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influence of cyanide on the structural and electronic properties of a series of organocobalt(TIM) complexes
The trans influence of anionic ligands on the nature of the cobalt-carbon bond in trans -[Co(TIM)RX] + -type complexes (R is a C-bound ligand and TIM is 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) was probed through the incorporation of cyanide as the second monoanionic a...
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| Published in: | New journal of chemistry 2024-07, Vol.48 (29), p.133-1337 |
|---|---|
| Main Authors: | , |
| Format: | Article |
| Language: | |
| Online Access: | Get full text |
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| Summary: | The
trans
influence of anionic ligands on the nature of the cobalt-carbon bond in
trans
-[Co(TIM)RX]
+
-type complexes (R is a C-bound ligand and TIM is 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) was probed through the incorporation of cyanide as the second monoanionic axial ligand (X). Salt metathesis reactions between KCN and the corresponding halide precursors readily generate
trans
-[Co(TIM)(C(CH
2
)Ph)(CN)]
+
(
1
),
trans
-[Co(TIM′′)(C(CH
3
)C
6
H
4
-4-
t
Bu)(CN)]
+
(
2
, TIM′′ is the reduced TIM derivative following the formation of an aza-cobalt-cyclopropane moiety), and
trans
-[Co(TIM)(CH
3
)(CN)]
+
(
3
). The molecular structures of
1
and
2
were established
via
single-crystal X-ray diffraction studies. FT-IR spectroscopy revealed a red-shift in the
ν
(C&z.tbd;N) stretching frequency from
1
to
3
to
2
. The absorption spectra of
1
-
3
exhibit d-d bands which are substantially blue-shifted from their halide precursors as a result of the enhanced ligand field imbued by the cyanide. Cyclic voltammograms of
1
and
3
consist of an irreversible Co
4+/3+
oxidation and an irreversible Co
3+/2+
reduction. In
2
, a reversible Co-centered reduction is observed at −1.75 V
vs
. Fc
1+/0
. Also reported are the crystal structures of
trans
-[Co(TIM)(CN)
2
]PF
6
(
4
),
trans
-[Co(TIM)(CH
3
)I]PF
6
(
5
) and
trans
-[Co(TIM)(CH
3
)
2
]PF
6
(
6
). The π-accepting capabilities of the cyanide reduce the dπ(Co)-π*(imine) backdonation in
4
, while the solely strong σ-donating nature of the -CH
3
ligands in
6
exerts a large
trans
influence and significantly increases the Co-TIM interactions.
The mutual
trans
influence of the axial ligands in a series of
trans
-[RCo(TIM)(CN)]
+
complexes was investigated using X-ray diffraction studies, absorption and FTIR spectroscopies, and cyclic voltammetry experiments. |
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| ISSN: | 1144-0546 1369-9261 |
| DOI: | 10.1039/d4nj02364a |