Zeolite-supported Molecular Metal Complex Catalysts - Atomically-Precise Methods for Synthesis of Solid Catalysts - page 29

and DFT calculations identifies reaction intermediates and spectators to
decipher a whole catalytic cycle. Advantages of using zeolites as support
materials and synthesizing structurally uniform supported species have
been demonstrated by various researchers. Miessner et al. reported the
synthesis and IR characterization of dealuminated zeolite Y-supported
rhodium dicarbonyl complexes. 18 The sharpness of the IR bands (n CO )
characterizing the supported rhodium species indicate their structural
uniformity. Because the initially prepared species have high structural
uniformity, their structure as well as structural changes under reactive
atmosphere can be investigated in detail. Goellner et al. investigated the
details of the structure of the dealuminated zeolite Y-supported rhodium
dicarbonyl by IR, EXAFS, and DFT calculations as described in Section
2.4.2. 19 Miessner investigated the structural changes of supported rhodium
dicarbonyls when they are treated in a flow of 10% H 2 in N 2 at 473-523 K and
suggested the formation of supported rhodium monocarbonyls on the basis
of IR spectroscopy data. 20 Vayssilov and R¨sch used DFT calculations to
examine the IR band assignments done by Miessner and suggested the
presence of dihydrogen and hydride ligands in addition to carbonyl lig-
ands. 21 More recently, Vityuk, Alexeev and Amiridis reported the synthesis
and characterization of zeolite-supported rhodium complex with carbonyl
and hydride ligands by the reaction of supported Rh(CO)(C 2 H 4 )withH 2 . 22
Liang et al. reported the synthesis of zeolite-supported rhodium diethene
complexes (supported Rh(C 2 H 4 ) 2 ) and demonstrate the dynamic uniformity
of the supported species using variable-temperature solid state NMR spec-
troscopy as described in Section 2.4.3. 23,24 Liang et al. also demonstrated
how the uniformity of supported species allows precise determination of
their chemistry. 25 Kletnieks et al. showed how the structural uniformity of
zeolite-supported molecular rhodium complexes allows one to investigate
reactivity of supported species and their functions in a catalytic cycle at an
unprecedented level as described in the Section 2.5.2. 26
In the first part of this chapter (Sections 2.2 and 2.3), the general synthesis
methods and characterization techniques of zeolite-supported metal complex
catalysts are described. In the second part (Section 2.4), several issues re-
garding the synthesis of zeolite-supported metal complexes with high struc-
tural uniformity as well as characterization techniques to examine structural
uniformity are described. Then, in the third part, investigations on reactivity
and catalytic performances of zeolite-supported molecular metal complex
catalysts are presented using some examples reported in the literature. In the
final part, future directions in addition to conclusions are stated.

d n 9 r 4 n g | 7

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2.2 Synthesis

2.2.1 Synthesis by an Ion-exchange Method
Zeolite-supported metal complex catalysts are often synthesized by an ion-
exchange method. 9,27

In a typical synthesis, a zeolite is contacted with an