The structures of FeCl 2 (btd) and NiCl 2 (btd) were determined by Rietveld refinement against PND data, using the DFT-optimised structures as a starting model (Fig. &). The DFT structures were produced by geometryoptimising models derived from the previously reported structure of CoCl 2 (btd). In our refinements, in addition to the metal and halide, we were able to refine the position of the btd ligand as rigid body, which rotates 2.9(1) • about the b-axis in FeCl 2 (btd) and 1.3(1) • in NiCl 2 (btd). The structure deviation from orthorhombic is much larger in these compounds than in low temperature FeCl 2 (pym), with a markedly larger β-angle and the btd lies further from the bc-plane (Tab. S4, S5).