Unique Aluminum Clusters Stabilized by Cation‐Ligand Cooperativity

Abstract

AbstractTwo novel cyclic Al3 clusters, Li2[Al3(PR2)6] ⋅ 2(Et2O) [R=Ph (1), Cy (2)] were synthesized through salt metathesis of metastable AlCl ⋅ (Et2O)n solutions with LiPR2. Both complexes were characterized by single crystal X‐Ray diffraction and their solid state and electronic structures are compared to previously reported cyclic Al3 clusters. Compounds 1 and 2 were further characterized using density functional theory (DFT) methods to understand the nature of the free electron and the three‐center two‐electron Al−Al bonds. Calculations revealed that both clusters are influenced by pseudo Jahn‐Teller distortion and are likely in equilibrium between two low energy bonding states. The solid‐state structures of 1 and 2 are unique among Al3 clusters, while the electronic structure is similar to the previously reported [Sit4Al3]. In aluminum chemistry, 1 and 2 are rare examples of clusters containing isoelectronic cores in different ligand environments. The effects of the phosphide ligand sphere and strongly coordinated lithium atoms are discussed in detail.