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Title: Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration

Journal Article · · ACS Catalysis
ORCiD logo [1];  [2];  [2]; ORCiD logo [3];  [3];  [3]; ORCiD logo [4]
  1. City Univ. (CUNY), NY (United States). Graduate Center, Dept. of Sciences, John Jay College
  2. City Univ. (CUNY), NY (United States). Graduate Center, Dept. of Sciences, John Jay College; City Univ. (CUNY), NY (United States). Hunter College, Dept. of Chemistry
  3. City Univ. (CUNY), NY (United States). Hunter College, Dept. of Chemistry
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Here, this paper reports the first example of dearomatization of ubiquitous terpyridine (tpy) ligands via 2'/6'-, 3'/5'-, or 4'-selective alkylation of the central pyridine ring. The reaction is mediated by the most abundant metal in the Earth’s crust, aluminum (Al), and depending on the conditions employed, exhibits ionic or radical character as suggested by experimental and computational analysis. In the latter case, intermediate formation of an AlIII complex supported by π-radical monoanionic ligand (tpy•)1– is apparent. The 3'/5'-alkylation leads to unprecedented zwitterionic Meisenheimer AlIII complexes, which were identified as efficient precatalysts for the selective hydroboration of C=O and C≡C functionalities. Turnover numbers (TONs) up to ~1000 place the corresponding complexes in the category of the most efficient Al catalysts reported to date for the title reaction. The acquired data suggest that aluminum monohydrides, or more likely dihydrides, could be relevant catalytic species. Alternatively, one can also imagine a mechanistic scenario in which the dearomatized “chemically noninnocent” ligand acts as hydride donor, and a detailed investigation of this is warranted in the future.

Research Organization:
Los Alamos National Laboratory (LANL)
Sponsoring Organization:
John Jay College; National Science Foundation (NSF); USDOE
Grant/Contract Number:
89233218CNA000001
OSTI ID:
1492666
Report Number(s):
LA-UR-18-24664
Journal Information:
ACS Catalysis, Journal Name: ACS Catalysis Vol. 9; ISSN 2155-5435
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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