Linked aryloxides ligands: synthesis and characterization of alkali metal clusters of a partial calix[n]arene

The ligands 2,6-bis(3-t-butyl-5-methyl-2-hydroxybenzyl)-4-methyl phenol (L) and 2,6-bis(3,5-di-t-butyl-2-hydroxybenzyl)-4-methyl phenol (L′) have been synthesized and structurally characterized. Intramolecular hydrogen-bonding interactions are evident between adjacent aryloxide groups, which orient the ligand in an s-shaped configuration with convergent oxygen donors. Deprotonation of L in THF with alkyl lithium reagents affords the u-shaped trimetallic cluster Li3L(THF)4 (1) with two lithium, each bridging to two oxygen atoms, situated on the rim of the ligand and one bound inside the cavity created by the aryl rings. The hexanuclear clusters Li6L2(Et2O)x and Li6L′2(Et2O)x are isolated from diethyl ether solutions, and the solvent molecules coordinated to the metals in these clusters can be replaced with THF producing Li6L2(THF)2 (2) or with dichloromethane yielding Li6L′2(CH2Cl2)2 (3). Treatment of L or L′ with either sodium methoxide or sodium hydride in diethyl ether generates the analogous sodium clusters. The cluster Na6L6(Me2CO)4 (4) was obtained from acetone while a polymeric material with bridging dichloromethane molecules, [Na6L′2(CH2Cl2)3]x (5), was isolated from dichloromethane solution. The metal clusters were all characterized by X-ray crystallography, and preliminary work has demonstrated that 1 is an ideal precursor for the preparation of reactive transition metal complexes.