Synthesis, structure, electrochemistry, and magnetic properties of face-sharing bioctahedral nickel complexes containing a N3Ni(μ-S2)(μ-X)NiN3 core (X = F−, Cl−, Br−, N3−, OH−)

Abstract

A series of isostructural dinickel complexes of the type [Ni2(LMe2H4)][X]2 (where (LMe2H4)2− represents a 28-membered macrocyclic N6S2 donor ligand, X = ClO4− (1a), I− (1b)) and [Ni2(LMe2H4)(μ-L′)][X] (X = ClO4−, L′ = F− (2a), Cl− (3a), OH− (5a), N3− (6a), X = BPh4–, L′ = F− (2b), Cl− (3b), OH− (5b), N3− (6b), X = Br−, L′ = Br− (4)) have been synthesized and characterized by IR, ESI-MS, UV–vis, cyclic voltammetry, SQUID magnetometry, and X-ray crystallography. The dications in 1a and 1b feature an edge sharing bis(square-pyramidal) N3Ni(μ-S2)NiN3 core, while the monocations of 2a-6b comprise a face-sharing bioctahedral N3Ni(μ-S)2(μ-L′)NiN3 core. The variation of the coordination geometry has a strong impact on the magnetic properties of the Ni complexes. 3a, 4, and 5a have an S = 2 ground state with a value for the magnetic exchange coupling constant J of +10.06 cm−1, (3a), J = +12.13 cm−1 (4) and J = +2.9(1) cm−1 (5a), while 1a, 1b, and 2a have an S = 0 ground state with J = −13.4 cm−1 (1a), −22.8 cm−1 (1b) and J = −0.56 cm−1 (2a) (H = – 2JS1S2). Broken symmetry density functional theory calculations have been performed to study the individual contributions of the coligand and thiolato-bridges to the overall magnetic behavior. The capability to propagate exchange interactions was found to increase in the order Br− < Cl− < N3− < OH− ∼ F−.