Synthesis, magnetic, and structural characterization of di-µ-(benzyloxo)-bis[(2,2,6,6-tetramethylheptane-3,5-dionato)copper(II)]

Abstract

The synthesis of the title compound is reported. The crystal and molecular structure of the dimer has been determined from three-dimensional counter X-ray data. The compound crystallizes in the triclinic space group P with one dimeric unit in a cell of dimensions a= 13.462(5), b= 6.064(2), c= 12.756(6)Å, α= 82.13(4), β= 11 5.61 (2), and γ= 90.56(3)°. Least-squares refinement of the structure based on 1 575 observations has led to an R factor (on F) of 0.065. The compound consists of discrete dimeric units which are well separated from each other. The geometry around copper is approximately square planar, with Cu–O distances ranging from 1.883(5) to 1.910(5)Å; Cu–Cu 2.970(2)Å, Cu–O–Cu 102.1 (2)°. The magnetic susceptibility of a powdered sample has been examined in the range 96.9–300.0 K. The dimer exhibits a large antiferromagnetic exchange interaction, the best fit to the Van Vleck dimer equation yielding 2J=–647 cm^–1 with 〈g〉= 2.18. This magnitude of 2J is much larger than that observed for analogous hydroxide-bridged compounds, and is taken as evidence in support of the conclusion that enhanced electron density at the bridge causes an increase in |J|.