Metal-ligand synergy driven functionalisation of alkylene linked bis(aldimine) on a diruthenium() platform. Cyclisation oxygenation
This article addresses the impact of metal-ligand redox cooperativity on the functionalisation of coordinated ligands. It demonstrates the structure-reactivity correlation of bis(aldimine) derived bis-bidentate L (Py-CH&z.dbd;N-(CH 2 ) n -N&z.dbd;CH-Py, with n = 2 (L1), 3 (L2), 4 (L3)) as a...
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Published in | Dalton transactions : an international journal of inorganic chemistry Vol. 53; no. 5; pp. 2167 - 218 |
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Main Authors | , , , , |
Format | Journal Article |
Published |
30.01.2024
|
Online Access | Get full text |
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Summary: | This article addresses the impact of metal-ligand redox cooperativity on the functionalisation of coordinated ligands. It demonstrates the structure-reactivity correlation of bis(aldimine) derived bis-bidentate L (Py-CH&z.dbd;N-(CH
2
)
n
-N&z.dbd;CH-Py, with
n
= 2 (L1), 3 (L2), 4 (L3)) as a function of the conformation (
syn
/
anti
) of its alkylene linker as well as the overall structural form (
cis
/
trans
) of (acac)
2
Ru
II
(μ-L)Ru
II
(acac)
2
complex moieties (
1-5
) possessing an electron-rich acetylacetonate (acac) co-ligand. A systematic variation of the bridging alkylene unit of L in Ru
II
/Ru
II
-derived
1-5
led to the following reactivity/redox events, which were validated through structural, spectroscopic, electrochemical and theoretical evaluations: (i) Cyclisation of the ethylene linked (
syn
conformation) bis-aldimine unit of L1
via
C-C coupling yielded pyrazine bridged (acac)
2
Ru
II
(μ-L1′)Ru
II
(acac)
2
,
1a
, while the corresponding
anti
-form (ethylene linker) of the metal-bound L1 in
2
((acac)
2
Ru
II
(μ-L1)Ru
II
(acac)
2
) led to oxygenation at the ligand backbone (bis-aldimine (L) → bis(carboxamido) (L′′))
via
O
2
activation to generate Ru
III
Ru
III
-derived (acac)
2
Ru
III
(μ-L1′′
2−
)Ru
III
(acac)
2
(
2a
). (ii) Consequently, propylene and butylene linked L2 and L3 bridged between two {Ru(acac)
2
} units in
3
and
4
/
5
underwent oxygenation of L to L′′ to yield diruthenium(
iii
) complexes
3a
and
4a
/
5a
, respectively. (iii) In contrast, analogous L bridged oxidised [(acac)
2
Ru
III
(μ-L)Ru
III
(acac)
2
](ClO
4
)
2
([
2
](ClO
4
)
2
-[
5
](ClO
4
)
2
) and [{(PPh
3
)
2
(CO)(H)Ru
II
}
2
(μ-L)](ClO
4
)
2
([
6
](ClO
4
)
2
-[
8
](ClO
4
)
2
) involving electron poor co-ligands failed to undergo the oxygenation of L irrespective of its
n
value, reemphasising the effective role of redox interplay between Ru
II
and L particularly in the presence of an electron-rich acac co-ligand in the functionalisation of the latter in
1a-5a
.
Redox-induced cyclisation or oxygenation of bis(aldimine) derived ligands on a selective {Ru(acac)
2
}
2
platform was conceived based on the alkylene conformation. |
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Bibliography: | For ESI and crystallographic data in CIF or other electronic format see DOI 2301886-2301890 and 2301763 2303128 Dedicated to Prof. Samar Kumar Das on the occasion of his 60th birthday celebration. https://doi.org/10.1039/d3dt03730d Electronic supplementary information (ESI) available: Spectroscopic/computational data. CCDC , |
ISSN: | 1477-9226 1477-9234 |
DOI: | 10.1039/d3dt03730d |