Theoretical and experimental investigations of ligand exchange in guanidinate ligand systems for group 13 metals

Abstract

The ligand exchange of guanidinate ligands between metal centres can play an important role in guanidinate chemistry, and ligand exchange between aluminium centres will form a dimeric intermediate. The synthesis and characterization of the dimer [Me₂NC(NⁱPr)₂]₂Al₂Cl₄ (1) is reported here: compound 1 crystallizes with a twisted boat conformation of its dimer ring. This compound decomposes to monomers at room temperature over four days, or within 18 hours at 90 °C. We undertook a detailed computational characterization of the reaction pathway, which supported the dimer structure and subsequent monomer formation. The ligand exchange route was also exploited for the synthesis of [MeC(NⁱPr)₂]₂AlCl (2), [EtC(NⁱPr)₂]₂AlCl (3), [MeC(NⁱPr)₂]₂GaCl (5), and [Me₂NC(NⁱPr)₂]₂GaCl (6).