Vanadium, tris

The reactions between TiCl., TiBr., TiCl, VCl, VCl, and VBr with a range of monodentate sulphur ligands, have been investigated. The ligands used include the aliphatic thioethers, R S, for R =Me, Et, Pr, and Bu, and tetrahydrothiophen and pentamethylenesulphide. Notable differences have been observed in the reactions of the halides of the two elements. Thus, whereas the tetrahalides of titanium form simple adducts with all ligands tried, vanadium(IV) chloride is reduced rapidly and quantitatively to the tervalent state. Furthermore, tervalent vanadium forms a series of well-defined complexes with sulphur ligands, but the complexes formed by tervalent... 

Organometallic compounds apart, oxidation states below - -2 are best represented by complexes with tris-bidentate nitrogen-donor ligands such as 2,2 -bipyridyl. Reduction by LiAlH4 in thf yields tris(bipyridyl) complexes in which the formal oxidation state of vanadium is -1-2 to —1. Magnetic moments are compatible with low-spin configurations of the metal but. 

Several vanadium (V) complexes were also studied by Aliwi [41] in 1988 as possible photoinitiators for the radical polymerization of MMA. These complexes are oxo-tris(ethoxo) vanadium (V), VO(OC2H5)3, oxo-tris-(triphenylsiloxy) vanadium (V), VO(Si(C6Hs)3)3,... 

Recently, Aiiwi and Abdullah [42] have investigated the photoinitiation of styrene by oxo-tris(dimethyl dithi-ocarbomato) vanadium (V) (VO(S2CN(CH3)2)3 using light of A = 365 nm. Spectroscopic and kinetic analyses... 

V(IV) complexes with the formula V(R2C fc)4 (R = Me, Et) were studied by Bradley et al. 11,12, 4, 5). The ethyl complex (5) is thermally unstable and air-sensitive. The thermal instability accounts for the formation of the vanadium tris(dithio-carbamate). The tetrakis(dithiocarbamato) complex is isomorphous with 4)... 

The first structurally characterized triarylzincate [Li(TMEDA)2][Zn 2,4,6-(Pr1)3G6H2 3] 59 was a byproduct of the lithiation of VC13(THF)3 with Li(2,4,6-(Pr1)3C6H2)3, in which the vanadium compound had been pre-reduced with metallic zinc.116 In the solid state, the compound consists of isolated, tetrahedrally coordinated lithium ions and trigonal-planar tris(tris(isopropyl)phenyl)zincate ions. The Zn-G bonds are equidistant (2.039(7) A), but the C-Zn-C bond angles are variable, ranging from 112.2(3)° to 125.4(3)°. 

The same N3O3 coordination sphere is exhibited by tris(picolinato)-vanadium(III) complex, rV(pic)3], the significantly distorted octahedral geometry of which is shown in Figure 7.13... 

In normal operations, however, the RCC unit routinely runs at 6-9000 ppm nickel plus vanadium on feedstocks with as high as 35-75 ppm nickel plus vanadium content. Presently several commercial residuum-type catalysts are giving good performance at these levels. Catalyst manufacturers continue to seek further improvement in performance in terms of activity, selectivity, and catalyst life, while also trying to hold down or even reduce overall cost. 

AIPO4-5 molecular sieve (BET surface area, 299 m g ) used in this study was prepared by the method of Wilson et al. [1j. VjOg/AIPO -S samples were prepared by impregnating with aqueous solutions of ammonium vanadate after removing templating agent in the AIPO -S by calcining at 530°C. The samples were dried at 110 C for 24 h then calcined in air at 550°C for 2 h. VAPO -S was prepared from gel mixture of phosphoric acid, pseudoboehmite, vanadium pentoxide, tri-propylamine and water (1.3 PrjN x AljOj PjOj 40 HjO) by crystallization at 165°C for 3 - 7 days [7. ... 

A series of 1% V2O5 catalysts was prepared by non aqueous impregnation of vanadium tri- isopropoxide oxide (final calcination in oxygen at 450/500 C) in order to investigate the influence of different oxide supports... 

The Tp hgands (i.e., tris(pyrazolyl)borates or scorpionates [13]) are close analogs to the Cp hgands (i.e., -cyclopentadienyl), and in connection with the chemistry of the Tp Cr complexes mentioned above, a recent example of O2-binding from vanadium chemistry is of interest, even though it is formally not organometalhc chemistry Reaction of the V(IV) complex... 

When Roscoe investigated them he found that vanadium is a tri- and pentavalent element of the phosphorus group. He also discovered that what Berzelius had taken for the metal was really the mononitride, VN, and that most of the vanadium compounds studied by the Swedish chemists had contained oxygen. 

We have also tried to look directly at the reduction of some organic substances such as -nitroaniline which can be reduced electrolytically to a very stable free radical, and with either vanadium(II) or chromium(II) we cannot see this free radical. 

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