7.8 mT). At higher ester-to-tungsten molar ratios, this complex undergoes deeper reduction to products containing tungsten in a lower oxidation state, and competitively, a parallel oxygen abstraction reaction yielding WOCl₃, acyl chloride and methyl chloride. The participation of these reactions in the formation of active WCl₆-based catalysts for methathesis of unsaturated esters is discussed.