232
A. Dhakshinamoorthy and H. Garcia
Pd leaching was found to be 0.17 ppm. Excellent yields were also achieved for a
wide variety of substrates including electron donating and withdrawing substituents,
large dimension aryl halides, heteroaryl halides and chloroarenes under remarkably
mild conditions that include the use of water as solvent, aerobic conditions and room
temperature (Scheme 7.7). Furthermore, the solid catalyst was recycled at least ten
times without any change in its catalytic performance.
One point to be addressed is whether or not the internal location of metal NPs
is beneficial from the catalytic point of view, increasing or not the activity. In this
regard, Cao and co-workers developed a simple direct anionic exchange method to
introduce Pd in a MOF, followed by subsequent chemical reduction with NaBH 4
to deposit Pd NPs on amino-functionalized MIL-53(Al)-NH 2 [40]. The structural
integrity of MIL-53(Al)-NH 2 was retained during the loading of Pd NPs. TEM images
of the resulting Pd/MIL-53(Al)-NH 2 showed that the mean diameter of Pd NPs was
3.12 nm and mostly found on the external surface of MIL-53(Al)-NH 2 . The catalytic
performance of Pd/MIL-53(Al)-NH 2 was investigated in the Suzuki–Miyaura crosscoupling reaction of bromobenzene with phenylboronic acid using Na 2 CO 3 as base in
water–ethanol mixture at 40 °C achieving 94% yield with a turnover number (TON)
of 198. Under identical conditions, the reaction of chlorobenzene and phenylboronic
acid afforded only trace yield of biphenyl [40]. Further, the activity of Pd/MIL53(Al) and Pd/C was found to be 45% (TON: 98) and 37% (TON: 88) under identical
conditions [40]. A series of aryl halides were coupled with phenylboronic acid to
obtain their respective biphenyl derivatives with yields ranging between 87 and 97%
under identical conditions. The catalyst was reused for five cycles with no appreciable
Scheme 7.7 Scope of
Pd/MIL-101(Cr)-NH 2 as
Suzuki–Miyaura catalyst for
the coupling of various aryl
halides and phenylbornonic
acid
Substrate
Product
Yield (%)
Br
MeO
MeO
99
Br
99
Br
EtO 2 C
EtO 2 C
84
S
Br
S
N
N
Br
99
99
A. Dhakshinamoorthy and H. Garcia
Pd leaching was found to be 0.17 ppm. Excellent yields were also achieved for a
wide variety of substrates including electron donating and withdrawing substituents,
large dimension aryl halides, heteroaryl halides and chloroarenes under remarkably
mild conditions that include the use of water as solvent, aerobic conditions and room
temperature (Scheme 7.7). Furthermore, the solid catalyst was recycled at least ten
times without any change in its catalytic performance.
One point to be addressed is whether or not the internal location of metal NPs
is beneficial from the catalytic point of view, increasing or not the activity. In this
regard, Cao and co-workers developed a simple direct anionic exchange method to
introduce Pd in a MOF, followed by subsequent chemical reduction with NaBH 4
to deposit Pd NPs on amino-functionalized MIL-53(Al)-NH 2 [40]. The structural
integrity of MIL-53(Al)-NH 2 was retained during the loading of Pd NPs. TEM images
of the resulting Pd/MIL-53(Al)-NH 2 showed that the mean diameter of Pd NPs was
3.12 nm and mostly found on the external surface of MIL-53(Al)-NH 2 . The catalytic
performance of Pd/MIL-53(Al)-NH 2 was investigated in the Suzuki–Miyaura crosscoupling reaction of bromobenzene with phenylboronic acid using Na 2 CO 3 as base in
water–ethanol mixture at 40 °C achieving 94% yield with a turnover number (TON)
of 198. Under identical conditions, the reaction of chlorobenzene and phenylboronic
acid afforded only trace yield of biphenyl [40]. Further, the activity of Pd/MIL53(Al) and Pd/C was found to be 45% (TON: 98) and 37% (TON: 88) under identical
conditions [40]. A series of aryl halides were coupled with phenylboronic acid to
obtain their respective biphenyl derivatives with yields ranging between 87 and 97%
under identical conditions. The catalyst was reused for five cycles with no appreciable
Scheme 7.7 Scope of
Pd/MIL-101(Cr)-NH 2 as
Suzuki–Miyaura catalyst for
the coupling of various aryl
halides and phenylbornonic
acid
Substrate
Product
Yield (%)
Br
MeO
MeO
99
Br
99
Br
EtO 2 C
EtO 2 C
84
S
Br
S
N
N
Br
99
99