Oxime ligand

A comprehensive study of the complex interfacial processes involved in the solvent extraction of cupric ion by oxime ligands represents one of the most detailed and successful studies carried out with the RDC [37,38]. Recently, the technique was also used to study the transfer of tetrabutylammonium cations [43] and the kinetics of partitioning of compounds between octanol and water [44]. In the latter study, Fisk and coworkers investigated the rates of partitioning of 23 compounds from octanol to an aqueous phase. The RDC arrangement used most frequently in this work is of the o/o/w type. So according to Eq. (15), and can be calculated from the gradient and intercept of... 

The inability of amines to deprotonate upon coordination, and thus to compensate the charge of the MOs+ core, can be overcome by combination with other types of donors-including N-donor groups-in the ligand, as has already been discussed above for oxocyclam. A prominent example is provided by technetium complexes of tetradentate amine oxime ligands. 

Co-extraction of Mo and Cu is potentially a problem with certain feed solutions,14 and again selectivities are very dependent on the nature of modifiers present in formulated reagents.142 The Mo species extracted have not been fully characterized, but may include a neutral dioxo complex, [Mo02L2], which can be assumed to have an N2022 donor set similar to that in the Cu11 complex, and molybdate complexes solvated by neutral phenolic oxime ligands such as [M0O4112 LI l].143 Formation of solvated forms of molybdic acid is supported by evidence that extraction is favorable at very low pH values and that the complexes are readily stripped by aqueous ammonia to produce ammonium molybdate,144... 

A somewhat different liquid/liquid system is found in the solvent extraction of copper. We have studied the system using heptane/water. These solvents are so immiscible that, as shown in Fig. 15, there is probably no extensive interphase region but a more sharply defined interface. We have shown that for the oxime ligand, Acorga P50 [4], written as HL, the mechanism of the reaction is as in Scheme 2 (Albery et al., 1984 Albery and Choudhery, 1988). 

Triangle of Cu atoms with triply bridging OH and SO groups. Oximate ligands chelate to one Cu and bridge to another yy... 

The cadmium complexes were also investigated potentiometrically. Using this method, the complexes of cadmium with asparagine [128], taurine [129], A -(6-ami-no-3-methyl-5-nitroso-4-oxo-3,4-dihydro-pyrimidin-2-yl)glycine [130], succinate and malate [131], acetate at different temperatures [132], pyridine oxime ligands [133], 2-hydroxypropene-l,3-diamine-Af,Af,Af, A -tetraacetic acid [134] were studied. The stoichiometry and stability constants of these complexes were determined. 

Complexes involving oxime ligands display a variety of reactivity modes that lead to unusual types of chemical compounds. As far as the oxime chemistry of platinum is concerned, these complexes are involved in facile deprotonation of the OH group with formation of oximato complexes, reduction of Pt(IV) species, Pt(II)-assisted reactions with coordinated allene," alkylation by ketones, oxime-ligand-supported stabilization of Pt(III)—Pt(III) compounds, oxidative conversion into rare nitrosoalkane platinum(II) species, and coupling with organocyanamides. ... 

PtCl (CH3)2C=NOH 3]CT in aqueous HCl the propanone oxime ligand from solid [PtCl (CH3)2C=NOH 3]Cl. 

Table 54 Selected Nickel(II) Complexes with Oxime Ligands...

Other nickel(II) complexes with oxime ligands are reported in refs. 1035-1038 and 1049-1056. 

A review article covering the synthesis, characterization and redox properties of imine-amine-oxime ligands has recently appeared.3030... 

The most common hydrox y oxime ligands are salicylaldoximes, complexes of which with copper(II), nickel(II) amd palladium(II), cobalt(II), iron(II), iron(HI) and manganese(II) have been investigated extensively including crystal and molecular structures13 of the first three. In an interesting study,71 the reactions of cobalt bis chelates of this type have been studied with aluminum isopropoxide. 

Most reactions in two-phase systems occur in a liquid phase following the transfer of a reactant across an interface these are commonly known as extractive reactions. If the transfer is facilitated by a catalyst, it is known as phase-transfer catalysis [2]. Unusually, reactions may actually occur at an interface (interfacial reactions) examples include solvolysis and nucleophilic substitution reactions of aliphatic acid chlorides [3 ] and the extraction of cupric ion from aqueous solution using oxime ligands insoluble in water [4], see Section 5.2.1.3(ii). 

VS = vacant site HL = acid form of oxime ligand HL = H++ L ... 

Fig. 5.11 Mechanism for the extraction of cupric ion as a complex with an oxime ligand.

For some metal complexes of o-quinone mono-oximes, an analysis of the charge distribution within the o-quinone mono-oxime ligands through crystallographic data is reported in Ref. 176. It is known [177] that intermediate structures between the form 940a and 940b can exist within these compounds (5.24) ... 

The discovery that the neutral, lipophilic 99mTcO complex 36, prepared by the reduction of Tc04 in the presence of the tetradentate propyleneamine oxime ligand, is able to cross the blood-brain barrier in both directions has stimulated much work in this area (19). 

---