Glyoximate complexes

Perez-Pina et al. [805] studied the use of triethanolamine and dimethyl-glyoxime complexing agents in absorptive cathodic stripping voltammetry of cobalt and nickel in seawater. Nickel and cobalt could be determined at levels down to 2 nM and 50 pM, respectively. 

Nickel Nickel dimethyl glyoxime complex extracted from water AAS 5 (ig/1 [899]... 

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). 

Rhodium(II) forms dimeric diamagnetic glyoximes, for example, Rh -(HDMG)4(Lewis base)2 (225, 226), which do not have intermolecular metal-metal interactions. The compaction conductivity of [Rh(HDMG)2py]2 (3.3 X 10-1 Q-i cm-i) (225) and the isostructural Rh2(HDMG)2(CO)2Cl2 (< 10 cm-i) (313) is consistent with the lack of metal-metal bonds between molecules. Iridium glyoxime complexes have not been reported. 

The poor solubility of dimethyl-glyoxime complexes has always restricted study of their interesting physical properties (crystalline Ni(dmgH)2is a familiar red gravimetric precipitate as well as a one-dimensional electrical conductor). We have reported the synthesis of a series of freely soluble carbocyclic bis-dioxime complexes of structural types 1 to 4. 

The stepwise solvolysis ofthe/rfl/w-[Co(dioxime)2(tu)a]+ions (dioxime = methyl-, dimethyl-, or methylpropyl-dioxime) has been studied, - and for the methyl-glyoxime complexes the rate constants and activation parameters for the two steps were resolved 10 A i = 10.0s = 23.5kcalmol S and AS = +7calK ... 

The reductions are effected in nature by ferredoxin (p. 1102). This behaviour can be reproduced surprisingly well by simpler, model compounds. Some of the best known of these are obtained by the addition of axial groups to the square-planar complexes of Co with Schiff bases, or substituted glyoximes (giving cobaloximes) as illustrated in Fig. 26.7. The reduced Co species of these, along with vitamin... 

Much of the recent literature relates to BfVbridged Co" cobaloximes based on dimethyl (89) or diphenyl glyoxime (104).110 The BfVbridged cobaloximes (e.g. 89) show greater stability to hydrolysis than analogous H-bridged species (e.g. 88). The diphenylglyoxime complexes (104) show enhanced air and hydrolytic stability... 

Bis(glyoximato)cobalt(II) complexes of the types Co(DH)2B2 and Co(DH)2B2 (DH = disubstituted glyoxime, B = base, e.g. pyridine or triphenylphosphine) reduce benzyl bromide in benzene and acetone solutions ... 

In the study of effects of ultrasound on the aqueous reactions of nickel, we found some interesting results, for example, the colloidal formation of Ni-DMG complex and degassing of NH3 during different experiments. When 25 ml of 0.001 M NiSC>4 solution was complexed with 5 ml of 1% dimethyl glyoxime (DMG) in faintly alkaline ammonia medium and sonicated for 30 minutes and compared with another set of 25 ml of complexed solution which was stirred mechanically, a colloidal solution of Ni-DMG complex was formed in sonicated condition. Particles of Ni-DMG complex did not settle even after keeping 3 1 h because of their smaller size, in sonicated solution, whereas in the unsonicated condition large particles of Ni-DMG complex settled down immediately. 

Nickel may he measured quantitatively hy several microanalytical gravimetric methods that include (l)formation of a red precipitate with dimethyl-glyoxime, (2) precipitation as a hlack sulfide with ammonium sulfide, (3) precipitating as a complex cyanide hy treating with alkali cyanide and bromine, and (4) precipitation as a yellow complex hy treating an ammoniacal solution of nickel with dicyandiamide sulfate (Grossman s reagent), followed hy the addition of potassium hydroxide. All of these methods can separate nickel from cobalt in solution. 

K[RuClj(H-dmg)2] and K[RuClj(H-dpg)2] (dmg and dpg=monoanions of dime-thyl-glyoxime and diphenylglyoxime) are made from K [Ru(H30)Cl5] and the ligands. As [complex]/PhIO/water they epoxidised cyclohexene, probably via a Ru (0)C1(H-L)3 species [640],... 

Many other nickel complexes, some of which have been shown to be planar by the methods mentioned in Section 5-3, have been found to satisfy the magnetic criterion. These include the nickel glyoximes,81... 

The complexes with unsubstituted and either alkyl- or aryl-substituted glyoximes have been prepared by the reaction of nickel(II) salts with the appropriate ligand in aqueous or ethanolic solution or an aqueous-ethanolic mixture. In most cases, the reaction is promoted by addition of ammonia as base and/or refluxing temperature. 

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... 

Conducting halogenated linear metal atom chain systems were first reported in 195095 and are now known for Ni and/or Pd complexes of glyoxime (GLY), DPG and BQD. The compounds are usually produced by treating a hot solution of the neutral complex in o-C6H4C12 with I2 and lustrous coloured crystals of the NIOS compound are obtained on cooling the solution. The limited range of compounds studied is shown in Table 3 and all have metal-over-metal stacked structures. 

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