ARYLOXY COMPLEXES AND CYCLOMETALATED ARYLOXY ALKYLIDENE COMPLEXES OF TUNGSTEN(VI) - APPLICATION TO THE METATHESIS OF FUNCTIONALIZED OLEFINS

In this review article, the synthesis of aryloxy complexes of tungsten with the general formula W(OAr)(x)Cl-6-x is described together with that of aryloxy (chloro)neopentylidene-tungsten complexes. The properties of these compounds in the metathesis of non-functionalized and functionalized olefins are reviewed. The aryloxy complexes of tungsten are good air-stable precursor catalysts when combined with organotin or -lead cocatalysts. In particular, depending on the cocatalyst and substituents on the aryloxide ligands, one can achieve either linear or cross-linked polydicyclopentadienes. One can also govern the induction period for the obtention of cross-linked polydicyclopentadiene, a phenomenon compatible with the requirements of the RIM processing. The cyclometallated neopentylidene tungsten complex 1 can be synthesized by two different routes, either from the W(OAr)(2)Cl-4 (OAr = -O-2,6-C6H3Cl2 or -O-2,6-C(6)H(3)Ph(2)) precursor or from the Schrock carbyne W(CCMe(3))(Cl-3)(dme). In both cases, when OAr = O-2,6-C(6)H(3)Ph(2), a metallation occurs by cleavage of the C-H bond in one substituting phenyl group. Complex 1 is probably one of the most active and stereoselective catalysts for metathesis of cis- and trans-2-pentene (total retention of the configuration of the starting olefin). Similarly, it selectively transforms 1-methyl-norbornene to 100% cis, 100% head-tail syndiotactic poly-1-methyl-norbornene. Complex 1 is also one of the most active catalysts for metathesis of functionalized olefins: with ethyl oleate 1 converts approximatively 250 equivalents of ethyl oleate into 9-octadecene and diethyl-9-octadecenedioate at 25 degrees C. Compound 1 converts approximatively 100 equivalents of unsubstituted diallyl ether into the corresponding 2,5-dihydrofurane, and it (as well as the bicomponent catalysts) is able to realize metathesis of omega-unsaturated glucosides into the corresponding di-glucosides. It is also able to convert cyclic and acyclic double bonds with thio-ether functionalities to the corresponding polymer or cyclic products. For example, 1 converts diallyl sulphide or related compounds to the corresponding 2,5-dihydrothiophene derivatives. Similarly, phosphorus, silicon and tin diallyl derivatives can be transformed into the corresponding cyclic compound E-CH2-CH=CH-CH2, E = P, Si, Sn.