Copper(II) thiocyanate

Copper thiocyanate is a coordination polymer with formula Cu₂. It is a black solid which slowly decomposes in moist air. It was first reported in 1838 by Karl Ernst Claus and its structure was determined first in 2018.

Structure

The structure of Cu₂ was determined via powder X-ray diffraction and consists of chains of Cu₂ linked together by weak Cu–S–Cu bonds into two-dimensional layers. It can be considered a Jahn–Teller distorted analogue of the mercury thiocyanate structure-type. Each copper is octahedrally coordinated by four sulfurs and two nitrogens. The sulfur end of the SCN⁻ ligand is doubly bridging.

Copper thiocyanate can be prepared from the reaction of concentrated solutions of copper and a soluble thiocyanate salt in water, precipitating as a black powder. With rapid drying, pure Cu₂ can be isolated. Reaction at lower concentrations and for longer periods of time generates instead copper(I) thiocyanate.

Copper thiocyanate, like copper(II) bromide and copper(II) chloride, is a quasi low-dimensional antiferromagnet and it orders at into a conventional Néel ground state.