Pyrrole‐2‐carbaldehyde Thiosemicarbazonates of Nickel(II) and Palladium(II): Synthesis, Structure, and Spectroscopy

Complexes of pyrrole‐2‐carbaldehyde thiosemicarbazones, [(C 4 H 4 N 4 )(H)C 2 =N 3 –N 2 (H)–C 1 (=S)–N 1 H R ; R = Ph, H 2 L 1 ; Me, H 2 L 2 ; H, H 2 L 3 ] with nickel(II) and palladium(II) are described. The reaction of nickel(II) acetate with H 2 L 1 in methanol in 1:1 molar ratio yielded a complex of composition, [Ni(κ 2 ‐N 3 ,S‐HL 1 ) 2 ] ( 1 ). Likewise reaction of NiCl 2 with H 2 L 2 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(κ 3 ‐N 4 ,N 3 ,S‐L 2 )(py)] complex, moreover a bis‐square‐planar complex, [Ni(κ 2 ‐N 3 ,S‐HL 2 ) 2 ] ( 2 ) was formed. However, in the presence of bipyridine (bipy), it yielded the addition product, [Ni(κ 2 ‐N 3 ,S‐HL 2 ) 2 (κ 2 ‐N, N‐bipy)] ( 3 ). Reaction of PdCl 2 (κ 2 ‐P, P–PPh 2 –CH 2 –PPh 2 ) with H 2 L 3 in toluene in the presence of triethylamine has yielded a complex of stoichiometry, [Pd(κ 3 ‐N 4 ,N 3 ,S–L 3 )(κ 1 ‐P–PPh 2 –CH 2 –P(O)Ph 2 ] ( 4 ). The ligands (HL 1 ) – and (HL 2 ) – are chelating to Ni II metal atom as anions binding through N 3 ,S‐donor atoms with pendant pyrrole groups, and (L 3 ) 2– is chelating to the Pd II metal atom as dianion through N 4 ,N 3 ,S‐donor atoms (pyrrole is N 4 ‐bonded). Fourth site in 4 is bonded to one P‐donor atom of PPh 2 –CH 2 –P(O)Ph 2 , whose pendant –PPh 2 group involves auto oxidation to –P(O)PPh 2 during reaction. These complexes were characterized using analytical data, IR, NMR ( 1 H, 31 P) spectroscopy and X‐ray crystallography. Complexes 1 , 2 , and 4 have square‐planar arrangement, whereas complex 3 is octahedral.