Iron(II) and nickel(II)-thiocyanato complexes of 1-alkyl-2-(arylazo)imidazole: single crystal X-ray structure of [Fe(MeaaiEt) 2(NCS) 2] (MeaaiEt = 1-ethyl-2( p-tolylazo)imidazole) and [Ni(MeaaiMe)(NCS) 2(H 2O) 2] · 2DMF (MeaaiMe = 1-methyl-2( p-tolylazo)imidazole)

Abstract

The reaction of green vitriol (FeSO 4,7H 2O) with 1-alkyl-2-(arylazo)imidazoles [RaaiR′ where R = H ( a), Me ( b); R′ = Me ( 1/ 3/ 5), Et ( 2/ 4/ 6)] and NH 4SCN in 1:2:2 mole proportion affords mononuclear bis-chelated [Fe(RaaiR′) 2(SCN) 2] ( 3, 4) complexes. Reaction of NiSO 4 · 6H 2O with 1-alkyl-2(arylazo)imidazole and ammonium thiocyanate (1:2:2 molar ratio) in methanol solution forms mononuclear monochelated thiocyanato complexes of the type [Ni(RaaiR′)(H 2O) 2(SCN) 2] · 2H 2O ( 5, 6). Slow diffusion of DMF solution of [Ni(MeaaiMe)(H 2O) 2(NCS) 2] in methanol has isolated the X-ray quality crystals. All the complexes are characterized by elemental, UV–Vis, IR, thermal and magnetic studies. In both cases, the distorted octahedral structure was confirmed by single crystal X-ray diffraction study of [Fe(MeaaiEt) 2(NCS) 2] ( 4b) and [Ni(MeaaiMe)(H 2O) 2(NCS) 2] · 2DMF ( 7). Variable temperature susceptibility measurements of [Fe(MeaaiEt) 2(NCS) 2] ( 4b) do not exhibit spin crossover property, which may be due to high structural distortion.