Pyrrole-2-carbaldehyde thiosemicarbazonates of Nickel(II) and palladium(II): Synthesis, structure, and spectroscopy

Article abstract of DOI:10.1002/zaac.201200012

Complexes of pyrrole-2-carbaldehyde thiosemicarbazones, [(C ₄H₄N⁴)(H)C²=N³-N ²(H)-C¹(=S)-N¹HR; R = Ph, H₂L ¹; Me, H₂L²; H, H₂L³] with nickel(II) and palladium(II) are described. The reaction of nickel(II) acetate with H₂L¹ in methanol in 1:1 molar ratio yielded a complex of composition, [Ni(I²-N³,S-HL ¹)₂] (1). Likewise reaction of NiCl₂ with H₂L² in 1:1 molar ratio in acetonitrile in the presence of triethylamine base followed by the addition of pyridine did not yield the anticipated [Ni(I³-N⁴,N³,S-L ²)(py)] complex, moreover a bis-square-planar complex, [Ni(I²-N³,S-HL²)₂] (2) was formed. However, in the presence of bipyridine (bipy), it yielded the addition product, [Ni(I²-N³,S-HL²) ₂(I²-N, N-bipy)] (3). Reaction of PdCl ₂(I²-P, P-PPh₂-CH₂-PPh ₂) with H₂L³ in toluene in the presence of triethylamine has yielded a complex of stoichiometry, [Pd(I³- N⁴,N³,S-L³)(I¹-P-PPh ₂-CH₂-P(O)Ph₂] (4). The ligands (HL ¹)^- and (HL²)^- are chelating to Ni^II metal atom as anions binding through N³,S-donor atoms with pendant pyrrole groups, and (L³)^2- is chelating to the Pd^II metal atom as dianion through N⁴,N ³,S-donor atoms (pyrrole is N⁴-bonded). Fourth site in 4 is bonded to one P-donor atom of PPh₂-CH₂-P(O)Ph ₂, whose pendant -PPh₂ group involves auto oxidation to -P(O)PPh₂ during reaction. These complexes were characterized using analytical data, IR, NMR (¹H, ³¹P) spectroscopy and X-ray crystallography. Complexes 1, 2, and 4 have square-planar arrangement, whereas complex 3 is octahedral. Copyright