Vanadium mixed complexes

When mixed with Et2AlCl, the vanadium(III) complex (87) polymerizes propylene at —78 °C in a living manner.241,242 Poor initiator efficiency ( 4%) and low activities were improved by employing complex (88) activities of lOOgmmol h bar 1 were reported and the polymerization of propylene remained living (Mw/Mn= 1.2-1.4) up to 40 °C.243 244 The synthesis of end-functionalized PP and PP copolymers has also been achieved using these initiators. 

The ESR spectra of a series of triarylboron anion radicals have been determined and show selective line-broadening effects (95). The radical anions of diborane, generated in an argon matrix at 77 K by irradiation with a-rays have been studied by ESR (121). The vanadium-aluminum complex obtained on mixing dichlorobis(7r-cyclopentadienyl)vanadium with ethylaluminum dichloride, a system that catalyzes the polymerization of ethylene to give a polymer with good characteristics, has been characterized by ESR and ultraviolet studies (44). 

Vanadium(V) complexes of ligands with mixed thiolate-hydroxylate functionalities have been structurally characterized both in solution and in the solid state (90).457 Oxidation of this complex resulted in a vanadium(V) 72, 72—disulfenate complex with an unprecedented coordination mode (91).457 Complexes with 2-thio-3-benzoylhydantoin have also been reported.458 In addition, a recent solution study of vanadate with dithiothreitol (DTT) showed that the study of these complexes is quite tractable even in aqueous solution.459 The first hydrazide vanadium complex with S-donor ligands was structurally characterized (92).460... 

Oxovanadium(IV) and -(V) complexes containing a mixed ON or ONS coordination sphere are abundant and have been reviewed. ] A selection is provided by the mononuclear complexes 33-40 in Figure 2.32. Complexes 33-38 contain vanadium in the oxidation state +V and complexes 39 and 40 in the oxidation state +IV. Vanadium(V) complexes can be based on the VOj (33,36) or the moiety (34, 38), commonly... 

New scorpionate oxovanadium complexes Syntheses and crystal structures of a series of vanadium(V) complexes with mixed ligands of poly(pyrazolyl)borates and substituted acetylacetonates i i n)9y N O R R = Me, Et 82... 

The tert-huty hydroperoxide is then mixed with a catalyst solution to react with propylene. Some TBHP decomposes to TBA during this process step. The catalyst is typically an organometaHic that is soluble in the reaction mixture. The metal can be tungsten, vanadium, or molybdenum. Molybdenum complexes with naphthenates or carboxylates provide the best combination of selectivity and reactivity. Catalyst concentrations of 200—500 ppm in a solution of 55% TBHP and 45% TBA are typically used when water content is less than 0.5 wt %. The homogeneous metal catalyst must be removed from solution for disposal or recycle (137,157). Although heterogeneous catalysts can be employed, elution of some of the metal, particularly molybdenum, from the support surface occurs (158). References 159 and 160 discuss possible mechanisms for the catalytic epoxidation of olefins by hydroperoxides. 

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... 

In another type of mixed ligand oxo-vanadium Schiff base complexes chloro-oxo-bis[N(4-bromophe-nyl) salicylideneiminato] vanadium (V) chelate, VOL2CI, and methoxo-oxobis[N(4-bromophenyl)sali-cylideneimine vanadium (V) chelate, VOL2OCH3 Aiiwi and Salih [43] show that these complexes are active pho-... 

Two separate publications (125, 126) described the synthesis of a number of carbonyl complexes of vanadium. The mononuclear species V(CO) , n = 1-6, have all been identified by using CO matrix-dilution experiments and mixed CO- CO isotope experiments while main-... 

Ethylene-propylene-diene terpolymers (EPDM), with their inherent complexity in structural parameters, owe their tensile properties to specific structures dictated by polymerization conditions, among which the controlling factor is the catalyst used in preparing the polymers. However, no detailed studies on correlation between tensile properties and EPDM structures have been published (l,2). An unusual vulcanization behavior of EPDMs prepared with vanadium carboxylates (typified by Vr g, carboxylate of mixed acids of Ccj-Cq) has been recently reported Q). This EPDM attains target tensile properties in 18 and 12 minutes at vulcanization temperatures of 150 and l60°C respectively, while for EPDMs prepared with V0Cl -Et3Al2Cl or V(acac) -Et2AlCl, about 50 and 0 minutes are usually required at the respective vulcanization temperatures, all with dieyclopentadiene (DCPD) as the third monomer and with the same vulcanization recipe. This observation prompted us to inquire into the inherent structural factors... 

The eight-coordinate vanadium complex V(S2CMe)4 contains both dodecahedral and square prismatic eight-coordinate molecules in the same crystal.322 Of particular interest is the chain-like, mixed valence platinum complex [Pt2(S2CMe)4( i-I)]A, which displays unusual electrical properties metallic conduction between 300 and 340 K and semiconducting properties below 300 K,323 whereas the analogous nickel complex, [Ni2(S2CMe)4(p-I)]x is a semiconductor.324... 

The stepwise stability constants for V complexes with glutamic, aspartic, W -ethylenediaminedisuccinic, and W -ethylenediamine-bis-(a-glutaric acid) have been reported.The 1 1 oxovanadium(iv) complex of 5-nitrosalicylic acid has been characterized = 710 nm), and the mixed species formed between vanadium(iv) with protocatechuic acid (H3L ) or gallic acid (H L ) and 4-aminoantipyrine (aant) have been identified spectroscopically as the 1 1 1 and 1 2 2 HL (HL ) aant complexes. The species present in solutions of and tartaric acid below pH 2 have been identified as [VO-... 

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