A robust Zintl cluster for the catalytic reduction of pyridines, imines and nitriles

Abstract

A boron functionalized phosphorus Zintl cluster was employed to catalytically hydroborate N-containing substrates. The catalyst could be recycled 9 times without loss in performance.

Zintl Clusters as a Platform for Lewis Acid Catalysis

“…Later, we reported the same cluster as an active catalyst in the hydroborative reduction of pyridines, imines, and nitriles. 25 We also demonstrated that a range of Zintl ions and phases could initiate the hydrophosphination of HPPh 2 across alkynes, alkenes, and imines. 26 Also in 2022, we prepared a metal-free heptaphosphane cluster with borane moieties linked via an aliphatic chain, ({C 8 H 14 }BCH 2 CH 2 SiMe 2 ) 3 P 7 (1).…”

“…In this 2022 work, the synthesis of a boron-functionalized [P 7 ] cluster was reported and found to facilitate the reduction of CO 2 to a methoxyborane with high activity and complete selectivity. Later, we reported the same cluster as an active catalyst in the hydroborative reduction of pyridines, imines, and nitriles . We also demonstrated that a range of Zintl ions and phases could initiate the hydrophosphination of HPPh 2 across alkynes, alkenes, and imines …”

Zintl Ions and Phases Promote the Catalytic Hydrophosphination of Alkynes, Alkenes, and Imines

“…Again, the greatest conversion was obtained when pyridine was employed as the solvent. Consistent with our previous report, when the unfunctionalized [Na(DME) x ] 3 [P 7 ] cluster was tested in the hydroboration of pyridines, imines, and nitriles, 21 addition of 18-c-6 improved conversion with complete consumption of 2a obtained within 15 min (12 h without 18-c-6). We postulate that the cation sequestering agent increases the solubility of the anionic species, increasing the effective loading in solution.…”

“…In 2022, we reported the first example of Zintl transition metal-free catalysis, when the boron-functionalized cluster [Na­(18-c-6)] 2 [(BBN)­P 7 ] ( 1 ) (also studied in this report) was found to facilitate the reduction of CO 2 to a methoxyborane. Later, we reported the same cluster as an active catalyst for the hydroboration of pyridines, imines, and nitriles . We also prepared the boron-tethered [P 7 ] cluster where the cluster and boron are linked via an aliphatic unit to mediate hydroboration catalysis; however with this system, the cluster is an innocent platform for boron catalysis .…”

“…Later, we reported the same cluster as an active catalyst for the hydroboration of pyridines, imines, and nitriles. 21 We also prepared the boron-tethered [P 7 ] cluster where the cluster and boron are linked via an aliphatic unit to mediate hydroboration catalysis; however with this system, the cluster is an innocent platform for boron catalysis. 22 As for transition metal-free heterogeneous Zintl catalysis, hydrogenation of alkynes has been the most widely explored.…”