Dinuclear Nickel(II) Pivalate with Μ-Aqua and Di-Μ-Pivalato Bridges Showing a Ferromagnetic Interaction

Abstract

Dinuclear nickel(II) complex, [Ni 2 {O 2 CC(CH 3) 3 } 4 (OH 2){HO 2 CC(CH 3) 3 } 4 ] (1), was synthesized and characterized by elemental analysis, IR and UV-Vis-NIR spectroscopy, and temperature dependence of magnetic susceptibilities (4.5-300 K). Single-crystal X-ray crystallography revealed a dinuclear core with μ-aqua and di-μ-pivalato bridges having monodentate pivalato and monodentate pivalic acid molecules. Magnetic data analysis showed a ferromagnetic interactions between the two nickel atoms with g = 2.251, J = 2.78 cm −1 , D = 3.75 cm-1 , and tip = 184 x 10-6 cm 3 mol-1 ; g = 2.253, J = 2.73 cm −1 , D =-3.26 cm-1 , and tip = 176 x 10-6 cm 3 mol-1. Introduction Copper(II) acetate is a well-known dinuclear metal complex, having a lantern-type (or paddlewheel-type) core composed of two copper(II) atoms and four acetato bridges as shown in Figure 1 (a) [1-9]. On the other hand, nickel(II) acetate is known as a mononuclear metal complex composed of one nickel(II) atom and two acetato and four aqua ligands shown in Figure 1 (b). Although a lantern-type dinuclear core was also found in some adducts of nickel(II) pivalate [10-12], the structure of the parent complex, nickel(II) pivalate, has not been elucidated yet. Therefore, we tried to reveal the molecular structure of nickel(II) pivalate by crystallizing the parent complex using various kinds of organic solvents. In this study, we isolated a crystalline material by recrystallizing the product from hexane. The isolated complex was characterized by elemental analysis, IR and UV-Vis-NIR spectroscopy, measurement of temperature dependence of magnetic susceptibilities (4.5-300 K), and single-crystal X-ray crystallography. The X-ray structure analysis of the complex revealed a different dinuclear core from the lantern-type dinuclear copper(II) complexes. Interestingly temperature dependence of magnetic susceptibilities (4.5-300 K) of the complex showed a ferromagnetic property. Herein, we report on the crystal structure, spectral features, and magnetic property of this complex.