Syntheses and Crystal Structures of Tetrakis(arylamidine)nickel( II ) Chloride and Bis[2,4‐dipyridyl‐1,3,5‐triazapentadienato]nickel( II )

The reaction of LiN(SiMe 3 ) 2 with arylnitrile, followed by the addition of anhydrous NiCl 2 gives ionic complexes of the general formula [Ni{H 2 NC(Ar)=NH} 4 ]Cl 2 (Ar = Ph 1 , p ‐tolyl 2 ). When the above reaction is carried out with cyanopyridine instead of arylnitrile under the same reaction conditions, neutral complexes of the general formula [{HN=C(Py)N=C(Py)NH} 2 Ni] (Py = 4‐pyridyl, 3 ; 3‐pyridyl, 4 ] are obtained. Compound 1 undergoes a metathesis reaction with sodium benzoate to give the neutral complex [(PhCO 2 ) 2 Ni {H 2 NC(Ph)=NH} 4 ] ( 5 ). Magnetic susceptibility measurements show that 1 − 4 are diamagnetic and that 5 is paramagnetic with two unpaired electrons. These results suggest that 1 − 4 are d 8 square‐planar complexes and 5 is an octahedral complex. The solid state structures of compounds 1 − 5 were determined by X‐ray crystallography. Structural analyses reveal that 1 and 2 form a one‐dimensional network through charge‐assisted hydrogen bonds; whereas 5 forms a one‐dimensional network through hydrogen bonds only. In complexes 3 and 4 , the 2,4‐dipyridyl‐1,3,5‐triazapentadienyl ligand behaves as a bidentate ligand forming a six‐membered ring with the metal ion. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)