Structural and electronic properties of the iron(II) and nickel(II) bis(ligand) complexes of 6-(5-methyl-1,2,4-oxadiazol-3-yl)-2,2 '-bipyridine - a terpyridine-based tridentate

Iron(II) and nickel(II) bis(ligand) complexes of 6-(5-methyl-1,2,4-oxadiazo l-3-yl)-2,2'-bipyridine (L) are described. The ligand field in the iron com plex is close to that at the singlet ((1)A(1)) reversible arrow quintet (T- 5(2)) crossover and magnetic and Mossbauer spectral evidence indicates that a spin transition occurs in salts of the iron complex but is centred above room temperature. The structures of [FeL2] [CF3SO3](2).CH3CN and [NiL2] [B F4](2).CH3CN were determined and both are very similar to the structures of the corresponding terpyridine complexes. Spectroscopic data indicate that for the iron complex pi-interaction between the metal and the ligand is les s than that in the terpyridine system. [FeL2] [CF3SO3](2).CH3CN is monoclin ic, space group P2(1)/c; a 8.232(5), b 25.273(10), c 17.306(10) Angstrom, b eta 92.37(3)degrees, Z 4; [NiL2] [BF4](2).CH3CN is monoclinic, space group P2(1)/c; a 8.136(2), b 17.558(2), c 23.783(7) Angstrom, beta 109.32(1)degre es, Z 4.