How Bulky Is a Bulky Ligand: Energetic Consequences of Steric Constraint in Ligand-Directed Cluster Assembly and Disassembly

Steric tuning of N-aryl groups of homologous amidinate ligands affords discrete dimeric and tetrameric copper(I) clusters in solid state, but they undergo dynamic dimer−dimer and tetramer−dimer interconversion in solution. A delicate interplay between steric constraint and mechanical stability shapes the reaction coordinate of this process. Thermodynamic and kinetic parameters dictating such cluster assembly and disassembly immediately suggest a means to experimentally quantify energies that are associated with ligand steric bulk.