Copper(I) Derivative of Pyridine-3-carbaldehyde-N-ethylthiosemicarbazone and Triphenylphosphine—First Case of Crystal Structure Study

The synthesis and crystal structure of pyridine-3-carbaldehyde-N-ethylthiosemicarbazone (3-pytscH-NHEt) 1, and its CuI complex of stoichiometry, [CuCl(3-pytscH-NHEt)(PPh3)2] 2, studied using single crystal X-ray crystallography, are reported in this paper. Crystal data: 1, monoclinic, P21/n, a = 6.6322(3), b = 21.1200(8), c = 7.2989(3) A; β = 91.883(4), T = 173(2), R factor = 0.0457; 2: triclinic, P-1, a = 19.3600(5), b = 20.6241(6), c = 23.8015(6) A,α = 92.647(2), β = 104.388(2), γ = 114.377(3), R factor = 0.0662. The thio-ligand, as a neutral entity, is coordinating to Cu through its S donor atom in complex 2. It has exhibited an unusual feature of forming four independent molecules (A, B, C, D) in the unit cell, with minor differences in the bond angles / distances / torsion angles. The geometry of each molecule of 2 is distorted tetrahedral. Crystal packing, as well as Infrared, electronic absorption and proton NMR spectroscopic studies, are also reported. Copper compound 2 represents the first example of a structurally studied copper coordination compound of 3-pyridyl based thiosemicarbazones. Copper(I) chloride with pyridine-3-carbaldehyde-N-ethylthiosemicarbazone and PPh3 in CH3CN yielded a copper compound, 2 (Green-Cl, blue-N; aqua-Cu, orange-S, magneta-P).