Pyridine-based complexes of copper(II) chloride and bromide: ligand conformation effects on crystal structure. Synthesis, structure and magnetic behavior of Cu(2-Cl-3-X′py)₂X₂ [X, X′ = Cl, Br]

Abstract

Reaction of copper(II) chloride or bromide with 2-chloro-3-bromopyridine or 2,3-dichloropyridine generates a family of compounds of the general formula L₂CuX₂ (1–4). X-ray crystallography shows that the bromide complexes (3-bromo-2-chloropyridine)dibromidocopper(II) (1) and (2,3-dichloropyridine)dibromidocopper(II) (3) are particularly unusual in that they crystallize with both the syn- and anti-conformation structures in the same crystal. A review of the literature on complexes of the formula (substituted-pyridine)₂CuX₂ suggests that these are the first examples of such complexes. The members of the family show a variety of magnetic behaviors and variable temperature magnetic susceptibility data indicate that 1 is essentially paramagnetic (θ = −0.9(1) K) while 3 is weakly ferromagnetic (J = 2.9(1) K). Compound 2 [(3-bromo-2-chloropyridine)dichloridocopper(II)] is fit by the uniform 1-D antiferromagnetic model (J = −19.6(1) K), while 4 [(2,3-dichloropyridine)dichloridocopper(II)] exhibits weak anti-ferromagnetic interactions (J = −3.68(3) K).

Keywords:

• Pyridines
• magnetism
• conformation
• Cu(II) halides

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 Triclinic, P-1. a = 7.862(1) Å, b = 14.809(2) Å, 15.220(2) Å, α = 62.442(6)°, β = 83.013(7)°, γ = 89.974(7)°; Z = 4.

2 Figures of molecules taken from the CCDC have been generated using Mercury 3.10.2. Obtained from the Cambridge Crystallographic Data Center.

Additional information

Funding

Financial support is gratefully acknowledged from the National Science Foundation (NSF; IMR-0314773) toward the purchase of the SQUID magnetometer, PCISynthesis Inc. (SEQENS) toward the purchase of the X-ray powder diffractometer, and The Kresge Foundation toward the purchase of both.