3 3 1 4 3
of exchangeable nitrate anions [n (NO + n (NO
2): 1380 cm21 (s); n 2):
Finally, the heterogenisation of the second metal component
of the system was attempted. Therefore, the anionic Co species,
21
1
786 cm (w)].
Prior to ion exchange (24 h; 60 °C), equimolar quantities (0.32 mmol/g
LDH) of Pd(NH Cl and BC-SO were mixed in 100 ml decarbonated
22
CoCl
4
was synthesised and ion-exchanged on a MgAlNO
3
)
3 4
2
3
10
LDH following literature procedures. §
bidistilled water to induce complex formation (1 h; 60 °C). Washing of the
solid and its lyophilisation are the last steps in the synthesis of the catalyst.
Preliminary tests with an anchored co-catalyst show very
promising results (entry 10, Table 1) as far as activity and
degree of leaching is concerned. Pd leaching is less than 5% (21
nmol), while Co leaching was determined to be only 0.5% of the
initial amount. It has been certified that in the conditions of
entry 2 (Table 1), the solid after filtration could be re-used.
In conclusion, it is shown that the immobilisation of a Pd–
The final catalyst contained 70 mmol Pd/g and 0.22 mmol BC-SO
3
/g, as
determined by ICP analysis and UV–Vis spectroscopy, respectively.
§ To a deep blue solution of 2.2 g of [Et N] [CoCl ] in 30 ml of
4
2
4
nitromethane, 1 g of the above-described MgAlNO
3
LDH was added. The
slurry was then stirred for 18 h at room temperature, filtered and washed
repeatedly with CH NO
3
2
until no blue colour remained in the filtrate.10
Finally, the resulting material was dried at room temperature. According to
ICP measurements the catalyst contained 0.93 mmol/g Co.
3
BC–SO complex on a MgAl LDH by anion exchange results in
a solid catalyst for the oxidative carbonylation of phenol that in
terms of activity is superior to the best homogeneous analogues.
Whereas Pd leaching is dependent on the relative concentration
of the other members in this complex catalytic system, it can be
reduced to losses of no more than 30 nmol. Although the
electron transfer chain needed to reoxidise Pd is a complex
system with components in a very delicate balance, we
succeeded in immobilising via a similar procedure the second
inorganic component of this system as well.
K. L. is indebted to IWT Flanders for a PhD grant. The
authors would also like to thank K. Broos for performing the
ICP measurements. This work was supported by the Belgian
Federal Government in the frame of an Interuniversity Attrac-
tion Pole on Supramolecular Chemistry and Catalysis.
1
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K. V. Shalyaev, G. L. Soloveichik, B. F. Johnson and D. W.
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1
6
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Notes and references
1
7, 45–50.
†
‡
TBAB = tetrabutylammonium bromide; Co(acac)
MgAlNO LDH was synthesised by coprecipitation in conditions of
constant pH of 9.5 0.2 (precursors:
O and Al(NO ·9H O; titration with 1 M NaOH). Its
3
used.
8 A. Vavasori and L. Toniolo, J. Mol. Catal., 1999, 139, 109–119.
9 M. T. Reetz, W. Helbig, S. A. Quaiser, U. Stimming, N. Breuer and R.
Vogel, Science, 1995, 267, 367; H. Bönnemann, W. Brijoux, R.
Brinkmann, E. Dinjus, T. Joußen and B. Korall, Angew. Chem., 1991,
103, 1344.
3
supersaturation and at
Mg(NO ·6H
structure is confirmed by X-ray analysis while the molar ratio [Mg/Al] is
determined to be 1.95 (ICP analysis). IR measurement shows the presence
a
±
)
3 2
2
)
3 3
2
10 E. Lopez-Salinas and Y. Ono, Microporous Mater., 1993, 1, 33–42.
CHEM. COMMUN., 2002, 2728–2729
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