N-heterocyclic Thiols based Copper Complexes: Syntheses, Structure and Catalytic Studies for Azide-Alkyne Cycloaddition Reaction

Treatment of [CuCl2(PPh3)2] with N-heterocyclic thiols, i. e., 4,6-dimethyl pyrimidine-2-thiol (dmpymSH), pyridine-2-thiol (pySH), resulted partially substituted product [CuCl(L)(PPh3)2] (L=C5H4NSH (pySH), SC4H(4,6-Me2N2H) (dmpymSH). However, similar reaction with [CuI(PPh3)]4 yielded a products [CuI(pySH)(PPh3)2] (py=C5H4N) and [CuI(dmpymSH)(PPh3)2] (dmpym=C4H(4,6-Me2N2); respectively. The molecular structure of complex [CuCl(dmpymSH)(PPh3)2].CH3CN (1 b) has been determined through the single crystal X-ray crystallography technique. All the synthesized complexes were fully characterized through various spectroscopic techniques (IR, 1H, 13C{1H}, 31P{1H} NMR). The complexes 1 a, 1 b, 2 a and 2 b showed excellent catalytic activities for azide-alkyne cycloaddition reaction in water as green solvent upto 90 % yield with 0.5 mol % of catalyst loading. Among all the synthesized complexes, compound [CuI(pySH)(PPh3)2] (2 a) turned up as a better catalyst with 90 % yield, applying 0.5 mol % catalyst. The synthesis of four mononuclear copper(I) complexes by using two different copper precursor [CuCl2(PPh3)2] and [CuI(PPh3)]4. Synthesized copper complexes showed excellent catalytic activity in azide-alkyne cycloaddition reactions.image