(Alkylidyne)tungsten Complexes Anchored to a Planar Tetraoxo Surface: Exhaustive Alkylation of a (Calixarene)tungsten Complex

摘要

The metal -alkylidyne group has had an extraordinary impact in organic synthesis and mainly in catalysis. A variety of metal fragments have been used, and a significant preference has emerged for the Group VI metals bearing alkoxo groups as ancillaryligands, because of their reactivity and their use as catalysts. In this context much attention has been devoted to coordination environments that can mimic an oxo surface. In order to synthesize model compounds containing the metal-alkylidyne group anchored to an oxo-complex, we function-alized a metal -calix[4]arene complex, starting with the [cis-Cl_2W(cal)] (1, cal = calix[4]arene). During these investigations we observed the isomerization of 1 to the [trans-CUW(cal)] (2). for which a selective synthesis is now available. This kind of isomerization is assisted by Lewis acids (WCl_6 excess, AlCl_3). Compound 2 has been identified both in solution (by NMR spectroscopy) and in the solid state (by X-ray analysis).