Thiosemicarbazone derivatives of nickel and copper: the unprecedented coordination of furan ring in octahedral nickel(ii) and of triphenylphosphine in three-coordinate copper(i) complexes

Abstract

The influence of substituents at the C²carbon of N¹-substituted thiosemicarbazones, {C₄H₃X–C²(CH₃)N³–N²H–C¹(S)N¹HR²} (X = O, S) on the geometry of nickel(II) complexes has been investigated. The presence of a methyl group at the C² position of 2-acetylfuran-N¹-substituted thiosemicarbazones {(C₄H₃O)–C²(CH₃)N³–N²H–C¹(S)N¹HR², R² = CH₃, HaftscN–Me; C₂H₅, HaftscN–Et; C₆H₅, HaftscN–Ph} induces unusual coordination by the furan ring and yielded high spin octahedral nickel(II) complexes, [Ni(κ³-O, N³, S-aftscN–R²)₂], CH₃1, C₂H₅2, and 2[Ni((κ³-O, N³, S-aftscN–Ph)₂] 3 (μ_eff = 2.98, 1; 2.96, 2; 2.92, 3). With 2-acetylthiophene-N¹-substituted thiosemicarbazones, {(C₄H₃S)-C²(CH₃)N³-N²H–C¹(S)N¹HR², R² = CH₃, HattscN–Me; C₂H₅, HattscN–Et; C₆H₅, HattscN–Ph}, N³, S chelated low spin trans square planar complexes, {[Ni(κ³-O, N³, S-attscN–R²)₂], R² = CH₃, 4; C₂H₅, 5; C₆H₅, 6} with pendant thiophene rings have been obtained. The bigger sized sulfur atoms of the thiophene rings form short intramolecular contacts with the deprotonated hydrazinic nitrogen atoms (S⋯N²) inhibiting its lability for possible coordination to nickel(II). Complexes have one independent molecule (1) or two independent molecules (2, 3) in their respective crystal lattices. The simultaneous presence of methyl groups at the C² and N¹ atoms of 2-acetylthiophene-N¹-methylthiosemicarbazone (HattscN–Me) have facilitated the binding of triphenylphosphine in three-coordinate copper(I) halide complexes, [CuX(η¹-S-HattscN–Me)(Ph₃P)] (X, Br, 7; Cl, 8), which represent an unusual donor set of ligands, namely, triphenylphosphine, sulfur of a thio-ligand and a halide.