Fitting χ -1 (T ) data to the Curie-Weiss law gave a Curie constant, C = 3.08(1) emu K mol -1 , in good agreement with the presence of high-spin Cr 2+ (C = 3 emu K mol -1 ) (Fig. &). The Curie-Weiss temperature is significant and negative, θ = -54.1(5) K, indicating net antiferromagnetic interactions (Fig. ), and isothermal magnetisation measurements carried out at 2 K show that saturation is not reached at fields of 5 T (Fig. ). While M (H) is linear in µ 0 H > 1 T, there is a small sigmoid feature at µ 0 H < 1 T consistent with minor paramagnetic impurities.