1,1-Dithiolates metal complexes

Near infrared absorbers include cyanin compounds, pyrylium compounds, phthalocyanine compounds, and dithiol metal complexes. Antistatic agents include long chain alkyl alcohols and fatty acid esters with polyhydric alcohols. Stearyl alcohol and behenyl alcohol are the especially preferred compounds. Anti-fogging agents include sorbitan fatty acid esters and glycerin fatty acid esters. 

Quinoline-5-sulfonic acid, 8-hydroxy-7-iodo-metal complexes absorptiometry, 549 Quinolinium salts in gravimetry, 535 Quinoxaline-2,3-dithiol metal complexes liquid-liquid extraction, 547... 

Metal complexes of 1,1-dithiolates have been reviewed by Coucou-vanis (1) Eisenberg (2) presented a systematic, structural review of dithiolato chelates, and Stokolosa ct al. (3) reviewed dithiophosphate complexes in detail. Earlier reviews (4-3) covered less recent work in greater detail. Following initial work by Delepine (9), 1,1-dithiolato complexes were more intensively studied between 1930 and 1941 (10-16). There is, however, continuous interest in the synthesis, characterization, electronic structures, and bonding of these complexes. 

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. 

Over the past decade a number of new covalently bonded TTF/ferrocene adducts have been reported [77, 78]. The crystal structure of the l,l -bis(l,3-dithiole-2-ylidine)-substituted ferrocene derivative has been published [77]. In this complex, ferrocene has essentially been incorporated as a molecular spacer between the two l,3-dithole-2-ylidene rings forming a stretched TTF molecule. This adduct, and its methyl-substituted derivative, have been combined with TCNQ to form charge-transfer complexes with room temperature powder conductivities of 0.2 S cm-1. Similar diferrocenyl complexes have been prepared with bis (dithiolene) metal complexes [79, 80]. 

Several studies suggest that LA and DHLA form complexes with metals (Mn2+, Cu2+, Zn2+, Cd2+, and Fe2+/Fe3+) [215-218]. However, in detailed study of the interaction of LA and DHLA with iron ions no formation of iron LA complexes was found [217]. As vicinal dithiol, DHLA must undoubtedly form metal complexes. However, the high prooxidant activity of DHLA makes these complexes, especially with transition metals, highly unstable. Indeed, it was found that the Fe2+-DHLA complex is formed only under anerobic conditions and it is rapidly converted into Fe3+ DHLA complex, which in turn decomposed into Fe2+ and LA [217]. Because of this, the Fe3+/DHLA system may initiate the formation of hydroxyl radicals in the presence of hydrogen peroxide through the Fenton reaction. Lodge et al. [218] proposed that the formation of Cu2+ DHLA complex suppressed LDL oxidation. However, these authors also found that this complex is unstable and may be prooxidative due to the intracomplex reduction of Cu2+ ion. 

M(dmit)2 complexes (dmit = C3S52- = l,3-dithiole-2-thione-4,5-dithio-late) constitute one of the most important subclasses. The most studied metal complexes are those of group 10 (Ni, Pd, Pt), which possess a square-planar geometry see for instance the molecular structure of the monoanion [Ni(dmit)2], Figure 42.73... 

High conductivity for transition metal complexes of TTF-dithiolate ligands have long been known, due to the mixing of n-d orbitals resulting in a small HOMO-LUMO gap [80]. At present, 17 is the most reliable metal in this category (ctrt = 4 X 10 S cmT, metallic down to 0.6 K) based on its purity, temperature dependencies of resistivity and magnetic susceptibility, and de Haas-van Alphen (dHvA) oscillations [48, 75]. 

Cassoux P, Valade L, Kobayashi H, Kobayashi A, Clark RA, Underhill AE (1991) Molecular metals and superconductors derived from metal complexes of l,3-dithiol-2-thione-4, 5-dithiolate (dmit). Coord Chem Rev 110 115-160... 

New metal complexes other than Ru have also been investigated. These include Fe complexes [117,118], Os complexes [119-122], Re complexes [123], and Pt complexes [124]. A nanocrystalline 2 solar cell sensitized by a square-planar platinum(II) complex containing 4,4 -dicarboxy-2,2 -bipyridine and quin-oxaline-2,3-dithiolate ligands showed an efficiency of 2.6% (Jsc = 6.14 mA/cm2... 

Transition metal complexes of unsaturated 1,2-dithiolates (metal dithiolenes) have attracted much attention because of their interesting structural and redox properties.169 Molybdenum dithiolene complexes have featured prominently170 in these studies and have special significance following the suggestion171,172 that the molybdenum-containing cofactor of the oxomolybdoen-zymes (Section 36.6.7) incorporates a molybdenum complex of an unsymmetrically substituted alkene-1,2-dithiolate. 

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