Palladium and platinum units grafted on the periphery of carbosilane dendrimers

Article abstract of DOI:10.1002/1099-0682(200209)2002:9<2477::AID-EJIC2477>3.0.CO;2-U

The reaction of a series of phosphanyl-terminated carbosilane dendrimers with palladium and platinum complexes was carried out. The new metallodendrimers containing PdCl(η³-2-MeC₃H₄) and PtCl₂ or Pt(C≡CPh)₂ as peripheral groups were characterized by ¹H, ¹³C, ²⁹Si, ³¹P, and ¹⁹⁵Pt NMR spectroscopy, and, in some cases, by mass spectrometry. The PtCl₂-containing species of the second-generation carbosilane dendrimer displays only one of the two possible stereoisomers. By comparison with the ³¹P NMR spectra of the model compounds cis-[PtCl₂(PPh₂CH₂ SiMe₃)₂] (4) and cis-[PtCl₂{Me₂Si(CH₂ PPh₂)₂}] (5), it was deduced that the PtCl₂ units are bound on the surface of the dendrimer through two phosphorus atoms belonging to the same branch. The palladium dendrimers were tested as catalysts in the hydrovinylation of styrene, and their activity was compared with that of the model catalyst [PdCl(η³-2-MeC₃H₄) (PPh₂CH₂SiMe₃)]. The crystal structures of 4, 5, and [Pt(C≡CPh)₂{Me₂Si(CH₂ PPh₂)₂}] (6) were solved by X-ray diffraction analysis. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.

Full text of DOI:10.1002/1099-0682(200209)2002:9<2477::AID-EJIC2477>3.0.CO;2-U

FULL PAPER
Palladium and Platinum Units Grafted on the Periphery of Carbosilane
Dendrimers
[a]
[a]
[a]
[a]
[a]
´
Monica Benito, Oriol Rossell,* Miquel Seco, Guillermo Muller, Juan I. Ordinas,
[b]
[b]
`
Merce Font-Bardia, and Xavier Solans
Keywords: Dendrimers / Alkynes / Homogeneous catalysis / Palladium / Platinum
The reaction of a series of phosphanyl-terminated carbosil-
ane dendrimers with palladium and platinum complexes was
carried out. The new metallodendrimers containing PdCl(η3-
2-MeC3H4) and PtCl2 or Pt(CϵCPh)2 as peripheral groups
were characterized by 1H, 13C, 29Si, 31P, and 195Pt NMR spec-
troscopy, and, in some cases, by mass spectrometry. The
PtCl2-containing species of the second-generation carbosil-
ane dendrimer displays only one of the two possible ste-
reoisomers. By comparison with the 31P NMR spectra of the
[PtCl2{Me2Si(CH2PPh2)2}] (5), it was deduced that the PtCl2
units are bound on the surface of the dendrimer through two
phosphorus atoms belonging to the same branch. The palla-
dium dendrimers were tested as catalysts in the hydrovi-
nylation of styrene, and their activity was compared with that
of the model catalyst [PdCl(η3-2-MeC3H4)(PPh2CH2SiMe3)].
The crystal structures of 4, 5, and [Pt(CϵCPh)2{Me2Si-
(CH2PPh2)2}] (6) were solved by X-ray diffraction analysis.
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
model compounds cis-[PtCl2(PPh2CH2SiMe3)2] (4) and cis- 2002)
Introduction
minal phosphanyl groups on the surface (1 and 2), and the
surface congestion on 3 is lower due to the presence of
CH2ϪCH2ϪSiMe2 spacers in the arms. The dendrimers
were obtained by a repetitive stepwise synthetic route of
hydrosilylation of the vinylic end groups of the dendrimer
with chlorosilanes followed by alkenylation with vinylmag-
nesium chloride.[3] Next, reaction with the tetramethylethyl-
enediamine complex of [(diphenylphosphanyl)methyl]li-
thium permitted the incorporation of terminal CH2PPh2
groups.
There is currently an interest in the synthesis of dendri-
mers and in the development of their chemistry.[1] Carbosil-
ane dendrimers have been widely used in recent years be-
cause they are very stable, both kinetically and thermodyn-
amically.[2] Moreover, peripheral groups, such as SiϪCl of-
fer the opportunity of introducing other functions through
the appropriate chemistry; such as the synthesis of carbosil-
ane dendrimers containing diphenylphosphane-terminated
groups.[3] Recently, we used these species as ‘‘dendrimer li-
gands’’ to coordinate a number of metal units (e.g.,
AuCl).[4] These units reacted, in turn, with metal anions to
give dendrimers decorated on the surface by transition
metal clusters.[5] We now report an extension of our previ-
ous efforts to graft palladium and platinum fragments on
the periphery of the dendrimers and the study of the react-
ivity of such types of species, including the use of palladium
compounds as catalytic precursors in the hydrovinylation
of styrene.
Platinum Dendrimers
Generally, the functionalization of the peripheral P-
branched dendrimers with transition metals is simply
achieved by taking advantage of the complexation ability
of these species.[6] For example, they have been treated with
complexes such as [Rh(acac)(COD)][7] or [Pd(µ-Cl)(η3-2-
MeC3H4)]2.[8] Several reports describe peripheral platinum-
containing dendrimers, but only one example shows plat-
inum centers bonded to phosphorus atoms.[7]
Results and Discussion
In this paper we have functionalized the surface of our
The carbosilane dendrimers chosen for this study are P-branched dendrimers with platinum by reaction with
listed in Scheme 1. They display different numbers of ter- [PtCl2(COD)]. We also synthesised the model compounds
[PtCl2(PPh2CH2SiMe3)2]
(4)
and
[PtCl2{Me2Si-
[a]
´
`
Departament de Quımica Inorganica, Universitat de Barcelona,
(CH2PPh2)2}] (5). Compound 4 was synthesised from
PPh2CH2SiMe3 (2 equiv.) and [PtCl2(COD)] (1 equiv.), and
5 from [PtCl2(COD)] (1 equiv.) and Me2Si(CH2PPh2)2 (1
equiv) (Scheme 2). Details of spectroscopy data of these
compounds are given in the Exp. Sect.
´
`
Martı i Franques 1Ϫ11, 08028 Barcelona, Spain
Fax: (internat.) ϩ 34-93/490-7725
E-mail: oriol.rossell@qi.ub.es
[b]
`
i Diposits
Departament de Cristal·lografia, Mineralogia
Minerals, Universitat de Barcelona,
´
`
Martı i Franques s/n, 08028 Barcelona, Spain
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487  WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ1948/02/0909Ϫ2477 $ 20.00ϩ.50/0
2477

O. Rossell et al.
Table 1. Selected bond lengths [A] and angles [°] for 4
FULL PAPER
˚
PtϪP(1)
PtϪP(2)
PtϪCl(1)
PtϪCl(2)
P(1)ϪPtϪP(2)
P(1)ϪPtϪCl(2)
P(2)ϪPtϪCl(2)
P(1)ϪPtϪCl(1)
P(2)ϪPtϪCl(1)
C(13)ϪP(1)ϪPt
C(29)ϪP(2)ϪPt
2.2401(9)
2.2545(8)
2.3563(8)
2.3506(9)
100.90(3)
169.85(3)
87.89(3)
P(2)ϪC(29)
Si(1)ϪC(13)
Si(2)ϪC(29)
P(1)ϪC(13)
P(2)ϪC(29)ϪSi(2)
C(17)ϪP(2)ϪPt
C(23)ϪP(2)ϪPt
Cl(2)ϪPtϪCl(1)
C(7)ϪP(1)ϪPt
C(1)ϪP(1)ϪPt
1.813(3)
1.892(4)
1.901(3)
1.825(3)
126.43(17)
110.46(11)
111.47(10)
86.70(3)
120.23(11)
112.43(12)
84.92(3)
172.88(3)
112.61(14)
118.06(10)
The phosphane ligands adopt a cis configuration, in spite
of the known fact that the bulky phosphane favors the
formation of trans isomers to minimize ligand interactions.
The PtϪCl bond lengths are in the expected range, and the
PtϪP distances are not elongated to any significant extent.
The angles around the platinum atom are in the range
84.92(3)° [P(1)ϪPtϪCl(1)] to 100.90(3)° [P(1)ϪPtϪP(2)].
The latter is intermediate between that found for
[PtCl2(PPh3)2] (97.8°)[9] and [PtCl2(PCy3)2] (107.6°).[10]
There is a steric tension between C(31) and the phenyl
group C(17), which implies an increase in the
Si(2)ϪC(29)ϪP(2) angle to 126.4°.
Scheme 1
Scheme 2
X-ray Crystal Structures of 4 and 5
A view of the compound cis-[PtCl2(PPh2CH2SiMe3)2] (4)
appears in Figure 1, and selected bond lengths and angles
are given in Table 1. The platinum atom has a planar coor-
dination with the slight tetrahedral distortion frequently
observed for d8 metal ions with bulky ligands.
Figure 2. View of the molecular structure of 5 together with the
atomic numbering scheme
The molecular structure of 5 is shown in Figure 2. Se-
lected bond lengths and angles are listed in Table 2. Com-
˚
Table 2. Selected bond lengths [A] and angles [°] for 5
PtϪP(1)
PtϪCl(1)
P(1)ϪC(1)
P(1)ϪC(7)
P(1)ϪPtϪCl(1)
Cl(1)ϪPtϪCl(1Ј)
C(14Ј)ϪSiϪC(14)
C(14)ϪSiϪC(13)
C(7)ϪPϪC(1)
PϪC(13)ϪSi
PϪPtϪPЈ
2.2456(16)
2.3440(17)
1.822(6)
1.810(6)
88.59(7)
87.40(10)
109.3(6)
114.3(4)
105.4(3)
118.1(4)
95.43(8)
Si(1)ϪC(14)
Si(1)ϪC(13)
P(1)ϪC(13)
1.845(7)
1.872(7)
1.806(7)
P(1)ϪPtϪCl(1Ј)
C(14Ј)ϪSiϪC(13)
C(13)ϪSiϪC(13Ј)
C(13)ϪPϪPt
C(7)ϪPϪPt
C(1)ϪPϪPt
175.98(6)
105.9(4)
107.5(4)
115.5(2)
113.9(2)
114.9(2)
Figure 1. ORTEP drawing of the molecular structure and num-
bering scheme of 4
2478
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487

Palladium and Platinum Units Grafted on the Periphery of Carbosilane Dendrimers
FULL PAPER
plex 5 contains a four-coordinate distorted square-planar 3558 Hz for 2a). Two silicon signals are observed for both
platinum center, with the chlorine ligands displaced by compounds, namely δ ϭ 8.98 ppm (Si0) and δ ϭ 4.04 ppm
˚
˚
Ϫ0.0052(1) A (Cl) and 0.0052(1) A [Cl(a)] from the (Si1) (CDCl3) for 1a, and δ ϭ 9.54 ppm (Si0) and δ ϭ 0.49
PtϪPϪP(a) plane. The ligand PP is bound in a bidentate ppm (Si1) ([D6]DMSO) for 2a. The 195Pt NMR spectra
fashion.
showed a triplet at δ ϭ Ϫ4320 ppm for 1a and at δ ϭ
It should be noted that the ligand 2,2-dimethyl-1,3-bis(di- Ϫ4482 ppm for 2a indicating the equivalence of the plat-
phenylphosphanyl)-2-silapropane is an analogue of dppp, inum atoms.
although the substitution of the CH2 unit for SiMe2 in the
It is worth noting that the PtCl2 units can be bound on
backbone not only increases complex solubility but also the surface of the dendrimer through two P atoms be-
provides an excellent NMR spectroscopic handle. The longing to the same branch, or alternatively, to different
PtϪP distances compare well with values reported in the branches. Accordingly, 2a can exhibit another stereoisomer,
compound [PtCl2(dppp)].[11] The shorter PtϪP bond 2aЈ (Scheme 4). A third possibility would be the simultan-
lengths also suggest that a stronger bond than normal re- eous interaction of the platinum fragment with two molec-
sults from the chelate ring formation.
The six-membered chelate
ules of dendrimer. However, in this case, the solubility of
comprising the resulting polymer species would probably be very low.
ring
PtϪPϪCϪSiϪCϪP adopts a twisted boat conformation, as
found, for example, in [Ni(NO3)2{Ph2PCH2Si(CH3)2-
CH2PPh2}].[12] It is noteworthy that the equivalent chelate
ring in [CoBr2{Me2Si(CH2PPh2)2}][13] adopts a chair con-
formation, presumably due to the tetrahedral metal center.
The chelate bite angle in 5 is 95.43(8)° (P1ϪPtϪP1Ј), some-
what shorter than that found for 4 and for the tetrahedral
metal compounds [CdCl2(PP)],[14] [CoCl2(PP)],[13] and
[HgI2(PP)][15] [PP ϭ Me2Si(CH2PPh2)2].
Synthesis
Scheme 4
Dendrimers 1 and 2 reacted with [PtCl2(COD)] in
CH2Cl2 at room temperature to give, after COD displace-
ment, the soluble, yellow, platinum-containing dendrimers
1a and 2a, respectively, within a few minutes (Scheme 3).
As mentioned earlier, the unique resonance in the 31P
NMR spectrum indicates that only one isomer is formed.
In order to assign it to 2a or 2aЈ, model compounds 4 and
5 are useful. Thus, for 4, the angle PϪPtϪP is 100.9° and
JPϪPt ϭ 3673 Hz (δ ϭ 4.2 ppm), while for 5, the PϪPtϪP
angle is 95.43° and JPϪPt ϭ 3560 Hz (δ ϭ 3.48 ppm). Al-
though both values are close, we tentatively propose that
the stereoisomer formed is 2a (JPϪPt ϭ 3558 Hz; δ ϭ 3.23
ppm), based on these data.
The FAB mass spectrum of 1a contains two ion peaks at
1665.0 (calcd. 1666) and 815.0 (calcd. 815.4) corresponding
to [M Ϫ Cl]ϩ and [M Ϫ 2 Cl]2ϩ, respectively. For 2a, ion
peaks at 1450, 954, and 707 were assigned to fragments [M
Ϫ 2 Cl]2ϩ, [M Ϫ 3 Cl]3ϩ, and [M Ϫ 4 Cl]4ϩ, respectively.
In contrast with the reported results for 1a and 2a, the
31P NMR spectrum of the reaction of 3 with [PtCl2(COD)]
to afford 3a, shows, along with a sharp signal at δ ϭ 4.4
ppm (t, JPϪPt ϭ 3683 Hz), another broad resonance at δ ϭ
3.7 ppm (JPϪPt ϭ 3545 Hz). This spectrum indicates the
presence of a mixture of stereoisomers, which was con-
firmed by the 195Pt NMR spectrum. However, attempts to
separate these isomers were unsuccessful. Electrospray spec-
trometry showed peaks corresponding to [M Ϫ n Cl]nϩ (n ϭ
2, 3, 4, 6).
Following the same methodology for 1a, 2a, and 3a,
novel organometallic dendrimers containing platinum
Scheme 3
The unique signal in the 31P NMR spectra of their solu- acetylide units were prepared. This class of derivatives has
tions clearly indicate that no mixture of compounds was been actively investigated in the design of polymeric trans-
formed, and reveal the complexation of platinum by the ition-metal complexes containing σ-bonded acetylide units
presence of platinum satellites (JPtϪP ϭ 3686 Hz for 1a and because of their potential use in catalytic processes and as
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487
2479

O. Rossell et al.
Table 3. Selected bond lengths [A] and angles [°] for 6
FULL PAPER
precursors to cluster-containing dendrimers.[16] Two ex-
amples of organometallic dendrimers with a backbone
composed of platinum acetylide units have been recently re-
ported.[17]
˚
PtϪC(13)
PtϪC(5)
P(1)ϪC(3)
SiϪC(2)
SiϪC(1)
1.945(9)
1.993(8)
1.799(6)
1.859(7)
1.870(8)
1.209(9)
1.148(10) C(14)ϪC(15)
87.3(3)
91.7(2)
171.2(2)
112.9(2)
110.0(3)
118.5(4)
177.7(8)
PtϪP(1)
PtϪP(2)
P(2)ϪC(4)
SiϪC(4)
SiϪC(3)
C(6)ϪC(7)
2.294(2)
2.299(2)
1.819(6)
1.867(7)
1.916(7)
1.461(10)
1.530(11)
175.8(2)
86.2(2)
95.21(8)
117.4(2)
117.4(3)
173.1(7)
We grafted Pt(CϵCPh)2 fragments onto the surface of
dendrimers
1
and
2
by treating them with
[Pt(CϵCPh)2(COD)]. According to the methodology fol- C(5)ϪC(6)
C(13)ϪC(14)
lowed in this paper, the model compound 6 was firstly syn-
C(13)ϪPtϪC(5)
thesised from Me2Si(CH2PPh2)2 and [Pt(CϵCPh)2(COD)].
C(5)ϪPtϪP(1)
C(13)ϪPtϪP(1)
C(13)ϪPtϪP(2)
P(1)ϪPtϪP(2)
C(4)ϪP(2)ϪPt
P(1)ϪC(3)ϪSi
C(6)ϪC(5)ϪPt
(Scheme 5).
C(5)ϪPtϪP(2)
C(3)ϪP(1)ϪPt
C(4)ϪSiϪC(3)
P(2)ϪC(4)ϪSi
C(5)ϪC(6)ϪC(7)
C(14)ϪC(13)ϪPt 175.2(8)
C(13)ϪC(14)ϪC(15) 172.1(9)
angles are collected in Table 3. Compound 6 is a nearly
square-planar 16eϪ platinum complex formed by a diphos-
phane ligand and two mutually cis-oriented acetylide
groups. The six atoms that form the chelate ring adopt a
boat conformation with no appreciable twist distortion
compared with that of 5. The PtϪC and PtϪP distances
are within the range of values quoted in the literature for
cis-acetylide complexes. Bond lengths and angles in the two
independent acetylide ligands are normal and the
PtϪCϵCϪC systems do not deviate significantly from lin-
earity (see Table 3).[18,19]
Scheme 5
The 195Pt{1H} NMR spectrum of 6 shows a resonance
at δ ϭ Ϫ3813 ppm (JPϪPt ϭ 2266 Hz) and the H NMR
1
spectrum reveales the coupling of the CH2 protons of the
CH2P fragment with the P and Pt nucleus (JHϪP ϭ 11.2 Hz
3
and JHϪPt ϭ 32.95 Hz). In accordance with its structure,
the Cα acetylene carbon resonances appear in the 13C{1H}
NMR spectrum at δ ϭ 104.9 ppm as a first-order doublet
The reaction of 2 with the platinum acetylide complex in
a 1:4 molar ratio gave 2b in a high yield. The analytical and
of doublets (2JCαϪPcis ϭ 20.1 Hz; JCαϪPtrans ϭ 150.2 Hz),
2
while the Cβ signal is found at δ ϭ 109.67 ppm as the typ-
1
spectroscopic (IR and H, 13C, 31P, 29Si, 195Pt NMR) data
ical A part of a second-order AXXЈ system [3JCβϪPcis
ϩ
are in agreement with the formula proposed for the new
complex. The most remarkable feature of the IR spectrum
is the presence of an absorption at 2117 cmϪ1 attributed to
the νCϵC stretching vibration, which is considerably shifted
to lower wavenumbers compared to that of the σ-alkynyl
precursor. The Cα alkynyl carbon resonance in the 13C{1H}
3JCβϪPtrans ϭ 35.5 Hz)]. These values are very close to those
´
reported by Fornies et al. in a series of cis-bis(alkynyl)plati-
num complexes.[18]
Crystal Structure of 6
NMR spectrum appears at δ ϭ 104.4 ppm (2JCαϪPcis
ϭ
The molecular structure of 6 was determined by X-ray
structure analysis (Figure 3). Selected bond lengths and
2
20.0 Hz; JCαϪPtrans ϭ 150.3 Hz); that of Cβ appears at δ ϭ
3
109.97 ppm [3JCβϪPcis ϩ JCβϪPtrans ϭ 32.0 Hz)]. The 195Pt
NMR spectrum shows a triplet with a coupling constant
(JPtϪP ϭ 2255 Hz), very similar to that found for 6, which,
along with the NMR spectroscopic data discussed above,
confirms the proposed structure for 2b.
As expected, the attachment of the acetylide group in-
creased its solubility considerably compared with that of 2a.
In contrast, the reaction of the platinum acetylide com-
pound with 1 gave a mixture of species. These species were
not analyzed because of their complexity. It seems that the
bite angle PϪPtϪP displayed in 1, as compared with 2, is
higher than that required for the complexation of the
Pt(CϵCPh)2 fragment.
Reaction with Co2(CO)8
Alkyne systems easily react with Co2(CO)8 to afford
C2[Co(CO)3]2 tetrahedrane clusters that can be used as a
part of the backbone dendritic connectivity or as peripheral
groups. This is a facile method for the introduction of mul-
Figure 3. ORTEP drawing of the molecular structure and num-
bering scheme of 6
2480
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487

Palladium and Platinum Units Grafted on the Periphery of Carbosilane Dendrimers
FULL PAPER
tiple metal clusters, but it has found little use in metalloden-
drimer chemistry,[20] although it is well known in the area MeC3H4)Cl on the surface of our dendrimers was achieved
The grafting of the palladium fragments Pd(η3-2-
of heterometallic stars.[21]
in good yields by treating 1 and 3 with the dinuclear allyl
This strategy was thus applied to our dendrimers, in an complex [Pd(µ-Cl)(η3-2-MeC3H4)]2 in THF at room tem-
attempt to form multiple {C2Co2(CO)6} cluster sites. A pre- perature (Scheme 8).
vious reaction between the model compound 6 and
Co2(CO)8 gave [Pt{C2PhCo2(CO)6}2{Me2Si(CH2PPh2)2}]
(7) (Scheme 6), the spectroscopic data of which are listed in
the Exp. Sect., thus permitting optimization of the reac-
tion conditions.
Scheme 6
Compound 2b was treated in dichloromethane at room
temperature with the octacarbonyldicobalt compound, and
the new species 2c was obtained in moderate yields after
2 h.
The incorporation of the carbonylmetal units was con-
firmed by the appearance of strong absorptions in the IR
spectrum at 2081, 2060, and 2016 cmϪ1, typical of [Co2(-
CO)6(RCCR)] clusters. Strong evidence of cluster formation
could not be inferred from the 13C NMR spectrum, given
the poor solubility of 2c. A single signal at δ ϭ 210 ppm
was assigned to the carbonyl carbon atoms. In the 1H NMR
spectrum the broad signal at δ ϭ 1.65 ppm is in agreement
with the diastereotopic and therefore nonequivalent nature
of the CH2ϪP protons. This fact was observed analogously
in the spectra of 2a and 2b. The 31P NMR spectrum shows
only one signal at δ ϭ 12.6 ppm flanked by platinum satel-
Scheme 8
lites. The Co2(CO)6 coordination caused an increase of the
coupling constant JPϪPt from 2254 Hz of 2b to 3496 Hz.
We are currently extending the chemical and structural as-
pects of these novel high-nuclearity species.
The synthesis of the new palladodendrimers 1d and 3d
was monitored by 31P NMR spectroscopy. In both cases,
the complete disappearance of the signal at δ ϭ Ϫ23 ppm
along with the emergence of a new one at δ ഠ 17 ppm
confirmed that the reaction occurred quantitatively. The
yellow compounds obtained were pure within the limits of
the NMR spectroscopic detection. They were soluble in the
most common organic solvents, and were characterized by
Palladium Dendrimers
Before the synthesis of the Pd-containing dendrimers, we
prepared the model compound [PdCl(η3-2-MeC3H4)-
(PPh2CH2SiMe3)] (8) by treating [Pd(µ-Cl)(η3-2-MeC3H4)]2
with PPh2CH2SiMe3 (Scheme 7).
1
elemental analyses, H, 13C, 31P, and 29Si NMR, as well as
by fast atom bombardment (FAB) or electrospray mass
spectrometry.
1
The H NMR spectra for 1d and 3d showed the reson-
Scheme 7
ances for the methyl, methylene, and ethylene protons with
The 31P NMR spectrum of 8 shows only one signal at chemical shifts in the corresponding regions of the spec-
δ ϭ 17.8 ppm and the 29Si NMR spectrum, another one at trum in the expected integrated ratio. The coordination of
δ ϭ 0.8 ppm. The H and 13C NMR spectra evidence the the palladium fragment to the dendrimer gives rise to the
1
presence of the allyl and the dendrimer ligands.
coupling of the H1 and H2 with the phosphorus nucleus
2481
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487

O. Rossell et al.
FULL PAPER
(3JHϪP ϭ 6.5 and 10 Hz) and the high-field shifts of the H3
The fact that 8, 1d, and 3d have an RCH2Si(CH3)2-
CH2PPh2 moiety in common permits the evaluation of the
steric effects caused only by changes in the dendrimeric
structure.
and H4 resonances (Scheme 9).
It is well known that active catalysts in hydrovinylation
reactions are cationic species, so we synthesised the cationic
species of our dendrimers in situ by adding Ag[BF4] to their
dichloromethane solutions and removing the silver chloride
by filtration. Otherwise, the cationic complexes stabilized
with CH3CN ligands were isolated as solids and their activ-
ity compared with that exhibited by the species prepared in
situ. In order to differentiate between the two types of spe-
cies, we will refer to the cationic dendrimers obtained in
situ as 1d؉, 3d؉, and 8؉, and the salts stabilized with
CH3CN as 1d*, 3d*, and 8*.
Scheme 9
The 13C NMR spectra confirmed the presence of the
above-mentioned groups. The 29Si NMR spectra display
clearly separated signals (two for 1d and four for 3d) for the
different types of silicon atoms in the molecules. These sig-
nals can be easily assigned on the basis of the chemical
shifts and the peak intensities. The presence of only one
signal in the 31P NMR spectra indicates that no mixture of
products is formed in the reaction.A solution of sodium
chloride in THF was added to the samples 1d and 3d in
order to improve the peak resolution in mass spectrometry.
Thus, FABMS showed the [M Ϫ Cl]ϩ peak at m/z ϭ 1923.6
for 1d (calcd. 1920.5), and the MS/ES, the peak [M Ϫ 3
{Pd(2-CH3-C3H4)Cl} Ϫ 3 Cl]3ϩ at m/z ϭ 1272.2 for 3d
(calcd. 1273.1) in accordance with the proposed formula.
Other fragments were also assigned (see Exp. Sect.).
The catalytic data obtained in the hydrovinylation of
styrene using the described compounds are shown in
Table 4.
Table 4. Hydrovinylation of styrene by palladium compounds
Entry[a] Precursor T [°C] t [h] Conversion[b] Selectivity[c] TOF/h[d]
1
8؉
15
25
25
25
25
25
25
15
15
25
25
25
25
2
94.2
80.3
85.7
95.9
85.9
96.0
94.4
91.6
94.4
100
92.1
100
97.6
94.9
465
1710
1695
440
550
620
1040
355
145
368
18
2
8؉
0.5 86.8
0.33 57.5
2
1
1
3
8؉
4
1d؉
1d؉
3d؉
8*
88.6
55.4
63.0
Catalytic Studies
5
One of the main applications of dendrimers is in catalysis.
The well-defined structure and the possibility of attaching
a large number of active sites makes them especially inter-
esting for catalyst immobilization and catalyst recycling.[22]
Recently, some palladium-containing carbosilane dendri-
mers have been used as catalysts in allylic alkylation reac-
tions[8] and in the selective hydrovinylation of styrene per-
formed in a continuous flow membrane reactor.[23] Here,
the palladium dendrimers 1d and 3d were tested as catalysts
in the hydrovinylation of styrene (Scheme 10), and their ac-
tivity was compared with that of the mononuclear model
complex [PdCl(η3-2-MeC3H4)(PPh2CH2SiMe3)] (8). Inter-
estingly, hydrovinylation of styrene produced 3-phenyl-1-
butene as a main product, this process being a model reac-
tion for the synthesis of compounds with pharmacological
activity.
6
7
0.75 78.5
8
8*
2
2
2
2
1
71.5
29.6
74.2
3.5
9
1d*
1d*
1d*
3d*
3d*
10
11[e]
12
13
43.0
425
380
1.5 57.4
[a]
Initial ethylene pressure, 15 bar; solvent: CH2Cl2; ratio styrene/
[b]
[c]
Pd 1000:1. Conversion of starting styrene. Selectivity:% of 3-
phenyl-1-butene respect to the total amount of arylbutenes formed.
[d]
[e]
TOF/h calculated as the total amount of arylbutenes formed.
In THF.
As can be seen from Table 4, activity is lower for the cat-
ionic dendritic precursors 1d؉ (or 1d*) and 3d؉ (or 3d*),
compared with the mononuclear precursor 8. The same ef-
fect was observed by Vogt and van Koten in similar hemil-
abile PO-stabilized dendritic precursors.[24] Probably, the
dendrimers block some of the space that olefins can use
in their approach to the palladium atoms, the active sites.
However, it is remarkable that the activity of the biggest
system 3d is higher or similar to that of 1d (Entries 5 and
6) in spite of the fact that the first shows 8 PPh2 groups in
comparison with the 4 PPh2 ligands displayed by the se-
cond. This interesting effect can be explained by the fact
that 3d has one methyl group over the neighboring Si while
bulkier ligands are attached to the neighboring Si in 1d.
This can be seen by comparing Entries 2, 5, 6, with 7, 10,
13. Moreover, Table 4 shows that the catalysts obtained in
situ in dichloromethane are better than those previously
isolated, due to the ineffective coordinating ability of the
Scheme 10
2482
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487

Palladium and Platinum Units Grafted on the Periphery of Carbosilane Dendrimers
FULL PAPER
CaH2 (CH2Cl2) under N2 prior to use. Elemental analyses (C, H)
solvent. When a solvent of greater coordination ability, like
THF, was used, an impressive decrease in activity was ob-
served (Entries 10 and 11). Formation of oligomers or
higher co-oligomers is not significant. In conclusion, it is
clear from our data that the catalytic activity is affected by
‘‘surface congestion’’.
The isomerization of the chiral product 3-phenyl-1-but-
ene to achiral (E) and (Z) internal olefins (Scheme 10) is
related to the conversion of the process. Thus, at high con-
´
were performed at the Servicio de Microanalisis del Centro de In-
´
vestigacion y Desarrollo del Consejo Superior de Investigaciones
1
Cientıficas (CSIC). H, 13C{1H}, 29Si{1H}, 31P{1H}, and 195Pt{1H}
´
NMR spectra were recorded at 25 °C with a Bruker 250 spectro-
meter. Chemical shifts are reported in ppm relative to external
standards (SiMe4 for 1H, 13C and 29Si, 85% H3PO4 for 31P and
H2PtCl6 for 195Pt) and coupling constants are given in Hz. Infrared
spectra were recorded with FT-IR 520 Nicolet or Impact 400 Nico-
let spectrometers in the 4000Ϫ400 cmϪ1 range as KBr pellets. MS
versions the consecutive isomerization reaction becomes (FAB and ES) spectra were recorded with a Fisons VGQuattro
spectrometer using NBA (3-nitrobenzyl alcohol) as a matrix for
FAB spectra. MALDI-TOF spectra were recorded with a Voyager
DE-RP (Perspective Biosystems) spectrometer using DHB (2,5-di-
important and consequently an increase of the internal ol-
efins is obtained (Table 4). It is well known that the iso-
merization occurs through the previous coordination of the
3-phenyl-1-butene to the catalyst. Thus, the coordination
ability of other molecules present in the reaction media de-
termines the selectivity. Obviously, in our case, the solvent
can compete with the 3-phenyl-1-butene. For example, Ent-
ries 1Ϫ3 and 8 indicate that the presence of stoichiometric
amounts of acetonitrile competes successfully with 3-
phenyl-1-butene and avoids its attachment to the catalyst,
thus improving the selectivity of the process. In conclusion,
in order to improve the selectivity of the process, a major
goal would be to find a ligand or a hemilabile bidentate
ligand with a coordinating ability towards the metallic sys-
tem intermediate between styrene and 3-phenyl-1-butene.
hydrobenzoic acid) as
a
matrix. The starting materials
Me2Si(CH2PPh2)2,[26]
[Pd(µ-Cl)(η3-2-Me-C3H4)]2,[27]
[PtCl2-
(COD)],[28] and [Pt(CϵCPh)2(COD)][29] were prepared according
to published procedures. Other reagents were purchased from com-
mercial suppliers and used as received.
Synthesis of Diphenyl[(trimethylsilyl)methyl]phosphane (PPh2CH2-
SiMe3): This phosphane, described in the literature,[30] was syn-
thesised by a different method here. To a suspension of the Grig-
nard reagent (slight excess) of (chloromethyl)trimethylsilane, pre-
pared from 1.77 g (14.4 mmol) of (chloromethyl)trimethylsilane
and 0.45 g (18.5 mmol) of magnesium in THF (50 mL), was slowly
added chlorodiphenylphosphane (2.95 g, 13.4 mmol); the resulting
mixture was stirred at room temperature for 30 min and hydrolysed
From Table 4 we can observe in all cases a decrease of the with an aqueous solution of NH4Cl (10%). The organic layer was
washed twice with water and dried with Na2SO4. Concentration of
this solution to dryness gave the desired phosphane as a colorless
oil (2.92 g, yield 80%). 1H NMR (250 MHz, CDCl3, 25 °C): δ ϭ
Ϫ0.25 (s, 9 H, CH3), 1.34 (s, 2 H, CH2), 7.28Ϫ7.34 (m, 6 H, C6H5),
7.45Ϫ7.50 (m, 4 H, C6H5) ppm. 31P NMR (101.26 MHz, CDCl3,
25 °C): δ ϭ Ϫ22.05 (s) ppm. 29Si NMR (49.66 MHz, CDCl3, 25
°C): δ ϭ 1.26 (d, J ϭ 14.7 Hz) ppm. 13C NMR (75.4 MHz, CDCl3,
25 °C): δ ϭ Ϫ0.2 (d, J ϭ 4.7 Hz, CH3), 14.6 (d, J ϭ 29.0 Hz, CH2),
128.1Ϫ141.2 (m, C6H5) ppm.
activity in increasing the reaction times, as a consequence of
the deactivation of the catalytic species. This effect is more
important for the dendrimers. The deactivation of the cata-
lyst is clearly observed when runs at different reaction times
are compared Ϫ Entries 4 and 5 or 12 and 13. This is evid-
enced by a decrease in the TOF number upon increasing
the reaction time, in the significant range of conversions.
The model compound 8 showed higher stability, but shorter
reaction times Ϫ Entries 2 and 3. Our preliminary results
showed similar loss of activity of 1d and 3d precursors. In-
terestingly, no precipitation of palladium black was ob-
served before total conversion. In order to obtain more con-
clusive results about the relative stability of these dendritic
systems as a function of their size we would need to test
the activity of catalyst based on higher generations.
Synthesis of [PtCl2(Me3SiCH2PPh2)2] (4): [PtCl2(COD)] (0.08 g,
0.21 mmol) was dissolved in CH2Cl2 (10 mL) and a solution of
PPh2CH2Si(Me2)CH2PPh2 (0.12 g, 0.43 mmol) in CH2Cl2 (10 mL)
was added. The solution was stirred overnight and then concen-
trated to dryness. The solid was recrystallized from CH2Cl2/Et2O
and dried under vacuum. Yield: 172 mg, 50%. 1H NMR (250 MHz,
2
CDCl3, 25 °C): δ ϭ Ϫ0.18 (s, 18 H, CH3), 1.72 (d, JHϪP ϭ 15.7,
In summary, the dendrimers studied in this paper are act- 3JHϪPt ϭ 32 Hz, 4 H, CH2P), 7.24Ϫ7.57 (m, 20 H, C6H5) ppm.
13C{1H} NMR (62.86 MHz, CDCl3, 25 °C): δ ϭ 0.9 (s, CH3), 18.3
ive for the hydrovinylation of styrene, but their activity is
(m, CH2P), 128.1Ϫ133.2 (m, C6H5) ppm. 29Si{1H} NMR
lower than that shown by the mononuclear model 8 and
(49.66 Hz, CDCl3, 25 °C):
δ ϭ
0.11 ppm. 31P{1H} NMR
other related palladium complexes containing different
phosphane ligands.[25] However, polynuclear complexes 1d
and 3d are more active compared with other dendritic cata-
lysts containing 8 and 12 terminal bidentate PO coordinat-
ing atoms on the surface.[24] Moreover, the good selectivity
of our dendrimers towards 3-phenyl-1-butene is remarkable.
(101.26 MHz, CDCl3, 25 °C): δ ϭ 4.2 (s, 1JPϪPt ϭ 3673.2 Hz) ppm.
195Pt{1H} NMR (53.54 MHz, CDCl3, 25 °C): δ ϭ Ϫ4318.0 (t)
ppm. ESMSϩ (CH2Cl2): m/z ϭ 775.7 [M Ϫ Cl]ϩ. MSFABϩ (THF):
m/z ϭ 810.2 [M]ϩ, 775.3 [M Ϫ Cl]ϩ. C32H42Cl2P2PtSi2 (810.80):
calcd. C 47.36, H 5.22; found C 48.26, H 5.43.
Synthesis of [PtCl2{Me2Si(CH2PPh2)2}] (5): Experimental condi-
tions and workup were identical to those for the preparation of 4.
Yield: 218 mg, 90%. 1H NMR (250 MHz, CD2Cl2, 25 °C): δ ϭ
Ϫ0.34 (s, 6 H, CH3), 1.77 (d, 4 H, 2JPϪH ϭ 12.3, 3JHϪPt ϭ 62.3 Hz,
CH2P), 7.4Ϫ7.8 (m, 20 H, C6H5) ppm. 13C{1H} NMR
Experimental Section
3
General: All reactions were carried out under dry nitrogen using
standard Schlenk techniques. Solvents were distilled from sodium/
benzophenone ketyl (THF and Et2O), CaCl2 and stored over mo-
(62.86 MHz, CD2Cl2, 25 °C): δ ϭ Ϫ0.1 (t, JCϪP ϭ 3.4 Hz, CH3),
12.2 (m, CH2P), 128.2Ϫ133.5 (m, C6H5) ppm. 29Si{1H} NMR
(49.66 MHz, CD2Cl2, 25 °C): δ ϭ Ϫ0.96 ppm. 31P{1H} NMR
1
lecular sieves (acetone) or dried with CaCl2 and distilled from (101.26 MHz, CD2Cl2, 25 °C): δ ϭ 3.5 (s, JPϪPt ϭ 3559.8 Hz,
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487
2483

O. Rossell et al.
FULL PAPER
1
PPh2) ppm. 195Pt{1H} NMR (53.54 MHz, CD2Cl2, 25 °C): δ ϭ 31P{1H} NMR (101.26 MHz, CDCl3, 25 °C): δ ϭ 1.6 (s, JPϪPt
ϭ
Ϫ4491.7 (t) ppm. MSFABϩ (CH2Cl2): m/z ϭ 687.2 [M Ϫ Cl]ϩ. 2258.1 Hz, CH2P) ppm. 195Pt{1H} NMR (53.54 MHz, CDCl3, 25
C28H30Cl2P2PtSi (722.58): calcd. C 46.54, H 4.19; found C 45.60,
H 4.23.
°C): δ ϭ Ϫ3813.0 (t) ppm. IR (KBr, cmϪ1): ν(CϵC) ϭ 2120.
ESMSϩ (CH2Cl2): m/z ϭ 854.1 [M]ϩ. C44H40P2PtSi (853.93): calcd.
C 61.89, H 4.72; found C 61.75, H 4.67.
Synthesis of 1a: Experimental conditions and workup were ident-
ical to those for the preparation of 4. Yield: 145 mg, 71%. 1H NMR
(250 MHz, CDCl3, 25 °C): δ ϭ Ϫ0.06 (br. s, 24 H, CH3), 0.75Ϫ1.44
Synthesis of 2b: Experimental conditions and workup were ident-
ical to those for the preparation of 6. Yield: 222 mg, 84%. 1H NMR
(250 MHz, CDCl3, 25 °C): δ ϭ Ϫ(0.38Ϫ0.16) (m, 12 H ϩ 16 H,
CH3, ϪCH2Ϫ), 1.60 (m, 16 H, ϪCH2P), 6.8Ϫ7.8 (m, 120 H, C6H5)
ppm. 13C{1H} NMR (62.86 MHz, CDCl3, 25 °C): δ ϭ Ϫ1.7 (s,
CH3Ϫ), 1.1 (s, ϪCH2Ϫ), 8.4 (s, ϪCH2Ϫ), 10.1 (m, ϪCH2P), 104.4
2
(br. s, 16 H, CH2), 1.92 (d, JHϪP ϭ 15.8 Hz, 8 H, CH2P),
7.00Ϫ7.70 (m, 40 H, C6H5) ppm. 13C{1H} NMR (62.86 MHz,
CDCl3, 25 °C): δ ϭ Ϫ0.6 (s, C1H3), 4.7 (s, ϪCH2Ϫ), 10.3 (s,
ϪCH2Ϫ), 16.2 (m, CH2P), 127.7Ϫ132.4, (m, C6H5) ppm. 29Si{1H}
NMR (49.66 MHz, CDCl3, 25 °C): δ ϭ 4.04 (s, Si1), 8.98 (s, Si0)
ppm. 31P{1H} NMR (101.26 MHz, CDCl3, 25 °C): δ ϭ 4.4 (s,
1JPϪPt ϭ 3686.4 Hz, PPh2) ppm. 195Pt{1H} NMR (53.54 MHz,
CDCl3, 25 °C): δ ϭ Ϫ4322.0 (t) ppm. ESMSϩ (THF): m/z ϭ 1665.0
[M Ϫ Cl]ϩ, 815.0 [M Ϫ 2 Cl]2ϩ. C68H88Cl4P4Pt2Si5 (1701.77):
calcd. C 47.99, H 5.21; found C 47.70, H 5.27.
2
2
(dd, JCαϪPcis ϭ 20, JCαϪPtrans ϭ 150.3 Hz, Cα), 109.97 (AXXЈ,
3JCβϪPtrans
ϩ
3JCβϪPcis ϭ 32.0 Hz, Cβ), 124.8Ϫ135.7 (m, C6H5).
29Si{1H} NMR (49.66 MHz, CDCl3, 25 °C): δ ϭ 2.85 (s, Si1), 9.66
(s, Si0) ppm. 31P{1H} NMR (101.26 MHz, CDCl3, 25 °C): δ ϭ 1.4
(s, JPϪPt ϭ 2254.4 Hz, PPh2) ppm. 195Pt{1H} NMR (53.54 MHz,
1
CDCl3, 25 °C): δ ϭ Ϫ4802.4 (t) ppm. IR (KBr, cmϪ1): ν(CϵC)
2117. C180H164P8Pt4Si5 (3495.87): calcd. C 61.84, H 4.73; found C
60.14, H 4.81.
Synthesis of 2a: Experimental conditions and workup were ident-
ical to those for the preparation of 4 Yield: 170 mg, 50%. 1H NMR
(250 MHz, [D6]DMSO, 25 °C): δ ϭ Ϫ(0.64Ϫ0.52) (s, 12 H ϩ 16
H, ϪCH3; ϪCH2Ϫ), 1.66Ϫ1.93 (m, 16 H, CH2P); 7.30Ϫ7.76 (m,
40 H, C6H5) ppm. 13C{1H} NMR (62.86 MHz, [D6]DMSO, 25 °C):
δ ϭ Ϫ2.8 (s, CH3Ϫ), 0.6 (s, ϪCH2Ϫ), 7.6 (s, ϪCH2Ϫ), 10.2 (m,
CH2P), 128.3Ϫ133.8 (m, C6H5) ppm. 29Si{1H} NMR (49.66 MHz,
Synthesis of [Pt{C2PhCo2(CO)6}2{Me2Si(CH2PPh2)2}] (7): Com-
pound 6 (0.09 g, 0.10 mmol) was dissolved in CH2Cl2 (10 mL) and
Co2(CO)8 (0.10 g, 0.29 mmol) was added as a solid. The mixture
was stirred at room temperature for 2 h. The resulting brown solu-
tion was concentrated to half the original volume and filtered
through a small column of alumina. The solution obtained was
[D6]DMSO, 25 °C): δ ϭ 0.49 (s, Si1), 9.54 (s, Si0) ppm. 31P{1H}
1
concentrated to dryness. Yield: 74 mg, 49%. H NMR (250 MHz,
1
NMR (101.26 MHz, [D6]DMSO, 25 °C): δ ϭ 4.1 (s, JPϪPt
ϭ
2
CDCl3, 25 °C): δ ϭ Ϫ0.61 (s, 6 H, CH3), 1.73 (d, JHϪP ϭ 10.6,
3558.4 Hz, PPh2) ppm. 195Pt{1H} NMR (53.54 Hz, [D6]DMSO, 25
°C): δ ϭ Ϫ4482.0 (s). ESMSϩ (CH2Cl2): m/z ϭ 1450.0 [M Ϫ 2
Cl]2ϩ, 954.0 [M Ϫ 3 Cl]3ϩ, 707.0 [M Ϫ 4 Cl]4ϩ. C116H124Cl8P8Pt4Si5
(2970.47): calcd. C 46.90, H 4.21; found C 46.60, H 4.27.
3JHϪPt ϭ 48.8 Hz, 4 H, CH2P), 7.46Ϫ7.81 (m, 30 H, C6H5) ppm.
13C{1H} NMR (62.86 MHz, CDCl3, 25 °C): δ ϭ 0.2 (s, CH3), 14.1
(m, CH2P), 128.2Ϫ137.6 (m, C6H5), 209.7 (s, CO) ppm. 31P{1H}
1
NMR (101.26 MHz, CDCl3, 25 °C): δ ϭ 13.2 (s, JPϪPt
ϭ
3498.9 Hz, CH2P) ppm. IR (CH2Cl2, cmϪ1): ν(CO) ϭ 2095 w, 2081
w, 2055 vs, 2014 vs, 1950 s. ESMSϩ (CH2Cl2): m/z ϭ 994.4 [M Ϫ
Co3(CO)9]ϩ, 967.5 [M Ϫ Co3(CO)10]ϩ, 853.4 [M Ϫ Co4(CO)12]ϩ.
C56H40Co4O12P2PtSi (1425.78): calcd. C 47.18, H 2.83; found C
47.01, H 2.85.
Synthesis of 3a: Experimental conditions and workup were ident-
ical to those for the preparation of 4. Yield: 220 mg, 65%. 1H NMR
(250 MHz, CDCl3, 25 °C): δ ϭ Ϫ0.22Ϫ0.00 (m, 84 H, CH3), 0.29
(br. s, 64 H, ϪCH2Ϫ), 1.59Ϫ1.64 (m, 16 H, CH2P), 7.29Ϫ7.59 (m,
80 H, C6H5) ppm. 13C{1H} NMR (62.86 MHz, CDCl3, 25 °C): δ ϭ
Ϫ6.6 (s, CH3), Ϫ4.2 (s, CH3), Ϫ1.6 (s, CH3), 2.8 (s, ϪCH2Ϫ), 4.5
(s, ϪCH2Ϫ), 6.7 (s, ϪCH2Ϫ), 9.4 (s, ϪCH2Ϫ), 10.3 (s, ϪCH2Ϫ),
16.3 (sbr, CH2P), 128.0Ϫ133.0 (m, C6H5) ppm. 29Si{1H} NMR
(49.66 MHz, CDCl3, 25 °C): δ ϭ 3.80 (s, Si3), 5.71 (s, Si1), 7.84 (s,
Si2), 9.32 (s, Si0) ppm. 31P{1H} NMR (101.26 MHz, CDCl3, 25
Synthesis of 2c: Experimental conditions and workup were identical
to those for the preparation of 7. Yield: 194 mg, 79%. 1H NMR
(250 MHz, CDCl3, 25 °C): δ ϭ Ϫ(0.74Ϫ0.32) (s, 12 H ϩ 16 H,
CH3Ϫ, ϪCH2Ϫ), 1.65 (br. m, 16 H, CH2P), 6.8Ϫ7.6 (m, C6H5)
ppm. 31P NMR (101.26 MHz, CD2Cl2, 25 °C): δ ϭ 12.68 (s,
1JPϪPt ϭ 3496.0 Hz, PPh2) ppm. IR (CH2Cl2, cmϪ1): ν(CO) ϭ 2100
w, 2081 s, 2060 vs, 2016 vs, 1989 ssh, 1890 w.
C228H164Co16O48P8Pt4Si5 (5783.28): calcd. C 47.35, H 2.86; found
C 47.09, H 2.94.
1
1
°C): δ ϭ 3.7 (s, JPϪPt ϭ 3545 Hz, PPh2), 4.4 (s, JPϪPt ϭ 3683 Hz,
PPh2) ppm. 195Pt{1H} NMR (53.54 MHz, CDCl3, 25 °C): δ ϭ
Ϫ4311.0 (t, major isomer), Ϫ4325.2 (t, minor isomer). ESMSϩ
(CH2Cl2): m/z ϭ 1968.3 [M Ϫ 2 Cl]2ϩ, 1298.6 [M Ϫ 3 Cl]3ϩ, 965.6
[M Ϫ 4 Cl]4ϩ, 631.0 [M Ϫ 6 Cl]6ϩ. C164H244Cl8P8Pt4Si17 (4004.99):
calcd. C 49.18, H 6.14; found C 48.89, H 6.25.
Synthesis of [PdCl(η3-2-MeC3H4)(PPh2CH2SiMe3)] (8): To a solu-
tion of [Pd(η3-C4H7)(µ-Cl)]2 (0.62 g, 1.57 mmol) in CH2Cl2
Synthesis of [Pt(CϵCPh)2{Me2Si(CH2PPh2)2}] (6): [Pt(Cϵ (30 mL), was added Me3SiCH2PPh2 (0.86 g, 3.14 mmol) and the
CPh)2(COD)] (0.16 g, 0.31 mmol) was suspended in acetone reaction mixture stirred for 30 min at room temperature. The solv-
(10 mL) and a solution of Me2Si(CH2PPh2)2 (0.14 g, 0.31 mmol) in ent was evaporated to dryness and the solid was washed with di-
acetone (10 mL) was added; resulting in a quick dissolution. The
resulting yellow solution was stirred at room temperature for 2 h
and then concentrated to dryness, washed with diethyl ether and
dried under vacuum. Crystals suitable for X-ray analysis were col-
ethyl ether and dried under vacuum. Yield: 1.18 g (80%). 1H NMR
(250 MHz, CDCl3, 25 °C): δ ϭ Ϫ0.04 (s, 9 H, CH3), 1.90 (s, 3 H,
2
CH3), 1.97 (d, JHϪP ϭ 14.3 Hz, 2 H, CH2P), 2.63 (s, 1 H, H4),
3
3.33 (br. s, 1 H, H3), 3.46 (d, JHϪP ϭ 10.1 Hz, 1 H, H2), 4.44 (dd,
lected from a CH2Cl2/Et2O mixture at Ϫ20 °C. Yield: 194 mg, 73%. 3JHϪP ϭ 6.9 Hz, JHϪH ϭ 2.8 Hz, 1 H, H1), 7.30Ϫ7.65 (m, 10 H,
1H NMR (250 MHz, CDCl3, 25 °C): δ ϭ Ϫ0.30 (s, 6 H, CH3), 1.70 C6H5) ppm. 13C{1H} NMR (75.4 MHz, CDCl3, 25 °C): δ ϭ 0.4
2
3
3
1
(d, JHϪP ϭ 11.2, JHϪPt ϭ 32.95 Hz, 4 H, CH2P), 6.80Ϫ7.70 (m,
(d, JCϪP ϭ 3.8 Hz, CH3), 14.4 (d, JCϪP ϭ 11.4 Hz, CH2P), 23.2
30 H, C6H5) ppm. 13C{1H} NMR (62.86 MHz, CDCl3, 25 °C): δ ϭ (s, CH3), 57.8 (s, Ccis), 76.9 (d, JCϪP
ϭ 33.2 Hz, Ctrans),
2
3
0.8 (t, JCϪP ϭ 3.4 Hz, CH3), 11.7 (m, CH2P), 105.0 (dd,
128.3Ϫ136.2 (m, C6H5) ppm. 29Si{1H} NMR (49.66 MHz, CDCl3,
2JCαϪPcis ϭ 20.1, JCαϪPtrans ϭ 150.2 Hz, Cα), 109.7 (AXXЈ, 25 °C): δ ϭ 0.82 (s) ppm. 31P{1H} NMR (101.26 MHz, CDCl3, 25
2
3JCβϪPcis
ϩ
3JCβϪPtrans ϭ 35.5 Hz, Cβ), 124.7Ϫ133.6 (m, C6H5) °C): δ ϭ 17.8 (s). C20H28ClPPdSi (469.36): C 51.18, H 6.01; found
ppm. 29Si{1H} NMR (49.66 MHz, CDCl3, 25 °C): δ ϭ 0.0 ppm. C 51.13, H 6.11.
2484
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487

Palladium and Platinum Units Grafted on the Periphery of Carbosilane Dendrimers
FULL PAPER
Synthesis of 1d: Experimental conditions and workup were ident-
ical to those for the preparation of 8. Yield 380 mg, 85%. 1H NMR
(250 MHz, CDCl3, 25 °C): δ ϭ Ϫ0.03, Ϫ0.07 (s, 24 H, CH3), 0.15
C196H300Cl8P8Pd8Si17 (4516.62): calcd. C 52.12, H 6.70; found C
52.34, H 7.13.
2
Synthesis of the Cationic Complexes 1d*, 3d* and 8*: To a solution
of 1d, 3d, or 8 (2.24 mmol) in CH2Cl2 (40 mL) were added a few
drops of acetonitrile and AgBF4 (0.45 g, 2.78 mmol). The mixture
was stirred for 1 h in the dark, and the AgCl formed was removed
by filtration through Celite. The resulting solution was concen-
trated and the addition of ether caused the precipitation of a white
solid as a resin, which was washed twice with ether and dried.
Yield: 60Ϫ70%. 1d*: 1H NMR (500 MHz, CDCl3, 25 °C): δ ϭ
Ϫ0.132 (s, 24 H, Me), 0.352 (s, 16 H, CH2), 1.914 (s, 12 H, Me),
2.310 (s, 12 H, NCCH3), 2.739 (s, 4 H, H4), 3.335 (s, 4 H, H3),
3.617 (s, 4 H, H2), 4.764 (s, 4 H, H1), 7.20Ϫ7.60 (m, 40 H, C6H5)
ppm. 13C NMR (62.90 MHz, CDCl3, 25 °C): δ ϭ Ϫ2.4 (s, 8 C,
Me), 1.0 (s, 8 C, CH2), 3.0 (s, NCCH3), 12.9 (s, 4 C, CH2P), 23.1
(s, 4 C, Me), 58.9 (s, 4 C, Ccis), 79.8 (d, J ϭ 27.12 Hz, 4 C, Ctrans),
129.0Ϫ136.6 (m, C6H5) ppm. 29Si NMR (49.66 MHz, CDCl3, 25
°C): δ ϭ 3.35 (s, 4Si) ppm, the core signal was not observed. 31P
NMR (101.26 MHz, CDCl3, 25 °C): δ ϭ 15.76 (s) ppm. 3d*: 1H
NMR (500 MHz, CDCl3, 25 °C): Spectrum similar to that of 1d*
but with very broad signals. 31P NMR (101.26 MHz, CDCl3, 25
°C): δ ϭ 14.5 (br. s) ppm. 8*: 31P NMR (101.26 MHz, CDCl3, 25
°C): δ ϭ 14.26 (s) ppm. 29Si NMR (49.66 MHz, CDCl3, 25 °C):
(s, 16 H, ϪCH2Ϫ), 1.96 (s, 12 H, CH3), 2.05 (d, JHϪP ϭ 15.0 Hz,
3
8 H, CH2P), 2.70 (s, 4 H, H4), 3.31 (s, 4 H, H3), 3.42 (d, JHϪP
ϭ
9.8 Hz, 4 H, H2), 4.39 (d, JHϪP ϭ 6.2 Hz, 4 H, H1), 7.44Ϫ7.66
3
(m, 40 H, C6H5) ppm. 13C{1H} NMR (62.86 MHz, CDCl3, 25 °C):
3
δ ϭ Ϫ 2.0 (s, CH3), 2.5 (s, ϪCH2Ϫ), 9.1 (d, JCϪP ϭ 4.8 Hz,
ϪCH2Ϫ), 12.8 (d, JCϪP ϭ 11.0 Hz, CH2P), 23.3 (s, CH3), 58.0 (s,
1
2
C
cis), 76.7 (d, JCϪP ϭ 32.0 Hz, Ctrans), 128.3Ϫ136.3 (m, C6H5)
ppm. 29Si{1H} NMR (49.66 MHz, CDCl3, 25 °C): δ ϭ 3.0 (s, Si1),
18.5 (s, Si0) ppm. 31P{1H} NMR (101.26 MHz, CDCl3, 25 °C): δ ϭ
17.4 (s, PPh2) ppm. MSFABϩ: m/z: 1923.6 [Mϩ
Ϫ Cl].
C84H116Cl4P4Pd4Si5 (1956.03): calcd. C 51.53, H 5.93; found C
52.07, H 6.17.
Synthesis of 3d: Experimental conditions and workup were ident-
ical to those for the preparation of 8. Yield: 430 mg, 82%. 1H NMR
(500 MHz, CDCl3, 25 °C): δ ϭ Ϫ0.26 (s, 12 H, C2H3), Ϫ0.13 (s,
24 H, C1H3), Ϫ0.09, Ϫ0.05 (s, 48 H, C3H3, C3ЈH3), 0.16Ϫ0.20 (m,
2
64 H, ϪCH2Ϫ), 1.86 (s, 24 H, C4H3), 1.90 (d, JHϪP ϭ 11.0 Hz,
2
CH2P), 1.90 (d, JHϪP ϭ 10.5 Hz, CHЈ2P), 2.61 (s, 8 H, H4), 3.30
3
3
(s, 8 H, H3), 3.41 (d, JHϪP ϭ 10.0 Hz, 8 H, H2), 4.37 (d, JHϪP
ϭ
4.6 Hz, 8 H, H1), 7.32Ϫ7.55 (m, 80 H, C6H5) ppm. 13C{1H} NMR
(62.86 MHz, CDCl3, 25 °C): δ ϭ Ϫ6.7 (s, C2H3), Ϫ4.5 (C1H3),
Ϫ2.1 (s, C3H3, C3ЈH3), 4.2 (s, ϪC1H2Ϫ, ϪC2H2Ϫ), 4.5 (s,
1
δ ϭ 1.31 (s) ppm. H NMR (500 MHz, CDCl3, 25 °C): δ ϭ Ϫ0.01
(s, 9 H, CH3), 1.85 (d, J ϭ 14.39 Hz, 2 H, CH2), 1.97 (s, 3 H, CH3),
2.32 (s, 3 H, NCCH3), 2.72 (s, 1 H, H4), 3.28 (s, 1 H, H3), 3.70 (d,
J ϭ 9.24 Hz, 1 H, H2), 4.93 (br. s, 1 H, H1), 7.30Ϫ7.60 (m, 10 H,
C6H5) ppm. 13C NMR (75.4 MHz, CDCl3, 25 °C): δ ϭ 0.3 (d, J ϭ
3.5 Hz, CH3), 2.8 (s, NCCH3), 14.9 (d, J ϭ 11.4 Hz, CH2), 23.1 (s,
CH3), 58.6 (s, CH2,cis), 80.7 (d, J ϭ 26.7 Hz, CH2,trans).
ϪC3H2Ϫ), 6.5 (d, ϪC5H2Ϫ), 8.9 (d, JCϪP ϭ 3.7 Hz, ϪC6H2Ϫ),
3
12.6 (d, 1JCϪP ϭ 11.0 Hz, CH2P), 23.1 (s, C4H3), 57.8 (s, Ccis), 76.4
(d, 2JCϪP ϭ 32.9 Hz, Ctrans), 128.2Ϫ136.1 (m, C6H5) ppm. 29Si{1H}
NMR (49.66 MHz, CDCl3, 25 °C): δ ϭ 3.14 (s, Si3), 5.72 (s, Si1),
8.04 (s, Si2), 9.43 (s, Si0) ppm. 31P{1H} NMR (101.26 MHz, CDCl3,
25 °C): δ ϭ 17.7 (s, PPh2). ESMSϩ (acetonitrile): m/z ϭ 2122.8 [M
Ϫ {Pd(2-CH3ϪC3H4)Cl} Ϫ 2 Cl]2ϩ, 2026.2 [M Ϫ 2 {Pd(2-CH3- Catalytic Reactions: Hydrovinylation reactions were performed in
C3H4)Cl} Ϫ 2 Cl]2ϩ, 1339.4 [M Ϫ 2 {Pd(2-CH3-C3H4)Cl} Ϫ 3 a stainless-steel autoclave fitted with an external jacket connected
Cl]3ϩ
,
1274.1 [M
Ϫ
3
{Pd(2-CH3-C3H4)Cl}
Ϫ
3
Cl]3ϩ
.
to a thermostatically controlled isobutyl alcohol bath maintained
Table 5. Crystal data and structure refinement for 4, 5, and 6
Compound
4
5
6
Empirical formula
Formula mass
Temperature
C32H42Cl2P2PtSi2·0.5H2O
819.77
C28H30Cl2P2PtSi
722.54
C44H40P2PtSi
853.88
293(2) K
293(2) K
293(2) K
˚
˚
˚
Wavelength
0.71069 A
0.71069 A
0.71069 A
Crystal system, space group monoclinic, P21/n
orthorhombic, Pcnb
monoclinic, P21/c
˚
˚
˚
Unit cell dimensions
a ϭ 9.9960(10) A
a ϭ 11.2090(10) A
a ϭ 18.108(5) A
˚
˚
˚
b ϭ 18.9050(10) A, β ϭ 91.2250(10)° b ϭ 14.7280(10) A
b ϭ 10.773(12) A, β ϭ 90.60(3)°
˚
˚
˚
c ϭ 19.5690(10) A
c ϭ 16.6540(10) A
2749.3(3) A
c ϭ 19.687(11) A
3840(5) A
3
3
3
˚
˚
˚
Volume
Z
3697.2(5) A
4
4
4
Calculated density
Absorption coefficient
F(000)
1.473 Mg/m3
4.112 mmϪ1
1636
1.746 Mg/m3
5.474 mmϪ1
1.477 Mg/m3
3.798 mmϪ1
1416
1704
Crystal size
Θ range for data collection
Index ranges
0.1 ϫ 0.1 ϫ 0.2 mm
2.27Ϫ28.89°
Ϫ11 Յ h Յ 10, 0 Յ k Յ 25,
0 Յ l Յ 26
0.1 ϫ 0.1 ϫ 0.2 mm
2.81Ϫ24.96°
0 Յ h Յ 12, 0 Յ k Յ 16,
0 Յ l Յ 19
0.1 ϫ 0.1 ϫ 0.3 mm
2.34Ϫ29.95°
Ϫ25 Յ h Յ 25, 0 Յ k Յ 15,
0 Յ l Յ 27
Reflections collected/unique 22007/8165 [R(int) ϭ 0.0462]
11504/2402 [R(int) ϭ 0.00309]
11092/11092 [R(int) ϭ 0.0926]
Refinement method
Data/parameters
Full-matrix least squares on F2
8165/364
Full-matrix least squares on F2 Full-matrix least squares on F2
2402/206
1.101
R1 ϭ 0.0329, wR2 ϭ 0.0728
R1 ϭ 0.0480, wR2 ϭ 0.0789
0.551 and Ϫ0.470
11092/433
0.756
R1 ϭ 0.0431, wR2 ϭ 0.0568
R1 ϭ 0.2656, wR2 ϭ 0.0899
0.420 and Ϫ0.365
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
R indices (all data)
0.899
R1 ϭ 0.0261, wR2 ϭ 0.0518
R1 ϭ 0.0608, wR2 ϭ 0.0557
0.619 and Ϫ0.600
Largest diff. peak and
Ϫ3
˚
hole (e A
)
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487
2485

O. Rossell et al.
I. Cuadrado, M. Moran, J. Losada, C. M. Cas-
FULL PAPER
to Ϯ 0.5 °C. The internal temperature was monitored by means of
a thermocouple. Internal temperature and pressure as a function
of time were registered with a Linseis L-200 Recorder. Gas chroma-
tography was run using an HP 5890 series two chromatograph.
[2b]
´
279Ϫ293.
ado, C. Pascual, B. Alonso, F. Lobete in: G. R. Newkome, Ad-
vances in Dendritic Macromolecules, JAI Press, Greenwich, CT,
[2c]
´
´
S. Arevalo, E. de Jesus, F. J. de la Mata, J. C.
1996, vol. 3.
´
Flores, R. Gomez, Organometallics 2001, 20, 2583Ϫ2592.
[3]
[4]
Hydrovinylation Reactions
´
M. Benito, O. Rossell, M. Seco, G. Segales, Inorg. Chim. Acta
1999, 291, 247Ϫ251.
a) 1d؉, 3d؉, and 8؉ as Catalysts: A mixture of 4.0 ϫ 10Ϫ5 mol of
the neutral palladium complex, 1d, 3d, or 8, AgBF4 (in a 1:4, 1:8,
and 1:1 molar ratio, respectively) and styrene (0.04 mol) in 10 mL
of freshly distilled CH2Cl2 was stirred for 5 min in the dark under
nitrogen. After filtering off the AgCl formed, the solution was
placed in a thermostatically controlled autoclave, which had previ-
ously been purged with successive applications of vacuum and ar-
gon. The autoclave was then pressurized with ethylene to 15 bar.
After the desired time, the autoclave was slowly depressurized and
10% HCl (10 mL) was added. The mixture was stirred for 10 min
in order to quench the catalyst. The CH2Cl2 layer was decanted
and dried with Na2SO4. The quantitative distribution of products
fractions was determined by GC analysis.
O. Rossell, M. Seco, A. M. Caminade, J. P. Majoral, Gold Bull.
2001, 34, 88Ϫ94.
M. Benito, O. Rossell, M. Seco, G. Segales, Organometallics
M. Benito, O. Rossell, M. Seco, G.
Segales, J. Organomet. Chem. 2001, 619, 245Ϫ251.
[6a] G. R. Newkome, E. He, C. N. Moorefield, Chem. Rev. 1999,
99, 1689Ϫ1746. [6b] J. P. Majoral, A. M. Caminade, Chem. Rev.
1999, 99, 845Ϫ880.
M. Bardajı, M. Kustos, A. M. Caminade, J. P. Majoral, B.
Chaudret, Organometallics 1997, 16, 403Ϫ410.
D. de Groot, J. C. de Wilde, R. J. van Haaren, J. N. H. Reek,
P. C. J. Kamer, P. W. N. M. van Leeuwen, E. B. Eggeling, D.
Vogt, H. Kooijman, A. L. Speek, A. W. van der Made, Chem.
Commun. 1999, 1623Ϫ1624.
G. K. Anderson, H. C. Clark, J. A. Davies, G. Ferguson, M.
Parvez, J. Crystallogr. Spectrosc. Res. 1982, 12, 449Ϫ458.
T. S. Cameron, H. C. Clark, A. Linden, A. M. Nicholas, M. J.
Hampden-Smith, Inorg. Chim. Acta 1989, 162, 9Ϫ10.
G. B. Robertson, W. A. Wickramasinghe, Acta Crystallogr.,
Sect. C 1987, 43, 1694Ϫ1697.
E. C. Alyea, G. Ferguson, B. L. Ruhl, R. Shakya, Polyhedron
1987, 6, 1223Ϫ1227.
P. R. Meehan, E. C. Alyea, R. P. Shakya, G. Ferguson, Poly-
hedron 1997, 17, 11Ϫ16.
P. R. Meehan, G. Ferguson, R. P. Shakya, E. C. Alyea, J.
Chem. Soc., Dalton Trans. 1997, 3487Ϫ3491.
E. C. Alyea, G. Ferguson, R. P. Shakya, P. R. Meehan, Inorg.
Chem. 1997, 36, 4749Ϫ4752.
J. Fornies, E. Lalinde, J. Chem. Soc., Dalton Trans. 1996,
[5] [5a]
´
[5b]
1999, 18, 5191Ϫ5193.
´
[6]
[7]
[8]
´
b) 1d*, 3d*, and 8* as Catalysts: A solution of 4.0 ϫ 10Ϫ5 mol of
the cationic palladium complexes, 1*, 3*, or 8*, and styrene (0.0400
mol) in freshly distilled CH2Cl2 (10 mL) was prepared under an
inert gas. The solution was transferred via syringe under argon into
the autoclave, which had previously been purged with successive
applications of vacuum and argon. Ethylene was admitted until the
initial pressure of 15 bar was reached. The workup procedure was
as already described.
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
X-ray Structure Determination of 4, 5 and 6: Block crystals of com-
pounds 4 and 5 were selected and mounted on a MAR345 dif-
fractometer with image plate detector. A crystal of 6 was mounted
on an EnrafϪNonius CAD4 four-circle diffractometer. Crystallo-
graphic and experimental details of both compounds are summar-
ized in Table 5. Data were collected at room temperature. Intensit-
ies were corrected for Lorentz and polarization effects in the usual
manner. The structures were solved by Direct Methods, using
SHELXS computer program and refined by full-matrix least-
squares methods with SHELX97 computer program.[31] The func-
tion minimized was Σw||Fo|2 Ϫ |Fc|2|2, where w ϭ [σ2(I) ϩ (0.0774
P)2]Ϫ1, and P ϭ (|Fo|2 ϩ 2 |Fc|2)/3; f, fЈ and fЈЈ were taken from
International Tables of X-ray Crystallography .[32] All H atoms
were computed and refined with an overall isotropic temperature
factor equal to 1.2 times the equivalent isotropic temperature factor
of the atoms, which were linked using a riding model. The supple-
mentary crystallographic data for this paper can be found in pub-
lications CCDC-181768 (4), -181770 (5), and -181769 (6.) These
data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/
retrieving.html or from the Cambridge Crystallographic Data
Centre, 12, Union Road, Cambridge CB2 1EZ, UK [Fax: (in-
ternat.) ϩ 44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
´
2587Ϫ2599 and references therein.
N. Ohshire, F. Takei, K. Onitsuka, S. Takahashi, J. Organomet.
Chem. 1998, 569, 195Ϫ202.
L. R. Falvello, J. Fornies, J. Gomez, E. Lalinde, A. Martin, M.
´
´
T. Moreno, J. Sacristan, Chem. Eur. J. 1999, 5, 474Ϫ491.
[19] [19a]
R. A. Mariezcurrena, S. E. Rasmusssen, Acta Chem.
A. Furlani, S. Licoccia, M.
V. Russo, A. C. Villa, C. Guastini, J. Chem. Soc., Dalton Trans.
W. Weigand, C. Robl, Chem. Ber. 1993,
J. D. Bradshaw, L. Guo, C. A. Tessier,
W. J. Youngs, Organometallics 1996, 15, 2582Ϫ2584.
Whiteford, C. V. Lu, P. J. Stang, J. Am. Chem. Soc. 1997, 119,
2524Ϫ2533. [19f] M. I. Bruce, B. C. Hall, P. J. Low, M. E. Smith,
B. W. Skelton, A. H. White, Inorg. Chim. Acta 2000,
300Ϫ302, 633Ϫ644.
D. Seyferth, T. Kugita, A. L. Rheingold, G. A. P. Yap,
Organometallics 1995, 14, 5362Ϫ5366. [20b] G. R. Newkome, C.
N. Moorefield, G. R. Baker, A. L. Johnson, R. K. Behera, An-
[19b]
Scand. 1973, 27, 2678Ϫ2680.
[19c]
1984, 2197Ϫ2206.
126, 1807Ϫ1809.
[19d]
[19e]
J. A.
[20] [20a]
Acknowledgments
gew. Chem. Int. Eng. Ed. 1991, 30, 1176Ϫ1178; Angew. Chem.
This work was supported by the DGICYT (Projects BQU2000-
0644 and PB97-0407-C05-04) and the CIRIT (Project 1999 SGR
00045). M. B. is indebted to the Ministerio de Ciencia y Tecnologia
for a scholarship.
[20c]
1991, 103, 1205Ϫ1207.
Chem. 1999, 588, 9Ϫ19.
C. Kim, I. Jung, J. Organomet.
[21]
E. C. Constable, O. Eich, D. Fenske, C. E. Housecroft, L. John-
ston, Chem. Eur. J. 2000, 6, 4364Ϫ4370.
[22] [22a]
J. W. J. Knappen, A. W. van der Made, J. C. de Wilde, P.
W. N. M. van Leeuwen, P. Wijkens, D. M. Grove, G. van Koten,
A. W. Kleij, R. A. Gossage,
J. T. B. M. Jastrzebski, J. Boersma, G. van Koten, Angew.
[1]
[1a]
[22b]
For reviews, see
D. A. Tomalia, A. M. Naylor, W. A. God-
Nature 1994, 372, 659Ϫ663.
dard III, Angew. Chem. Int., Ed. Engl. 1990, 29, 138Ϫ175; An-
[1b]
gew. Chem. 1990, 102, 119Ϫ157.
A. W. Bosman, H. M.
Chem. Int. Eng. Ed. 2000, 39, 176Ϫ178; Angew. Chem. 2000,
[22c]
Jansen, E. W. Meijer, Chem. Rev. 1999, 99, 1665Ϫ1688.
112, 179Ϫ181
G. E. Oosterom, J. N. H. Reek, P. C. J.
[2] [2a]
H. Frey, C. Lach, K. Lorenz, Adv. Mater. 1998, 10,
Kamer, P. W. N. M. van Leeuwen, Angew. Chem. Int. Eng. Ed.
2486
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487

Palladium and Platinum Units Grafted on the Periphery of Carbosilane Dendrimers
FULL PAPER
[27]
2001, 40, 1828Ϫ1849; Angew. Chem. 2001, 113, 1878Ϫ1901.
Y. Tatsuno, T. Yoshiba, S. Otsuka, Inorg. Synth. 1990, 28,
342Ϫ345.
J. X. McDermott, J. F. White, G. M. Whitesides, J. Am. Chem.
Soc. 1976, 98, 6521Ϫ6528.
R. J. Cross, M. F. Davidson, J. Chem. Soc., Dalton Trans.
1986, 1987Ϫ1992.
B. E. Cooper, W. J. Owen, J. Organomet. Chem. 1970, 21,
329Ϫ332.
G. M. Sheldrick, SHELXL-97, Universität Göttingen, 1997.
International Tables of X-ray Crystallography, Kynoch Press,
1974, vol. IV, p. 99Ϫ100 and 149.
[22d]
D. Astruc, F. Chardac, Chem. Rev. 2001, 101, 2991Ϫ3023.
[22e]
[28]
[29]
[30]
V. Maraval, R. Laurent, A. M. Caminade, J. P. Majoral,
Organometallics 2000, 19, 4025Ϫ4029.
[23]
[24]
N. J. Hovestad, E. B. Eggeling, H. J. Heidbüchel, J. T. B. H.
Jastrzebski, U. Kragl, W. Keim, D. Vogt, G. van Koten, Angew.
Chem. Int. Ed. 1999, 38, 1655Ϫ1658; Angew. Chem. 1999,
111, 1763Ϫ1765.
[31]
[32]
E. V. Eggeling, N. J. Hovestad, J. T. B. H. Jastrzebski, D. Vogt,
G. van Koten, J. Org. Chem. 2000, 65, 8857Ϫ8865.
G. Muller, J. I. Ordinas, J. Mol. Cat. A 1997, 125, 97Ϫ108.
E. C. Alyea, K. J. Fisher, T. P. Shakya, A. E. Vogioukas, Synth.
React. Inorg. Met. Org. Chem. 1988, 18, 163Ϫ178.
[25]
[26]
Received March 21, 2002
[I02147]
Eur. J. Inorg. Chem. 2002, 2477Ϫ2487
2487