Transition metal complexes dithiocarbamates

Metal complexes of ligands containing a sulfur donor in conjunction with nitrogen, oxygen or a second sulfur have been reviewed in the past [11-13]. For example, reviews of the coordination compounds of dithiophosphates [14], dithiocarbamates [15, 16], dithiolates [17], dithiodiketonates [18], and xanthates [16] have appeared. The analytical aspects [19] and the spectral and structural information of transition metal complexes of thiosemicarbazones [20, 21] have been reviewed previously. Recent developments in the structural nature of metal complexes of 2-heterocyclic thiosemicarbazones and S-alkyldithiocarbazates, depicted below, are correlated to their biological activities. 

Keywords Controlled Polymerization Living Radical Polymerization Iniferter Chain-End Structure Molecular Weight Control Block Copolymer Dithiocarbamate Disulfide Nitroxide Transition Metal Complex... 

Ammonium dithiocarbamates can be prepared through reaction (11). With HC1 or H2S04 at lower temperatures the free acids are formed. Only one transition metal complex (37) is known, with a pseudo-octahedral coordination of Ni four sulfur atoms of the dithiocarbamate in the equatorial plane and two pyridine solvent molecules at the apical positions. Sulfides can be eliminated from monosubstituted dithiocarbamates to give isothiocyanates.53... 

The ligand field strength of the ligands is between that of the dithiocarbamates and water.49 IR studies show characteristic bands near 1250, 1100, 1020 and 550 cm-1.93 The contribution of the resonance form (85) in transition metal complexes is less than that of the analogous structure in the dithiocarbamates.60 The electron density on the metal is not very high, which accounts for the fact that abnormal high oxidation states are exceptional and a strong interaction of bases with the square planar nickel (and some other metal) xanthates is found.94... 

The metal complexes of diethyl dithiophosphate were first investigated in 1931,134 when it was shown that the transition metal complexes [M((EtO)2PS2 ] (n = 2 or 3) were similar to those of xanthates and dialkyl dithiocarbamates, containing a four-membered XSMS (X = C or P) ring. A... 

On the other hand several transition metal complexes,e.g. dithiocarbamate and 2-hydroxylacetophenone oxime partixipate in the photostabilization of polymers (3,70-76). 

From these early studies, dithiocarbamates and their transition metal complexes soon found a host of applications. For example, as a result of their insoluble nature they are widely used in inorganic analysis (3,4). They can also be used to separate different metal ions by high-performance liquid chromatography (HPLC) (5-10) and capillary gas chromatography (GC) (11, 12), and find use as rubber vulcanization accelerators (13), fungicides (14), and pesticides (15). Concomitant with the development of these applications came a burgeoning interest in their general transition metal chemistry and the characteristics and properties of the complexes formed. 

Dithiocarbamates can also be prepared from diamines. For example, as early as 1872, Hofmann (97) reported the reaction of carbon disulfide with 1,2-diaminoethane. Later in the 1960s, addition of 2 equiv of sodium hydroxide and carbon disulfide to 1,2-diaminoethane was shown to afford the bis(dithiocarba-mate) compound in an exothermic reaction (98-102) 1,6-diaminohexane behaving in a similar manner (98). A wide range of polymeric transition metal complexes have been prepared using these salts (98). All are insoluble in water and common organic solvents, and some examples have been developed as fungicides (14, 31). 

Fabretti et al. (103) showed that a similar transformation can be effected with piperazine and again a wide range of polymeric transition metal complexes have been prepared, as have related derivatives of the dithiocarbamate derived from homopiperazine (Fig. 12) (104). 

The dithiocarbamate ligand contains three NMR nuclei and thus diamagnetic transition metal complexes especially can be characterized by and... 

Coordinated transition metal redox-active macrocycles, 39 108-124 ammonium cation, 39 128-133 crown ether and bis crown ether ligands containing bipyridyl transition metal recognition sites, 39 111 crown ether dithiocarbamate and dithiolene complexes, 39 123-124 metalloporphyrin crown ether compounds, 39 108-109... 

Mdssbauer spectra of bonding and structure in, 15 184-187 reactions with diborane, 16 213 stabilization of, 5 17, 18-19 cyanates, 17 297, 298 cyanide complexes of, 8 143-144 cyclometallated bipyridine complex, 30 76 diazene complexes, 27 231-232 dinitrogen complexes, 27 215, 217 diphosphine complexes of, 14 208-219 dithiocarbamates, 23 253-254 -1,2-dithiolene complexes, 22 323-327 hydrogen bonding, 22 327 halide complexes with phosphine, etc., 6 25 hexaflouride, structure, 27 104 hydride complexes, 20 235, 248-281, see also Transition metal-hydride complexes... 

In many complexes, mixed oxidation states for the transition metals are found. Complex (41) is a diamagnetic compound with the actual composition (42).68 Copper dithiocarbamates are synthesized not only with copper in the oxidation states I, II or III but also with the metal in mixed oxidation states III and I (43, 44, 45), II and I (46, 47) and even III and I [48, 49).56 Complex (50), which has two isomeric structures a and / , has Ru either in a trapped oxidation state II,in or in a delocalized oxidation state of 2.5. The /J-isomer is the most stable.69 Slow, controlled potential electrochemical oxidation of (51) yields (52), in which the metal has a trapped oxidation state II,HI.70... 

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>. 

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