Vanadium propene complexes

The asymmetric oxidation of sulphides to chiral sulphoxides with t-butyl hydroperoxide is catalysed very effectively by a titanium complex, produced in situ from a titanium alkoxide and a chiral binaphthol, with enantioselectivities up to 96%342. The Sharpless oxidation of aryl cinnamyl selenides 217 gave a chiral 1-phenyl-2-propen-l-ol (218) via an asymmetric [2,3] sigmatropic shift (Scheme 4)343. For other titanium-catalysed epoxidations, see Section V.D.l on vanadium catalysis. 

Red-ox type catalysts are mostly used in oxidation or related types of reactions. For instance, vanadium catalysts containing ions of different valence state are used in the oxidation of benzene to maleic anhydride. Bismuth molybdate catalyst can be used both for the oxidation or ammoxidation of propene. Anchored metal-complex catalysts combine the advantage of both homogeneous and heterogeneous catalysts, however in these catalysts the molecular character of the active sites is maintained. In the last generation of this type of catalysts, heteropolyacids are fixed first to the support and in the second step different metal-complexes are anchored to the heteropolyacid. In this way highly active and stable catalyst have been prepared for different reactions. ... 

No allyl complexes of titanium or vanadium have yet been reported. We have prepared allyl-bis(cyclopentadienyl)-titanium [I] by various methods, of which the following is the most convenient one. Red bis(cyclopentadienyl)-titanium dichloride [II] in tetrahydrofuran solution was reduced to the green monochloride by means of zinc powder (1). When the reduction was completed, one equivalent of allylmagnesium chloride was added to the solution, the col r of which changed to violet. The reaction mixture was evaporated in vacuo, and the residue exuacted with pentane. When the violet pentane solution was concentrated to saturation and cooled to -80 , purple crystals of [I] precipitated. After two recrystallizations from pentane pure [I] was obtained in 36%yield. Analysis found 21,8%Ti 70,89%C 7,01%H calc, for (CgHg TifC Hg) 21,86%Ti 71,24%C 6,89%H. Melting point . 118 C (decomp.). Reaction of [I] with octanol gave propene in 80% of the theoretical yield. 

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