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(SiMe3)2 with arylnitrile, followed by the addition of anhydrous NiCl2 gives ionic complexes of the general formula [Ni{H2NC(Ar)=NH}4]Cl2 (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}2Ni] (Py = 4‐pyridyl, 3; 3‐pyridyl, 4] are obtained. Compound 1 undergoes a metathesis reaction with sodium benzoate to give the neutral complex [(PhCO2)2Ni {H2NC(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 d8 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)