Comparison of the Pawley derived unit cell volume and lattice parameters with the composition determined from NMR shows linear, Vegard's law-type behaviour. We find that the interlayer spacing, c, expands on incorporation of bod, with the M-L-M distance, b, in turn shortening. The contraction along b can be explained by the shorter N-N distance in bod than btd, which would predict b btdb bod = 0.40 Å, which is in quantitative agreement with the fitted value of 0.391(7) Å. The significant interlayer expansion cannot be easily rationalised by differences in the size between btd and bod, but seem rather to reflect subtle differences in the angle between N-Ni-N axes of neighbouring Ni octahedra, though may also suggest that the interlayer vdW forces are weaker for bod than btd. The relative lack of change along the a axis suggests that the NiCl 2 chain is relatively unperturbed by the differences in Ni-N bonding and that changes in intermolecular forces between bod and btd are not a driving factor. We find no evidence of superlattice reflections indicative of long-range ordering of the bod and btd ligands, and no clear evidence of structured diffuse scattering that would be a signature of local ordering, though this can be challenging to detect in powder diffraction measurements of 2D compounds. Having developed this solid-solution series, we then investigated their physical properties, focussing on the mechanical compressibility and magnetic properties. We measured the compressibility of these materials using high pressure synchrotron X-ray powder diffraction at the I15 beamline of Diamond light source, using a hydraulic pressure cell to obtain the fine pressure resolution required [Fig. ]. This cell allows measurements from ambient to 0.4 GPa with pressure increments of ∆P = 0.02 GPa. We used silicone oil AP-100 as a pressure transmitting medium , which should be hydrostatic and non-penetrating in this pressure regime. We investigated here the doped samples synthesised directly using solid-state synthesis because they were more crystalline. The lattice parameters were refined using Pawley refinement. A limited number of impurity peaks were identified and fitted using additional structure free peaks [ESI Section S2.2, Figs. S4-12, Tables ].