We recently reported the zinc analogue of this complex, 2b. Further insight into the bonding in these complexes was obtained through DFT computational methods. Both the NBO and QTAIM analysis on 2a and 2b is consistent with their assignment as scomplexes. Inspection of the MOs for this complex supports the assignment since the key bonding interactions can be conceptualised within the Dewar-Chatt-Duncanson framework (supporting information, Figure ). The degree of covalent character is more significant for the Zn analogue 2b over the Mg analogue 2a. This is clear from lower positive charge accumulation on Zn, along with the larger Wiberg Bond Indices (WBIs)