Loading…
Electronic structure and catalytic aspects of [Ru(tpm)(bqdi)(Cl/H2O)]n, tpm = tris(1-pyrazolyl)methane and bqdi = o-benzoquinonediimineElectronic supplementary information (ESI) available. CCDC 904797 and 904798. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2dt32402d
The diamagnetic complexes [Ru(tpm)(bqdi)(Cl)]ClO 4 ([ 1 ]ClO 4 ) (tpm = tris(1-pyrazolyl)methane, bqdi = o -benzoquinonediimine) and [Ru(tpm)(bqdi)(H 2 O)](ClO 4 ) 2 ([ 2 ](ClO 4 ) 2 ) have been synthesized. The valence state-sensitive bond distances of coordinated bqdi [C-N: 1.311(5)/1.322(5) Å in...
Saved in:
| Main Authors: | , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Online Access: | Get full text |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | The diamagnetic complexes [Ru(tpm)(bqdi)(Cl)]ClO
4
([
1
]ClO
4
) (tpm = tris(1-pyrazolyl)methane, bqdi =
o
-benzoquinonediimine) and [Ru(tpm)(bqdi)(H
2
O)](ClO
4
)
2
([
2
](ClO
4
)
2
) have been synthesized. The valence state-sensitive bond distances of coordinated bqdi [C-N: 1.311(5)/1.322(5) Å in [
1
]ClO
4
; 1.316(7)/1.314(7) Å in molecule
A
and 1.315(6)/1.299(7) Å in molecule
B
of [
2
](ClO
4
)
2
] imply its fully oxidised quinonediimine (bqdi
0
) character. DFT calculations of
1
+
confirm the {Ru
II
-bqdi
0
}
versus
the antiferromagnetically coupled {Ru
III
-bqdi&z.rad;
−
} alternative. The
1
H NMR spectra of [
1
]ClO
4
in different solvents show variations in chemical shift positions of the NH (bqdi) and CH (tpm) proton resonances due to their different degrees of acidity in different solvents. In CH
3
CN/0.1 mol dm
−3
Et
4
NClO
4
, [
1
]ClO
4
undergoes one reversible Ru
II
Ru
III
oxidation and two reductions, the reversible first electron uptake being bqdi based (bqdi
0
/bqdi&z.rad;
−
). The electrogenerated paramagnetic species {Ru
III
-bqdi
0
}(
1
2+
) and {Ru
II
-Q&z.rad;
−
}(
1
) exhibit Ru
III
-type (
1
2+
: <
g
> = 2.211/Δ
g
= 0.580) and radical-type (
1
:
g
= 1.988) EPR signals, respectively, as is confirmed by calculated spin densities (Ru: 0.767 in
1
2+
, bqdi: 0.857 in
1
). The aqua complex [
2
](ClO
4
)
2
exhibits two one-electron oxidations at pH = 7, suggesting the formation of {Ru
IV
&z.dbd;O} species. The electronic spectral features of
1
n
(
n
= charge associated with the different redox states of the chloro complex: 2+, 1+, 0) in CH
3
CN and of
2
2+
in H
2
O have been interpreted based on the TD-DFT calculations. The application potential of the aqua complex
2
2+
as a pre-catalyst towards the epoxidation of olefins has been explored in the presence of the sacrificial oxidant PhI(OAc)
2
in CH
2
Cl
2
at 298 K, showing the desired selectivity with a wide variety of alkenes. DFT calculations based on styrene as the model substrate predict that the epoxidation reaction proceeds through a concerted transition state pathway.
Redox series including {Ru
II
(bqdi
0
)Cl/H
2
O}
n
+
, {Ru
III
(bqdi
0
)Cl}
2+
, {Ru
II
(bqdi&z.rad;
−
)Cl}
0
, {Ru
III
(bqdi
0
)OH}
2+
, {Ru
IV
(bqdi
0
)O}
2+
and the application of the aqua complex for a selective epoxidation process are reported. |
|---|---|
| ISSN: | 1477-9226 1477-9234 |
| DOI: | 10.1039/c2dt32402d |