Synthesis and characterisation of a chiral lanthanoid cluster with an unusually exposed cubane core via concomitant deesterification of ethyl acetate

An unusual chiral lanthanoid cluster has been synthesised and characterised that exhibits a cubane cage motif with a remarkably exposed central core. This discovery stems from the use of a new asymmetric diketone ligand, (Z)-3-hydroxy-3-methyl-1-(1,2:3,4-di-O-isopropylidene-α-d-galactopyranose)prop-2-en-1-one (Hmgp), which incorporates both a methyl terminus and a protected d-galactose moiety to induce chirality. Reaction of this ligand with hydrated holmium chloride results in the formation of a cubane cluster, Ho₄(μ₃-OH)₄(η²-mgp)₆(μ-η²-mgp)(μ-η²-Ac)(H₂O)₂] (1), which bears seven chiral ligands that form a highly shielded hemisphere and an acetate co-ligand that is postulated to form via deesterification of ethyl acetate.