Preparation and characterisation of dinuclear nickel(II) complexes containing N _3Ni(μ _(1,3)-SO _3R) _2(μ-O _2CR)NiN _3 cores: Crystal structures and magnetic properties of [Ni _2(L2)(O _2CCH _3)] BPh _4 and [Ni _2(L2)(O _2CPh)]BPh4 [H2L2 = macrocyclic ligand with a N6(SO3)

摘要

The preparation and characterisation of two new macrocyclic Ni ~II complexes containing N _3Ni(μ _(1,3)-SO _3R) _2(μ-O _2CR)NiN _3 cores are described. Complexes [Ni _2(L2)(O _2CMe)] ~+ (4) and [Ni _2(L2)(O _2CPh)] ~+ (5), where (L2) ~(2-) represents a macrocyclic hexaaza-bis(phenylsulfonato) ligand, were synthesised by H _2O _2 oxidation of the respective parent complexes, [Ni _2(L1)(O _2CMe)] ~+ (1) and [Ni _2(L1)(O _2CPh)] ~+ (2), supported by the corresponding hexaaza-bis(thiophenolate) macrocycle(L1) ~(2-). The compounds were characterised by means of elemental analysis, mass spectrometry, IR and UV/Vis spectroscopy. The crystal structures of the tetraphenylborate salts of 4 and 5 show that the bridging thiophenolato functions in 1 and 2 are in both cases converted to μ _(1,3)-bridging sulfonato groups. The conversion to the sulfonato groups is accompanied by a drastic increase of the Ni?Ni distance from 3.483(1) ? in 1 and 3.491(1) ? in 2 to 4.543(1) ? in 4 and 4.5725(8) ? in 5. The magnetic properties are also affected. In contrast to 1 and 2, which exhibit an intramolecular ferromagnetic exchange interaction (S = 2 ground state), the spins of the nickel(II) (S _i = 1 ions) in 4 and 5 are weakly antiferromagnetically coupled, the coupling constants J (H = -2JS _1S _2) being -2.0 cm ~(-1) (4) and -2.3 cm ~(-1) (5), to produce a diamagnetic (S = 0) ground state. Supporting DFT (density functional theory) calculations substantiate the experimental results.