Formation of bis(μ-tetrazolato)dinickel(II) complexes with N, N, O-donor Schiff bases via in situ 1,3-dipolar cyclo-additions: isolation of a novel bi-cyclic trinuclear nickel(II)-sodium(I)-nickel(II) complex

A dinuclear and a novel bi-cyclic hetero trinuclear bis(mu-tetrazolato) bridged nickel(II) Schiff base complexes [Ni-2(L-1)(2)(PTZ)(2)] (1) and [Ni-2(L-2)(2)(PTZ)(2)Na(H2O)]ClO4 center dot H2O (2) {where HL1 = 2-((2-(dimethylamino)ethylimino) methyl)-6-methoxyphenol, HL2 = 2-((2-(methylamino) ethylimino) methyl)-6-methoxyphenol and HPTZ = 5-(2-pyridyl) tetrazole} have been synthesized by in situ 1,3-dipolar cyclo-addition and characterized by spectral analysis, X-ray crystallography, and variable-temperature magnetic susceptibility measurements. Both the complexes crystallize in monoclinic space group P2(1)/c. Both the complexes feature double mu-NN'-tetrazolato bridged dinickel(II) structures, in which each nickel(II) is coordinated meridionally by a depronated terdentate Schiff base [(L-1)(-)for 1 and (L-2)(-) for 2] and two nitrogen atoms of the (PTZ)(-). A nitrogen atom from a symmetry related bridging (PTZ)(-)coordinates to complete the distorted octahedral geometry of nickel(II). The phenoxo and methoxo oxygen atoms from two [NiL2] units and a water molecule coordinate to a sodium(I) to form the unique bi-cyclic trinuclear nickel(II)-sodium(I)nickel( II) core in complex 2. Very strong p. p stacking is observed in complex 2 to form a supramolecular chain. The variable-temperature (1.8-300 K) magnetic susceptibility measurements show the presence of anti-ferromagnetic coupling between two nickel(II) centers for both complexes with J = -2.14(1) cm(-1) (for 1) and J = -1.20(2) cm(-1) (for 2). To obtain a better understanding of the magnetic exchange mechanism, quantum mechanical (DFT) calculations have been performed. The calculated J values [Jtheo = -4.53 cm(-1) (for 1) and Jtheo = -2.48 cm(-1) (for 2)] are in agreement with the values obtained experimentally.