Syntheses and ligand exchange experiments of N,N-dialkylcarbamate bridged {Al3(μ3-O)}7+ complexes†

Although a number of oxo-bridged trinuclear transition metal complexes have been synthesised and investigated in recent decades, comparable aluminum compounds have received much less attention. The {Al-3(mu(3)-O)}(7+) carbamate complexes [Al-3(mu(3)-O)(OOC-pyrr)(6)(pyrrH)(3)](+)[Cl](-) (1a), [Al-3(mu(3)-O)(OOC-pip)(6)(pipH)(3)](+)[Cl](-) (2a), [Al-3(mu(3)-O)(OOC-pyrr)6(pyridine)(3)](+)[Cl](-) (1b) and [Al-3(mu(3)-O)(OOC-pip)(6)(pyridine)(3)](+)[Cl](-) (2b) are presented and elucidated by single crystal structure analyses ((1a), (2a) and (1b)) as well as temperature-dependent twodimensional NMR spectra. The complexes (1a) and (2a) were prepared by CO2 insertion into Al-N bonds of tris(dialkylamido)alanes followed by targeted hydolysis. It was found that the neutral ligands of compounds (1a) and (2a) are exchangeable by pyridine ligands resulting in the formation of compounds (1b) and (2b). Further ligand exchange experiments possibly allow the preparation of MOF-like {Al-3(mu(3)-O)}(7+) coordination polymers.