Vanadium complexes pyridine

Shaver, A., J.B. Ng, D.A. Hall, B. Soo Lum, and B.I. Posner. 1993. Insulin-mimetic peroxo vanadium complexes Preparation and structure of potassium oxodiper-oxo(pyridine-2-carboxylato)vanadate(V), K2[V0(02)2(C5H4NC00)]-2H20, and potassium oxodiperoxo(3-hydroxypyridine-2-carboxylato)vanadate(V), K2[V0(02)2 (0HC4H3NC00)]3H20, and their reactions with cysteine. Inorg. Chem. 32 3109-3113. 

NCjHi], Ethanamine, 1,1-dimethyl-, tungsten complex, 27 301 NC,Hj, Pyridine, vanadium complex,... 

Dinuclear vanadium complexes with bridging diazenido(2—). The ligands are 2,6-bis(l-iminoethyl)pyridine (53)h h mesityl(l—) (54),h l 2-dimethylaminophenyl(l—) and pyridine (55),h l tolane, trimethylphosphine and dimethylamino-Cp(l—) (56),and benzamidinate(l —) (57).P 1 The complexes 54 and 55, containing (r-aUcyls, produce ammonia and hydrazine on protonation. 

CjHjN, Pyridine, osmium complex, 28 234 vanadium complex, 27 308... 

The role of steric influences on the formation of various vanadium amidinate complexes in the oxidation states +2 and +3 has been studied in detail. The reaction of VCl2(TMEDA)2 and of VCl3(THF)3 with 2 equivalents of formamidinate salts afforded dimeric V2[HC(NCy)2l4 (cf. Section IV.E) with a very short V-V multiple bond and [ [HC(NCy)2 V(/i-Cl)l2 which is also dimeric (Scheme 107). The formation of V2[HC(NCy)2l4 was shown to proceed through the intermediate monomeric [HC(NCy)2l2V(TMEDA), which was isolated and fully characterized. The dinuclear structure was reversibly cleaved by treatment with pyridine forming the monomeric [HC(NCy)2l2V(py)2. ... 

The kinetics of the reaction between [V(salen)] in pyridine and oxygen have been determined and interpreted in terms of the formation of a [V(salen)] -oxygen adduct. This reinforces the view that vanadium(iii) complexes can act as oxygen carriers. The oxidation of the 1,2-cyclohexanediaminetetra-acetic acid complex of V " has been studied in solutions of pH 6—12. ... 

Table 4 Complexes of Vanadium(II) with Pyridine and Picolines...

Tetrahedral blue-black compounds [VL4](SCN)3 (L = en or Me4en) were prepared188 from K3[V(NCS)6] and their electronic spectra are comparable to other tetrahedral vanadium(III) complexes with substituted pyridines (see Section 33.4.3.2). 

Early publications on [VO(/3-diketonato)2] have been reviewed.355 More recently, complexes with benzoyl m-nitroacetanilide, benzoyl acetanilide545 and l,l -(l,3-phenylene)-bis(butane-1,3-dione546 have been synthesized. Other [VO(/S-dik)2] adducts have been isolated, for example [VO(acac)2] adducts with a series of pyridine N-oxides547 and several pyridine carboxamides, 48 and [VO(bzac)2] adducts with pyridine, methylamine, isoquinoline and 4-picoline.549 Equilibrium constants of 1 1 and 2 1 adducts of pyrazine with [VO(tfacac)2] have been determined (equation 38).550 In the 2 1 complex, the pyrazine bridge between two equatorial sites of adjacent vanadium atoms promotes a weak exchange interaction. The nitroxide radical 2,2,6,6-tetramethylpiperidinyl N-oxide also forms an adduct with [VO(hfacac)2] in which there is a strong interaction between the electrons on the metal and nitroxide.551... 

The reaction of vanadium salts (VC14, V202(S04)2, V(OCOMe)4, VO(acac)2) and porphyrin gives a complex which, after work-up, is isolated as a very stable oxovanadium(IV) species, VO(Por) (for VO(OEP), V—O = 1.620(2)A, V—= 2.102A, A(N4) = 0.543 A).17 -21 In the presence of a large excess of nitrogenous ligand such as pyridine and piperidine, it forms a six-coordinate complex with a small equilibrium constant (K = 10 I-10 21 M-1).18 The effect of / substituents on the association constant (Kx) is expressed by the Hammett equation (equation 4). 

Thus, the hydrodesulfurization process is a very complex sequence of reactions due, no doubt, to the complexity of the feedstock. Furthermore, the fact that feedstocks usually contain nitrogen and oxygen compounds (in addition to metal compounds) increases the complexity of the reactions that occur as part of the hydrodesulfurization process. The nitrogen compounds that may be present are typified by pyridine derivatives, quinoline derivatives, carbazole derivatives, indole derivatives, and pyrrole derivatives. Oxygen may be present as phenols (Ar-OH, where Ar is an aromatic moiety) and carboxylic acids (-C02H). The most common metals to occur in petroleum are nickel (Ni) and vanadium (V) (Reynolds, 1997). 

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