Transition metals with dimethyl sulfoxide

Complexes of 3d transition metals with adenine (Ad) and/or the mono-deprotonated anion (Ad-) or adenosine (Ado) were prepared by refluxing a mixture of Ad or Ado with the appropriate hydrate metal perchlorate dissolved in triethylorthoformate and ethanol. Both the syntheses 3 and characterization , have been described previously. Hydrated metal perchlorates, adenine, and adenosine used in electrochemical experiments were used as received from Aldrich. All electrochemical experiments were performed in dimethyl sulfoxide (Me2S0) (Aldrich) containing 0.1 M tetra-butylammonium perchlorate (TBAP) (Eastman Kodak). Me2S0 was purified by fractional crystallization using a method similar to that described for purification of pyridine s. s recrystallized and dried in vacuo... 

This review is intended as an account of the coordination chemistry of both dimethyl sulfoxide and the higher sulfoxides, with particular reference to the mode of bonding and the extent to which this affects the chemistry of transition-metal sulfoxide complexes. No attempt has been made to provide an exhaustive listing of all known sulfoxide complexes, many of which contain coordinated sulfoxide moieties only coincidentally to their other important functions. 

It has recently been shown that alkyl sulfoxides are good solvents for transition metal halides, and many adducts can be isolated 42, 84, 167, 227, 231). Nickel perchlorate takes up six dimethyl sulfoxide ligands, but the chloride apparently only three. It has been shown from the reflectance spectrum and from the high magnetic moment 42) that this compound should be formulated as [Ni(DMSO)6][NiCl4], in which the anion is tetrahedral. Infrared spectra 43, 127) show that the dimethyl sulfoxide coordination is through oxygen. Similar compounds are found with tetrahydro-thiophenoxide 84) ... 

The coordination chemistry of sulfoxides with transition metals is a much-studied topic.87 Academic interest has often centred on their ambidentate donor ability, while dimethyl sulfoxide (DMSO) is of intrinsic importance as one of the most effective aprotic solvents known. Higher sulfoxides have found application in the extraction of metals during refining processes and some potential in the separation of platinum group metals has been noted.88... 

Diphenyl sulfoxide and dimethyl sulfoxide are oxidized electrochemically to the coiresponding sulfones in acetonitrile and 1 M H2SO4, respectively. The product yields are enhanced the presence of transition metal salts or oxides of W, V, Mo or Se. In some cases sulfonic acid salts are formed with C—S cleavage. Sulfoxides react with oxygen under photochemical conditions to give sulfones in good yields. ... 

The oxidation of OH by [Fe(CN)6] in solution has been examined. Application of an electrical potential drives the reaction electrochemically, rather than merely generating a local concentration of OH at the anode, as has been suggested previously, to produce both O and [Fe(CN)6] in the vicinity of the same electrode. With high [OH ] or [Fe(CN)6] /[Fe(CN)6] ratio, the reaction proceeds spontaneously with a second-order rate constant of 2.2 x 10 M s at 25 °C. Under anaerobic conditions, iron(III) porphyrin complexes in dimethyl sulfoxide solution are reduced to the iron(II) state by addition of hydroxide ion or alkoxide ions. Excess hydroxide ion serves to generate the hydroxoiron(II) complex. The oxidation of hydroxide and phenoxide ions in acetonitrile has been characterized electrochemically " in the presence of transition metal complexes [Mn(II)L] [M = Fe,Mn,Co,Ni L = (OPPh2)4,(bipy)3] and metalloporphyrins, M(por) [M = Mn(III), Fe(III), Co(II) por = 5,10,15,20-tetraphenylpor-phinato(2-), 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphinato(2-)]. Shifts to less positive potentials for OH and PhO are suggested to be due to the stabilization of the oxy radical products (OH and PhO ) via a covalent bond. Oxidation is facilitated by an ECE mechanism when OH is in excess. 

Poraij-Koshits MA (1978) Structural effects of mutual influence of ligands in transition- and non-transition-metal complexes. Koordinatsionnaya Khimiya 4 842-866 (in Russian) Hartley FR (1973) The cis- and trans-effects of ligands. Chem SocRev 2 163-179 Russell DR, Mazid MA, Tucker PA (1980) Crystal structures of hydrido-tris(triethyl-phosphine)platinum(II), fluoro-tris(triethylphosphine)platinum(lD, and chloro-tris(trieth-ylphosphine)platinum(II) salts. J Chem Soc Dalton Trans 1737-1742 Blau R, Espenson J (1986) Correlations of platinum-195-phosphorus-31 coupling constants with platinum-hgand and platinum-platinum bond lengths. Inotg Chem 25 878-880 Belsky VK, Konovalov 1, Kukushkin VYu (1991) Structure of cis-dichloro-(dimethyl-sulfoxide)-(pyridine)platinum(II). Acta Cryst C47 292-294... 

A new class of substituted ionic polyacetylenes was synthesized by metathesis polymerization with transition metal-containing catalysts [77]. The monomers used were dihexyldipropargylammonium salts with bromide and tosylate as anions. It was found that MoClj-based catalytic systems were very effective for the cyclopolymerization of ionic monomers. The resulting dark red polymers exhibited good solubility in polar organic solvents such as methanol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), THE, and CHCI3, which indicates their ionic nature. The structure of the polymers was confirmed by IR, UV-visible, and H and NMR spectroscopy. Doping the polymers with I, resulted in a substantial increase of conductivity (10 S/cm) compared with the undoped state (10" S/cm). 

Frontal polymerization works with a wide variety of systems and has been demonstrated with neat liquid monomers such as methacrylic acid, (d, 8-10) n-butyl acrylate (10), styrene, methyl methacrylate, and triethylene glycol dimethacrylate (77). Fronts can also be performed with solid monomers such as acrylamide (with initiator) (72) or transition metal nitrate acrylamide complexes (without initiator) (75). Pojman et al. demonstrated frontal polymerization of acrylamide, methacrylic acid and acrylic acid, each in dimethyl sulfoxide or dimethyl formamide (14). Frontal curing of epoxy resins has been demonstrated with aliphatic curing agents (75). 

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