Lewis acid fragmentation of a lithium aryloxide cage: generation of new heterometallic aluminium–lithium species

Abstract

Heterometallic aluminium-lithium species were prepared by the fragmentation reaction of the hexametallic cage compound [Li{2,6-(MeO)(2)C(6)H(3)O}](6) (1) with alkyl aluminium derivatives. Depending on the aluminium precursor, the species formed present different nuclearities in the solid state as shown by single crystal X-ray analysis. Spectroscopic and computational studies have been performed to study the nuclearity of the synthesized compounds in solution.

Aluminum Alkali Metalate Derivatives: Factors Driving the Final Nuclearity in the Crystal Form

“…Starting with the metalated phenol, [Na{2,6‐(MeO) 2 C 6 H 3 O}] 6 ( Na2H6S ; Figure ) in the solid state has a hexametallic structure that exhibits a central hexagonal prism core generated by the stacking of two hexagonal rings. This arrangement has been previously observed in the analogous lithium derivative [Li{2,6‐(MeO) 2 C 6 H 3 O}] 6 , reported by us, and follows the ring stacking principle postulated by Snaith et al Each ring is composed of three sodium atoms and three oxygen atoms from the aryloxide groups. These oxygen atoms show a µ 3 coordination, bridging three sodium atoms, two of them located in the same face as the oxygen and a third one in the other.…”

“…As shown, the heterometallic derivatives formed can be seen as stemming from the breakage of the initial aryloxide cage [M{2,6‐(MeO) 2 C 6 H 3 O}] 6 , however, it is surprising that the nuclearity is not the same for all the metals. In particular, the lithium derivative [AlLiMe 3 {2,6‐(MeO) 2 C 6 H 3 O}] 3 ( AlLi1H ) is hexametallic (Figure ) whereas the Na and K ( AlM1S ) ones are tetrametallic. In these systems, an intriguing aspect is which factors drive the formation of the dinuclear or hexanuclear species.…”

“…In this context, our work is focused on the study of heterometallic ‐ate species containing aluminum and alkali metals with well‐defined structures . We are interested in preparing aluminates with functionalized aryloxide groups as bridging ligands.…”

“…In particular, a phenol bearing donor groups placed in ortho positions, 2,6‐dimethoxyphenol, has been chosen as the ligand precursor. In our previous work, we isolated new heterometallic ‐ate species of different stoichiometry and nuclearity: [AlLiMe 3 {2,6‐(MeO) 2 C 6 H 3 O}] 3 ( AlLi1H , where 1H accounts for a single hexagon) and [AlLiMe 2 {2,6‐(MeO) 2 C 6 H 3 O} 2 ] 2 ( AlLi3S , where 3S accounts for three squares) from the reaction of the hexametallic lithium aryloxide cage [Li{2,6‐(MeO) 2 C 6 H 3 O}] 6 ( Li2H6S where 2H and 6S account for two hexagons and six squares, respectively) with two different aluminum precursors, [AlMe 3 ] 2 and [Al{2,6‐(MeO) 2 C 6 H 3 O}Me 2 ] 2 {[Al(OR)Me 2 ]} (Scheme ) . Then, we extended the study to sodium and potassium aryloxides [M{2,6‐(MeO) 2 C 6 H 3 O}] 6 ( M2H6S ) by using [Al(OR)Me 2 ] as the aluminum precursor, which led to the isolation of the species [AlMMe 2 {2,6‐(MeO) 2 C 6 H 3 O} 2 ] n ( AlNa3S and AlK3S for M = Na and K) with central Al 2 M 2 cores analogous to the lithium one …”

Aluminum Aryloxide Compounds as Very Active Catalysts for Glycidyl Methacrylate Selective Ring‐Opening Polymerization

“…Aluminum is the most abundant metal in the earth's crust, and aluminum compounds are also active catalysts in polymerization processes . We are interested in derivatives with functionalized aryloxide groups, as additional functionalities in the ring can influence the structure and reactivity of the species prepared . If the substituents are bulky, the formation of high‐nuclearity species can be prevented and low‐nuclearity compounds are generated, which are usually more reactive than the oligomeric analogues .…”