Zeolite-supported Molecular Metal Complex Catalysts - Atomically-Precise Methods for Synthesis of Solid Catalysts - page 35

Table 2.2 Rh-O distances characterizing Rh(CO) 2 (acac) and supported metal
complexes.

Schematic drawing
of molecular or
supported metal
complex

d n 9 r 4 n g | 7

Zeolite
support

Rh-O
distance (Å)

Characterization
technique Remarks

Precursor
Rh(CO) 2 (acac)

None 2.040 XRD

Chemisorbed
species

Hb 2.12 EXAFS

Chemisorbed
species

HY 2.15 EXAFS

HSSZ-42 2.08

(average
value)

Mixture EXAFS Chemisorbed þ

physisorbed
species

.

Adapted from ref. 56.

ligands are readily removed from the precursor. When the transport re-
striction is significant, however, the supported metal complexes are inferred
to be concentrated near the pore mouths of the zeolites.
Because commercially available zeolites have the limitation in the pore
aperture of 0.73 nm, synthesis of new zeolites having larger apertures is
desired. Numerous advances have been made in syntheses of new zeolites in
the past few decades and there are some excellent reviews and topics
available. 5,57-70 Syntheses of extra-large pore zeolites (412 MR), 57 layer ex-
panded zeolites with large side pockets within layers, 58 and two-dimensional
zeolite nanosheets 59-70 with large side pockets 64,66,67,70 are suitable for ac-
commodating large metal complex precursors. Synthesis of two-dimensional
zeolites is an emerging area in zeolite synthesis. 59,62 Two-dimensional
zeolites are interesting particularly if they have large side pockets wherein
metal complexes are anchored.
Lu et al. anchored the same iridium complex, Ir(Z 2 -C 2 H 4 ) 2 (acac), within
one-dimensional channels of HSSZ-53 zeolite. 71 SSZ-53 zeolite is a 14-ring
extra-large pore zeolite with pore dimensions of 6.4 8.7 Å, which is large