Arylpalladium complexes with a silsesquioxanate ligand. Preparation and structures in the solid state and in solution

Article abstract of DOI:10.1021/om0610492

The reaction of the incompletely condensed silsesquioxane (c-C ₅H₉)₇Si₇O₉(OH) ₃ with [Pd(C₆H₃Me₂-2,4)(I)(bpy)] produced a complex with a Pd-O bond, [Pd(C₆H₃Me ₂-2,4){(c-C₅H₉)₇Si₇O ₁₀(OH)₂}(bpy)]. Palladium complexes having a silsesquioxanate ligand, [Pd(Ar){R₇Si₇O ₁₀(OH)₂}(tmeda)] (Ar = C₆H₅, C ₆F₅, C₆H₃F₂-2,4; R = c-C₅H₉, i-C₄H₉), were prepared by the reaction of the silsesquioxane R₇Si₇O ₉-(OH)₃ with arylpalladium iodo complexes, [Pd(Ar)(I)(tmeda)] (tmeda = N,N,N′,N′-tetramethylethylenediamine), in the presence of Ag₂O. These complexes were characterized by multinuclear (¹H, ¹³C{¹H}, ¹⁹F{ ¹H}, and ²⁹Si{¹H}) NMR spectroscopy, and the structure of [Pd(C₆F₅){(c-C₅H₉) ₇Si₇O₁₀(OH)₂}(tmeda)] was determined by X-ray crystallography. Temperature-dependent ¹H and ¹⁹F{¹H} NMR spectra revealed the dynamic behavior of the complexes on the NMR time scale.

Full text of DOI:10.1021/om0610492

1402
Organometallics 2007, 26, 1402-1410
Arylpalladium Complexes with a Silsesquioxanate Ligand.
Preparation and Structures in the Solid State and in Solution
Neli Mintcheva, Makoto Tanabe, and Kohtaro Osakada*
Chemical Resources Laboratory (R1-3), Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku,
Yokohama 226-8503, Japan
ReceiVed NoVember 15, 2006
The reaction of the incompletely condensed silsesquioxane (c-C5H9)7Si7O9(OH)3 with [Pd(C6H3Me2-
2,4)(I)(bpy)] produced a complex with a Pd-O bond, [Pd(C6H3Me2-2,4){(c-C5H9)7Si7O10(OH)2}(bpy)].
Palladium complexes having a silsesquioxanate ligand, [Pd(Ar){R7Si7O10(OH)2}(tmeda)] (Ar ) C6H5,
C6F5, C6H3F2-2,4; R ) c-C5H9, i-C4H9), were prepared by the reaction of the silsesquioxane R7Si7O9-
(OH)3 with arylpalladium iodo complexes, [Pd(Ar)(I)(tmeda)] (tmeda ) N,N,N′,N′-tetramethylethylene-
diamine), in the presence of Ag2O. These complexes were characterized by multinuclear (1H, 13C{1H},
19F{1H}, and 29Si{1H}) NMR spectroscopy, and the structure of [Pd(C6F5){(c-C5H9)7Si7O10(OH)2}(tmeda)]
was determined by X-ray crystallography. Temperature-dependent 1H and 19F{1H} NMR spectra revealed
the dynamic behavior of the complexes on the NMR time scale.
been employed as the precursors of silica-based catalysts with
encapsulating Pd oxide nanoparticles.4 Vogt and co-workers
reported palladium complexes having mono- and bidentate
phosphite ligands functionalized with silsesquioxanes.5 There
have been no reports on palladium complexes with O-bonded
silsesquioxanate ligands derived from incompletely condensed
silsesquioxanes. Recently, several research groups, including
ours, identified Pt complexes with mono- and bidentate silses-
quioxanate ligands.6 Although Pt and Pd complexes with
O-bonded alkoxo7,8 and aryloxo9 ligands have been widely
investigated during the last few decades, the corresponding
silanolate complexes having a M-O-Si bond (M ) Pd, Pt)
are much rarer.10-12 These silsesquioxanate or silanolate com-
plexes of Pd and Pt mostly contain phosphines as auxiliary
ligands. In this paper, we present our results for the preparation,
Introduction
Transition-metal complexes having an incompletely con-
densed silsesquioxane as a ligand are considered as suitable
soluble model compounds for silica-supported catalysts in
organic synthesis.1 Such metallasilsesquioxanes that contain
early transition metals may act as molecular catalysts in
polymerization epoxidation and the metathesis reactions of
alkenes.2 Metal clusters protected by silsesquioxanes and
metallasilsesquioxanes immobilized on polysiloxanes catalyze
olefin epoxidation and CH4 and NH3 oxidation reactions.3
Palladium complexes with silsesquioxane-amine ligands and
cubic silsesquioxanes have
* To whom correspondence should be addressed. E-mail: kosakada@
res.titech.ac.jp.
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10.1021/om0610492 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 02/06/2007

Arylpalladium Silsesquioxanate Complexes
Organometallics, Vol. 26, No. 6, 2007 1403
characterization, and dynamic behavior in solution of arylpal-
ladium silsesquioxane complexes having chelating N-donor
ligands.
Complexes 2 and 3 in toluene solutions decomposed upon
heating at 60 °C, while the bpy-coordinated complex 1 was
stable at that temperature. The higher stability of 1 as compared
to that of 2 or 3 in solution may be ascribed to stable
coordination of the bpy ligand compared with that of tmeda.
Complexes 1-5 were isolated as analytically pure solids and
were characterized by 1H, 13C{1H}, 19F{1H}, and 29Si{1H} NMR
spectroscopy and/or X-ray crystallography. Figure 1 displays
the molecular structure of 4, as determined by X-ray crystal-
lography. Selected bond lengths (Å) and angles (deg) are
summarized in Table 1. The square-planar Pd(II) center is
bonded to the chelating diamine ligand, a C6F5 group, and an
O atom from a silanol site of the silsesquioxane. The Pd-O
bond length (2.000(2) Å) is within the range of the bonds
reported for aryloxo-palladium complexes (1.979-2.129 Å)9b-f
and alkoxo-palladium complexes (2.020-2.134 Å)8a,c and is
slightly longer than that in the siloxopalladium complex [Pd-
(C6F5)(OSiPh3)(tmeda)] (1.986(3) Å),11 which may be ascribed
to the high degree of electron-withdrawing character of the
silsesquioxanate ligand compared with that of the OSiPh3
ligand.2a Pt complexes with silsesquioxanate or silanolate and
phenyl ligands at trans positions, trans-[Pt{R7O10Si7(OH)2}-
(Ph)(PEt3)2] (R ) c-C5H9, i-C4H9) (Pt-O ) 2.129(3), 2.113-
(2) Å)6c and trans-[Pt{OSiMe2(C6H4CF3-4)}(Ph)(PPh3)2] (Pt-O
) 2.091(4) Å),12 contain a Pt-O bond that is longer than the
Pd-O bond of 4, partly because of the trans influence of the
phenyl ligands in the complexes being greater than that of the
chelating tmeda ligand. The Pd-N and Pd-C bond lengths of
4 are similar to those reported for [Pd(C6F5)(OSiPh3)(tmeda)]11
and [Pd(Me)(OR)(tmeda)] (R ) alkyl).8b The fact that the Pd-
N1 distance (2.133(2) Å) is longer than the Pd-N2 distance
(2.066(2) Å) in 4 suggests that the trans influence of the C6F5
group is greater than that of the silsesquioxanate ligand. The
Pd-O-Si angle (133.0(1)°) is similar to those for the reported
platinum silsesquioxane complexes (134.6(2) and 130.2(2)°)6c
and the siloxopalladium complex [Pd(C6F5)(OSiPh3)(tmeda)]
(137.9(2)°).11
Results and Discussion
The reaction of the incompletely condensed silsesquioxane
(c-C5H9)7Si7O9(OH)3 with [Pd(C6H3Me2-2,4)(I)(bpy)] in the
presence of Ag2O yielded a Pd complex with a monodentate-
coordinated silsesquioxanate ligand, [Pd(C6H3Me2-2,4){(c-
C5H9)7Si7O10(OH)2}(bpy)] (1), as shown in eq 1. Aryl(iodo)-
palladium complexes, [Pd(Ar)(I)(tmeda)] (Ar ) C6H5, C6F5,
C6H3F2-2,4; tmeda ) N,N,N′,N′-tetramethylethylenediamine),
also reacted with the silsesquioxanes R7Si7O9(OH)3 (R )
c-C5H9, i-C4H9) at room temperature to produce complexes with
a silsesquioxanate ligand, [Pd(Ar){R7Si7O10(OH)2}(tmeda)] (2,
Ar ) C6H5, R ) c-C5H9; 3, Ar ) C6H5, R ) i-C4H9; 4, Ar )
C6F5, R ) c-C5H9; 5, Ar ) C6H3F2-2,4, R ) c-C5H9), as shown
in eq 2. The reaction requires more time than the preparation
The crystal structure of 4 shows two intramolecular hydrogen
bonds (O11-H1‚‚‚O1 and O12-H2‚‚‚O11) similarly to sils-
esquioxanate complexes containing platinum6c or iron.13 The
coordinated oxygen (O1) and an OH group (O11-H1) form a
strong hydrogen bond (O1‚‚‚O11 ) 2.612(2) Å, O11-
H1‚‚‚O1 ) 169(4)°), and the O‚‚‚O distance is within the range
of strong O-H‚‚‚O hydrogen bonds (2.50-2.65 Å).14 The other
hydrogen bond (O12-H2‚‚‚O11) has an O‚‚‚O distance
(O11‚‚‚O12 ) 2.772(3) Å) longer than O1‚‚‚O11 and an
O12-H2‚‚‚O11 angle (159(6)°) smaller than O11-H1‚‚‚O1.
As a result, the O12-H2‚‚‚O11 hydrogen bond between the
OH groups is weaker than the O11-H1‚‚‚O1 hydrogen bond
between the OH group and the coordinated O atom. Fluoro-
alkoxide and aryloxide ligands bonded to Pt and Pd were
reported to form adducts having O-H‚‚‚O hydrogen bonds
between the alcohol or phenol and the coordinated oxy-
gen.8a-c,9b,c,e The O‚‚‚O distances (2.56-2.66 Å) of the com-
plexes indicate strong or medium hydrogen bonds. The crystal-
lographic data of 4 show that the C6F5 group is almost
perpendicular to the coordination plane, similarly to many other
aryl complexes of d8 transition metals with a square-planar
configuration. The O12‚‚‚F1 distance (3.062(3) Å) is shorter
than the sum of the van der Waals radii (3.88 Å)15 and is slightly
of trans-[Pt{R7O10Si7(OH)2}(Ph)(PEt3)2] (R ) c-C5H9, i-C4H9)
(1-3 days).6c
(10) (a) Fukuoka, A.; Sato, A.; Mizuho, Y.; Hirano, M.; Komiya, S.
Chem. Lett. 1994, 1641-1644. (b) Fukuoka, A.; Sato, A.; Kodama, K.;
Hirano, M.; Komiya, S. Inorg. Chim. Acta 1999, 294, 266-274.
(11) Ruiz, J.; Vicente, C.; Rodr´ıguez, V.; Cutillas, N.; Lo´pez, G.; de
Arellano, C. R. J. Organomet. Chem. 2004, 689, 1872-1875.
(12) Mintcheva, N.; Nishihara, Y.; Mori, A.; Osakada, K. J. Organomet.
Chem. 2001, 629, 61-67.
(13) Liu, F.; John, K. D.; Scott, B. L.; Baker, R. T.; Ott, K. C.; Tumas,
W. Angew. Chem., Int. Ed. 2000, 39, 3127-3130.
(14) Gilli, P.; Bertolasi, V.; Ferretti, V.; Gilli, G. J. Am. Chem. Soc.
1994, 116, 909-915.
(15) Bondi, A. J. Phys. Chem. 1964, 68, 441-451.

1404 Organometallics, Vol. 26, No. 6, 2007
MintcheVa et al.
Figure 1. ORTEP drawing of 4 with ellipsoids at the 50% probability level. Hydrogen atoms, except OH hydrogens, and cyclopentyl
substituents attached to Si atoms are omitted for simplicity.
Table 1. Selected Bond Distances (Å) and Angles (deg) of 4
formation is more significant and results in a detectable electron
density peak due to the H2 atom between O11 and O12 atoms
rather than between the O12 and F1 atoms in the final D map.
The IR and 29Si{1H} and 13C{1H} NMR spectra of 1-5
showed the coordination of the silsesquioxanate ligand to the
Pd center. The IR spectra of 1-5 show a broad band from 3200
to 3350 cm-1 due to the νO-H vibration of the hydroxy group
engaged in O-H‚‚‚O hydrogen bonding. The peaks at 731, 733,
735, 730, and 730 cm-1, observed for 1-5, respectively, are
Pd-O1
2.000(2)
2.133(2)
2.066(2)
2.003(3)
89.75(9)
90.8(1)
Si1-O1
1.606(2)
2.612(2)
2.772(3)
Pd-N1
O1‚‚‚O11
O11‚‚‚O12
Pd-N2
Pd-C1
O1-Pd-N1
O1-Pd-C1
N1-Pd-N2
N2-Pd-C1
O1-Pd-N2
C1-Pd-N1
174.62(9)
133.0(1)
169(4)
Pd-O1-Si1
O11-H1‚‚‚O1
O12-H2‚‚‚O11
85.5(1)
93.9(1)
159(6)
175.23(9)
longer than the distances of the O-H‚‚‚F hydrogen bonds
reported (O‚‚‚F < 2.97 Å).16 This molecule conformation having
close contact between the F and O atoms (Figure 1b) suggests
the presence of a weak interaction between the OH group and
F atom, although competing O12-H2‚‚‚O11 hydrogen bond
(16) (a) Howard, J. A. K.; Hoy, V. J.; O’Hagan, D.; Smith, G. T.
Tetrahedron 1996, 52, 12613-12622. (b) Wiechert, D.; Mootz, D.; Dahlems,
T. J. Am. Chem. Soc. 1997, 119, 12665-12666. (c) Barbarich, T. J.; Rithner,
C. D.; Miller, S. M.; Anderson, O. P.; Strauss, S. H. J. Am. Chem. Soc.
1999, 121, 4280-4281. (d) Li, H.; Lee, G.-H.; Peng, S.-M. Inorg. Chem.
Commun. 2003, 6, 1-4.

Arylpalladium Silsesquioxanate Complexes
Organometallics, Vol. 26, No. 6, 2007 1405
Figure 2. 1H NMR spectra of 1 at room temperature in C6D6.
Scheme 1
Scheme 2
Chart 1
four silicon nuclei (two of them magnetically equivalent) from
the silsesquioxane backbone resonate between -64 and -69
ppm. The chemical shifts and the ratio of intensities of the
signals are similar to those of previously reported monodentate
platinum silsesquioxane complexes.6c The 29Si{1H} NMR
spectrum of 5 exhibited six signals in a 1:1:1:2:1:1 ratio. The
signals for the two silicon nuclei of the uncoordinated Si-OH
groups of 5 appeared as two independent peaks with very close
chemical shifts (-55.3 and -55.6 ppm). The two Si nuclei are
in different magnetic environments in the molecule. The single
peak for the two Si nuclei found for 2-4 is ascribed to the
agreement of peak positions or to the dynamic behavior of the
molecule in solution (vide infra).
assigned to the νSi-O vibrations of coordinated silanol groups
and are in agreement with the IR data of reported monodentate-
coordinated silsesquioxanates.6c
The 13C{1H} NMR spectrum of 1 shows seven signals
corresponding to the CH carbon atoms of cyclopentyl substit-
uents, which is in agreement with the 29Si{1H} NMR spectral
results. The 13C{1H} NMR spectra of 2-4 exhibit five signals
for the methyne carbons of C5H9 groups (for 2 and 4) and the
CH2 carbon atoms of isobutyl substituents of 3, in a 1:1:2:2:1
peak ratio in the range 22.4-26.4 ppm. One of the signals is at
downfield positions (25.6 (2), 26.4 (3), 25.2 ppm (4)) compared
Complex 1 exhibits seven 29Si{1H} NMR peaks for each of
the 29Si nuclei of the molecule. The 29Si{1H} NMR spectra of
2-4 consist of five signals in a 1:2:1:1:2 ratio, indicating the
apparent Cm local symmetry of the silsesquioxanate ligand. The
signal for two magnetically equivalent SiOH silicon nuclei and
the signal for the silicon nucleus bonded to the coordinated
oxygen appeared in the range from -55 to -58 ppm. The other

1406 Organometallics, Vol. 26, No. 6, 2007
MintcheVa et al.
Figure 3. Variable-temperature 19F{1H} NMR spectra of 4 in toluene-d8.
Figure 4. Variable-temperature 19F{1H} NMR spectra of 5 in toluene-d8.
with the other signals and is assigned to the carbon of an alkyl
group bonded to the Si atom of the Si-O-Pd group. The ratios
of the peaks are in agreement with the ratio of 29Si NMR signals.
The chemical shifts of the aromatic carbon atoms of 2-4 are
in good agreement with those reported for [PdI(C6H5)(tmeda)]
and [PdI(C6F5)(tmeda)].17 Two doublets of 4 with a coupling
constant of 230-240 Hz were observed and assigned to Co and
Cm of the C6F5 group. The assignment of 13C NMR signals for
the difluorophenyl ligand of 5 is based on a C-H COSY
diagram and the C-F coupling constants. The signals for the
C-F carbons appear as a doublet of doublets at 164.63 and
161.05 ppm with the following coupling constants: JCF ) 230
Hz, 3JCF ) 11 Hz and JCF ) 240 Hz, 3JCF ) 12 Hz. The signal
observed at 138.47 ppm due to the ortho CH carbon atom shows
3
coupling with two F nuclei (3JCF ) 19 Hz, JCF ) 7.4 Hz). A
2
doublet of doublets at 101.45 ppm (2JCF ) 33 Hz, JCF ) 24
Hz) and an apparent triplet due to similar 13C-19F coupling
constants (122.73 ppm, 2JCF ) 40 Hz) are attributed to the two
CH carbon atoms at the meta position.
1
The H NMR spectrum of 1 in C6D6 at room temperature
shows two signals at 2.71 and 2.38 ppm for ortho or para CH3
hydrogens. As shown in Figure 2, the OH hydrogen signals are
observed as two broad signals at 10.1 and 8.7 ppm. They are
assigned to O-H‚‚‚OPd hydrogen and O-H‚‚‚OH hydrogen,
(17) Martinez-Viviente, E.; Pregosin, P. S.; Tschoerner, M. Magn. Reson.
Chem. 2000, 38, 23-28.

Arylpalladium Silsesquioxanate Complexes
Organometallics, Vol. 26, No. 6, 2007 1407
1
Figure 5. Variable-temperature H NMR spectra of 5 in toluene-d8.
Chart 2
The activation of the O1‚‚‚H2 and O12‚‚‚H1 hydrogen bonds
of the structure on the left, accompanied by the formation of
new hydrogen bonds, O1‚‚‚H1 and O11‚‚‚H2, leads to the
structure shown on the right. This concerted process of 2 and 3
takes place more rapidly than the NMR time scale, although
complex 1 undergoes this switching of hydrogen bonds more
slowly and exhibits two 1H NMR signals for the OH hydrogens
at room temperature.
We reported that trans-[Pt{R7O10Si7(OH)2}(Ph)(PEt3)2]
(R ) c-C5H9, i-C4H9) exhibits two signals for ortho hydrogens
of the phenyl ligand at -50 °C and that they undergo
coalescence with an increase in temperature.6c Two processes
are able to account for the dynamic behavior of the molecule.
One involves the rotation of the Pd-C bond, shown in part i of
Scheme 2, even though the concurrent activation of the Pd-O
and O-H bonds and the formation of new Pd-O and O-H
bonds (part ii of Scheme 2) would also result in appearance of
a single OH hydrogen peak. The latter process was proposed
to account for the temperature-dependent NMR spectra of not
only trans-[Pt{R7O10Si7(OH)2}(Ph)(PEt3)2]6c but also the Pd and
Pt alkoxide or aryloxide complexes with alcohols (or phenols)
associated via O-H‚‚‚O hydrogen bonds.
Variable-temperature 1H and 19F{1H} NMR studies of 4 and
5 in toluene-d8 revealed the unique dynamic behavior of the
molecules. Figure 3 shows the temperature-dependent 19F{1H}
NMR spectra of 4. The spectrum at -80 °C exhibits two pairs
of signals for the ortho fluorine atoms of the C6F5 ligand. The
pairs of signals are assigned to two conformational isomers, A
and B, in Chart 1. Isomer B corresponds to the crystallographi-
cally determined structure (Figure 1) that contains hydrogen
bonds O11-H1‚‚‚O1 and O12-H2‚‚‚O11 and shows close
contact between O12 and the Fa atom. It shows a pair of 19F-
{1H} NMR signals due to a perpendicular relationship between
the aryl plane and the coordination plane.
respectively, because the former group contains a stronger
O-H‚‚‚O hydrogen bond than the latter. The low magnetic field
positions of the peaks indicate the formation of O-H‚‚‚O
hydrogen bonding in solution. NMR and calorimetric studies
of Pd, Pt, and Rh complexes with fluoroalkoxide or aryloxide
ligands and associated alcohols or phenols through O-H‚‚‚O
hydrogen bonds8a-c,9b,c,e,18 showed large association constants
in solution. The formation constants of [Rh(OAr)(OHAr)-
(PMe3)3] are comparable with those between proton donors and
anionic electron-pair donors.18
1
The H NMR spectra of 2-5 in toluene-d8 exhibit a single
broad signal of OH hydrogens of silsesquioxane in the range
of 7.8-9.0 ppm at room temperature, similarly to those of the
Pt and Sn complexes with incompletely condensed silsesqui-
oxanate ligands.6c,19 The two OH hydrogens of 2 and 3 under
different circumstances are observed as a single broad signal
owing to rapid exchange, as shown in Scheme 1.
Structure A has another combination of O and H atoms
forming hydrogen bonds within the silsesquioxanate ligand
(O11-H1‚‚‚O12 and O12-H2‚‚‚O1), and it also gives rise to
a pair of 19F{1H} NMR signals for ortho F nuclei. Although
the two isomers are distinguishable by 19F{1H} NMR at low
(18) Duchateau, R.; Dijkstra, T. W.; Severn, J. R.; van Santen, R. A.;
Korobkov, I. V. Dalton Trans. 2004, 2677-2682.
(19) Kegley, S. E.; Schaverien, C. J.; Freudenberger, J. H.; Bergman,
R. G.; Nolan, S. P.; Hoff, C. D. J. Am. Chem. Soc. 1987, 109, 6563-6565.

1408 Organometallics, Vol. 26, No. 6, 2007
MintcheVa et al.
temperatures, at -50 °C the NMR signals coalesce to give rise
to two signals for the ortho fluorine nuclei. This indicates that
a mutual exchange between A and B is taking place on the NMR
time scale, which is similar to the exchange shown for 2 in
Scheme 1. The structural change involves the switching of
hydrogen bonds and may accompany a change in the conforma-
tion induced by the rotation of the Pd-O bond to a limited
extent. The spectrum at 0 °C shows a broad signal for the ortho
fluorine nuclei, suggesting that another dynamic behavior occurs
at this temperature and renders all fluorine atoms at the ortho
position equivalent. Mutual exchange between A and A′ and
that between B and B′ (Chart 1) account for the NMR spectra
change. They correspond to the dynamic behavior of 2 in
Scheme 2; either the rotation of the Pd-C bond or the
metathesis-type switching of the Pd-O and O-H bonds is able
to make the two ortho positions of the aryl ligand of the
complexes equivalent. The 19F{1H} NMR spectrum of 4 at -80
°C indicated the presence of two isomers, A and B, although
the 1H NMR spectra of 2 at low temperatures were not helpful
in distinguishing the corresponding isomers.
or two signals depending on the temperature (-50, -80 °C).
This result may be ascribed to the presence of isomers in
Chart 2.
Conclusion
The first crystal structure of palladium silsesquioxane con-
taining a monodentate O-coordinated silsesquioxane ligand was
obtained. Arylpalladium silsesquioxanate complexes with a
diamine ligand and three types of aryl groups were synthesized
and characterized. The dynamic behavior of phenylpalladium
silsesquioxane complexes (2 and 3) in solution involves the
rotation of a Ph ring around the Pd-C bond and the rapid
exchange of H atoms between both O-H‚‚‚O hydrogen bonds.
Fluoro-substituted phenylpalladium complexes (4 and 5) re-
vealed the presence of conformational isomers and their mutual
exchange on the NMR time scale.
Experimental Section
General Procedures. All manipulations of the complexes were
carried out using standard Schlenk techniques under an argon or
nitrogen atmosphere. Toluene and hexane for the reactions were
dried using a Grubbs type solvent system stored under nitrogen.20
Aryliodopalladium(II) complexes, [Pd(Ar)(I)(tmeda)] (Ar ) C6H5,
C6H3F2-2,4, C6F5; tmeda ) N,N,N′,N′-tetramethylethylenediamine),
and [Pd(I)(C6H3Me2-2,4)(bpy)] were prepared by oxidative addition
of iodoarene to Pd(dba)2 (dba ) dibenzylideneacetone)21 in the
presence of tmeda (or bpy), as previously reported.22-24 The
silsesquioxanes 1,3,5,7,9,11,14-heptacyclopentyltricyclo[7.3.3.1(5,-
11)]heptasiloxane-endo-3,7,14-triol ((c-C5H9)7Si7O9(OH)3) and
1,3,5,7,9,11,14-heptaisobutyltricyclo[7.3.3.1(5,11)]heptasiloxane-
endo-3,7,14-triol ((i-C4H9)7Si7O9(OH)3) are commercially available
products of Aldrich Chemical Co. Ag2O was purchased from Wako
Pure Chemical Ind., Ltd. The reagents were used without any
purification. 1H, 13C{1H}, 19F{1H}, and 29Si{1H} NMR spectra were
recorded on Varian Mercury 300 and JEOL EX-400 spectrometers.
The 19F{1H} NMR spectra of 5 at different temperatures are
shown in Figure 4. The spectrum at 25 °C shows two signals at
-122.0 and -96.7 ppm, which are assigned to the fluorine
nuclei at the para and ortho positions, respectively. The signal
for the para fluorine nucleus is temperature-independent,
whereas that for the ortho fluorine nucleus is temperature-
dependent. Decreasing the temperature to -80 °C gives rise to
three signals in a ratio of approximately 1:1:2 for ortho fluorine
1
1
atoms. Figure 5 shows the VT H NMR spectra of 5. The H
NMR spectrum of 5 at 50 °C (part iv in Figure 5) shows the
displacement of three multiple signals (at 6.54, 6.90, and 7.50
ppm) for three nonequivalent hydrogens from the difluoro-
substituted phenyl group. According to the C-H COSY diagram
and F-H coupling constants in CDCl3 solution, they are
assigned to two nonequivalent Hm atoms (Hm and H′m) and Ho,
respectively. The signal for Hm (located between Fo and Fp) is
temperature-independent, whereas the signal for H′m overlaps
with solvent peaks at low temperatures. The signal for Ho splits
into two components at -50 °C (part ii in Figure 5).
1
Chemical shifts of the signals in H and 13C{1H} NMR spectra
were adjusted to the residual peaks of the solvents used. Peak
positions in the 29Si{1H} and 19F{1H} NMR spectra were referenced
to external standard SiMe4 in C6D6 (or CDCl3) and CF3COOH in
toluene-d8, respectively. IR absorption spectra were recorded on a
Shimadzu FT/IR-8100 spectrometer. Elemental analyses were
carried out with a LECO CHNS-932 or Yanaco MT-5 CHN
autocorder. New complexes obtained undergo decomposition
without melting upon heating. The temperature of starting decom-
position (dec pt) is shown for each complex.
Preparation of [Pd{(c-C5H9)7Si7O10(OH)2}(C6H3Me2-2,4)-
(bpy)] (1). To a solution of [PdI(C6H3Me2-2,4)(bpy)] (136 mg, 0.30
mmol) in toluene (15 mL) were added (c-C5H9)7Si7O9(OH)3 (262
mg, 0.30 mmol) and Ag2O (84 mg, 0.36 mmol). The reaction
mixture was heated at 60 °C for 27 h and then filtered through
Celite. The solvent was evaporated under reduced pressure, and
the crude product was washed with hexane (3 × 5 mL) to afford
1 as a yellow solid (380 mg, 94%). Anal. Calcd for C53H83N2O12-
PdSi7: C, 51.24; H, 6.65; N, 2.26. Found: C, 50.93; H, 6.55; N,
2.20. Dec pt: 178 °C. 1H NMR (300 MHz, CDCl3, room
Chart 2 depicts four possible conformational isomers of 5
existing in solution. Structures C and D have the ortho fluorine
atom of the C6H3F2 ligand and the OH groups of the silsesqui-
oxanate ligand on the same side of the coordination plane and
have positions of O-H‚‚‚O hydrogen bonding that differ from
each other, similarly to A and B in Chart 1. Structures E and F
have the ortho fluorine atom and OH group on opposite side of
the coordination plane. The coalescence of the NMR signals is
due to dynamic processes involving a mutual conversion
between C and D or E and F similarly to Scheme 1, and that
between C and E or D and F similarly to Scheme 2. The 19F-
{1H} NMR signals at -91.0 and -97.8 ppm assigned to C and
D appear at different positions, similarly to the corresponding
fluorine atoms of A and B. Isomers E and F exhibit a single
1
19F{1H} NMR signal at -99.1 ppm. The H NMR spectrum
shows two signals for the ortho hydrogen, even at -80 °C. It
(20) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518-1520.
(21) Ukai, T.; Kawazura, H.; Ishii, Y.; Bonnet, J. J.; Ibers, J. A.
J. Organomet. Chem. 1974, 65, 253-266.
may be ascribed to a 19F{1H} NMR peak position (ca. 2500
1
Hz) that is much larger than and different from the H NMR
peak difference (ca. 500 Hz).
(22) Markies, B. A.; Canty, A. J.; de Graaf, W.; Boersma, J.; Janssen,
M. D.; Hogerheide, M. P.; Smeets, W. J. J.; Spek, A. L.; van Koten, G.
J. Organomet. Chem. 1994, 482, 191-199.
The 1H NMR signals of OH hydrogens of 5 are more
complicated than those of the OH hydrogen atoms of 2 and 4.
Two weak and broad signals at 8.18 and 8.55 ppm are observed
at 25 °C. Increasing the temperature leads to one broad signal
at 8.2 ppm, whereas the spectra at low temperatures show one
(23) Hughes, R. P.; Ward, A. J.; Golen, J. A.; Incarvito, C. D.; Rheingold,
A. L.; Zakharov, L. N. Dalton Trans. 2004, 2720-2727.
(24) Yagyu, T.; Osakada, K.; Brookhart, M. Organometallics 2000, 19,
2125-2129.

Arylpalladium Silsesquioxanate Complexes
Organometallics, Vol. 26, No. 6, 2007 1409
Table 2. Crystallographic Data and Details of Refinement of
4
CH pentyl), 27.06, 27.10, 27.14, 27.18, 27.31, 27.34, 27.39, 27.66,
27.68, 28.93 (28C, CH2 pentyl), 47.54 (N(CH3)2), 51.39 (N(CH3)2),
57.84 (CH2), 63.38 (CH2), 122.67 (PdC6H5 para), 125.84 (PdC6H5
meta), 135.05 (PdC6H5 ortho), 148.65 (PdC6H5 ipso). 29Si{1H}
NMR (79 MHz, C6D6, 0.02 M Cr(acac)3, room temperature):
δ -55.76, -56.57, -64.47, -64.95, -67.53 (1:2:1:1:2). IR data
(KBr): 3200 (br, w), 2949 (s), 2865 (s), 1560 (w), 1474 (m), 1458
(w), 1246 (m), 1100 (vs), 930 (m), 878 (m), 804 (w), 763 (w), 733
empirical formula
formula wt
cryst color
cryst dimens (mm)
cryst syst
space group
a (Å)
C47H81F5N2O12PdSi7
1264.15
pale yellow
0.70 × 0.30 × 0.15
monoclinic
P21/n (No. 14)
13.260(2)
24.742(3)
18.376(2)
102.788(1)
5879(1)
(w), 698 (w), 502 (m) cm-1
.
b (Å)
c (Å)
Preparation of [Pd{(i-C4H9)7Si7O10(OH)2}(C6H5)(tmeda)] (3).
To a solution of [PdI(C6H5)(tmeda)] (64 mg, 0.15 mmol) in toluene
(8 mL) were added (i-C4H9)7Si7O9(OH)3 (119 mg, 0.15 mmol) and
Ag2O (42 mg, 0.18 mmol). The reaction mixture was stirred at
room temperature for 8 days. After filtration through Celite and
removal of the solvent, the crude product was dissolved in 1 mL
of hexane and kept at -20 °C for 2 days to afford a yellow solid
(117 mg, 71%). Anal. Calcd for C40H86N2O12PdSi7: C, 44.07; H,
7.95; N, 2.57. Found: C, 43.57; N, 2.62; H, 7.63. Dec pt: 126 °C.
1H NMR (300 MHz, CDCl3, room temperature): δ 0.26 (d, 4H,
CH2 iBu, JHH ) 6.9 Hz), 0.49 (d, 2H, CH2 iBu, JHH ) 6.6 Hz),
0.55 (d, 2H, CH2 iBu, JHH ) 6.9 Hz), 0.62 (d, 4H, CH2 iBu, JHH
) 6.9 Hz), 0.71 (d, 2H, CH2 iBu, JHH ) 6.9 Hz), 0.83 (d, 12H,
CH3 iBu, JHH ) 6.6 Hz), 0.88 (d, 6H, CH3 iBu, JHH ) 6.6 Hz),
0.94 (d, 6H, CH3 iBu, JHH ) 6.6 Hz), 0.99 (m, 18H, CH3 iBu), 1.6
(m, 2H, CH iBu), 1.8 (m, 4H, CH iBu), 2.1 (m, 1H, CH iBu), 2.43
(s, 6H, N(CH3)2), 2.52 (m, 2H, NCH2), 2.57 (s, 6H, N(CH3)2), 2.65
(m, 2H, NCH2), 6.83-6.89 (m, 3H, PdC6H5 para and meta), 7.30
(d, 2H, PdC6H5 ortho, JHH ) 6.6 Hz), 8.8 (br, 2H, OH). 13C{1H}
NMR (100 MHz, CDCl3, room temperature): δ 22.74, 22.87, 22.93,
23.35, 26.45 (1:1:2:2:1, 7C, CH2 iBu), 23.81, 23.95, 23.97, 24.10,
24.87 (2:1:1:2:1, 7C, CH iBu), 25.64, 25.76, 25.80, 25.93, 26.01,
26.25 (2:2:2:3:3:2, 14C, CH3 iBu), 47.38 (N(CH3)2), 51.31 (N(CH3)2),
57.70 (CH2), 63.31 (CH2), 122.80 (PdC6H5 para), 125.88 (PdC6H5
meta), 135.30 (PdC6H5 ortho), 148.76 (PdC6H5 ipso). The signals
for CH, CH2, and CH3 carbon atoms of isobutyl substituents were
assigned by the DEPT method. 29Si{1H} NMR (79 MHz, CDCl3,
0.02 M Cr(acac)3, room temperature): δ -56.98, -57.78, -66.54,
-67.08, -69.17 (ratio 2:1:2:1:1). IR data (KBr): 3250 (br, w),
2953 (s), 2869 (s), 1566 (w), 1466 (m), 1458 (w), 1402 (w), 1366
(w), 1331 (w), 1229 (m), 1100 (vs), 959 (m), 907 (m), 853 (w),
â (deg)
V (Å3)
Z
4
calcd density (g cm-3
F(000)
)
1.428
2648
5.312
43 230
13 384
0.031
µ (cm-1
no. of rflns measd
no. of unique rflns
Rint
)
no. of variables
R1 (I > 2.00σ(I))
wR2 (I > 2.00σ(I))
goodness of fit
754
0.0444
0.1288
0.994
temperature): δ 0.8-1.2 (m, 7H, CH pentyl), 1.2-2.0 (m, 56H,
CH2 pentyl), 2.27 (s, 3H, CH3), 2.47 (s, 3H, CH3), 6.69 (d, 1H,
PdC6H4 meta, JHH ) 7.8 Hz), 6.74 (s, 1H, PdC6H4 meta′), 7.01 (t,
1H, H5′ bpy, JHH ) 6.6 Hz), 7.39 (d, 1H, PdC6H4 ortho, JHH ) 7.2
Hz), 7.43 (m, 1H, H5 bpy), 7.55 (1H, OH), 7.73 (d, 1H, H6′ bpy,
JHH ) 5.4 Hz), 7.82 (t, 1H, H4 bpy, JHH ) 7.5 Hz), 8.01-8.23
(overlapped 3H, H3,3′ bpy and H4′ bpy), 9.11 (d, 1H, H6 bpy, JHH
) 4.5 Hz), 9.6 (1H, OH). 1H NMR (300 MHz, C6D6, room
temperature): δ 1.1-1.4 (m, 7H, CH pentyl), 1.4-2.2 (m, 56H,
CH2 pentyl), 2.38 (s, 3H, CH3), 2.71 (s, 3H, CH3), 6.05 (t, 1H, H5′
bpy, JHH ) 6.3 Hz), 6.95 (s, 1H, PdC6H4 meta′), 7.08 (d, 1H,
PdC6H4 meta, JHH ) 7.8 Hz), 7.22 (m, 3H, overlapped H5 bpy and
H3,3′ bpy), 7.49 (m, 2H, H4,4′ bpy), 7.76 (d, 1H, H6′ bpy, JHH ) 5.4
Hz), 7.83 (d, 1H, PdC6H4 ortho, JHH ) 7.8 Hz), 8.7 (1H, OH),
9.31 (dd, 1H, H6 bpy, JHH ) 4.8, 1.8 Hz), 10.1 (1H, OH). 13C{1H}
NMR (100 MHz, C6D6, room temperature): δ 21.08 (CH3), 23.11,
23.16, 23.31, 23.39, 23.79, 23.83, 24.24 (7C, CH pentyl), 25.10,
25.22 (CH3), 27.59-29.45 (28C, CH2 pentyl), 121.69 (C4′ bpy),
123.23 (C3′ bpy), 124.94 (PdC6H3 meta), 125.63 (C5′ bpy), 126.20
(C5 bpy), 128.53 (C3 bpy), 130.16 (PdC6H3 meta′), 132.88 (PdC6H3
para), 135.99 (C6′ bpy), 138.37 (PdC6H3 ortho), 138.86 (PdC6H3
ortho′), 140.06 (PdC6H3 ipso), 149.63 (C6 bpy), 151.72 (C4 bpy),
152.33 (C2′ bpy), 156.22 (C2 bpy). The peak positions of H and C
atoms were assigned using H-H COSY and C-H COSY diagrams.
29Si{1H} NMR (79 MHz, C6D6, 0.02 M Cr(acac)3, room temper-
ature): δ -54.83, -56.11, -56.71, -64.46, -64.76, -66.54,
-67.58. IR data (KBr): 3300 (br w), 2950 (s), 2865 (s), 1599 (w),
1468 (w), 1447 (m), 1244 (m), 1109 (vs), 900 (m), 764 (m), 731
804 (w), 770 (w), 735 (m), 698 (w), 484 (m) cm-1
.
Preparation of [Pd{(c-C5H9)7Si7O10(OH)2}(C6F5)(tmeda)] (4).
To a solution of [PdI(C6F5)(tmeda)] (54 mg, 0.10 mmol) in toluene
(5 mL) were added (c-C5H9)7Si7O9(OH)3 (87 mg, 0.10 mmol) and
Ag2O (28 mg, 0.12 mmol). The reaction mixture was stirred at
room temperature for 10 days, after that it was filtered through
Celite. The solvent was evaporated and the product was recrystal-
lized from hexane (1 mL) at -20 °C as pale yellow crystals suitable
for X-ray crystallography (98 mg, 75%). Anal. Calcd. for
C47H81F5N2O12PdSi7: C, 44.65; N, 2.22; F, 7.51; H, 6.46. Found:
C, 44.79; N, 2.20; F, 7.62; H, 6.32. Dec pt: 182 °C. 1H NMR (400
MHz, C7D8, room temperature): δ 1.0-1.4 (m, 7H, CH pentyl),
1.4-2.0 (m, overlapped 56H, CH2 pentyl and 4H, NCH2), 1.66 (s,
6H, NCH3), 2.36 (s, 6H, NCH3), 7.8 (br, 2H, OH). 19F{1H} NMR
(376 MHz, C7D8, room temperature): δ -120.7 (br, 2F ortho),
-162.5 (t, 1F para, JFF ) 20 Hz), -165.3 (m, 2F meta, JFF ) 20
Hz). 13C{1H} NMR (100 MHz, CDCl3, room temperature): δ 22.44,
22.54, 22.73, 22.79, 25.20 (1:1:2:2:1, 7C, CH pentyl), 27.04-27.56,
28.98 (28C, CH2 pentyl), 48.38 (NCH3), 52.54 (NCH3), 59.21
(NCH2), 63.54 (NCH2), 135.60 (d, C6F5 meta, JFC ) 237 Hz),
147.75 (d, C6F5 ortho, JFC ) 231 Hz). The signals assigned as ipso
and para carbons were not observed, due to low intensity. 29Si-
{1H} NMR (79 MHz, CDCl3, 0.02 M Cr(acac)3, room tempera-
ture): δ -56.49, -56.88, -65.17, -65.69, -68.34 (1:2:1:1:2). IR
data (KBr): 3350 (br, w), 2949 (s), 2867 (s), 1500 (m), 1456 (s),
1246 (m), 1100 (vs), 959 (s), 909 (m), 808 (m), 789 (w), 770 (w),
(w), 502 (m) cm-1
.
Preparation of [Pd{(c-C5H9)7Si7O10(OH)2}(C6H5)(tmeda)] (2).
To a solution of [PdI(C6H5)(tmeda)] (64 mg, 0.15 mmol) in toluene
(8 mL) were added (c-C5H9)7Si7O9(OH)3 (131 mg, 0.15 mmol) and
Ag2O (42 mg, 0.18 mmol). The reaction mixture was stirred at
room temperature for 8 days. The gray suspension was passed
through a Celite pad, and the Celite was washed with 4 mL of
toluene. The solvent was evaporated under reduced pressure. Then
1 mL of hexane was added and the solution was kept at -20 °C to
give 2 as a yellow solid (150 mg, 85%). Anal. Calcd for
C47H86N2O12PdSi7: C, 48.08; H, 7.38; N, 2.39. Found: C, 47.87;
1
H, 7.16; N, 2.46. Dec pt: 159 °C. H NMR (300 MHz, CDCl3,
room temperature): δ 0.71 (m, 1H, CH pentyl), 0.98 (m, 6H, CH
pentyl), 1.3-2.0 (m, 56H, CH2 pentyl), 2.43 (s, 6H, N(CH3)), 2.50
(m, 2H, NCH2), 2.61 (s, 6H, N(CH3)), 2.65 (m, 2H, NCH2), 6.80-
6.90 (m, 3H, PdC6H5 meta and para), 7.28 (d, 2H, PdC6H5 ortho),
8.6 (br, 2H, OH). 13C{1H} NMR (100 MHz, CDCl3, room
temperature): δ 22.54, 22.63, 22.67, 23.08, 25.64 (1:1:2:2:1, 7C,
730 (w), 505 (m) cm-1
.

1410 Organometallics, Vol. 26, No. 6, 2007
MintcheVa et al.
Preparation of [Pd{(c-C5H9)7Si7O10(OH)2}(C6H3F2-2,4)(tme-
da)] (5). To a solution of [PdI(C6H3F2-2,4)(tmeda)] (46 mg, 0.10
mmol) in toluene (5 mL) were added (c-C5H9)7Si7O9(OH)3 (87 mg,
0.10 mmol) and Ag2O (28 mg, 0.12 mmol). The reaction mixture
was stirred at room temperature for 10 days. After completion of
the reaction the gray suspension was filtered through Celite. The
solvent was evaporated under reduced pressure, and 1 mL of hexane
was added to the crude product. The solution was cooled to
-20 °C to give 5 as a pale yellow solid (89 mg, 74%). An analogous
reaction was performed at 60 °C for 24 h and afforded the same
product 5. Anal. Calcd for C47H84F2N2O12PdSi7: C, 46.65; N, 2.31;
F, 3.14; H, 7.00. Found: C, 46.31; N, 2.23; F, 3.20; H, 6.88. Dec
X-ray Crystallography. Crystals of 4 suitable for X-ray
diffraction study were mounted on a glass capillary tube. The data
were collected to a maximum 2θ value of 55.0°. A total of 720
oscillation images were collected on a Rigaku Saturn CCD area
detector equipped with monochromated Mo KR radiation (λ )
0.710 73 Å) at -160 °C. A sweep of data was done using ω scans
from -110.0 to 70.0° in 0.5° steps, at ø ) 45.0° and φ ) 0.0°.
The detector swing angle was -20.42°. A second sweep was
performed using ω scans from -110.0° to 70.0° in 0.5° step, at ø
) 45.0° and φ ) 90.0°. The crystal-to-detector distance was 44.84
mm. Readout was performed in the 0.070 mm pixel mode.
Calculations were carried out by using the program package Crystal
Structure, version 3.7 for Windows. A full-matrix least-squares
refinement was used for the non-hydrogen atoms with anisotropic
thermal parameters. Hydrogen atoms except for the OH hydrogens
of 4 were located by assuming the ideal geometry and were included
in the structure calculation without further refinement of the
parameters. Crystallographic data and details of refinement are
summarized in Table 2.
1
pt: 162 °C. H NMR (400 MHz, CDCl3, room temperature): δ
0.96 (m, 7H, CH pentyl), 1.1-2.8 (m, 72H, CH2 pentyl and tmeda),
6.39 (m, 1H, C6H3F2 meta, JHH ) 8 Hz, JHF ) 3 Hz), 6.59 (m, 1H,
C6H3F2 meta′, JHH ) 8 Hz, JHF ) 3 Hz), 7.28 (m, 1H, C6H3F2
1
ortho, JHH ) 8 Hz, JHF ) 5 Hz), 8.2 (br, 2H, OH). H NMR (400
MHz, C7D8, room temperature): δ 1.1-1.4 (m, 7H, CH pentyl),
1.4-2.1 (m, 72H, CH2 pentyl and tmeda), 6.54 (m, 1H, C6H3F2
meta), 6.90 (m, 1H, C6H3F2 meta), 7.50 (m, 1H, C6H3F2 ortho),
8.18 (br, 1H, OH), 8.55 (br, 1H, OH). 19F{1H} NMR (376 MHz,
C7D8, room temperature): δ -96.7 (br, Fo), -122.0 (m, Fp). 13C-
{1H} NMR (100 MHz, CDCl3, room temperature): δ 22.50, 22.59,
23.06, 25.16 (2:2:2:1, 7C, CH pentyl), 27.06-27.66, 28.89 (28C,
CH2 pentyl), 47.94 (N(CH3)), 52.04 (br, N(CH3)), 58.34 (NCH2),
Acknowledgment. N.M. thanks the Japanese Society for
Promotion of Science for a postdoctoral fellowship for foreign
researchers (2004-2006). This work was financially supported
by a Grant-in-Aid for Scientific Research for Young Chemists
(No. 17750049) and for Scientific Research on Priority Areas,
from the Ministry of Education, Culture, Sport, Science, and
Technology Japan, and by the 21st Century COE Program
“Creation of Molecular Diversity and Development of Func-
tionalities”.
2
2
63.55 (NCH2), 101.45* (dd, C6H3F2 meta, JCF ) 33 Hz, JCF
)
24 Hz), 109.57 (d, C6H3F2 ipso, 2JCF ) 19 Hz), 122.73* (d, C6H3F2
2
3
meta′, JCF ) 40 Hz), 138.47* (dd, C6H3F2 ortho′, JCF ) 19 Hz,
3JCF ) 7.4 Hz), 161.05 (dd, C6H3F2 para or ortho, JCF ) 240 Hz,3JCF
) 12 Hz), 164.63 (dd, C6H3F2 para or ortho, JCF ) 230 Hz,3JCF
)
11 Hz,). Signals marked with an asterisk were assigned by 2D
dimensional NMR spectroscopy. 29Si{1H} NMR (79 MHz, CDCl3,
0.02 M Cr(acac)3, room temperature): δ -55.3, -55.6, -56.1,
-65.3, -65.8, -66.4 (1:1:1:2:1:1). IR data (KBr): 3300 (br, w),
2949 (s), 2865 (s), 1590 (w), 1468 (m), 1389 (w), 1258 (m), 1100
(vs), 955 (m), 909 (w), 843 (w), 804 (m), 770 (w), 730 (w), 502
Supporting Information Available: Crystallographic data for
4 as a CIF file. This material is available free of charge via the
Internet at http://pubs.acs.org.
(m) cm-1
.
OM0610492