Bond Dissociation Energies of Metallo-supramolecular Building Blocks: Insight from Fragmentation of Selectively Self-Assembled Heterometallic Metallo-supramolecular Aggregates

A series of selectively self-assembled metallo-supramolecular square-like macrocycles with unsymmetric ditopic linkers and two different types of metal corners, i.e., {Pd(η³-2-Me-C₃H₄)} and {M(dppp)} with dppp = 1,3-bis(diphenylphosphino)propane and M = Pd²⁺ or Pt²⁺, have been studied in the gas phase using collision-induced dissociation. The aggregates show distinct fragmentation patterns determined by ligand length, i.e, aggregate size, and type of metal corner. Information on relative binding strength can be deduced. This is of particular interest for (methylallyl)Pd as a relatively new building block in metallo-supramolecular chemistry. The phosphane end of the unsymmetric ligand connected to (η³-2-Me-C₃H₄)Pd is bound significantly stronger than its pyridine end to (dppp)Pt and (dppp)Pd. These results are corroborated by DFT calculations.