Photochemical processes for dithiocarbamate metal complexes. Photochemistry of NiII(n-Bu2NCS2)2 complex in CCl4

Laser flash photolysis was used to study the nature and reactions of intermediates in photochemistry of the dithiocarbamate NiII(S2CN(n-Bu)2)2 complex in CCl4 (ligand (n-Bu)2NCS2−dtc−). It is shown that a nanosecond laser pulse (308 nm) results in absorption bands with maxima at 370 and 500 nm, belonging to the radical ClNiII(dtc)(dtc) complex whose coordination sphere contains a dithiocarbamate radical dtc, coordinated by one sulfur atom with the central metal ion. This intermediate complex forms, in the reaction with the initial Ni(dtc)2 complex, the ClNiII(dtc)(dtc)[NiII(dtc)2] dimer during 20–30 μs. For several milliseconds the dimer adds another initial complex and transforms into the Cl(dtc)NiII(dtc)[NiII(dtc)2]2 trimer. The reaction between two trimer molecules leads (for several tens of seconds) both to the recombination of coordinated dtc radicals and to the liberation of the final product, the thiuram disulfide molecule ((n-Bu)2NCS2S2CN(n-Bu)2≡tds). The disproportionation of two ClNiII(dtc) complexes results in the precipitating NiCl2 complex which is insoluble in CCl4.

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► Photochemistry of dithiocarbamate Ni(II) complex is determined by electron transfer to CCl4 molecule.
► Primary Ni-dtc radical complex reacts with initial complexes and forms sequentially dimer and then trimer complexes.
► Trimer in second order reaction decays with formation of final products – thiuramdisulfide and two ClNi(dtc) complexes.