Synthesis, characterization and C-H amination reactivity of nickel iminyl complexes
Metalation of the deprotonated dipyrrin ( AdF L)Li with NiCl 2 (py) 2 afforded the divalent Ni product ( AdF L)NiCl(py) 2 ( 1 ) ( AdF L: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine). To generate a reactive synthon on which to explore oxidative group transfer, we used potassium graphi...
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| Vydané v: | Chemical science (Cambridge) Ročník 11; číslo 5; s. 126 - 1268 |
|---|---|
| Hlavní autori: | , , , , , |
| Médium: | Journal Article |
| Jazyk: | English |
| Vydavateľské údaje: |
CAMBRIDGE
Royal Soc Chemistry
05.02.2020
Royal Society of Chemistry Royal Society of Chemistry (RSC) The Royal Society of Chemistry |
| Predmet: | |
| ISSN: | 2041-6520, 2041-6539 |
| On-line prístup: | Získať plný text |
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| Shrnutí: | Metalation of the deprotonated dipyrrin (
AdF
L)Li with NiCl
2
(py)
2
afforded the divalent Ni product (
AdF
L)NiCl(py)
2
(
1
) (
AdF
L: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine). To generate a reactive synthon on which to explore oxidative group transfer, we used potassium graphite to reduce
1
, affording the monovalent Ni synthon (
AdF
L)Ni(py) (
2
) and concomitant production of a stoichiometric equivalent of KCl and pyridine. Slow addition of mesityl- or 1-adamantylazide in benzene to
2
afforded the oxidized Ni complexes (
AdF
L)Ni(NMes) (
3
) and (
AdF
L)Ni(NAd) (
4
), respectively. Both
3
and
4
were characterized by multinuclear NMR, EPR, magnetometry, single-crystal X-ray crystallography, theoretical calculations, and X-ray absorption spectroscopies to provide a detailed electronic structure picture of the nitrenoid adducts. X-ray absorption near edge spectroscopy (XANES) on the Ni reveals higher energy Ni 1s → 3d transitions (
3
: 8333.2 eV;
4
: 8333.4 eV) than Ni
I
or unambiguous Ni
II
analogues. N K-edge X-ray absorption spectroscopy performed on
3
and
4
reveals a common low-energy absorption present only for
3
and
4
(395.4 eV) that was assigned
via
TDDFT as an N 1s promotion into a predominantly N-localized, singly occupied orbital, akin to metal-supported iminyl complexes reported for iron. On the continuum of imido (
i.e.
, NR
2−
) to iminyl (
i.e.
,
2
NR
−
) formulations, the complexes are best described as Ni
II
-bound iminyl species given the N K-edge and TDDFT results. Given the open-shell configuration (
S
= 1/2) of the iminyl adducts, we then examined their propensity to undergo nitrenoid-group transfer to organic substrates. The adamantyl complex
4
readily consumes 1,4-cyclohexadiene (CHD)
via
H-atom abstraction to afford the amide (
AdF
L)Ni(NHAd) (
5
), whereas no reaction was observed upon treatment of the mesityl variant
3
with excess amount of CHD over 3 hours. Toluene can be functionalized by
4
at room temperature, exclusively affording the
N
-1-adamantyl-benzylidene (
6
). Slow addition of the organoazide substrate (4-azidobutyl)benzene (
7
) with
2
exclusively forms 4-phenylbutanenitrile (
8
) as opposed to an intramolecular cyclized pyrrolidine, resulting from facile β-H elimination outcompeting H-atom abstraction from the benzylic position, followed by rapid H
2
-elimination from the intermediate Ni hydride ketimide intermediate.
Nickel-supported nitrenoids exhibit iminyl character, as determined by multi-edge XAS and TDDFT analysis, demonstrate efficacy for C-H activation and nitrene transfer chemistry. |
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| Bibliografia: | Electronic supplementary information (ESI) available. CCDC For ESI and crystallographic data in CIF or other electronic format see DOI 1953729-1953733 10.1039/c9sc04879k ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 content type line 23 USDOE Office of Science (SC), Basic Energy Sciences (BES) AC02-76SF00515 |
| ISSN: | 2041-6520 2041-6539 |
| DOI: | 10.1039/c9sc04879k |