Vanadium-Ligand Complexes

Aliwi and coworkers have investigated many vanadium (V) chelate complexes as photoinitiators for vinyl polymerization [36-43]. The mixed ligand complex of chloro-oxo-bis(2,4-pentanedione) vanadium (V). VO(a-cac)2 Cl is used as the photoinitiator of polymerization... 

The unsubstituted complexes [Mo(R2dtc>4] and [W(R2dtc)4] have been prepared by methods described earlier for synthesis of the vanadium-group complexes. They are 8-coordinate, with four bidentate dithiocar-bamate ligands (157). 

Koopman s theorem is found to be valid only in the case of the vanadium (dA) complex 9. The amount of orbital reorganization is increasing considerably in the series 9-14-15-16. It is also found that strong metal-ligand interaction combined with low symmetry leads to extensive delocalization of the outer valence MO s especially in the cylobutadiene complex 16, only two orbitals with >80% metal character are found for which the convenient term essential 3d metal orbital would be justified. 

L — maltolate the coordination environment of the vanadium in K[V02(malt)2] H2O is approximately octahedral, the two 0x0 ligands being in cis positions. [K(H20)e] units link adjacent vanadium(V) complex anions to give a chain structure 166). The main products of aerobic oxidation of [V O(dmpp)2l in aqueous solution are [V02(dmpp)] and [VOo(dmpp)2]. High pH favors these V products, whereas at low pH V species predominate 171). Vanadium(V) also forms a VO(OR)(malt)2 series, readily prepared from ammonium vanadate, maltol, and the appropriate alcohol in a water-alcohol-dichloromethane medium 172), and 3-hydroxy-4-pyridinonate analogues V0(0R)L2 on oxidation of their oxovanadium(IV) precursors in solution in the appropriate alcohol ROH 168). 

Vanadium(v) Complexes.—0-Donor Ligands. A large number of metal... 

The kinetics and stoicheiometry of the oxidation of oxovanadium(iv) by peroxide have been studied and continuous-flow e.s.r. techniques used to investigate the intermediate which appears to be a vanadium(v) complex with a paramagnetic ligand, formulated as either [OVOO,aq] or [V02(H02). aq]. Six- and seven-co-ordinate vanadium(v) has been identified by. Y-ray crystallography in the peroxo-complexes (NH4)[V0(02)2-Nh ]36o (NH4)4[0 V0(02)2 2] respcctively. and seven-co-ordination... 

Table 5. Selected bond length and angles for [VO(dipic)(Me2NO)(H2O)].0.5H2O and other known seven-coordinate dipicolinato-vanadium(V) complexes with ternary peroxo or hydroxylamido ligands.

Only three general reviews on vanadium(IV) complexes have been given 355-357 others deal with subnormal magnetic complexes,358 ESR spin probes,354 vanadium(IV) halides,6 optical spectra and phosphorus donor ligands,359 vanadium porphyrins128 and annual reviews for 1979, 1980 and 1981. 

Table 11 Some Vanadium(IV) Complexes Containing N-heterocyclic Ligands...

From equation (30), whether a tris chelate is formed depends on the donor ability of the ligand. Several vanadium(IV) complexes with 1,2-dihydroxybenzenes formed from solutions of the ligand, VOSO4 and thallium(I) acetate.498 The compounds are of two types (I) T12[V(RC6H302)3] (R = H, 3-Me, 4-Me, 3-MeO) and (II) T12[V0(RC6H302)2] (R = CHO). 

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