Synthesis and characterization of platinasilsesquioxane complexes and their reaction with arylboronic acid

Article abstract of DOI:10.1021/om100880h

Phenyl(iodo)platinum complexes having a 2,2′-bipyridine (bpy) or 1,2-bis(diphenylphosphino)ethane (dppe) ligand react with incompletely condensed silsesquioxane (c-C₅H₉)₇Si₇O ₉(OH)₃ in the presence of Ag₂O to yield platinasilsesquioxane complexes [Pt{(c-C₅H₉) ₇Si₇O₁₀(OH)₂}(C₆H ₅)(L)] (1, L = bpy; 2, L = dppe). NMR spectroscopy revealed their square-planar structures with an O-coordinated silsesquioxanate ligand and O-H...O hydrogen bonds within the ligand. Both complexes undergo transmetalation of p-methoxyphenylboronic acid to afford unsymmetrical diarylplatinum complexes [Pt(C₆H₄OCH₃-p)(C ₆H₅)(L)] (3, L = bpy; 4, L = dppe).

Full text of DOI:10.1021/om100880h

Organometallics 2011, 30, 187–190 187
DOI: 10.1021/om100880h
Synthesis and Characterization of Platinasilsesquioxane Complexes and
Their Reaction with Arylboronic Acid
Neli Mintcheva,†,‡ Makoto Tanabe,‡ and Kohtaro Osakada*,‡
†Department of Chemistry, University of Mining and Geology “St. Ivan Rilski ”, Students’ town, Sofia 1700,
Bulgaria, and ‡Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1-3 Nagatsuta,
Midori-ku, Yokohama 226-8503, Japan
Received September 11, 2010
Summary: Phenyl(iodo)platinum complexes having a 2,20-
bipyridine (bpy) or 1,2-bis(diphenylphosphino)ethane (dppe)
ligand react with incompletely condensed silsesquioxane
(c-C5H9)7Si7O9(OH)3 in the presence of Ag2O to yield platina-
silsesquioxane complexes [Pt{(c-C5H9)7Si7O10(OH)2}(C6H5)-
(L)] (1, L=bpy; 2, L=dppe). NMR spectroscopy revealed
their square-planar structures with an O-coordinated silses-
chlorosilane, leading to double silylation of the ligand.6 Fur-
ther studies on the reactions of organic molecules with the
silsesquioxane complexes would reveal their new chemical
properties. In this paper we present our results on trans-
metalation of aryl groups from boron to the highly reactive
Pt-O-Si bond from platinasilsesquioxane complexes.
quioxanate ligand and O-H O hydrogen bonds within the
3 3 3
Results and Discussion
ligand. Both complexes undergo transmetalation of p-methoxy-
phenylboronic acid to afford unsymmetrical diarylplatinum
complexes [Pt(C6H4OCH3-p)(C6H5)(L)] (3, L=bpy; 4, L=dppe).
Preparation of Platinasilsesquioxane Complexes. The reac-
tion of silsesquioxane containing trisilanols (c-C5H9)7Si7O9-
(OH)3 with [PtI(Ph)(L)] (L=2,20-bipyridine (bpy); 1,2-bis-
(diphenylphosphino)ethane (dppe)) in the presence of Ag2O
affords platinum complexes with an O-coordinated silses-
quioxanate ligand, [PtPh{(c-C5H9)7Si7O10(OH)2}(L)] (1, L=
bpy, yield 95%; 2, L=dppe, yield 62%), as shown in Scheme 1.
Complexes 1 and 2 are thermally stable, and their NMR
spectra do not change even after 5 days at 60 °C. The 31P{1H}
NMR spectrum of 2 displays two signals flanked with 195Pt
satellites (39.4 ppm, JPtP=1654 Hz and 29.7 ppm, JPtP=4127
Hz). The respective 31P-195Pt coupling constants fall in the
typical range of the phosphine ligands bonded at trans posi-
tions of an aryl ligand and of an O-ligand in Pt(II) com-
plexes.2a,7-9 Both complexes show 29Si{1H} NMR spectra
that consist of five signals in 1:2:1:1:2 ratio. These signals are
typical for the silsesquioxane framework with Cs symmetry
and often observed in the spectrum of transition metal com-
plexes having a monodentate silsesquioxanate ligand.3,5,10
13C{1H} NMR signals with the same intensity are observed
in the range 22.5-26.6 ppm and are assigned to the CH car-
bons of the cyclopentyl groups.
Introduction
Transition metal complexes with silsesquioxanate ligands
are regarded as molecular models of the metal catalysts sup-
ported on a silica surface or precursors of the heterogeneous
catalysts.1 Pt(II) and Pd(II) complexes with silsesquioxanes
were investigated by Abbenhuis, Johnson, and Vogt.2 We also
reported preparation of the pallada- and platinasilsesquiox-
ane complexes such as [Pd(Ar){R7Si7O10(OH)2}(tmen)] and
trans-[M(Ar){R7Si7O10(OH)2}(PR03)2] (M = Pt, Pd; Ar =
C6H5, C6F5; R=c-C5H9, i-C4H9; PR03=PMe3, PEt3, PMe2-
Ph; tmen=N,N,N0,N0-tetramethylethylenediamine). The com-
plexes show fluxional NMR spectra due to dynamic exchange
of the hydrogen bonds in the silsesquioxanate ligand.3-5
A palladium complex with an O,O0-coordinated bidentate
silsesquioxanate ligand, [Pd{R7Si7O11(OH)}(bpy)], reacts with
*To whom correspondence should be addressed. E-mail: kosakada@
res.titech.ac.jp.
1
The H NMR spectra of 1 and 2 in toluene-d8 at 25 °C
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contain OH hydrogen peaks at 8.8 and 8.3 ppm, respectively.
Their low magnetic field positions are ascribed to intramo-
lecular hydrogen bonding in the complexes, similar to the
reported platina- and palladasilsesquioxane complexes.3-6
As can be expected,11 the signals are shifted to low magnetic
field with decreasing temperature and reach 11.6 ppm (1) and
10.1 ppm (2) at -80 °C. Change of the concentration of 1
(6) Tanabe, M.; Mutou, K.; Mintcheva, N.; Osakada, K. J. Organomet.
Chem., doi:10.1016/j.jorganchem.2010.09.029.
(7) Clarke, M. L.; Heydt, M. Organometallics 2005, 24, 6475.
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Chim. Acta 2002, 330, 72.
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75.
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Lett. 2001, 3, 589. (b) Wachter-Jurcsak, N.; Detmer, C. A. Org. Lett. 1999,
1, 795.
(3) Mintcheva, N.; Tanabe, M.; Osakada, K. Organometallics 2006,
25, 3776.
(4) Mintcheva, N.; Tanabe, M.; Osakada, K. Organometallics 2007,
26, 1402.
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tallics 2008, 27, 519.
r
2010 American Chemical Society
Published on Web 12/07/2010
pubs.acs.org/Organometallics

188 Organometallics, Vol. 30, No. 1, 2011
Mintcheva et al.
Scheme 1
from 40 mM to 5 mM at 25 °C causes a shift of the OH
hydrogen peak from 8.54 ppm to 8.23 ppm. Signals of the
bipyridine hydrogens are also influenced by the concentra-
tion. All the bipyridine hydrogen signals are broadened at
boric acid, and the trisilanol (Scheme 2). The former reaction
mixture was separated into the orange insoluble residue,
composed of 3 and of H3BO3 or its condensation product,
and the THF/hexane solution that contains (c-C5H9)7-
Si7O10(OH)3, which is isolated in 69% yield. The evidence
for formation of boric acid is its 1H NMR signals in acetone-
d6.8 The silsesquioxane (c-C5H9)7Si7O10(OH)3 can be easily
isolated from the above THF/hexane filtrate and identified
by comparison of the FAB and 1H and 29Si NMR spectro-
scopic data with an authentic sample.16
0
low concentration. The peripheral H3,3 , H4, and H5 hydro-
gen signals appear at 8.23, 7.81, and 7.38 ppm at [1]=40 mM,
respectively, while they are shifted to 8.52, 7.92, and 7.55 ppm
in a dilute solution (5 mM), as shown in Figure 1. Signals of
0
the hydrogens close to the Pt center (H6, H6 ) are affected to a
negligible degree. The above NMR results, including broad-
ening of the signals, may be attributed to partial dissociation
of the silsesquioxanate ligand from 1. Another possible ex-
planation may be intermolecular interaction of the complex
molecules in the solution. X-ray analysis of palladium com-
plexes with bipyridine and O,O0-coordinated silsesquioxa-
nate ligands revealed an associative interaction between the
bipyridine planes of the molecules.6 The origin of the NMR
change depending on the concentration is not clear at present.
Formation of Diarylplatinum Complexes from the Silses-
quioxane Complexes and Arylboronic Acid. Hydroxopalla-
dium species are regarded as an intermediate of synthetic
organic reactions using arylboronic acids as the aryl source
and Pd complexes as the catalyst such as Suzuki-Miyaura
coupling.12 The Pd-OH species can be generated from hy-
drolysis of the halopalladium complexes by OH- and undergo
transmetalation on reaction with arylboronic acid in the
catalytic cycles. The reaction of arylboronic acid with a hydro-
xopalladium complex forms an arylpalladium complex or
biaryl via transmetalation.13 The transfer of an organic
group from B to the transition metal center is accelerated by
addition of bases such as F-, OH-, or OR-7,14 or by reaction
with cationic platinum or palladium complexes.15 We expec-
ted the reactions of arylboronic acids with the silsesquioxa-
nate ligand of the above Pt complexes.
X-ray crystallography of 3 and 4 (Figure 2) showed a square-
planar geometry around the platinum center, which is coordi-
nated to two N-donor atoms of the bipyridine ligand in 3 or two
P atoms from dppe in 4 and two C atoms from the phenyl and
methoxyphenyl rings at the cis position. The Pt-N, Pt-P, and
Pt-C bond distances are in the typical range in comparison
with those of previously reported diarylplatinum com-
plexes.8,17 The Pt-P1 bond length (2.301(2) A) in 4 is
˚
˚
elongated slightly from Pt-P2 (2.283(2) A) due to a stronger
trans influence of the phenyl ligand, whereas the electron-
withdrawing effect of a methoxy group in the aryl ligand
˚
shortens the distance Pt-C1 (2.106(6) A) compared with
˚
Pt-C8 (2.115(7) A). Despite the unsymmetrical diaryl li-
gands, the two Pt-N bonds and Pt-C1 and Pt-C8 bonds in
3 are very similar. This is in accord with the H NMR
spectrum, which shows three signals at 8.64, 7.35, and 6.74
1
0
ppm for bypiridine hydrogens H6,6 , H3,3 , and H4,4 and two
0
0
0
closely located signals at 6.18 and 6.13 ppm assigned to H5
and H5 of bpy. The doublet signals with coupling H-H and
Pt-H at 7.93 ppm (JHH=8.7 Hz, JPtH=78 Hz) and 8.09 ppm
(JHH=6.6 Hz, JPtH=60 Hz) for ortho hydrogens of aryl and
phenyl ligands, respectively, are observed quite similarly.
In summary, we obtained and characterized new platinum
complexes with O-coordinated silsesquioxanate and bpy or dppe
ligands. Their reactions with arylboronic acid produce diarylpla-
tinum complexes by transmetalation of an aryl group from B to Pt.
Platinasilsesquioxane complexes 1 and 2 react with an equi-
molar amount of (p-methoxyphenyl)boronic acid in THF or
benzene solution to produce unsymmetrical diarylplatinum com-
plexes [Pt(C6H4OCH3-p)(C6H5)(L)] (3, L=bpy; 4, L=dppe),
Experimental Section
General Procedures. All manipulations of the complexes were
carried out using standard Schlenk techniques under argon or nitrogen
(12) (a) Miyaura, N.; Yamada, K.; Suginome, H.; Suzuki, A. J. Am.
Chem. Soc. 1985, 107, 972. (b) Adamo, C.; Amatore, C.; Ciofini, I.; Jutand,
A.; Lakmini, H. J. Am. Chem. Soc. 2006, 128, 6829.
(13) (a) Nishihara, Y.; Onodera, H.; Osakada, K. Chem. Commun. 2004,
192. (b) Osakada, K.; Onodera, H.; Nishihara, Y. Organometallics 2005, 24, 190.
(14) (a) Miyaura, N. J. Organomet. Chem. 2002, 653, 54. (b) Suzaki, Y.;
Osakada, K. Organometallics 2006, 25, 3251.
(15) (a) Siegmann, K.; Pregosin, P. S.; Venanzi, L. M. Organometal-
lics 1989, 8, 2659. (b) Nishikata, T.; Yamamoto, Y.; Miyaura, N. Organo-
metallics 2004, 23, 4317.
(16) (a) Pescarmona, P. P.; van der Waal, J. C.; Maschmeyer, T. Eur.
J. Inorg. Chem. 2004, 978. (b) Feher, F. J.; Budzichowski, T. A.; Blanski,
R. L.; Weller, K. J.; Ziller, J. W. Organometallics 1991, 10, 2526.
(17) (a) Klein, A.; Hausen, H. D.; Kaim, W. J. Organomet. Chem.
1992, 440, 207. (b) Plutino, M. R.; Scolaro, L. M.; Albinati, A.; Romeo, R.
J. Am. Chem. Soc. 2004, 126, 6470. (c) Deacon, G. B.; Elliott, P. W.; Erven,
A. P.; Meyer, G. Z. Anorg. Allg. Chem. 2005, 631, 843.

Note
Organometallics, Vol. 30, No. 1, 2011 189
Figure 1. 1H NMR spectra of 1 in CDCl3 at 5, 10, and 40 mM.
Scheme 2
atmosphere. Hexane and toluene were purified by using a solvent
purification system (Glass Contour). Phenyl(iodo)platinum(II)
compexes [PtI(Ph)(bpy)] and [PtI(Ph)(dppe)] were prepared by
ligand replacement of 1,5-cyclooctadiene from [PtI(Ph)(cod)]
with 2,20-bipyridine and dppe, respectively, as previously re-
ported.18 Silsesquioxane 1,3,5,7,9,11,14- heptacyclopentyltri-
cyclo[7.3.3.1(5,11)]heptasiloxane-endo-3,7,14-triol, (c-C5H9)7-
Si7O9(OH)3, was prepared according to the literature.16a Ag2O,
bpy, dppe, and p-methoxyphenylboronic acid were purchased
from Wako Pure Chemical Ind., Ltd. and were used without any
purification. 1H, 13C{1H}, 31P{1H}, and 29Si{1H} NMR spectra
were recorded on Varian Mercury 300 or Bruker Biospin Avance
III 400 spectrometers. Chemical shifts of the signals in 1H and
13C{1H} NMR spectra were adjusted to the residual peaks of the
solvents used. Peak positions in the 29Si{1H} and 31P{1H} spectra
were referenced to external standard SiMe4 in CDCl3 or C6D6,
and 85% H3PO4 in C6D6, respectively. IR absorption spectra
were recorded on a Shimadzu FT/IR-8100 spectrometer. Ele-
mental analyses were carried out using a LECO CHNS-932 or
Yanaco MT-5 CHN autorecorder at the Center for Advanced
Materials Analysis, Technical Department, Tokyo Institute of
Technology.
at 60 °C for 27 h. The gray solid was removed by filtration through
Celite, and the filtrate was evaporated under reduced pressure.
In order to remove a toluene completely, the residue was washed
with 5 mL of hexane three times. The solution was evaporated
until a yellow solid was formed, then was dried in vacuo to give 1
(186 mg, 95%). Anal. Calcd for C51H78N2O12Si7Pt: C, 47.02; H,
6.03; N, 2.15. Found: C, 47.19; H, 6.30; N, 2.01. 1H NMR (300
MHz, CDCl3, rt): δ 0.56 (m, 1H, CH-pentyl), 0.94 (m, 3H, CH-
pentyl) 1.14 (m, 3H, CH-pentyl), 1.4-2.0 (m, 56H, CH2-pentyl),
0
6.84 (t, 1H, PtC6H5-p, JHH = 6 Hz), 6.96 (d, 1H, H5 -bpy,
JHH =6.9 Hz), 7.03 (t, 2H, C6H5-m, JHH =7 Hz), 7.35-7.38
(overlapped 3H, C6H5-o and H5-bpy), 7.81 (td, 1H, H4-bpy,
0
JHH=8, 1.5 Hz), 8.07 (d, 1H, H6 -bpy, JHH=8.1Hz), 8.15 (td,
0
1H, H4 -bpy, JHH=7.8, 1.2 Hz), 8.23 (t, 2H, H3,3 -bpy, JHH
0
=
8.4 Hz), 8.54 (s, 2H, OH), 9.37 (d, 1H, H6-bpy, JHH=4.5 Hz).
13C{1H} NMR (100 MHz, CDCl3, rt): δ 22.47, 22.57, 22.81,
23.20, 24.03 (1:2:2:1:1, 7C, CH-pentyl), 27.11, 27.14, 27.21,
27.25, 27.30, 27.38, 27.46, 27.51, 27.54, 27.87 (28C, CH2-pentyl),
0
0
0
122.39 (C6 -bpy), 122.78 (C5 -bpy), 124.21 (C3 -bpy), 126.26
(C6H5-p), 126.37 (C6H5-m þ C5-bpy), 137.58 (C6H5-o), 137.82
0
(C4 -bpy), 138.05 (C4-bpy), 140.72 (C6H5-i), 148.31 (C6-bpy),
0
151.36 (C3-bpy), 153.29 (C2 -bpy), 156.91 (C2-bpy). The peak
Preparation of [Pt{(c-C5H9)7Si7O10(OH)2}(C6H5)(bpy)] (1).
To a toluene (10 mL) suspension of [PtI(C6H5)(bpy)] (83 mg,
0.15 mmol) were added (c-C5H9)7Si7O9(OH)3 (131 mg, 0.15 mmol)
and Ag2O (46 mg, 0.20 mmol). The reaction mixture was heated
positions for all H and C atoms were assigned according to
H-H and C-H COSY diagrams. 29Si{1H} NMR (79.3 MHz,
CDCl3, 0.02 M Cr(acac)3, rt): δ -54.62, -56.60, -64.75, -65.17,
-67.45 (1:2:1:2:1). IR data (KBr): 3350brw., 2950s, 2865s,
1603w, 1574w, 1468w, 1449m, 1244m, 1115vs, 951m, 910m,
764m, 737w, 727w, 702w, 500m, 447w.
(18) Clark, H. C.; Manzer, L. E. J. Organomet. Chem. 1973, 59, 411.

190 Organometallics, Vol. 30, No. 1, 2011
Mintcheva et al.
Figure 2. ORTEP drawings of (a) 3 and (b) 4 with thermal ellipsoids at 30% probability. Hydrogen atoms are omitted for clarity.
˚
(a) One of the two crystallographically independent molecules is shown. Selected bond distances (A) and angles (deg) of 3: Pt-N1 =
2.104(8); 2.095(7), Pt-N2 = 2.098(6); 2.098(6), Pt-C1 = 2.00(1); 2.002(9), Pt-C8 = 2.007(8); 2.006(8), N1-Pt-N2 = 77.7(3);
˚
77.4(2), N1-Pt-C8 = 97.8(3); 98.9(3), N2-Pt-C1 = 97.6(3); 98.1(3), C1-Pt-C8 = 86.9(3); 85.8(3). (b) Selected bond distances (A)
and angles (deg) of 4: Pt-P1 = 2.301(2), Pt-P2 = 2.283(2), Pt-C1 = 2.106(6), Pt-C8 = 2.115(7); P1-Pt-P2 = 85.81(7), P1-Pt-C1
= 93.7(2), P2-Pt-C8 = 94.6(2), C1-Pt-C8 = 86.1(2).
0
H4,4 -bpy), 6.81(3H, PtC6H5-m, p), 7.01(d, 2H, PtC6H4-m, JHH=8.4
Preparation of [Pt{(c-C5H9)7Si7O10(OH)2}(C6H5)(dppe)] (2).
To a toluene (10 mL) suspension of [PtI(C6H5)(dppe)] (120 mg,
0.15 mmol) were added (c-C5H9)7Si7O9(OH)3 (131 mg, 0.15 mmol)
and Ag2O (46 mg, 0.20 mmol). The reaction mixture was stirred
at room temperature for 10 days. When the conversion was com-
plete, the gray solid containing Ag2O and AgI was removed by
filtration through Celite and the filtrate was evaporated under
reduced pressure. Recrystallization from 1 to 2 mL of ether solu-
tion at -20 °C gives 2 (143 mg, 62%). Anal. Calcd for C67H94-
O12Si7P2Pt: C, 52.08; H, 6.13. Found: C, 52.02; H, 6.02. The
same reaction takes place under heating at 60 °C for 48 h, but
minor byproducts are formed and they obstruct crystallization
of the final desired complex. Complex 2 can also be obtained by
reaction of hydroxoplatinum complex [Pt(OH)(C6H5)(dppe)]
and (c-C5H9)7Si7O9(OH)3 for 24 h at 60 °C. 1H NMR (300 MHz,
C6D6, rt): δ 1.18 (m, 7H, CH-pentyl), 1.4-2.0 (m, 56H, CH2-
pentyl), 6.94 (m, 12 H, PC6H5-m,p), 7.04 (m, 2H, PtC6H5-m),
7.21 (1H, PtC6H5-p), 7.38 (m, 4H, PC6H5-o), 7.61 (t, 2H,
PtC6H5-o, JPtH =45 Hz), 7.96 (m, 4H, PC6H5-o), 8.4 (s, 2H,
OH). 31P{1H} NMR (121.5 MHz, C6D6, rt): δ 39.4 (s, P trans to
0
Hz), 7.35 (t, 2H, H3,3 -bpy, JHH=7.5 Hz), 7.93 (d, 2H, PtC6H4-o,
JHH=8.7 Hz, JPtH=78 Hz), 8.09 (d, 2H, PtC6H5-o, JHH=6.6 Hz,
0
PtH=60 Hz), 8.64 (t, 2H, H6,6 -bpy, JHH=6.3 Hz).
J
Reaction of [(C6H4OCH3-p)B(OH)2] with 2. The reaction of
(C6H4OCH3-p)B(OH)2 and 2 takes place at 60 °C for 15 min in
THF-d8 and for 30 min in C6D6 and gives 4 in 100% yield cal-
culated by NMR signals. 1H NMR (400 MHz, C6D6, rt): δ 1.85
(m, 4H, PCH2), 3.30 (s, 3H, OCH3), 6,72 (td, 2H, PtC6H4-m,
JHH=8 Hz), 6.88 (t, 1H, PtC6H5-p, JHH=8 Hz), 7.00 (m, 12H,
PC6H5-m, p), 7.06 (m, 2H, PtC6H5-m), 7.50 (m, 12H, PC6H5-o),
7.54 (td, 2H, PtC6H4-o, JHH =8 Hz), 7.68 (q, 2H, PtC6H5-o,
JHH=8 Hz, JPtH=60 Hz). 31P{1H} NMR (400 MHz, C6D6, rt): δ
42.0 (d, JPP=5 Hz, JPtP=1694 Hz), 41.3 (d, JPP=5 Hz, JPtP
=
1670 Hz). Complex 4 was isolated from the reaction mixture of a
THF solution (5 mL) of [Pt{(c-C5H9)7Si7O10(OH)2}(C6H5)(dppe)]
(2) (140 mg, 0.09 mmol) and (C6H4OCH3-p)B(OH)2 (13.6 mg,
0.09 mmol), which was heated at 60 °C for 30 min. The solution
was concentrated under reduced pressure, and 10 mL of hexane
was added. Cooling at -20 °C gave a white residue, which was
filtrated off, washed with water, and dried under vacuum to yield 4
C6H5, JPtP=1654 Hz), 29.7 (s, P trans to silsesquioxane, JPtP
=
4127 Hz). 29Si{1H} NMR (79.3 MHz, C6D6, 0.02 M Cr(acac)3,
rt): δ -55.12, -57.20, -65.33, -65.58, -68.24 (1:2:1:1:2).
13C{1H} NMR (100.4 MHz, C6D6, rt): δ 23.21, 23.37, 23.60, 24.00,
26.62 (7C, CH-pentyl, 1:1:2:2:1), 27.5-28.8 (CH2-pentyl and
dppe), 123.39 (PtC6H5-p), 128.67 (d, PC6H5-p, J = 13 Hz),
129.08 (d, PC6H5-o, J=9 Hz), 131.09 (d, PC6H5-o0, J=9 Hz),
132.04 (s, PtC6H5-m), 133.30 (d, PC6H5-i, J=11 Hz), 134.13
(d, PC6H5-i0, J=12 Hz), 137.90 (s, PtC6H5-o). IR data (KBr):
3300brw, 2948s, 2865s, 1572w, 1451w, 1435m, 1244m, 1100vs,
920m, 828m, 731w, 690m, 548w, 498m, 450w.
(63 mg, 88%). Anal. Calcd for C39H36P2OPt H2O: C, 58.86;
3
H, 4.81. Found: C, 58.86; H, 4.69. Single crystals of 4were obtained
by recrystallization from a C6D6/hexane solution. Evaporation of
water washings and the THF/hexane filtrate yields H3BO3 (2.8 mg,
50%) and (c-C5H9)7Si7O9(OH)3 (53 mg, 67%), respectively,
which were characterized analogously to the above reaction.
X-ray Crystallography. Crystals of 3 and 4 suitable for X-ray
diffraction study were mounted on MicroMounts (MiTeGen).
The crystallographic data were collected on a Rigaku Saturn CCD
area detector equipped with monochromated Mo KR radiation
Reaction of [(C6H4OCH3-p)B(OH)2] with 1. To 4 mL of THF
solution of [Pt{(c-C5H9)7Si7O10(OH)2}(C6H5)(bpy)] (1) (80 mg,
0.06 mmol) was added (C6H4OCH3-p)B(OH)2 (9.2 mg, 0.06 mmol),
and the mixture was heated at 60 °C for 4 h. After that the solu-
tion was concentrated under reduced pressure and 10 mL of hexane
was added. Cooling at -20 °C gave an orange residue, which was
filtrated off, washed with water, and dried in vacuo to produce
[Pt(bpy)(C6H5)(C6H4OCH3-p)] (3) (24 mg, 75%). Evaporation
of water washings yielded H3BO3 (2mg, 54%). 1H NMR (300 MHz,
acetone-d6, rt): δ 5.81 (s, OH, boroxine), 2.88 (s, OH, boric acid).
Hexane filtrate was evaporated to dryness, washed with acetone,
and dried in vacuo to give (c-C5H9)7Si7O9(OH)3 (36mg, 69%). FAB:
m/z 875. 29Si NMR (79 MHz, CDCl3, rt): δ -57.29, -65.96, -66.85
˚
(λ=0.71073 A) at 150 K. Calculations were carried out using the
program package Crystal Structure, version 3.8, for Windows. The
positional and thermal parameters of non-hydrogen atoms were
refined anisotropically on F2 by the full-matrix least-squares method.
Hydrogen atoms were placed at calculated positions and refined with
a riding mode on their corresponding carbon atoms. Crystallo-
graphic data and details of refinement of 3 and 4 are summarized in
the Supporting Information.
Acknowledgment. N.M. thanks the Japanese Society for
Promotion of Science and the Bulgarian Science Fund,
project DO-02-233, for the financial support.
(3:1:3). Data for 3: Anal. Calcd for
C23H20N2OPt
3
H2O: C, 49.91; H, 4.01; N, 5.06. Found: C, 50.46; H, 3.90; N, 5.01.
Supporting Information Available: Crystallographic data for
3 and 4 as CIF files and a table. This material is available free of
charge via the Internet at http://pubs.acs.org.
1H NMR (300 MHz, C6D6, rt): δ 3.50 (CH3O), 6.13 (t, 1H, H5-bpy,
0
JHH =6.5 Hz), 6.18 (t, 1H, H5 -bpy, JHH =6.5 Hz), 6.74 (m, 2H,