Preparation and Characterization of Dinuclear Nickel(II) Complexes Containing N3Ni(1, 3-SO3R)2(-RCN4)NiN3 Cores: Crystal Structures and Magnetic Properties

The preparation and characterization of three new mixed ligand macrocyclic [Ni2L2(L)]+ complexes are described, where (L2)2 represents a supporting macrocyclic hexaaza-bis(phenylsulfonato) ligand and L a tetrazolato ligand. The complexes [Ni2(L2)(CN4H)]BPh4 (4), [Ni2(L2)(CN4Me)]BPh4 (5), and [Ni2(L2)(CN4Ph)]BPh4 (6) were synthesized by H2O2 oxidation of the corresponding [Ni2(L1)(CN4H)]BPh4 (1), [Ni2(L1)(CN4Me)]BPh4 (2), and [Ni2(L1)(CN4Ph)]BPh4 (3) complexes supported by the corresponding hexaaza-bis(thiophenolate) macrocycle. The compounds were characterized by means of elemental analysis, mass spectrometry, IR, and UV/Vis spectroscopy. The crystal structures of compounds 46 show that the bridging thiophenolate functions in 13 are in all cases converted to 1, 3-bridging sulfonate groups to generate N3Ni(1, 3-SO3R)2(-RCN4)NiN3 cores. The conversion to the phenylsulfonato groups is accompanied by a drastic increase of the Ni center dot center dot center dot Ni distances from 3.455(1) angstrom in 1, 3.425(1) angstrom in 2, and 3.443(1) angstrom [3.450(1) angstrom] in 3 to 4.2796(5) angstrom [4.3375(6) angstrom] in 4, 4.3402(6) angstrom in 5, and 4.2607(4) angstrom in 6. Upon oxidation the magnetic properties are affected. In contrast to 13, which exhibit an intramolecular ferromagnetic exchange interaction (S = 2 ground state), the spins of the nickel(II) (Si = 1) ions in 46 are antiferromagnetically coupled, the coupling constants J being 1.39 cm1 (4), 1.43 cm1 (5), and 1.60 cm1 (6) (H = 2JS1S2) to yield a diamagnetic S = 0 ground state. DFT (density functional theory) calculations were carried out to substantiate the experimental results.