Synthesis and Characterization of the Adducts of Bis(O-ethyldithiocarbonato)copper(II) with Substituted Pyridines

Monomeric five coordinated adducts of bis(O-ethyldithiocarbonato)copper(II) of general formula [Cu(C2H5OCS2)2(L)], [L = 2-, 3-, 4-methylpyridines and 2-, 3-, 4-ethylpyridines] have been synthesized and characterized by elemental analysis, i.r. and electronic spectroscopy, magnetic and conductivity measurements. Analytical results show that the adducts have 1？:？1 stoichiometry. The adducts were found to be paramagnetic and their magnetic moments at room temperature lie within the 1.81–1.94？B.M. range and this indicates the presence of one unpaired electron. All the adducts have distorted square pyramidal geometry. 1. Introduction O-Alkyldithiocarbonates, popularly known as xanthates derivatives, have found a wide pra ctical application as addition to lubricating oils, antioxidants for polyolefins, and so forth. However, alkylxanthates are mainly used in flotation concentration of nonferrous metal sulfide ores. These are extensively used as pharmaceuticals, fungicides, pesticides, and quite recently in therapy for HIV infections [1–3]. Divalent transition metals xanthates are partly unsaturated and can therefore form 1？:？1 adducts with electron donors such as neutral nitrogen, oxygen, phosphorus, or sulfur donors in which the coordination geometry ranges from square pyramidal to trigonal bipyramidal [4]. Such adducts of many transition metals such as Ni, Zn, Mn, V, Pt, and Pd are well studied, but little attention has been paid to the xanthates of copper owing to their instability. Here we report synthesis and investigation of the 1？:？1 adducts of some adducts of copper(II)xanthates with substituted pyridines such as 2-, 3-, 4-methylpyridines and 2-, 3-, 4-ethylpyridines. 2. Experimental 2.1. Preparation of Potassium Salt of O-ethyldithiocarbonate Potassium salt of ethyl xanthate was prepared by the method reported in literature [5]. Into a 500？mL round bottomed flask, fitted with a reflux condenser, was placed 0.75 mole of potassium hydroxide pellets and 120？g of ethanol. The reaction mixture was heated under reflux for 1 hour. The mixture was then cooled and liquid from the residual solid was decanted off into another dry 500？mL flask. To this flask was added 45？mL (0.75 mole) of carbon disulfide slowly with constant shaking. The residual solid yellow mass was filtered (after cooling in ice) on a sintered glass funnel at the pump. It was washed with three 25？mL portions of ether. The resulting potassium salt of ethyl xanthate was dried in a vacuum desiccator over anhydrous calcium chloride. The yield was about 75？g. It was then recrystallized from