Copper complexes dithiocarbamates

For the spectrophotometric method, the evolved carbon disulfide is reacted with copper acetate and diethylamine to form a yellow copper complex which can be measured at 435 nm." The recoveries range between 70 and 90%. Reproducibility of this method was improved by reducing the time and the mode of sample pretreatment. Since all alkylenebis(dithiocarbamates) decompose to carbon disulfide by acid degradation, the above analytical methods are not selective. The result is the measured total residues of all alkylenebis(dithiocarbamates) related products. However, this method is recommended as standard method S15 for alkylenebis(dithiocarbamates) by the German Research Association. ... 

Although transesterification and transamidation reactions of simple carbonyl ligands are usually associated with the involvement of a co-ordinated nucleophile, there are some well-documented processes which unambiguously involve attack by an external nucleophile upon a co-ordinated electrophile. Dithiocarbamate complexes contain a chelated. S, 5"-bonded dithioamide ligand and undergo facile transamination reactions upon treatment of the copper complexes with amines (Fig. 3-22). 

Similarly, nickel(ll) and copper(ll) transition metal dithiocarbamate ion-pair receptors 21, containing amide-and crown ether-recognition sites, bind alkali metal cations and various anions. The sandwich K+ complex of the nickel(ll) receptor cooperatively enhanced the binding of acetate anion, while the copper(ll) receptor electrochemi-cally can sense anions and cations via perturbation of the copper(n)/copper(m) dithiocarbamate redox couple <2002JSU89>. 

Many free-radical scavengers (including dithiols and dithiocarbamates) have potential therapeutic usefulness as radioprotective agents. Copper complexes are known to be scavenging agents for the superoxide radical, which is believed to play a role in the induction of radiation damage. The toxic effects of superoxide are believed to lie in its ability to reduce metal ions, for example Cu(II) to Cu(I),... 

Analogous steric effects of bulky substituents at the nitrogen atom have been also reported for copper(II) dithiocarbamate complexes [71]. 

Willis (W12) has recently summarized the principles and applications of this method. A short note appeared recently regarding the use of atomic absorption spectrometry for serum and urine copper analysis (B15). The sensitivity of this method for copper is rather less than for such other biologically important trace metals as magnesium, zinc, and sodium. The sensitivity can be improved by extracting the copper as dithiocarbamate or pyrollidinedithiocarbamate complex (A7) into methyl isobutyl ketone. While this method is less sensitive than some others, it is nevertheless very specific and the apparatus is only moderately expensive. 

The choice of accelerator also has an effect on the quality of adhesion between cord and rubber. The accelerator should not form a stable copper complex which dissolves in the rubber. This would be quite corrosive to the brass plating. In this respect, benzothiazoles and their sulfenamides are much better than dithiocarbamates. DCBS is a particularly good sulfenamide accelerator for rubber-to-brass adhesion. 

Plasma copper exists in two forms 5% is loosely bound to albumin, and the remainder exists in the form of copper complexes. Copper forms ionic bonds with either an imidazole or a carboxyl group of the amino acid of albumin. Loosely bound copper reacts readily with dithiocarbamate, and therefore has been called the directly reacting copper. It is generally assumed but not established that the albumin that binds this copper plays an important role in transporting copper in the blood. 

Thus the results from the studies of copper bis-dithiocarbamate complex reactions with tin(22) antimony(22) and copper(23) halides show formation of copper(II) mixed-ligand complexes. 

The acid digest is taken up in water and suitable complexing agents, which prevent interference by other metals are added. Copper is then extracted from this solution with carbon tetrachloride, as the coloured copper diethyl dithiocarbamate complex, and the colour is evaluated spectrophotometrically at 432 nm. 

Table 1 Solubility Parameters of Dithiocarbamate Ligands and Solubilities of Their Copper Complexes in Supercritical CO2 at 60 C and 230 atm...

Copper complexes of bis(2,2 -dipyridyl)dithiocarbamate have been prepared upon insertion of carbon disulfide into the copper-nitrogen bonds of the corresponding 2,2 -dipyridylamine (dpa) complexes (195, 196). Kumar and Tuck (195) initially noted this behavior for [Cu(dpa)] , [Cu(dpa)2], and [Cu(dpa)(dppe)l [dppe = l,2-bis(diphenylphosphino)ethane], but characterization was made only on the basis of the presence of characteristic v(C—S) and v(C—N) bands in their IR spectra. Later, this was confirmed by the X-ray crystal structure of [Cu(S2Cdpa)2], formed upon slow evaporation of a carbon disulfide solution of [Cu(dpa)2] (Eq. 21) (196). The transformation is actually quite complex as in the dpa complex, metal coordination is through the nitrogen atoms of the pyridyl rings (197), and thus a rearrangement to the amide form must occur prior to carbon disulfide insertion. 

An exciting development in dithiocarbamate chemistry is the synthesis by Beer and co-workers (325,1489) of a range of supramolecular complexes containing nickel(II), zinc(II), and copper(II) bis(dithiocarbamate) centers. These include the preparation of nano-sized resorcarene-based polymetallic assemblies, copper(II) dithiocarbamate macrocycles (62,326,1469,1470), crown-ether derivatives (1471), cryptands (492), and catenanes (544). Details of this work are given in this section and also within the copper and zinc sections (Section IV.H.l and IV.I.l). 

Dithiocarbamates stabilize copper in the +1, +2, and +3 oxidation states, with copper(II) bis(dithiocarbamate) complexes, first reported by Delepine (2) being most common. Later, Cambi and Coriselli (1662) detailed the synthesis of a range of these and also copper(I) dithiocarbamate complexes, and in the 1960s copper(III) complexes were prepared (1663). Over the past 20 years, some significant new developments have been made and a wide range of applications has been established. 

A number of other synthetic routes have also been developed toward copper bis(dithiocarbamate) complexes. Two groups have prepared the bis(2,2 -dipyr-idyl)dithiocarbamate complex 447 (Fig. 221) upon insertion of carbon disulfide... 

Closely related are vanadium-copper complexes [VCu4(p -S>4(S2CN C4HgO)4 (SPh) ] n = 1-3) (Fig. 236), in which copper centers are linked by sulfido bridges to vanadium, and each copper carries either a dithiocarbamate or thiolate ligand (700,1747,1748). Vanadium-51 NMR studies suggest that in solution the different complexes are in equilibrium with one another. 

Dithiocarbamate complexes of copper have been sythesized at a high rate. Reports of new complexes include the morpholine-4- (44), thio-morpholine, AT-methylpiperazine-4-, and piperidine- (291) dithiocarba-mates. Novel, polymeric complexes of the type Cu(pipdtc)2 (CuBr) in = 4, or 6) and Cu(pipdtc)2 (CuCl)4 have been prepared by reactions of[Cu(pipdtc)2] with the respective copper halide in CHCla-EtOH (418). The crystal structures of the polymers are known to consist of sheets of individual [Cu(pipdtc)2] molecules linked to polymeric CuBr chains via Cu-S bonds. A series of copper(I) dtc complexes have been the subject of a Cu and Cu NQR-spectral study (440). 

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