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

Abstract

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 Al III 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.

Authors:
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)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Science Foundation (NSF); John Jay College; USDOE
OSTI Identifier:
1492666
Report Number(s):
LA-UR-18-24664
Journal ID: ISSN 2155-5435
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 9; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Inorganic and Physical Chemistry; Organic Chemistry

Citation Formats

Zhang, Guoqi, Wu, Jing, Zeng, Haisu, Neary, Michelle C., Devany, Matthew, Zheng, Shengping, and Dub, Pavel A. Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration. United States: N. p., 2018. Web. doi:10.1021/acscatal.8b04096.
Zhang, Guoqi, Wu, Jing, Zeng, Haisu, Neary, Michelle C., Devany, Matthew, Zheng, Shengping, & Dub, Pavel A. Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration. United States. doi:10.1021/acscatal.8b04096.
Zhang, Guoqi, Wu, Jing, Zeng, Haisu, Neary, Michelle C., Devany, Matthew, Zheng, Shengping, and Dub, Pavel A. Mon . "Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration". United States. doi:10.1021/acscatal.8b04096.
@article{osti_1492666,
title = {Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration},
author = {Zhang, Guoqi and Wu, Jing and Zeng, Haisu and Neary, Michelle C. and Devany, Matthew and Zheng, Shengping and Dub, Pavel A.},
abstractNote = {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.},
doi = {10.1021/acscatal.8b04096},
journal = {ACS Catalysis},
number = ,
volume = 9,
place = {United States},
year = {2018},
month = {12}
}

Journal Article:
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This content will become publicly available on December 31, 2019
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