Oximes nickel complexes

Transition metal hydroxyoxime complexes have been reviewed very recently.2507 Their use in both analytical chemistry and extraction metallurgy is well known. The square planar structure of the bis chelate complex NiL (347) with the deprotonated 2-hydroxybenzaldoxime (HL) is typical of this series of nickel complexes.2508 Their bis adducts, NiLJ, with bases such as py, substituted pyridines and cyclomethyleneimines, are six-coordinate.2509 The acyl oxime (H2L) complexes are similar to the aforementioned complexes being either square planar bis chelates Ni(HL)2 (348) or octahedral bis adducts, Ni(HL)2B2.2507 When the acyl oxime acts as a dibasic ligand L, the corresponding (NiL) complexes are insoluble and involve extensive polymerization. 

There are quite a number of organic oximes and ketones which are useful in analysis because they form colored, insoluble, coordination complexes with many metals. Cupferron, already mentioned by King, and dimethylglyoxime, whose nickel complex was established by Pfeiffer (51), are typical. 

Formaldoxime, which is commonly used to determine Mn, can also serve as a reagent for nickel since it forms a brown nickel complex (e = 1.84-10" at 473 nm) [26]. Other oxime reagents for determining Ni include 2-hydroxyacetophenone oxime [27], diacetylmonoxime... 

Holm and coworkers found that thiolates, amidates and oximates were most effective at making higher nickel oxidation states accessible (25), However, the studies noted in the previous section showed that in O2 reactions of their Ni(II) complexes, amidates and thiolates were themselves readily oxidized in a manner that precludes catalysis. Oximates have been shown to support stable nickel complexes in both the Ni(III) and Ni(IV) oxidation states (26-28), They also lack the a- and P-hydrogen atoms that are most prone to oxidative abstraction by high valent metals, thereby additionally satisfying the second design criterion. 

Nickel complexes of amino oximes (26 R = alkyl HRabo) and (27 Haboen when n = 2, Habopn when n — 3) have been investigated at various pH values by Murmann and their structures have been elucidated by X-ray and neutron diffraction techniques. The structural study of Cu(Haboen)Br has disclosed the presence of dimeric [Cu2(Haboen)2] " cations. ... 

The nickel(IV) oxime, bis(6-amino-3-methyl-4-azahexa-3-ene-2-one oxime)nickel(IV), and the nickel(III) oxime, (15-amino-3-methyl-4,7,10,13-tetraazapentadeca-3-ene-2-one oxime)nickel(III), complexes react with hydro-quinone. Proton-related equilibria for both the nickel complexes and the hydroquinone could be elucidated from the kinetic details. For reactions with the complexes and the hydroquinone could be elucidated from the kinetic details. For reactions with the Ni(III) complex there is evidence of an inner-sphere process. The [NiL(TCCat)] complex (TCCatH2 = tetrachlorocatechol L = 2,4,4-trimethyl-1,5,9-triazacyclododec-l-ene) forms a 1 1 adduct with tetrachloro-1,2-benzoquinone. Spectroscopic evidence suggests that this compound can be described formally as a quinone adduct of a Ni(I)-semiquinone moiety arising from inner-sphere ligand oxidation. The crystallographically determined structure (11) is shown below. Several copper complexes of a vareity of semiquinones also exist in solution in equilibrium with the corresponding catechol complexes. ... 

The second series of related materials was based on the (3,4-didodecyloxyphenyl)diaminodi-oxime derivative (73). Vicinal dioximes are capable of coordinating through N,N or N,0 sites of the oxime groups. Upon the complexation, the ligands fold back, and the transition metal complexes are V,V-coordinated with a square-planar structure. Both isomeric forms were selectively isolated for the nickel complexes, but only the anii-isomer for the palladium complex. The two uwti-complexes complexes exhibited a Colh phase ((73) M = Ni Cr 78 Colh H7 I M = Pd Cr 80 Colh 131 I). Most astonishing, however, was the observation of a Colh phase for the isomeric amphi-mckel complex ( , Z-isomer), between 66 °C and 145 °C. Not only was the existence of mesomorphism surprising and unexpected, but the mesophase stability also increased with respect to the anti-complex. 

The development of metal complexes, particularly those based on nickel, resulted in compounds which exhibited relatively low extinction coefficients in the near ultraviolet region and yet in many instances were found to be superior in performance to the currently available ortho-hydroxyaromatic compounds [3,5]. This finding resulted in a search for some other feasible mechanistic function. As carbonyl photolysis was considered to be an important initiation process which gives rise to both free radicals and backbone cleavage, then deactivation or quenching of the excited-state precursor should prove an effective means of photoprotection. Effective structures in this respect were tris(dibenzoylmethanato) chelates of Fe and Cr (Structure 5), nickel oxime chelates (Structure 6), and the nickel complex of Structure 7, nick-el(ii) 2,2 -thiobis(4-f-octylphenolato)- -butylamine. 

Other studies involving nickel(IV) complexes have been published. Schlemper and Murman prefer a nickel(II)-diradical description of a formal nickel(IV)-oxime complex. Panda and co-workers have examined substitution properties of the inert [Ni(dmg)3] ion and the kinetics of reduction by [FeCCN) ] . The product is [Ni(dmgH)2] and the mechanism involves rate-determining outer-sphere one-electron transfer from [Fe(CN)6] to [Ni(dmg)3] and its protonated forms with formation of a nickel(III) intermediate which subsequently is reduced in a fast step. 

Catalyst synthesis for methanol oxidation/cyclic voltammetry Nickel electrode modified by nickel dimethylgly-oxime complex NaOH solution Dimethylglyoxime ligand deposition on the mechanically pretreated nickel disc... 

In 1965, Breslow and Chipman discovered that zinc or nickel ion complexes of (E)-2-pyridinecarbaldehyde oxime (5) are remarkably active catalyst for the hydrolysis of 8-acetoxyquinoline 5-sulfonate l2). Some years later, Sigman and Jorgensen showed that the zinc ion complex of N-(2-hydroxyethyl)ethylenediamine (3) is very active in the transesterification from p-nitrophenyl picolinate (7)13). In the latter case, noteworthy is a change of the reaction mode at the aminolysis in the absence of zinc ion to the alcoholysis in the presence of zinc ion. Thus, the zinc ion in the complex greatly enhances the nucleophilic activity of the hydroxy group of 3. In search for more powerful complexes for the release of p-nitrophenol from 7, we examined the activities of the metal ion complexes of ligand 2-72 14,15). 

Hultgren, V. M. Atkinson, I. M. Beddoes, R. L. Collison, D. Garner, C. D. Helliwell, M. Lindoy, L. F. Tasker, P. A. Formation of folded complexes retaining intramolecular H-bonding in the extraction of nickel(II) by phenolic oxime and aliphatic diamine ligands. Chem. Commun. 2001, 573-574. 

Examples of template procedures in which the ring-closing condensation involves reaction at a centre other than a donor atom have been documented. In an early synthesis of this type, the reaction of bis-(dimethylglyoximato)nickel(n) (62) with boron trifluoride was demonstrated to yield the corresponding complex of the N4-donor macrocycle (63) (Schrauzer, 1962 Umland Thierig, 1962). In this reaction the proton of each bridging oxime linkage is replaced by a BF2+ moiety. X-ray... 

Huynk et al. [218] also used differential pulse cathodic stripping voltammetry for the determination of cobalt and nickel in seawater by dimetbylgly-oxime complexation. They report detection hmits of 0.002 pg/1 for cobalt and 0.005 xg/l for nickel. 

Barlot and Medard (Refs 2 3) describe an analytical procedure for nickel nitrohydrazinate decompose the complex cautiously (to avoid an explosion) by means of coned H2S04 and determine Ni content by means of dimethylgly-oxime. Determine the hydrazine content by means of an iodate soln... 

Oxime-type ligands (9) and (10) have been found to stabilize authentic Ni111 and NiIV complexes, respectively, when the nickel(II) complexes are oxidized by K2S2Og in alkaline solution. 

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