Stacked planar molecules in antiferromagnetic di-isothiocyanato-bis(thiourea)chromium(II), a new structural type for chromium(II)

Abstract

The Structure of [Cr(NCS)₂(tu)₂] where tu is thiourea, comprises trans-planar units stacked along the a axis in infinite parallel chains with a Cr ⋯ Cr separation of 3.97 Å. The separation between sulphur atoms in neighbouring chains is less than a van der walls diameter, and so S ⋯ S interactions may contribute to the stack formation. Other bond lengths in the co-ordination sphere are Cr–NCS 2.026(3)Å and Cr–S(tu) 2.486(1)Å. The temperature dependent magnetic behaviour (µ_eff.= 453 at 291 K and 4.05 at 90 K) can be reproduced by substituion of J=–2.7 cm^–1 and g= 1.96 in Smith and Friedberg's expression for antiferromagnetism in a chain of interacting spin with S= 2. The weak interaction probably arises from direct Cr ⋯ Cr interaction but weak interchain interaction cannot be excluded.