Stable monovalent aluminum(i) in a reduced phosphomolybdate cluster as an active acid catalyst

Low-valent aluminum Al(i) chemistry has attracted extensive research interest due to its unique chemical and catalytic properties but is limited by its low stability. Herein, a hourglass phosphomolybdate cluster with a metal-center sandwiched by two benzene-like planar subunits and large steric-hindrance is used as a scaffold to stabilize low-valent Al(i) species. Two hybrid structures, (H3O)(2)(H(2)bpe)(11)[Al-III(H2O)(2)](3){[Al-I(P(4)MoV6O(31)H(6))(2)](3)center dot 7H(2)O (abbr. Al-6{P4Mo6}(6)) and (H3O)(3)(H(2)bpe)(3)[Al-I(P(4)MoV6O(31)H(7))(2)]center dot 3.5H(2)O (abbr. Al{P4Mo6}(2)) (bpe = trans-1,2-di-(4-pyridyl)-ethylene) were successfully synthesized with Al(i)-sandwiched polyoxoanionic clusters as the first inorganic-ferrocene analogues of a monovalent group 13 element with dual Lewis and Bronsted acid sites. As dual-acid catalysts, these hourglass structures efficiently catalyze a solvent-free four-component domino reaction to synthesize 1,5-benzodiazepines. This work provides a new strategy to stabilize low-valent Al(i) species using a polyoxometalate scaffold.

Automated summary

Low-valent aluminum Al(i) species were successfully stabilized using a hourglass phosphomolybdate cluster as a scaffold in this study. The resulting structures, with the Al(i) sandwiched polyoxoanionic clusters, acted as dual-acid catalysts in a domino reaction to synthesize 1,5-benzodiazepines. This work presents a new strategy for stabilizing low-valent Al(i) species using polyoxometalate scaffolds.