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ChemComm
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COMMUNICATION
Journal Name
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Scheme 3. Proposed Mechanism for Binary Ru-CNC/KOCO2tBu Catalyzed Hydroboration
of CO2
In summary, we have developed a binary catalyst system
comprising a cationic Ru-CNC pincer complex and an alkali
metal salt for an efficient and mild hydroboration of CO2. The
alkali metal salts derived from a strong base and a weak acid
represents an efficient catalyst system with cationic Ru-CNC
pincer complex (12). It demonstrated good activities in
producing HCOOBpin selectively up to 76% at r.t. and 1 atm
CO2 within 30 min. The binary catalytic system using
geometrically restricted Ru-CNC pincer complex also shows
better selectivity for the formation of HCOOBpin as compared
to other single component Ru phosphine complexes. The
synergistic use of a small amount of an inexpensive alkali
metal reagent to activate the borane can render it more active
to CO2 hydroboration using otherwise inactive catalysts.
Financial support from EDB-GSK (R143-000492-592),
A*STAR (R-143-000-566-305), SERC-A*STAR (1526004162) and
IMRE-A*STAR (IMRE/15-2C0252), is gratefully acknowledged. C.
K. Ng thanks A*STAR, Singapore, for his graduate scholarship.
Technical support from staff at CMMAC at NUS Department of
Chemistry is greatly appreciated.
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Notes and references
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t
reactions between HBpin and KOCO2 Bu were unsuccessful.
t
However, upon adding an excess of HBpin to KOCO2 Bu in THF-d8,
a broad peak appeared in the 11B {1H} NMR spectrum at ~2.7
ppm which may suggest the formation of boron “ate” species
similar to B.
4 | J. Name., 2012, 00, 1-3
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