Vanadium complexes butadiene

Valinomycin metal complexes, 969 Vanadium complexes acetylacetone exchange reactions, 380 1,4-diaza-l,3-butadiene, 209 dioxygen mononuclear, 321 hydrazido(2-), 148 hydroxamic adds, 506 phthalocyanines, 865 polypyrazolylborates, 248 porphyrins, 824 dioxygen adducts, 325... 

Scheme 43. The Fischer-type see Fischer-type Carbene Complexes) vanadium complexes are prepared by treatment of (butadiene)hafhocene (81) or (butadiene)zirconocene with CpV(CO)4 (Scheme 44). The equilibrium mixture reacts with cyclopentanone to give the adduct complex (82). - ...

Stereoselective oxycarborative addition is also achieved in cycloaddition and cyclooligomeriza-tion reactions. Thus, hetero-Diels-Alder reactions of dienes and aldehydes are not only catalyzed by main group Lewis acids, but also by transition metal complexes 10°. Tris[3-(heptafluoropropyl-hydroxymethylene)-( + )-camphorato]europium [( + )-Eu(hfc)3] and similar vanadium complexes have been used as the chiral catalyst in [4 + 2] cycloadditions of various achiral and chiral dienes to aldehydes63 67-101. With achiral silyloxydienes only moderate asymmetric inductions are observed, however, with chirally modified dienes, high double diastereoselectivities are achieved. Thus, the reaction of benzaldehyde with 3-terf-butyldimethylsilyloxy-l-(/-8-phenvl-menthoxy)-l.3-butadiene (1) gives (2/ .6/ )-4-wf-bntyldimethylsilyloxy-5,6-dihydro-6-phenyl-2-[(17 ,3/ ,45 )-8-phenylmenthoxy]-2f/-pyran (2) in 95% yield with a diasteieoselectivity of 25 1 ss. After crystallization and hydrolysis with trifluoroacetic acid, optically pure (2/ )-2,3-di-hydro-2-phenyl-4-(4//)-pyranone (3) is obtained in 87% yield. 

Bradley, S. Camm, K. D. Furtado, S. J. Gott, A. L. McGowan, P. C. Podesta, T. J. Thomton-Pett, M. Synthesis and structure of amino-functionahzed cyclopentadienyl vanadium complexes and evaluation of their butadiene polymerization behavior. Organometallics 2002, 21, 3443-3453. 

The vapor-phase oxidation (VPO) of butadiene with air at 200—500°C produces maleic anhydride [108-31-6]. Catalysts used are based on vanadium and molybdenum oxides (89,90). Alternatively, when using a catalyst containing Al, Mo, and Ti, butadiene undergoes a complex series of condensations and oxidations to form anthraquinone at 250°C (91). 

Allylvanadium complexes (see Allyl Complexes) are synthesized by allylation with Grignard reagents as shown in Scheme 25. Another synthetic route lies in the allylation of a vanadium anionic species with allylic chloride. Codimerization of vanadium-coordinated diphenylacetylene (tolane) and 1,3-butadiene affords the allyl complex (49) (Scheme 26). ... 

Of the group VB elements, tt complexes have been reported only for vanadium. The complexes (diolefin)V(CO)2(C6H5) obtained by UV irradiation of V(CO)4(C5H5) with butadiene, 2,3-dimethylbutadiene, and 1,3-cyclohexadiene have been reviewed earlier (219, 268). 

FIGURE 17.6 A bis(imino)pyridyl vanadium(III) complex, 2,6-[(2,6-/-Pr2C6N3)N=C(Me)]2 (C5H3N) VCl3] (6), active for the trans-1,4 polymerization of butadiene. (From Colamarco, E. MiUone, S. Cuomo, C. Grassi, A. Macromol. Rapid Commun. 2004, 25, 450-454. With permission.)... 

Reaction of the diene complexes Cp2M(butadiene) (M = Zr, Hf) with CpV(CO)4 leads to the vanadium carbene complex 23. In the case of M = Hf, complex 23 is in equililnium widi the carbene 24. These complexes react with various ketones to form nine-membeied mctallaoxy vanadium carbenes.2W... 

In the butadiene complexes of vanadium, chromium, molybdenum, tungsten and manganese (Table 7) the butadiene has replaced two carbonyl groups and presumably bonds to these two co-ordination positions of the metal. 

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