Synthesis of organo(siloxo)platinum and -palladium complexes and preparation of supported nanoclusters by facile ligand reduction

Article abstract of DOI:10.1016/S0020-1693(99)00210-8

A series of organosiloxo complexes of platinum and palladium, MR(OSiPh₃)(L₂) (M = Pt, Pd; R = Me, Et, Ph; L₂ = cod, dppe), has been prepared and characterized. The square planar geometries of PtPh(OSiPh₃)(cod) and PtEt(OSiPh₃)(cod) are confirmed by X-ray structure analysis. In the reactions with hydrogen at 0°C and 1 atm, the siloxo complexes of Pt and Pd are reduced readily to give agglomerates of nanoclusters with complete hydrogenation of the ligands. The reduction activities of the siloxo and alkoxo complexes are higher than those of the corresponding alkyl complex PtMe₂(cod). This high activity in reduction is applied to the preparation of supported Pt or Pd nanoclusters on silica, and the siloxo complexes adsorbed on silica are reacted with hydrogen at mild conditions. The resulting Pt/SiO₂ gives a smaller mean diameter than that prepared from H₂PtCl₆/SiO₂.

Full text of DOI:10.1016/S0020-1693(99)00210-8

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Inorganica Chimica Acta 294 (1999) 266–274
Synthesis of organo(siloxo)platinum and -palladium complexes and
preparation of supported nanoclusters by facile ligand reductionꢀ
Atsushi Fukuoka 1, Akihiro Sato, Kin-ya Kodama, Masafumi Hirano,
Sanshiro Komiya *
Department of Applied Chemistry, Tokyo Uni6ersity of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan
Received 14 January 1999; accepted 19 April 1999
Abstract
A series of organosiloxo complexes of platinum and palladium, MR(OSiPh3)(L2) (M=Pt, Pd; R=Me, Et, Ph; L2=cod, dppe),
has been prepared and characterized. The square planar geometries of PtPh(OSiPh3)(cod) and PtEt(OSiPh3)(cod) are confirmed
by X-ray structure analysis. In the reactions with hydrogen at 0°C and 1 atm, the siloxo complexes of Pt and Pd are reduced
readily to give agglomerates of nanoclusters with complete hydrogenation of the ligands. The reduction activities of the siloxo and
alkoxo complexes are higher than those of the corresponding alkyl complex PtMe2(cod). This high activity in reduction is applied
to the preparation of supported Pt or Pd nanoclusters on silica, and the siloxo complexes adsorbed on silica are reacted with
hydrogen at mild conditions. The resulting Pt/SiO2 gives a smaller mean diameter than that prepared from H2PtCl6/SiO2. © 1999
Elsevier Science S.A. All rights reserved.
Keywords: Siloxo complexes; Platinum complexes; Palladium complexes; Crystal structures; Nanoclusters
and alumina are impregnated with metal salts and they
are reduced with hydrogen at high temperature (200–
1. Introduction
400°C). However, the particle size and distribution are
Small metal particles with diameters in the range
still controlled insufficiently for the monodispersed
1–10 nm (i.e. nanoclusters)2 attract current interest
metal nanoclusters by the conventional methods. On
since they are expected to display unique physical and
the other hand, organometallic compounds are attrac-
chemical properties [1]. One major application of the
tive precursors due to their well-characterized structures
metal nanoclusters is heterogeneous catalysis, in which
and potential high activity in reduction at mild condi-
supported platinum catalysts are used extensively in
tions. In the past 20 years, supported organometallic
practical reactions such as naphtha-reforming and
NOx-removal processes [2]. The conventional prepara-
tive method of supported metal catalysts is impregna-
tion and hydrogen reduction; the supports such as silica
compounds, in particular metal carbonyl clusters, were
widely applied to heterogeneous catalytic reactions, and
in many cases better catalytic performances were ob-
tained than those by the conventional catalysts from
metal salts [3].
One of the new preparative methods of nanoclusters
ꢀ Dedicated to Professor D.F. Shriver on the occasion of his 65th
is the reduction of low valent metal complexes under
birthday.
mild conditions, in which metal atoms are extruded
from labile organometallics with concomitant removal
of ligands [1a]. By using this method, low-valent com-
plexes of Pt [4], Pd [5], Ru [6], and Ir [7] were reduced
to give highly dispersed nanoclusters in solutions or on
supports. Organoplatinum complexes were also used as
precursors in chemical vapor deposition [8].
* Corresponding author. Fax: +81-42-388 7500.
E-mail addresses: fukuoka@design.cat.hokudai.ac.jp (A. Fukuoka),
komiya@cc.tuat.ac.jp (S. Komiya)
1 Also corresponding author: Present address: Catalysis Research
Center, Hokkaido University, Sapporo 060-0811, Japan. Fax: +88-
11-706 4957.
2 According to Lin and Finke [7], we define nanoclusters as parti-
cles smaller than 10 nm and colloids as bigger ones.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00210-8

A. Fukuoka et al. / Inorganica Chimica Acta 294 (1999) 266–274
267
Table 1
Organosiloxo complexes [9] of transition metals are
Crystallographic data for 2 and 3
in a class of alkoxo complexes [10], and they are
important not only as precursors in sol-gel chemistry
but also as intermediates in several homogeneous
catalyses. We are interested in the R–M–O–Si bonds
of the siloxo complexes, which may be structure models
of active sites on M/SiO2 catalysts in hydrocarbon
conversions. As a part of our study on the reactivity
of organoplatinum(II) and related complexes, we
found that facile reduction took place for novel
organo(siloxo)platinum(II) complexes at 1 atm and 0°C
[11]. Here we describe the details of synthesis, charac-
terization, reactivity of the Pt and Pd siloxo complexes,
and their application to the preparation of metal nan-
oclusters on supports.
2
3
Formula
C28H32OSiPt
607.74
triclinic
C32H32OSiPt
655.78
triclinic
M (g mol−1
)
Crystal system
Space group
(
(
P1 (no. 2)
P1 (no. 2)
,
a (A)
10.522(2)
13.351(3)
9.602(2)
104.44(2)
109.96(2)
84.42(2)
1227.6(5)
2
10.557(4)
13.702(7)
10.334(4)
104.94(5)
99.32(3)
69.79(4)
1350(1)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
1.644
1.612
,
Radiation (A)
Mo Ka
0.71069
57.40
Mo Ka
0.71069
52.86
v(Mo Ka) (cm−1
Temperature
2q (°)
)
2. Results and discussion
rt
rt
6B2qB55
ꢀ–2q
5986
5072
0.028
3B2qB55
ꢀ–2q
6586
4979
0.030
2.1. Preparation and characterization of Pt and Pd
complexes
Scan type
No. of collected reflections
No. of unique reflections
a
R
Organoplatinum(II) and -palladium(II) complexes
prepared and used in this work are as follows:
PtMe(OSiPh3)(cod) (1), PtEt(OSiPh3)(cod) (2), PtPh-
(OSiPh3)(cod) (3), PtMe(OCPh3)(cod)(HOCPh3) (4), Pt-
Me(OPh)(cod) (5), PtMe(SPh)(cod) (6), PtMe(OSiPh3)-
(dppe) (7), PtMe2(cod) (8), PtMeCl(cod) (9), PdMe-
(OSiPh3)(cod) (10), PdMe(OSiPh3)(cod)(HOSiPh3) (11)
(cod=1,5-cyclooctadiene, dppe=1,2-bis(diphenylphos-
phino)ethane).
Metathetical reactions of PtRCl(cod) (R=Me, Et,
Ph) or [PtR(cod)](NO3) with NaOSiPh3 in THF under
nitrogen gave new siloxo complexes of platinum 1–3
(Eq. (1)). The complexes were purified by recrystalliza-
tion; for example, colorless blocks of 1 were obtained
from Et2O/hexane. In the preparation of the alkoxo
analog 4, isolation of PtMe(OCPh3)(cod) was unsuc-
cessful but PtMe(OCPh3)(cod)(HOCPh3) (4) was ob-
tained in the presence of 1 equiv. of Ph3COH, in which
a Ph3COH molecule is hydrogen-bonded to the OCPh3
ligand. The Pd siloxo analogs 10 and hydrogen-bonded
11 were prepared in the same procedures (Eqs. (1) and
(2)).
b
Rw
0.035
3.66
0.022
1.67
Goodness-of-fit
a R=ꢀ[ꢁFoꢁ−ꢁFcꢁ]/ꢀꢁFoꢁ.
b Rw=[ꢀ(w(ꢁFoꢁ−ꢁFcꢁ)2/ꢀꢁFoꢁ ]
.
2 1/2
data are summarized in Table 1, and selected bond
distances and angles in Table 2. Fig. 1 shows ORTEP
drawings of 2 and 3, in which both complexes have
square planar geometries at Pt. For the ethyl complex
2, the Pt–O bond distance is 2.003(4) A, which is in the
typical range of Pt–O bonds (1.99–2.07 A) reported for
,
,
alkoxoplatinum complexes such as Pt(OMe)2(dppe), Pt-
Me(OMe)(dppe),
and
PtMe(OCH(CF3)2)(PMe3)2-
(HOCH(CF3)2) [10c]. The Pt–O–Si angle of 139.5(3)°
is larger than the Pt–O–C angles for the above
alkoxoplatinum complexes (117–123°), but the angle
is in the typical range of those for siloxo complexes
[12]. The Pt–C(3) and Pt–C(4) bond distances
Table 2
,
Selected bond distances (A) and angles (°) for 2 and 3
−NaCl
2
MRCl(cod)+NaOSiPh3TꢀHꢀFꢀ,ꢀ−ꢀꢀ20ꢀ°ꢁCMR(OSiPh3)(cod)
Pt–O
2.003(4)
2.297(6)
2.099(7)
1.586(4)
1.44(1)
Pt–C(1)
Pt–C(4)
Pt–C(8)
C(3)–C(4)
Pt–O–Si
2.052(6)
2.309(6)
2.112(7)
1.37(1)
(1)
Pt–C(3)
Pt–C(7)
Si–O
M=Pt; R=Me (1), Et (2), Ph (3)
M=Pd; R=Me (10)
C(7)–C(8)
139.5(3)
PdMeCl(cod)+NaOSiPh3
−NaCl
3
Pt–O
1.992(3)
2.096(5)
2.296(5)
1.589(3)
1.331(6)
Pt–C(1)
Pt–C(8)
Pt–C(12)
C(7)–C(8)
Pt–O–Si
2.010(4)
2.113(4)
2.285(4)
1.376(6)
+HOSiPh3ꢀꢀꢀꢀꢀꢀꢀꢀꢁPdMe(OSiPh3)(cod)(HOSiPh3)
THF, −20°C
Pt–C(7)
Pt–C(11)
Si–O
11
(2)
The molecular structures of 2 and 3 have been deter-
C(11)–C(12)
144.2(2)
mined by X-ray structure analysis. Crystallographic

268
A. Fukuoka et al. / Inorganica Chimica Acta 294 (1999) 266–274
Fig. 1. ORTEP drawings of (a) PtEt(OSiPh3)(cod) (2) and (b) PtPh(OSiPh3)(cod) (3).
1
distances trans to Et are longer than the Pt–C(7) and
Pt–C(8) trans to OSiPh3, reflecting stronger trans influ-
ence of Et than that of OSiPh3 (see below).
[10f]. On the other hand, in the H NMR of 11 in C6D6
the signal of OH was not detected; however, the signal of
o-H of OSiPh3 appeared at l 7.9 slightly higher than l 8.1
for 10, approaching l 7.6 of free Ph3SiOH. This implies
the fast exchange of OSiPh3 with Ph3SiOH in the solution
state. Similarly, the 13C{1H} NMR of 11 gave signals due
to a set of Ph carbons, which also implies the fast exchange
of 11 with Ph3SiOH. Acidolysis of 10 with dry HCl in
Et2O produced CH4 (95%), Ph3SiOH (93%), and
PdCl2(cod) (88%). In contrast, the similar reaction of 11
gave CH4 (96%), Ph3SiOH (199%), and PdCl2(cod) (86%),
which supports the presence of Ph3SiOH in 11.
All the new siloxo and alkoxo complexes were charac-
terized by analytical and/or spectroscopic methods. In the
1H NMR of 1 in C6D6, a singlet peak due to the methyl
protons appeared at l 0.95 with 195Pt satellites. The
olefinic protons of COD resonated at l 3.5 and 5.2 with
195Pt satellites, whose coupling constants are in accord
with the trans influence of Me and OSiPh3 in the square
planar geometry; the high field signal with a larger JH–Pt
is due to the olefinic protons trans to OSiPh3 and the low
field one with a smaller JH–Pt to those trans to Me. The
1
13C{1H} NMR of 1 is consistent with the H NMR; the
2.2. Reduction of Pt and Pd complexes
methyl carbon gave a singlet peak at l 6.9 with 195Pt
satellites, and the olefinic carbons trans to OSiPh3
resonated at l 74.5 and those trans to Me at l 114.0. The
IR spectrum of 1 gave a strong band of w(Si–O) at 990
In the investigation of reactivity of the siloxo com-
plexes, the reaction with hydrogen smoothly proceeded at
1 atm and room temperature to form metal colloids.
Therefore, we performed the detailed study on the
reduction of siloxo and related complexes of platinum and
palladium.
Treatment of the THF solution of 1 with H2 (1 atm) at
0°C precipitated readily a black solid with formation of
gas. The GLC, GC-MS, and 1H NMR analyses revealed
that the gas and liquid products were methane, triphenyl-
silanol, and cyclooctane in quantitative yields. The black
solid gave no IR peaks, indicating the absence of organic
ligands and products on the solid surface. In the transmis-
sion electron microscopy (TEM) observation of the solid,
small particles of ca. 3 nm were seen to form agglomer-
ates. These results show that the reaction of 1 with H2
results in the complete reduction of the metal and ligands
(Eq. (3)).
cm−1
.
When 3 equiv. of Ph3SiOH were added to the C6D6
solution of 1, the 1H NMR signal of o-H (l 8.0) of OSiPh3
was shifted to high field (l 7.7), thus approaching l 7.6 of
free Ph3SiOH with increase in the peak intensity. This
shows that the OSiPh3 ligand exchanges rapidly with free
Ph3SiOH in the solution state. In fact, in the solid state of
the Pd analog of 1, hydrogen-bonded PdMe(OSiPh3)-
(cod)(HOSiPh3) (11) was isolated. For the IR spectrum of
11 in KBr, the Si–O frequencies were observed at 916 (s)
and 900 (sh) cm−1; the former can be ascribed to the
OSiPh3 ligand and the latter to the hydrogen-bonded
HOSiPh3. Moreover, a broad peak of hydrogen-bonded
O–H was seen at 2300–2700 cm−1 as reported for other
Pd alkoxo complexes having hydrogen-bonded alcohols

A. Fukuoka et al. / Inorganica Chimica Acta 294 (1999) 266–274
269
Table 3
Reduction of Pt and Pd complexes MMeX(cod) with hydrogen a
Sample
Reaction temperature
(°C)
Reaction time
(h)
Yield (%)
CH4
HX
C8H16
PtMe(OSiPh3)(cod) (1)
PtMe(OCPh3)(cod)(HOSiPh3) (4)
PtMe(OPh)(cod) (5)
PtMe(SPh)(cod) (6)
PtMe(SPh)(cod) (6)
PtMe(OSiPh3)(dppe) (7)
PtMe2(cod) (8)
PtMe2(cod) (8)
PtMeCl(cod) (9)
PdMe(OSiPh3)(cod) (10)
PdMe(OCPh3)(cod)(HOSiPh3) (11)
1/SiO2
0
0
0
0
50
0
0
rt
0
0
0
1
1
1
1
1
1
1
1
1
1
1
2
3
6
3
96
94
94
0
95
0
0
186
0
100
100
96
98
186
100
90
182
86
0
nd
0
–
–
0
99
199
80
76
–
99
89
90
0
nd
–
0
93
0
92
101
85
80
78
80
0
0
rt
0
5/SiO2
8/SiO2
10/SiO2
78
a Reaction conditions: [complex]=0.02 M in THF, 0°C, H2 1 atm.
Pt(CH3)(OSiPh3)(C8H12)+3H2 ꢀꢀꢀꢀꢀꢁPt(0)+CH4
MeX(cod) by changing the ligand X is summarized as
follows: OSiPh3:OCPh3\OPhꢀSPh, Cl, Me.
THF, 0°C
1
+Ph3SiOH+C8H16
(3)
For the reduction of 1, the yields of products were
plotted against reaction time as shown in Fig. 3, where
free COD and cyclooctene were detected at the early
stage of the reaction. Therefore, the reaction of 1 with
H2 led to the reduction of methyl and triphenylsiloxo
groups with liberation of COD, which was subse-
quently reduced to cyclooctane via cyclooctene.
Induction periods were observed for the Pt complexes
in Figs. 2 and 3, which suggested an autocatalytic
process. To clarify the role of the Pt colloids in the
reduction of 1, the following experiments were per-
formed (Fig. 4). In the reaction of 1 with H2 in diglyme
([1]=0.020 M) at −19°C, the reaction was stopped at
ca. 50% conversion after 115 min to form a mixture of
1 and Pt metals. To the resulting mixture was added 1
or 2 equiv. of 1 in diglyme (0.020 M), and in this case
Reductions of other Pt and Pd complexes were per-
formed under the same conditions, and yields of ligand
hydrogenation are summarized in Table 3. It is notable
that the alkoxo (including siloxo and phenoxo) com-
plexes of Pt and Pd gave quantitative yields of methane,
cyclooctane, and corresponding alcohols. In contrast,
no reaction took place for PtMe(SPh)(cod) (6),
PtMe2(cod) (8), or PtMeCl(cod) (9) at 0°C; thus show-
ing the great effect of X in a series of PtMeX(cod)
complexes. The reduction of 6 and 8 proceeded at
higher reaction temperatures as reported in the CVD
study using 8 [8a]. Substitution of COD to DPPE in 7
inhibited completely the reduction. These results imply
that higher reduction activities are obtained for the
complexes having more labile ligands.
The reduction activities of the Pt and Pd complexes
were compared using the formation rate of methane3.
Fig. 2 depicts plots of yields of methane versus time at
0°C and 1 atm in THF. Pd complexes 10 and 11 gave
higher rates than Pt complexes, reflecting the general
higher reactivity of Pd over Pt complexes. Interestingly,
among the PtMeX(cod) complexes the reduction rates
of siloxo and alkoxo complexes 1 and 4 were faster
than those of the phenoxo complex 5. As described
above, complexes 6–9 gave no formation of methane.
Accordingly, the order of reduction activity for Pt-
3 The reduction rate for 1 was independent of the rate of rotation
of the magnetic stirring bar, confirming that the reduction was not
limited by the diffusion of hydrogen. In this work, 200 rpm was used
as a standard rate of rotation.
Fig. 2. Plots of yields of CH4 vs. time in the reduction of Pt and Pd
complexes. Conditions: [complex]=0.02 M in THF, 0°C, H2 1 atm.

270
A. Fukuoka et al. / Inorganica Chimica Acta 294 (1999) 266–274
Fig. 3. Plots of product yields in the reduction of 1. Conditions:
[1]=0.02 M in THF, 0°C, H2 1 atm.
Fig. 5. Effects of addition of Ph3SiOH or COD in the reduction of 1.
Conditions: [1]=0.02 M in diglyme, 0°C, H2 1 atm.
the induction period was not observed. Moreover, the
reduction rate was enhanced slightly, however, the de-
termination of the reaction kinetics was unsuccessful.
For the CVD on glass or Teflon using PtMe2(cod) and
related Pt(II) complexes with hydrogen, Puddephatt
showed a half-order dependence on the concentration
of the precursor complex, and that the reduction pro-
cess is catalyzed by a preformed platinum metal [8b].
Randall and Whitesides reported that the reduction of
PtMe2(cod) (8) with platinum black is zero-order de-
pendent, which indicates the heterogeneous hydrogena-
tion on the surface of platinum black [13]. In our case,
it seems that the surface area of forming Pt particles is
insufficient for heterogeneous zero-order reaction, thus
providing the complicated reaction profile. Addition of
COD and Ph3SiOH slowed the reduction rate (Fig. 5),
implying that the adsorption of Pt complex on the Pt
surface is inhibited by forming COD and Ph3SiOH.
From these results and considerations, we propose that
the reduction of 1 is catalyzed by the forming Pt metals
(Fig. 6).
The reason for high reduction activity of siloxo and
alkoxo complexes is not yet clear. However, the siloxo
groups are more labile than SPh, Me, or Cl, as shown
by the fast exchange with free silanol. This may result
in enhanced adsorption activity of the complexes on the
forming Pt metals. Although we performed the test
reactions of 1 with several hydrosilanes to study the
initial reduction step, observation of Pt hydride or
1
other intermediates was unsuccessful in H NMR even
at low temperature.
2.3. Preparation of Pt/SiO2 and Pd/SiO2 from
organometallics
Since the siloxo and alkoxo complexes of Pt and Pd
were highly susceptible to reduction by hydrogen, we
applied the high activity in reduction to the preparation
of supported metal catalysts. The complexes were ad-
sorbed on silica gel, and the resulting solid was reduced
similarly with hydrogen in THF. The color of the solid
changed from white to dark gray, and the ligands were
hydrogenated completely as shown in Table 3.
Ph3SiOH was also recovered in good yields from the
supernatant liquid without adsorption on the silica
surface.
The TEM image of Pt/SiO2 from 1 (designated as
Pt(1)/SiO2) is exhibited in Fig. 7 (1 wt% Pt). Black
Fig. 4. Effect of addition of Pt colloids in the reduction of 1.
Conditions: [1]=0.02 M in diglyme, −19°C, H2 1 atm.
Fig. 6. Possible mechanism for the reduction of 1 with H2.

A. Fukuoka et al. / Inorganica Chimica Acta 294 (1999) 266–274
271
Fig. 7. TEM images of (a) Pt(1)/SiO2 and (b) Pt(12)/SiO2.
points seen in the bright field image were identified
as crystalline Pt by their selected area diffraction. From
the histogram of Pt particle size, the mean diameter of
Pt was 8.2 nm (Fig. 8). In contrast, conventional Pt(12)/
SiO2 was prepared from H2PtCl6·6H2O (12) and subse-
quent O2 oxidation and H2 reduction at 400°C. In the
TEM of Pt(12)/SiO2, the mean diameter was 13.2 nm.
In addition, the Pt particles of Pt(1)/SiO2 were dis-
tributed more homogeneously than those of Pt(12)/
SiO2. Similarly, Pt/SiO2 samples were obtained from 5
at 0°C and from 8 at room temperature, and the mean
diameters were 5.3 and 9.9 nm, respectively. For
Pd(10)/SiO2 prepared from 10, the mean diameter of Pd
was 7.6 nm. Hence, the benefits of reduction of Pt and
Pd compounds are the smaller size and the homoge-
neous distribution of metal particles on the silica sur-
face. It seems that the mild reaction conditions of 0°C
and 1 atm prevent the aggregation of metal particles on
the support surface.
without contamination. (3) The reduced ligands are
separated easily by filtration. (4) The Pt particles are
smaller than those of conventional Pt/SiO2 from
H2PtCl6·6H2O and their distribution is homogeneous.
In summary, we prepared and characterized several
siloxo and alkoxo complexes of Pt and Pd. Owing to
the highly labile character of the siloxo and alkoxo
ligand, reduction of the complexes with hydrogen pro-
ceeded under very mild conditions to give metal nano-
clusters. Organometallics are useful precursors for
nanoclusters, and fine tuning of labile ligands would
enable the true control of particle size and distribution.
3. Experimental
3.1. General
The present preparative method of nanoclusters from
the siloxo and alkoxo complexes of Pt and Pd has the
following advantages. (1) The conditions are mild: 1
atm and below room temperature. (2) Hydrogen as a
reductant is separated easily from the reaction solution
All manipulations were performed under a nitrogen
or argon atmosphere using standard Schlenk techniques
[14,15]. Solvents were dried over and distilled from
appropriate drying agents under nitrogen: hexane,
toluene, Et2O, THF, diglyme, and dioxane from Na/
Fig. 8. Histograms of the Pt nanocluster diameters for (a) Pt(1)/SiO2 and (b) Pt(12)/SiO2.

272
A. Fukuoka et al. / Inorganica Chimica Acta 294 (1999) 266–274
benzophenone ketyl. NMR solvents were freeze–
pump–thaw degassed and vacuum-transferred from ap-
propriate agents (C6D6 from Na; CDCl3 from P4O10). Pt
complexes were prepared according to the literature
methods with some modifications: PtMeCl(cod) [16],
PtEtCl(cod) [17], PtPhCl(cod) [16], PtMe(SPh)(cod) (6)
[18], PtMe2(cod) (8) [16], PdMeCl(cod) (9) [19],
Ph3SiONa [20]. KOPh, KSPh, and NaOCPh3 were pre-
pared from potassium (or sodium) with PhOH, PhSH,
or Ph3COH. NMR spectra were obtained on JEOL
FX-200, EX-270, and LA-300 spectrometers. IR spectra
were measured on a JASCO FT-IR 5M spectrometer.
Elemental analyses were performed with a Perkin-Elmer
2400 series II CHN analyzer. Melting points were mea-
sured under nitrogen using a Yazawa capillary melting
apparatus and the values were not corrected. Gas chro-
matography was performed using a Shimadzu GC-
8APF with columns of Porapak Q for gases and of PEG
20M for liquids. GC-MS was measured on a Shimadzu
GCMS QP2000A using a PEG20M capillary column.
Transmission electron microscopy was performed using
a Hitachi H-700H microscope.
C), 7.2–7.3 (m, 9H, OSiPh3 m- and p-H), 8.0 (m, 6H,
OSiPh3 o-H).
PtPh(OSiPh3)(cod) (3) was prepared from PtPh-
Cl(cod) and NaOSiPh3; colorless blocks from Et2O/hex-
ane; yield 56%; m.p. 145–146°C (dec.). This complex
was identified by spectroscopic methods and X-ray
1
analysis. IR (KBr, cm−1): 990 (s, w(Si–O)); H NMR
(200 MHz, C6D6): l 1.0–2.0 (m, 8H, COD CH2), 3.8
(br, JH–Pt=68 Hz, 2H, COD ꢂCH trans to O), 5.4 (br,
J
H–Pt=26 Hz, 2H, COD ꢂCH trans to C), 6.9–7.4 (m,
5H, Pt–Ph), 7.2–7.3 (m, 9H, OSiPh3 m- and p-H), 7.8
(m, 6H, OSiPh3 o-H). 13C{1H} NMR (68 MHz, C6D6):
l 26.9 (s, JC–Pt=21 Hz, COD CH2), 31.7 (s, JC–Pt=17
Hz, COD CH2), 78.1 (s, JC–Pt=211 Hz, COD ꢂCH
trans to O), 116.0 (br, COD ꢂCH trans to C), 124–141
(m, Pt–Ph), 127–130 (m, OSiPh3 m- and p-C), 135.8 (s,
OSiPh3 o-C).
A similar reaction of PtMeCl(cod) with NaOCPh3
resulted in the formation of a mixture of PtMe-
(OCPh3)(cod) and PtMe(OCPh3)(cod)(HOCPh3) (4),
and isolation of the former was unsuccessful. However,
in the presence of 1.1 equiv. of Ph3COH, 4 was isolated;
white needles from THF/hexane; yield 54%; m.p. 65–
66°C (dec.). This complex was identified by spectro-
scopic methods. IR (KBr, cm−1): 1040 (sh, w(C–O)),
3.2. Preparation of complexes
1
1020 (s, w(C–O)), 1000 (m, w(C–O)); H NMR (200
A typical procedure for PtMe(OSiPh3)(cod) (1) is
given. A Schlenk flask was charged with PtMeCl(cod)
(349.2 mg, 0.9871 mmol) and NaOSiPh3 (356.5 mg,
1.195 mmol). THF (15 ml) was added at room temper-
ature and the solution was stirred for 3 h. The mixture
was evaporated to dryness and the resulting solid was
extracted with toluene. After the filtered solution was
again evaporated to dryness, the solid was extracted
with Et2O and addition of hexane gave colorless blocks
of 1 (363.1 mg); yield 62%; m.p. 133–134°C (dec.). Anal.
Calc. for C27H30OSiPt: C, 54.62; H, 5.09. Found: C,
MHz, C6D6): l 0.57 (s, JH–Pt=78 Hz, 3H, CH3),
1.2–2.0 (m, 8H, COD CH2), 3.5 (br, JH–Pt=62 Hz, 2H,
COD ꢂCH trans to O), 5.5 (br, JH–Pt=27 Hz, 2H, COD
ꢂCH trans to C), 7.1–7.2 (m, 18H, Ph m- and p-H), 7.5
(m, 12H, Ph o-H).
PtMe(OPh)(cod) (5) was prepared from PtMeCl(cod)
and KOPh; colorless needles from Et2O/hexane; yield
56%; m.p. 100–101°C (dec.). Anal. Calc. for C15H20OPt:
C, 43.79; H, 4.90. Found: C, 43.36; H, 4.61%. IR (KBr,
1
cm−1): 980 (s, w(C–O)); H NMR (200 MHz, C6D6): l
0.94 (s, JH–Pt=78 Hz, 3H, CH3), 1.2–1.9 (m, 8H, COD
CH2), 3.6 (br, JH–Pt=68 Hz, 2H, COD ꢂCH trans to
O), 5.3 (br, JH–Pt=27 Hz, 2H, COD ꢂCH trans to C),
6.9 (t, JH–H=7 Hz, 1H, OPh p-H), 7.2 (m, 2H, OPh
o-H), 7.3 (t, JH–H=7 Hz, 2H, OPh m-H).
1
54.08; H, 5.37%. IR (KBr, cm−1): 990 (s, w(Si–O)); H
NMR (200 MHz, C6D6): l 0.95 (s, JH–Pt=75 Hz, 3H,
CH3), 1.0–2.0 (m, 8H, COD CH2), 3.5 (br, JH–Pt=68
Hz, 2H, COD ꢂCH trans to O), 5.2 (br, JH–Pt=27 Hz,
2H, COD ꢂCH trans to C), 7.2–7.3 (m, 9H, OSiPh3 m-
and p-H), 8.0 (m, 6H, OSiPh3 o-H). 13C{1H} NMR (68
MHz, C6D6): l 6.9 (s, JC–Pt=643 Hz, CH3), 27.3 (s,
PtMe(OSiPh3)(dppe) (7) was prepared from PtMe-
Cl(dppe) and NaOSiPh3; yellow powders from Et2O/
hexane; yield 37%; m.p. 193–194°C (dec.). This complex
was identified by spectroscopic methods. IR (KBr,
JC–Pt=22 Hz, COD CH2), 31.8 (s, JC–Pt=21 Hz, COD
CH2), 74.5 (s, JC–Pt=227 Hz, COD ꢂCH trans to O),
114.0 (s, JC–Pt=28 Hz, COD ꢂCH trans to C), 127–129
(m, OSiPh3 m- and p-C), 135.9 (s, OSiPh3 o-C).
1
cm−1): 996 (s, w(Si–O)); H NMR (200 MHz, C6D6): l
0.98 (dd, JH–P=8 and 4 Hz, 3H, JH–Pt=60 Hz, CH3),
1.3–1.9 (m, 4H, DPPE CH2), 6.8–7.1 (m, 12H, DPPE
m- and p-H), 7.2–7.3 (m, 9H, OSiPh3 m- and p-H),
7.4–7.9 (m, 8H, DPPE o-H), 8.0–8.2 (m, 6H, OSiPh3
o-H).
PdMe(OSiPh3)(cod) (10) was prepared from PdMe-
Cl(cod) and slight excess NaOSiPh3 in THF at −20°C.
Colorless blocks were obtained by recrystallization from
Et2O at −20°C; yield 62%; m.p. 107°C (dec.).
PtEt(OSiPh3)(cod) (2) was prepared from PtEtCl(cod)
and NaOSiPh3; colorless blocks from Et2O/hexane;
yield 62%; m.p. 102–103°C (dec.). Anal. Calc. for
C28H32OSiPt: C, 55.34; H, 5.31. Found: C, 54.93; H,
1
5.37%. IR (KBr, cm−1): 1012 (s, w(Si–O)); H NMR
(200 MHz, C6D6): l 1.0–2.0 (m, 13H, CH2CH3 and
COD CH2), 3.5 (br, JH–Pt=73 Hz, 2H, COD ꢂCH trans
to O), 5.3 (br, JH–Pt=34 Hz, 2H, COD ꢂCH trans to

A. Fukuoka et al. / Inorganica Chimica Acta 294 (1999) 266–274
273
,
Anal. Calc. for C27H30OSiPd: C, 64.21; H, 5.99. Found:
C, 63.89; H, 6.07%. IR (KBr, cm−1): 990 (s, w(Si–O));
1H NMR (300 MHz, C6D6): l 1.04 (s, 3H, CH3),
1.4–1.8 (m, 8H, COD CH2), 4.0 (br, 2H, COD ꢂCH
trans to O), 5.6 (br, 2H, COD ꢂCH trans to C), 7.2–7.4
(m, 9H, OSiPh3 m- and p-H), 8.0 (m, 6H, OSiPh3 o-H).
13C{1H} NMR (75 MHz, C6D6): l 12.7 (s, CH3), 26.9
(s, COD CH2), 30.7 (s, COD CH2), 93.4 (s, COD ꢂCH
trans to O), 124.2 (s, COD ꢂCH trans to C), 127–129
(m, OSiPh3 m- and p-C), 135.9 (s, OSiPh3 o-C), 142.7
(s, OSiPh3 ipso-C).
Mo Ka radiation (u=0.71069 A) in the 6B2qB55°
range, and 5986 reflections were collected. Absorption
correction was applied to the intensity data. The struc-
ture was solved by the heavy-atom methods [21] and
refined by a full matrix least-squares techniques using
the teXan program [22]. The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included
but not refined. Final R and Rw values are 0.028 and
0.035 for 5072 reflections with ꢁFoꢁ\3|ꢁFoꢁ.
3.5. Reduction of Pt and Pd complexes with hydrogen
PdMe(OSiPh3)(cod)(HOSiPh3) (11) was prepared
from PdMeCl(cod), NaOSiPh3, and Ph3SiOH (ratio
1.0:1.3:1.0) in THF at −20°C. Colorless blocks were
obtained by recrystallization from Et2O at −20°C;
yield 55%; m.p. 118°C (dec.). Anal. Calc. for
C45H46O2Si2Pd: C, 69.17; H, 5.93. Found: C, 69.16; H,
5.97%. IR (KBr, cm−1): 2700–2300 (w, w(O–H)), 916
A typical procedure for 1 is given. A three-way
Schlenk flask was charged with 1 (0.020 mmol) and
THF (1 ml), and the mixture was freeze–pump–thaw
degassed. The flask was placed in a thermostat at 0°C,
and filled with hydrogen (1 atm, ca. 40 molar excess)
through a septum rubber using a hypodermic syringe
needle. The mixture was stirred at 200 rpm, and the gas
phase was periodically analyzed by GLC (Porapak Q)
to determine the amount of produced methane. After
the reaction, the flask was opened and cyclooctane was
analyzed by GLC (PEG 20 M). The mixture was evap-
orated to dryness, and after adding C6D6 the yield of
Ph3SiOH was determined by 1H NMR comparing
Ph3SiOH (o-H of Ph) and dioxane as an internal stan-
dard. The resulting black solid was washed with Et2O
and was dried under vacuum.
1
(s, w(Si–O)), 900 (sh, w(Si–O)); H NMR (300 MHz,
C6D6): l 0.98 (s, 3H, CH3), 1.4–1.7 (m, 8H, COD
CH2), 4.0 (br, 2H, COD ꢂCH trans to O), 5.6 (br, 2H,
COD ꢂCH trans to C), 7.2–7.3 (m, 18H, Ph m- and
p-H), 7.9 (m, 12H, Ph o-H). 13C{1H} NMR (75 MHz,
C6D6): l 13.3 (s, CH3), 26.8 (s, COD CH2), 30.5 (s,
COD CH2), 94.4 (s, COD ꢂCH trans to O), 124.2 (s,
COD ꢂCH trans to C), 127–130 (m, OSiPh3 m- and
p-C), 135.9 (s, OSiPh3 o-C), 139.9 (s, OSiPh3 ipso-C).
3.3. Acidolysis of the complexes
3.6. Preparation of Pt/SiO2 and Pd/SiO2
The procedure for 1 is given. A sample tube was
charged with 1 (21.5 mg, 0.0362 mmol) and degassed.
Concentrated H2SO4 (1 ml) was added by a hypodermic
syringe, and after 4 h the gas phase was analyzed by gas
chromatography (Porapak Q): CH4 97% yield. Acidoly-
sis with HCl was performed in a Schlenk tube, where 1
(20.6 mg, 0.0347 mmol), HCl in Et2O (1.324 M, 26 ml),
and Et2O (2 ml) were added. After freeze–pump–thaw
degassing, the mixture was stirred at room temperature
for 5 h. Gaseous product was analyzed by GLC: CH4
2%. The mixture was evaporated to dryness, and to the
resulting solid was added C6D6. The H NMR showed
the formation of PtMeCl(cod) (77%) and Ph3SiOH
(80%).
Products and yields in acidolysis with conc. H2SO4:
2, C2H6 (94%); 10, CH4 (100%); 11, CH4 (93%). With
HCl: 10, CH4 (95%), Ph3SiOH (93%), PdCl2(cod)
(88%); 11, CH4 (96%), Ph3SiOH (199%), PdCl2(cod)
(86%).
Silica gel (JRC-SIO-4, Catalysis Society of Japan,
374 m2 g−1, 60–100 mesh) was dried under vacuum
(10−3 Torr) at 200°C for 2 h. To a mixture of the silica
(571.4 g) and THF (10 ml) was added a THF solution
of 1 (17.4 mg) under nitrogen. After stirring for 3 h, all
of 1 was adsorbed on the silica, which was confirmed
by the 1H NMR of the supernatant liquid. THF (10 ml)
was added to the resulting solid, and the mixture was
stirred at 0°C and 2000 rpm after introduction of
hydrogen (1 atm). When the yield of methane reached
ca. 100% in the GLC of the gas phase, the reaction was
stopped. From the GLC of the supernatant liquid, the
yield of cyclooctane was 85%. The liquid was evapo-
rated to dryness, and the yield of Ph3SiOH was 80%
from the 1H NMR of the resulting solid. The solid
Pt(1)/SiO2 was washed with Et2O and dried under
vacuum.
Conventional Pt(12)/SiO2 was prepared by the im-
pregnation method. To a mixture of silica (ca. 0.5 g)
and water (10 ml) was added a water solution (10 ml)
of H2PtCl6·6H2O (ca. 13 mg). After stirring for 24 h,
the mixture was evaporated to dryness and the resulting
solid was dried under vacuum (10−3 Torr). The solid
was oxidized by O2 flow at 400°C for 2 h, and was
cooled to room temperature with Ar flow. Subse-
1
3.4. X-ray structure analyses of 2 and 3
A typical procedure for 2 is given. A crystal of
suitable size was sealed in a thin-glass capillary under
nitrogen. The intensity data were collected at room
temperature on a Rigaku AFC-5R diffractometer using

274
A. Fukuoka et al. / Inorganica Chimica Acta 294 (1999) 266–274
M. Ichikawa, Adv. Catal. 38 (1992) 283. (f) A. Fukuoka, M.
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3643.
quently, the solid was reduced by H2 flow at 400°C for
2 h.
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3.7. TEM of Pt/SiO2 and Pd/SiO2
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The powdered sample was dispersed in butanol and
the mixture was mixed by ultrasound. The image was
obtained at 200 kV and original magnification was
250 000×. Histograms of particle size were obtained
from the following sample populations: Pt(1)/SiO2 162,
Pt(5)/SiO2 291, Pt(8)/SiO2 240, Pt(12)/SiO2 303, Pd(10)/
SiO2 303.
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4. Supplementary material
The bond distances and angles, atomic coordinates,
anisotropic displacement parameters, observed and cal-
culated structure factors for the X-ray crystallography
of 2 and 3 are available.
Acknowledgements
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We thank Professor T. Noma for useful advice on
TEM. This work was supported by Tokuyama Science
Foundation and by a Grant-in-Aid for Scientific Re-
search from the Ministry of Education, Science, Sports
and Culture, Japan.
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