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Published on: February 15, 2016
Formally Triplet Aluminyl Anions within the [Al2Pd2]2- Cluster Stabilized by All-Metal Double Aromaticity
Pengfei Chen1, Xinggao Ji1, Zhao Zhao1
1State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
None:
While triplet carbenes have been stabilized through spin delocalization, capturing triplet aluminyl anions─isoelectronic counterparts of carbenes─has remained an unsolved challenge in main-group chemistry. All previously reported aluminyl anions exhibit a singlet ground state, despite the use of diverse ligand frameworks. Herein, we report the first example of formally triplet aluminyl anions within bimetallic clusters, [((CH3)2C(CH2NPiPr2)2)2Al2Pd2]M2 (M = Li, Na, K). These clusters are obtained via chemical reduction of a σ-aromatic Al(II) precursor, [((CH3)2C(CH2NPiPr2)2)2Al2Pd2]. Combined structural and theoretical analyses reveal that each Al(I) center bears two electrons, which exhibit significant electron delocalization across the cluster. This delocalization confers four-center two-electron (4c-2e) σ and 4c-2e π double aromaticity to the [Al2Pd2]2- unit, providing the necessary stabilization for the two Al(I) centers. This work not only demonstrates the viability of formally triplet aluminyl anions but also establishes electron delocalization as a general strategy for stabilizing electron-rich main-group systems.
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