Further evaluation of the secondary interactions by the QTAIM method provided valuable insights regarding the underlying factors which dictate the binding modes preference of the XB-catalysed TS1 of the halide abstraction reaction. The presence of non-covalent secondary interactions acts as anchor points, enhancing the interactions between the substrate and the catalyst. In the case of the CAT9 catalysed reaction, these interactions were identified between the phenyl ring of the substrate and the phenyl rings of the catalyst (see Tables S6-S9 and Figure ). These specific interactions play a critical role in facilitating and stabilising the unexpected monodentate binding mode of the CAT9 catalyst.