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Chemical Science
Page 6 of 8
ARTICLE
Journal Name
Conflicts of interest
DOI: 10.1039/C8SC05600E
There are no conflicts to declare.
Acknowledgements
This work was supported by the National Key Basic Research
Program of China (No. 2013CB834802), the National Natural
Science Foundation of China (21801163), STU Scientific
Research Foundation for Talents (NTF18003) and Basic
Research Program of Shenzhen (JCYJ20160229123546997,
JCYJ20160530184056496). We thank Dr. Xiao-Yong Chang for
solving the X-ray crystal structure of (Bu4N)4[Pt2(P2O5(BF2)2)4].
Fig. 5 UV-vis absorption spectral change during steady state photolysis of Ptpop-BF2-IV
(3 × 10-5 M) in the presence of p-methoxybenzyl alcohol (0.1 M) in degassed CH3CN. The
arrow indicates the direction of the change in absorbance upon light irradiation.
at 337 and 408 nm. This can be ascribed to the direct reaction of
the substrate and the triplet excited [Pt2(pop-BF2)4]4-, likely via
hydrogen atom abstraction to give a mixed-valence [Pt2(pop-
BF2)4(H)]4-. For Ptpop-III, the addition of indoline (c1) resulted
in emission quenching with a kq of 4.7 × 108 dm3 mol-1 s-1. The
intensity of the TA maximum at ~470 nm decayed quickly with
a time constant of 0.86 μs, and a concomitant growth of the
TA signal at 390 nm, with a time constant of 0.83 μs (Fig. 4c–d).
The latter TA spectral profile is long-lived (Fig. S1; τ = 72 μs),
and resembles that obtained in the presence of H-atom donors
such as 2-propanol and nBuSnH.20 This suggests that the triplet
excited Ptpop-III reacts with indoline via hydrogen atom
abstraction to give a [Pt2(pop)4(H)]4- species during the
photocatalysis.
Notes and references
1
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2
Steady state photolysis of Ptpop-BF2-IV in the presence of
p-methoxybenzyl alcohol (0.1 M) in degassed CH3CN gave a
new, broad absorption band centered at 350 nm within 20
seconds as shown in Fig. 5. This absorption band is stable
without apparent decay in 1 hour at room temperature. In
addition, light irradiation of Ptpop-BF2-IV in the presence of p-
methoxybenzyl alcohol (30 equiv., 0.15 M) in CD3CN generated
3
1
new H NMR signals from -7.0 to -9.4 ppm (Fig. S2), which
could be assigned to the formation of platinum hydride species
in the photochemical reactions. Therefore, the formation of
broad absorption band centered at 350 nm during steady state
photolysis as shown in Fig. 5 may be ascribed to the
conversion of Ptpop-BF2-IV to platinum hydride species via
hydrogen atom abstraction.
4
5
6
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Conclusion
In summary, here we have described binuclear platinum(II)
diphosphite complexes as practical and efficient
photocatalysts for oxidant-free acceptorless dehydrogenation
of alcohols, including aliphatic alcohols, and N-heterocycles in
high yields even under substrate-limiting conditions. The
reaction can be used for constructing lactones, quinazolin-
4(3H)-ones and C-N bonds. The unique reactivity of binuclear
platinum(II) diphosphite complexes, as well as the wide
substrate scope, mild reaction conditions and scalability of the
protocol, underscore the utility and versatility of these
photocatalysts for organic transformations with practical
relevance.
8
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6 | J. Name., 2012, 00, 1-3
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