Trends upon changing the B site transition metal ion are also present within each tetraalkylammonium set (TPrA, TBuA and TPnA). The trend in Tm is the same in each case, i.e. Co < Fe < Mn. These reductions were however, more subtle than the effect of changing the A site cation, resulting in for example a lowering in Tm from 150 °C for [TPnA][Mn(dca)3], to 137 °C for [TPnA][Fe(dca)3] and then to 106 °C for [TPnA][Co(dca)3] (Table ). This follows the trend in ionic radius, which decreases in the order Mn > Fe > Co and consistent with hard-soft/acid-base theory as suggested previously.