Photochemistry of [Re(bipy)(CO)3(PPh3)]+ (bipy = 2,2′-bipyridine) in the presence of triethanolamine associated with photoreductive fixation of carbon dioxide: participation of a chain reaction mechanism
Abstract
The complex
fac-[Re(bipy)(CO)
3
(PPh
3
)]
+
1
+
(bipy = 2,2′-bipyridine) was
converted into a formate complex
fac-[Re(bipy)(CO)
3
{OC(O)H}] 2 in
a 52.2% yield by irradiation in the presence of triethanolamine (teoa)
and CO
2
. This photochemical fixation of CO
2
proceeds via a unique reaction mechanism: (i
)
irradiation of 1+ in teoa–dimethylformamide
(dmf) resulted in the efficient formation of
fac-[Re(bipy)(CO)
3
(teoa)]
+
3
+
and
fac-[Re(bipy)(CO)
3
(dmf)]
+
4+ in a quantum yield of 16.9; (ii)
the ligand substitution was explained in terms of a chain mechanism
involving an initial electron transfer from teoa to excited
1+, followed by substitution of the PPh
3
ligand of 1 with teoa and dmf to give 3 and
4; subsequent electron exchange of 3 and 4
with 1+ leads to the formation of
3+ and 4+ accompanied by the
regeneration of 1; (iii) the formate complex
2 was formed in a quantum yield of
1.1 × 10
-3
upon excitation of
3+ and 4+ in the presence of
CO
2
; (iv) further irradiation after the formation of
2 resulted in the photocatalytic reduction of CO
2
to
CO in a quantum yield of 0.05.
)
irradiation of 1+ in teoa–dimethylformamide
(dmf) resulted in the efficient formation of
fac-[Re(bipy)(CO)
3
(teoa)]
+
3
+
and
fac-[Re(bipy)(CO)
3
(dmf)]
+
4+ in a quantum yield of 16.9; (ii)
the ligand substitution was explained in terms of a chain mechanism
involving an initial electron transfer from teoa to excited
1+, followed by substitution of the PPh
3
ligand of 1 with teoa and dmf to give 3 and
4; subsequent electron exchange of 3 and 4
with 1+ leads to the formation of
3+ and 4+ accompanied by the
regeneration of 1; (iii) the formate complex
2 was formed in a quantum yield of
1.1 × 10
-3
upon excitation of
3+ and 4+ in the presence of
CO
2
; (iv) further irradiation after the formation of
2 resulted in the photocatalytic reduction of CO
2
to
CO in a quantum yield of 0.05.
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