Blocking and bridging ligands direct the structure and magnetic properties of dimers of pentacoordinate nickel(ii)

Abstract

Dinuclear pentacoordinate nickel(II) complexes of the formula [(NiTp*)₂(μ-L)] (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate; L = oxalate (1); oxamate (2); oxamidate (3); OC(4-Cl-C₆H₄N)C(4-Cl-C₆H₄N)O (4)) and {[Ni(N₃-mc)]₂(μ-L)}(PF₆)₂ (N₃-mc = 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene; L = oxalate (5); oxamate (6)) have been synthesized and spectroscopically characterized (IR, ¹H NMR). X-ray structures of 1–5 show nickel(II) in a square pyramidal geometry and different supramolecular interactions. Magnetic measurements for 1–6 show strong antiferromagnetic interactions across the bridging ligand [1: J = −36.8 cm⁻¹, g = 2.16; 2: J = −43.6 cm⁻¹, g = 2.12; 3: J = −51.1 cm⁻¹, g = 2.12; 4: J = −39.7 cm⁻¹, g = 2.18; 5: J = −35.4 cm⁻¹, g = 2.20; 6: J = −44.3 cm⁻¹, g = 2.18]. Magneto-structural correlations between the magnitude of the magnetic coupling and the different blocking ligands, the different bridging ligands, the distortion of the coordination environment of Ni(II) and the planarity between the bridging ligand and the basal plane of the Ni(II) environment have been established for all complexes.