As a simple probe of the "goodness-of-fit" between pairs of ligands, a geometric model was initially considered. The coordination of 1 and 2 trans to each other across Pd(II) ions was equated to a planar trapezoid (Fig. ). The lengths (D) of the two parallel sides relate to the distance between coordinating atoms for the diverging ligand 1 (Dd) and the converging ligand 2 (Dc). Assuming a Pd-N distance of 2.02 Å (mean distance from CSD; ESI section S4), the remaining two sides would each be equal to 4.04 Å. The angles between coordinating groups (Θ; Fig. ) for both the converging (Θc) and diverging ligands (Θd) thus make up the four internal angles of the trapezoid. With the D and Θ values known for one ligand, it is possible to calculate corresponding idealised values for a perfectly matched partner ligand.