Oxime complexes

The interfacial transfer kinetics were then investigated by perturbing the equilibrium, through the depletion of Cu + in the aqueous phase, by reduction to Cu at an UME located in close proximity to the aqueous-organic interface. This process promoted the transfer of Cu into the aqueous phase, via the transport and decomplexation of the cupric ion-oxime complex, resulting in an enhanced steady-state current at the UME. Approach curve measurements of i/i oo) vs. d allowed the kinetics of the transfer process to be determined unambiguously [9,18]. 

The structures of the oxime complex Co(NO)(dmg)2 (84) and its diphenylglyoxime analog exhibit strongly bent Co—NO groups, which are easily oxidized to the corresponding nitro compound.353 A mechanistic study of NO transfer from Co(NO)(dmg)2 to hemoglobin established that the reaction involves NO association with the protein subsequent to dissociation of NO from the Co complex.354 This mechanism is also consistent with the observation of nitrato complexes in reactions... 

Although oxime complexes of Co share many of the physical properties of their imine relatives, the presense of an ionizable OH group attached to the coordinated N=C group leads to these ligands binding in their anionic forms. For this reason, the trivalent oxidation state is preferred in the Co coordination chemistry of oximes. 

Alkyl Co oxime complexes have been used as chain transfer catalysts in free radical polymerizations.866,867 Regioselective hydronitrosation of styrene (with NO in DMF) to PhCMe=NOH is catalyzed by Co(dmg)2(py)Cl in 83% yield.868,869 Catalytic amounts of the trivalent Co(dmg2tn)I2 (192) (X = I) generate alkyl radicals from their corresponding bromides under mild reaction conditions, allowing the selective preparation of either saturated or unsaturated radical cyclization products.870... 

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. 

Starting from the Ni mrao-formyloctaethylporphyrin oxime complex, the meso-cyanooctaethylporphyrin N-oxide complex has been synthesized for the first time. The double addition of the nitrile oxide to 2,5-norbornadiene afford a porphyrin dimer, whose structure has been established by X-ray diffraction analysis (485). The 1,3-dipolar cycloaddition reaction of w< .so-tetraarylporphyrins with 2,6-dichlorobenzonitrile oxide yields isoxazoline-fused chlorins and stereoiso-metric bacteriochlorins. The crystal structure of one of bacteriochlorins has been characterized by X-ray diffraction (486, 487). 

The 36d-LAH complex was applied to the reduction of ketone oximes and their O-tetrahydropyranyl and O-methyl derivatives to optically active amines (69). Results for a variety of phenyl alkyl and dialkyl ketones are shown in Table 4. The predominant amines formed all were of the S absolute configuration with optical purities up to 56%. The oxime hydroxy group presumably reacts with the less hindered H2 in the 36d-LAH complex (cf. Scheme 6) to form an oxime complex (45), which probably undergoes infermolecular hydride transfert of H2 from a second molecule of the 36d-LAH complex (Scheme 8). Asymmetric reduction with the ethanol-modified 36d-LAH reagent gave amines of R con-... 

Interest is mounting in this state, promoted once again by its possible implication in biological systems. Galactose oxidase, for example, is a copper enzyme which catalyses the oxidation of galactose to the corresponding aldehyde. The tervalent oxidation state may be prepared from Cu(II) by chemical, anodic and radical oxidation. Cu(III) complexes of peptides and macrocycles have been most studied, particularly from a mechanistic viewpoint. The oxidation of I" by Cu(III)-deprotonated peptide complexes and by imine-oxime complexes have a similar rate law... 

It is supposed that hydrogen bonds between halogen atoms of the superacid and the a-hydrogens of the oxime in the Lewis acid-oxime complex can play a role in the hydride transfer either by inter- or by intra-molecular processes. 

C8H7CI2NO2 3 5 -Dichloro-2 -hydroxy-acetophenone oxime Complexing agent Extraction-photomehic Gravimetric Photomehic Be, Cd, Co, Mn, Ni, U, V, Zn Co, V Pd Mn, U 3... 

C11H9N02 2-Hydroxy- 1-naphdialdehyde oxime Complexing agent Gravimetric Extraction Extraction-photometric Ce V Mn Ni, U 3, 38, 39... 

CiiHuNjOjS 4-(2 -Thiazolylazo) resacetophenone oxime Complexing agent Photometric Cu, Ni, Os, Pd, V Th, U 40-42... 

C14H21JN3U3N 1 - Pheny Ipropanone-1 - pentylsulfonylhydrazone-2- oxime Complexing agent Cd, Co, Cu, Ni, Pb 59... 

C8H7NO3 2-Oxo-4 -hydroxyphenyl- acetaldehyde oxime Complexing agent Extraction-photometric Co, Ni, Pd Pd 81, 82... 

Nonsteroidal antiinflammatory drugs, interaction with lithium, 36 66 No-phonon transition, 35 324 Norbomadiene complexes with cobalt, 12 286 with copper, 12 328, 330, 331 with gold, 12 348, 349 with group VIB metals, 12 231 with group VnB metals, 12 241 with iron, 12 265 with palladium, 12 314 with platinum, 12 319 with rhodium, 12 300-302 with ruthenium, 12 278, 279 with silver, 12 340-342, 344, 346 Norbomylsiloxane, 42 226, 228 Notch receptor proteins, 46 473, 475 h (N)" oxime complexes, osmium, 37 260 h (N,0) oxime complexes, osmium, 37 260 (NPr ljiFeCfrdto),], magnetization versus temperature, 43 230... 

To be consistent, the same conclusion should be drawn for the dimethyl-oxime complexes. The difficulty here is to answer the question as to why other flat, uncharged, molecules do not stack in a similar fashion. It is believed that in fact they would do so were it not for factors such as mutual repulsion of u-electrons, as in condensed hydrocarbons (214). An examination of the bond lengths shown in Fig. 10 indicates that in the dimethyl-glyoxime complexes the ir-bonding is not nearly so extensive as commonly imagined. Similarly, it is known that aromatic donor-acceptor complexes, e.g, quinhydrone, stack in a fashion very similar to the dimethylglyoximc complexes (166a), and also show abnormal dichroism (182). 

Replacement of the hydrogen bonds in oxime complexes with boron bridges leads to macrocyclic complexes such as those from dimethyl glyoxime (equation 59).201,202 This kinetic template technique has been used for the encapsulation of metals inside cage ligands.203 204... 

Bora-substituted aza macrocycles are formed by reaction of oxime complexes with boron compounds, e.g. (32) and (33) are formed with boron trifluoride. 

Using a quadridentate ligand derived from 1,3-propanediamine and 2,3-butanedione the cobalt-oxime complex (61) was prepared, and again in presence of the chiral base quinine (60) this was used to hydrogenate benzil according to equation (54) in an optical yield of 79%.277 These cobalt systems permitted only low turnover numbers to be achieved. 

Complex 49 was converted to the oxime complex 52. Reaction of 52 with organocuprate, followed by treatment with AC2O and CO, afforded the interesting but rather unstable [(1,2,3,4- /)-1 -0V-acctoxy-A-rnethoxyarnino)-5-c < /o-acyl-1.3-cyclohexadiene] complex 55 via 53 and 54 [15]. 

Fig. 75 Catalytic cyclopropanation using a cobalt camphor quinone oximate complex...

Costa G., Tavagnacco C., Mahajan R. Electrocatalytic dioxygen reduction in the presents of cobalt and rhodium-oximes complexes. Bulletin of electrochemistry 1998 14(2) 78-85. 

The four variations of this technique are to be found in Table 14.2. The schemes of operation are shown in Fig. 14.6. Important applications for trace metals are the use of anodic stripping voltammetry (ASV) to determine trace quantities of copper, cadmium, lead and zinc, and adsorptive stripping voltammetry (AdSV) of trace quantities of nickel and cobalt—pre-concentration by adsorption accumulation of the oxime complexes followed by reduction to the metal is employed, as reoxidation of these metals in ASV is kinetically slow and does not lead to well-defined stripping peaks. 

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