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Bisimino-functionalized dibenzo[a,c]acridines as highly conjugated pincer frameworks for palladium(II): synthesis, characterization and catalytic performance in Heck coupling

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journal contribution
posted on 19.12.2016, 12:53 by Qaiser Mahmood, Erlin Yue, Wenjuan Zhang, Gregory A. Solan, Tongling Liang, Wen-Hua Sun
A new pair of highly conjugated ligands, 10-[1-(arylimino)ethyl]-14-[(arylimino)methyl]dibenzo[a,c]acridine (aryl = 2,6-Me₂Ph L1, 2,6-Et₂Ph L2) incorporating both aldimine and ketimine units, have been prepared by a straightforward sequence of organic transformations from phenanthrene-9,10-dione. Cyclopalladation occurs readily at ambient temperature on treating L1 or L2 with PdCl₂(NCCH₃)₂ in aprotic solvents to afford exclusively (NketimineNC)Pd(II) chloride pincer complexes Pd1 or Pd2, respectively. By contrast in methanol, Pd1 or Pd2 are isolated as the minor product with aldehyde-containing Pd3 or Pd4 as the major one, the result of hydrolysis of the pendant aldimine units in Pd1 and Pd2, respectively. All the ligands and palladium complexes have been characterized by FT-IR, ¹H and ¹³C NMR spectroscopy, mass spectrometry and elemental analysis; the molecular structures for L1, Pd1, Pd2, Pd3 and Pd4 are also reported. Using low catalyst loadings (0.0005–0.002 mol%) and elevated temperatures (140–200 °C), Pd1–Pd4 are able to efficiently mediate the coupling of haloarenes with vinyl-containing substrates with turnover numbers as high as 174000; the effects of steric/electronic variation within the substrate and NNC-pincer complex on catalyst performance are examined.

History

Citation

Organic Chemistry Frontiers, 2016, 3 (12), pp. 1668-1679

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Chemistry

Version

AM (Accepted Manuscript)

Published in

Organic Chemistry Frontiers

Publisher

Royal Society of Chemistry

issn

2052-4110

eissn

2052-4129

Acceptance date

26/09/2016

Copyright date

2016

Available date

27/09/2017

Publisher version

http://pubs.rsc.org/en/Content/ArticleLanding/2016/QO/C6QO00469E#!divAbstract

Notes

The file associated with this record is under a 12 month embargo from publication in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.

Language

en

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