Group 5 Metal Complexes Vanadium

In this work ion-exchange and gel-permeation chromatography coupled with membrane filtration, photochemical oxidation of organic metal complexes and CL detection were applied to the study of the speciation of cobalt, copper, iron and vanadium in water from the Dnieper reservoirs and some rivers of Ukraine. The role of various groups of organic matters in the complexation of metals is established. 

III. Complexes with Scandium, Titanium, and Vanadium Group Metals. 182... 

Compared with metal enolates, there have been very few reports on the direct structural analysis and theoretical studies of ynolates. An X-ray crystal structure of a vanadium complex of lithium ynolate with a porphyrinogen ligand (56) is reported. This metal complex was incidentally formed from VCl3(THF)3 with tetralithium salt of the octaethyl-porphyrinogen ligand. In this complex, the lithium cation seems to interact with the 7T-electrons of the ynolate. The four atoms of the ynolate group in 56 are not collinear due to a partial sp character of the group in this complex. 

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. 

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