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.对同系脒基配体(homologous amidinate ligands)的N-芳基进行空间位阻调控，可在固态下合成得到离散的二聚与四聚铜(I)团簇(copper(I) clusters)；但此类团簇在溶液中会发生动态的二聚体-二聚体与四聚体-二聚体互变过程。空间位阻约束与结构机械稳定性之间的微妙相互作用，调控了该过程的反应坐标(reaction coordinate)。支配这类团簇组装与解组装过程的热力学与动力学参数，直接提供了一种实验手段，可用于量化与配体空间位阻体积(ligand steric bulk)相关的能量。