Synthesis and characterization of diplatinum complexes containing bridging μ-η2-H-SiHAr ligands. X-ray crystal structure determination of {(Ph3P)Pt[μ-η2-H-SiHAr]}2 (Ar = 2,4,6-(CF3)3C6

Article abstract of DOI:10.1021/om000602r

Dinuclear Pt-Si complexes, [(Ph₃P)Pt(μ-η²-H-SiHAr)]₂ (Ar = 2-isopropyl-6-methylphenyl (IMP), 2,4,6-trimethoxyphenyl (TMP), 2,4,6-trimethylphenyl (Mes), pentaphenylphenyl (PPP), 2,4,6-tris(trifluoromethyl)phenyl (R_F

Full text of DOI:10.1021/om000602r

5500
Organometallics 2000, 19, 5500-5510
Syn th esis a n d Ch a r a cter iza tion of Dip la tin u m
Com p lexes Con ta in in g Br id gin g µ-η2-H-SiHAr Liga n d s.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of
{(P h 3P )P t[µ-η2-H-SiHAr ]}2 (Ar ) 2,4,6-(CF 3)3C6H2, C6P h 5)
J . Braddock-Wilking,* Y. Levchinsky, and N. P. Rath
Department of Chemistry, University of MissourisSt. Louis, 8001 Natural Bridge Road,
St. Louis, Missouri 63121
Received J uly 13, 2000
Dinuclear Pt-Si complexes, [(Ph3P)Pt(µ-η2-H-SiHAr)]2 (Ar ) 2-isopropyl-6-methylphenyl
(IMP), 2,4,6-trimethoxyphenyl (TMP), 2,4,6-trimethylphenyl (Mes), pentaphenylphenyl (PPP),
2,4,6-tris(trifluoromethyl)phenyl (RF)) have been synthesized from the reaction of ArSiH3
with (Ph3P)2Pt(η2-C2H4). These complexes were characterized by multinuclear NMR and IR
spectroscopy and X-ray crystallography (PPP and RF systems). The dinuclear complexes
contain a 3c-2e nonclassical interaction for Pt‚‚‚H‚‚‚Si, which is supported by spectroscopic
and crystallographic data. Both cis and trans isomers are formed when Ar ) IMP, TMP,
Mes, and these complexes are fluxional on the NMR time scale. Only the trans isomer is
generated with Ar ) PPP, RF. These complexes exhibit an unusual low-field 1H NMR
resonance for the terminal Si-H and an upfield shift for the bridging hydride. X-ray
crystallographic analysis of the PPP and RF systems (also previous results for IMP) reveal
two different Si-Pt distances, with the longer distance corresponding to the Pt‚‚‚H‚‚‚Si
interaction.
Sch em e 1
In tr od u ction
The study of complexes containing a transition-
metal-silicon bond has grown significantly in the last
two decades.1 There are a variety of synthetic methods
known for the formation of complexes containing a
M-Si bond, but by far the most facile and versatile
route involves addition of a Si-H bond in a hydrosilane
to a transition-metal center. The reaction can proceed
to the limit of full addition of the Si-H bond or may be
“arrested” at an earlier stage to give a complex contain-
ing a “nonclassical” M‚‚‚H‚‚‚Si interaction.1a,2 Silicon-
hydrogen bond activation is implicated in a number of
transition-metal-catalyzed reactions such as the inter-
action of hydrosilanes with transition metals in the
formation of silicon oligomers and polymers (metal-
catalyzed dehydrocoupling).3
the nature of the groups bound to silicon and to
platinum. Primary silanes containing moderately bulky
ligands generally afford bis(silyl)platinum species (Pt-
Si2) or dinuclear Pt2Si2 complexes that contain bridging
silylene moieties (µ-SiR2).1,4,5 The bis(silyl)platinum
complexes have been proposed as precursors to di-
nuclear Pt2Si2 complexes.4 However, tertiary silanes
(and some secondary silanes) generally yield mono-
nuclear complexes such as L2Pt(H)Si (L ) phosphine;
Scheme 1).1 Hydridoplatinum silyl complexes prepared
from primary silanes are rare.
The addition of a Si-H bond to a coordinatively
unsaturated platinum(0) complex (i.e., [Pt(PR3)2]) can
provide a variety of different products, depending upon
* To whom correspondence should be addressed. Tel: (314) 516-
6436. Fax: (314) 516-5342. E-mail: jwilking@umsl.edu.
(1) (a) Corey, J . Y.; Braddock-Wilking, J . Chem. Rev. 1999, 99, 175.
(b) Eisen, M. S. In The Chemistry of Organic Silicon Compounds;
Rappoport, Z., Apeloig, Y., Eds.; Wiley: New York, 1998; Vol. 2, p 2037.
(c) Tilley, T. D. In The Silicon Heteroatom Bond; Patai, S., Rappoport,
Z., Eds.; Wiley: New York, 1991; p 245. (d) Tilley, T. D. In The
Chemistry of Organic Silicon Compounds; Patai, S., Rappoport, Z.,
Eds.; Wiley: New York, 1989; p 1416. (e) Aylett, B. J . Adv. Inorg. Chem.
Radiochem. 1982, 25, 1.
A number of complexes are known which contain
bridging silylene units (µ-SiR2) between two metals
(metals in groups 4 and 6-10).5 Several of these
(2) Schubert, U. Adv. Organomet. Chem. 1990, 30, 151.
(4) (a) Shimada, S.; Tanaka, M.; Honda, K. J . Am. Chem. Soc. 1995,
117, 8289. (b) Heyn, R. H.; Tilley, T. D. J . Am. Chem. Soc. 1992, 114,
1917. (c) Michalczyk, M. J .; Recatto, C. A.; Calabrese, J . C.; Fink, M.
J . J . Am. Chem. Soc. 1992, 114, 7955.
(5) (a) Ogino, H.; Tobita, H. Adv. Organomet. Chem. 1998, 42, 223.
(b) Braddock-Wilking, J .; Levchinsky, Y.; Rath, N. P. Submitted for
publication.
(3) (a) Gauvin, F.; Harrod, J . F.; Woo, H. G. Adv. Organomet. Chem.
1998, 42, 363. (b) Yamashita, H.; Tanaka, M. Bull. Chem. Soc. J pn.
1995, 68, 403. (c) Tilley, T. D. Acc. Chem. Res. 1993, 26, 22. (d) Corey,
J . Y. Adv. Silicon Chem. 1991, 1, 327. (e) Tilley, T. D. Comments Inorg.
Chem. 1990, 10, 37. (f) Curtis, M. D.; Epstein, P. S. Adv. Organomet.
Chem. 1981, 19, 213.
10.1021/om000602r CCC: $19.00 © 2000 American Chemical Society
Publication on Web 11/11/2000

Diplatinum Complexes Containing µ-η2-H-SiHAr Ligands
Organometallics, Vol. 19, No. 25, 2000 5501
defined by 2c-2e M-Si bond distances.1 A more reliable
technique for establishing the presence of a M‚‚‚H‚‚‚Si
Ch a r t 1
1
interaction is by H NMR spectroscopy. A substantial
1
lowering of the J SiH coupling constant (20-100 Hz vs
∼150-200 Hz for a normal Si-H bond) is observed for
complexes containing a M‚‚‚H‚‚‚Si interaction.1a,2
Recently, we reported the preparation of the dinuclear
platinum complex [(Ph3P)Pt(µ-η2-H-SiH(IMP)]2 (IMP
) 2-isopropyl-6-methylphenyl), which contains a non-
classical Pt‚‚‚H‚‚‚Si interaction.10 In our continued
efforts to understand the steric and electronic factors
that influence the Si-H addition to metals, we exam-
ined the reactivity of several bulky primary silanes with
selected Pt(0) precursors. Herein, we report the sto-
ichiometric reactions of the sterically hindered arylsi-
lanes ArSiH3 (Ar ) 2-isopropyl-6-methylphenyl (IMP,
1),10 2,4,6-trimethoxyphenyl (TMP, 2),11 2,4,6-trimeth-
ylphenyl (Mes, 3),12 2,3,4,5,6-pentaphenylphenyl (PPP,
4),13 2,4,6-tris(trifluoromethyl)phenyl (RF, 5)14) with
(Ph3P)2Pt(η2-C2H4), which provided the dinuclear com-
plexes [(Ph3P)Pt(µ-η2-H-SiH(Ar)]2 (6-10), respectively.
All of these new derivatives contain a nonclassical 3c-
2e interaction involving platinum, hydrogen, and silicon
(Pt‚‚‚H‚‚‚Si).
bridging silylene complexes also possess a hydrogen that
bridges the metal and the silicon. The majority of the
examples are from metals of the middle to late transi-
tion series (i.e., Ru, Rh, Pt).5a Complexes containing
platinum triad metals that possess a nonclassical M‚‚‚
H‚‚‚Si (3c-2e) interaction are rare. Stone and co-
workers prepared a number of complexes with the
general formula [(R′3P)Pt(µ-η2-H-SiR2)]2 (II in Chart
1; R′3P ) Cy3P, But MeP, PhPri P, Ph3P; SiR2 ) SiMe2,
Resu lts
Syn th esis a n d Sp ectr oscop ic Ch a r a cter iza tion .
Reaction of (Ph3P)2Pt(η2-C2H4) with 1 equiv of ArSiH3
(1-5) in benzene (or toluene) solutions at room tem-
perature afforded complexes of the general formula
{(Ph3P)Pt[µ-η2-H-SiH(Ar)]}2 (6-10) in good yield (69-
97% for 6-9, 19% for 10). Complexes 6-8 were isolated
as a mixtures of trans (6a -8a ) and cis (6b-8b) isomers
(in a ratio of 3:1 for 6; 3:2 for both 7 and 8)15 (eq 1).
2
2
SiPh2) from the reaction of (R′3P)Pt(η2-C2H4)2 with R2-
SiH2 at room temperature.6 Tessier et al. recently
reported the formation of several diplatinum complexes,
two of which contain Pt‚‚‚H‚‚‚Si interactions as in
{(R3P)Pt[µ-η2-H-Si(Hex)(Pt(PR3)2H)]}2 (III in Chart 1;
R ) Et, Pr).7 Kim and Osakada have prepared several
dipalladium systems of the general formula [(L)Pd(µ-
η2-H-SiR2)Pd(L)n] (where L ) PMe3, PEt3, PMePh2, R
) Ph (n ) 1 (IV in Chart 1; and also n ) 2 for PMe3); L
) PMe3, or PEt3, SiR2 ) SiMePh, n ) 1; IV in Chart 1)
that contain Pd‚‚‚H‚‚‚Si interactions.8
Confirmation of a M‚‚‚H‚‚‚Si interaction is customar-
ily obtained by X-ray crystallography and/or 1H NMR
spectroscopy. Elongated M‚‚‚H, Si‚‚‚H, and M‚‚‚Si dis-
tances are expected in a nonclassical interaction. How-
ever, these key distances may not provide conclusive
evidence for the presence of a M‚‚‚H‚‚‚Si interaction,
since hydrides are often difficult to locate by X-ray
crystallography and their distances are sometimes
approximate. The average Si-H distance in an orga-
nosilane is usually set at 1.5 Å.9 Schubert has suggested
an upper limit of 2.0 Å for any interaction between Si
and H.2 In addition, M-Si distances can vary over a
wide range and the 3c-2e distances overlap the range
Complexes 9 and 10 were isolated as the trans isomer
only. The reaction occurred instantly for silanes 1-3
(but more slowly for 4 and 5) with vigorous gas evolution
followed by rapid precipitation of the microcrystalline
(6) Auburn, M.; Ciriano, M.; Howard, J . A. K.; Murray, M.; Pugh,
N. J .; Spencer, J . L.; Stone, F. G. A.; Woodward, P. J . Chem. Soc.,
Dalton Trans. 1980, 659.
(7) Sanow, L. M.; Chai, M.; McConnville, D. B.; Galat, K. J .; Simons,
R. S.; Rinaldi, P. L.; Youngs, W. J .; Tessier, C. A. Organometallics 2000,
19, 192.
(8) (a) Kim, Y.-J .; Lee, S.-C.; Park, J .-I.; Osakada, K.; Choi, J .-C.;
Yamamoto, T. Organometallics 1998, 17, 4929. (b) Kim, Y.-J .; Lee, S.-
C.; Park, J .-I.; Osakada, K.; Choi, J .-C.; Yamamoto, T. J . Chem. Soc.,
Dalton Trans. 2000, 417.
(9) See footnote 8 in: Kawachi, A.; Tanaka, Y.; Tamao, K. Organo-
metallics 1997, 16, 5102.
(10) Levchinsky, Y.; Rath, N. P.; Braddock-Wilking, J . Organome-
tallics 1999, 18, 2583.
(11) Levchinsky, Y.; Rath, N. P.; Braddock-Wilking, J . J . Organomet.
Chem. 1999, 588, 51.
(12) (a) Malisch, W.; Hindahl, K.; Ka¨b, H.; Reising, J .; Adam, W.;
Prechtl, F. Chem. Ber. 1995, 128, 963. (b) So¨ldner, M.; Sˇandor, M.;
Schier, A.; Schmidbaur, H. Chem. Ber./ Recl. 1977, 130, 1671.
(13) Generously provided by Professor Peter P. Gaspar and Mark
Autry, Washington University, St. Louis, MO.
(14) Molander, G. A.; Corrette, C. P. Organometallics 1998, 17, 5504.
(15) The ratio of isomers was determined from the relative intensi-
ties of the Si-H resonances in the 1H NMR spectrum.

5502 Organometallics, Vol. 19, No. 25, 2000
Braddock-Wilking et al.
Ta ble 1. Selected NMR Sp ectr oscop ic Da ta for 6-10
1H(Pt‚‚‚H‚‚‚Si)a 1H(Si-H)a
31P{1H}a
Ar
cis
trans
cis
trans
cis
37.7
trans
IMP (6)10
2.17b-d
2.38d
k
2.17b,d,e
8.42
8.92
38.1
J ) 137, 78f
J ) 216g
J ) 4279h
J ) 244i
J ) 60j
J ) 4276h
J ) 261i
J ) 60j
J ) 137, 72f
TMP (7)
Mes (8)
PPP (9)
2.44d
2.28d
0.35
8.65
8.95
41.2
41.0
J ) 160, 79f
J ) 159, 74f
J ) 4389h
J ) 278i
J ) 64j
J ) 4388h
J ) 285i
J ) 65j
8.52
8.95
38.2
38.9
J ) 135, 73f
J ) 136, 75f
J ) 4264h
J ) 252i
J ) 60j
J ) 4250h
J ) 282i
J ) 60j
7.48
38.7
J ) 48g
J ) 650l
J ) 112f
J ) 25m
J ) 7n
J ) 4368h
J ) 305i
J ) 63j
RF (10)
2.10d
8.41d
35.9
J ) 4337h
J ) 216i
J ) 63j
Chemical shifts are given in ppm, and coupling constants are given in Hz. Spectra were obtained in C6D6. b Located by EXSY experiment.
a
c 1.45 ppm in CD2Cl2. J values are not resolved. e 1.49 ppm in CD2Cl2.
J
J
.
J
.
1J PtP
.
J
.
J .
PP
Obscured by other peaks.
d
f 2
g 1
h
i 2
j 3
k
PtH
SiH
PtP
l 1
m
n
.
2J SiH
.
2J PH
.
PtH
off-white product. Complex 6 could also be prepared
from Pt(PPh3)4 in 70% yield, but the reaction proceeded
at a slower rate (ca. 2 h).10 These solids are relatively
air stable, as are solutions in either aromatic solvents
or CD2Cl2 for several days or for months at -35 °C.
However, fairly rapid decomposition in CDCl3 and THF
was observed. Complexes 610 and 7-10 were character-
ized by 1H, 31P{1H}, and 29Si{1H} NMR (1H-29Si HMQC),
IR, and elemental analyses and, in some cases, 2D
However, the chemical shift could be determined from
the 1H-1H EXSY experiment. The 1J SiH coupling for the
Pt‚‚‚H‚‚‚Si moiety for 6-8 and 10 could not be resolved
due to overlapping resonances or extensive coupling to
other nuclei. However, the bridging hydride in 9 was
found at 0.35 ppm in the 1H NMR spectrum as a doublet
(coupling to 31P) with two sets of Pt and Si satellites
1
with J SiH ) 48 Hz (Table 1; Figure 1b).
The chemical shift assignment for the terminal and
bridging hydrides was supported by deuterium labeling
in 8-d 4. For example, the terminal Si-H resonances for
{(Ph3P)Pt[µ-η2-H-SiH(Mes)]}2 (8) were observed at 8.52
ppm (cis) and 8.95 ppm (trans) in the 1H NMR spectrum.
The bridging Pt‚‚‚H‚‚‚Si resonance of 8a appeared at
2.27 ppm as a broad doublet between two Ar-Me peaks.
1
experiments (e.g., 1H-1H EXSY and H-31P COSY), as
well as X-ray crystallography (6a ,10 9, and 10 only).
Some of the most significant properties of 6-10 are
found in the NMR and X-ray crystallographic data.
These complexes showed several similar spectroscopic
features; one complex will be described in detail, and
the remaining NMR data are summarized in Table 1.
The 1H NMR spectrum for 6-10 (C6D6) revealed
terminal Si-H resonances at quite low field between
∼8 and 9 ppm. The chemical shift for the terminal Si-H
in 9 was obscured by aromatic resonances but was
determined by a 2D 1H-29Si HMQC experiment (δ 7.48).
For complexes 6-8 these resonances were flanked by
two sets of Pt satellites, which confirmed inequivalent
coupling of the terminal Si-H to each Pt center. Figure
1 shows the terminal (7a ,b only) and bridging hydrides
in the 1H NMR spectrum (7a ,b and 9). Complex 10
showed a broad resonance for the terminal Si-H moiety,
and coupling to Pt was not resolved. No coupling was
observed between the terminal Si-H and the phospho-
rus atoms for 6-10.
1
The H NMR spectrum of 8-d 4 was identical with the
1H spectrum of 8, except that the terminal and bridging
hydride resonances were missing. On the other hand,
2
the H NMR spectrum of 8-d 4 exhibited terminal and
bridging deuterium resonances for both isomers of
{(Ph3P)Pt[µ-η2-D-SiD(Mes)]}2 as broad peaks (2.28 and
8.93 ppm for 8a -d 4; 1.49 and 8.51 ppm for 8b-d 4). The
one-bond platinum coupling, 1J PtD, was found to be 102
1
Hz, which corresponds to a J PtH value of 662 Hz.17 The
value of the coupling constant supports the presence of
a nonclassical 3c-2e interaction, since typical values
1
for J PtH (where H is terminal) are typically greater than
800 Hz.18
1
A H-1H EXSY experiment revealed that 6-8 were
fluxional on the NMR time scale at room temperature.
To the best of our knowledge, the chemical shifts for
the terminal Si-H unit in 6-10 represent the most
remote downfield resonances reported for a terminal
Si-H group. In general, Si-H resonances appear be-
(16) Williams, E. A. In The Chemistry of Organic Silicon Com-
pounds; Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989; Part
1, Chapter 8.
1
(17) The following equation was used to transform J PtD into 1J PtH
:
1
tween 3 and 5.5 ppm in the H NMR spectrum for free
J HX/J DX ) γHX/γDX (γHX ) 26.7519; γDX ) 4.1066): Silverstein, R. M.;
Bassler, G. C.; Morrill, T. C. In Spectroscopic Identification of Organic
Compounds, 5th ed.; Wiley: Toronto, Canada, 1991; p 187.
(18) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.
hydrosilanes or M-Si-H species.1a,16 The bridging Pt‚‚‚
H‚‚‚Si resonances of 6 and 8 were not resolved in
benzene due to overlap with the Ar-Me resonances.

Diplatinum Complexes Containing µ-η2-H-SiHAr Ligands
Organometallics, Vol. 19, No. 25, 2000 5503
F igu r e 2. 31P{1H} NMR spectrum of 7 (202 MHz, C6D6).
Sch em e 2
the molecule contains one 195Pt nucleus. The multiplicity
of the satellites is due to coupling between inequivalent
phosphorus nuclei when one of the Pt nuclei is NMR
active. Additionally, 10 more lines are expected for an
AA′XX′ spin system when two 195Pt nuclei are present;
however, all 10 lines were not observed and thus the
1J PtPt value could not be measured.20
1
F igu r e 1. Selected 500 MHz (C6D6) H NMR data for (a)
compounds 7a ,b and (b) compound 9 ({31P} decoupled). The
asterisk denotes an impurity.
Both terminal and bridging hydrides for each complex
were found to undergo an exchange process with ∆Gq
≈ 15-17 kcal/mol,19 with coalescence temperatures of
342-356 K. These complexes are stable to brief heating
to ∼80 °C and exhibit no change in the cis/trans ratio
upon cooling to room temperature. The proposed mech-
anism for the fluxional process involves a simultaneous
exchange of the terminal and bridging hydrides (Scheme
2) with concomitant cis-trans isomerization.
The 31P NMR spectra of 6-10 exhibit part of an
AA′XX′ spin system pattern for a dinuclear platinum
complex containing one phosphine ligand at each metal
center. Figure 2 shows the 31P{1H} NMR spectrum for
7a ,b. An intense central singlet (for each isomer) is
observed near 40 ppm for those molecules containing
no NMR-active 195Pt nuclei. Each central line is flanked
by two sets of Pt satellites that appear as doublets when
The 29Si chemical shifts for 6-10 were measured from
1
a H-29Si HMQC experiment and were found to be in
the range of 125-175 ppm with the most downfield shift
found for 9. The 29Si chemical shift values for 6-10
differ by g200 ppm relative to the corresponding free
ArSiH3.21
The Si-H stretching frequency for 6-10 appeared in
the infrared region as a strong band at ∼2100 cm-1
,
whereas the bridging hydride appeared as a broad band
at 1620-1650 cm-1. 8-d 4 exhibited Si-D and Pt‚‚‚D‚‚‚
Si stretching frequencies at lower energies due to
deuterium labeling. For example, the Si-H stretching
vibration in 8 appeared as a strong band at 2122 cm-1
,
whereas the corresponding Si-D band in 8-d 4 was
observed at 1542 cm-1 22
Similarly, the Pt‚‚‚H(D)‚‚‚Si
.
stretching bands were 1618 cm-1 for 8 and 1157 cm-1
for 8-d 4.
(19) The coalescence temperature was determined by studying the
terminal Si-H region. It is assumed that 8-d 4 also undergoes the same
isomerization process. The 31P-31P EXSY experiment for 7 showed a
correlation between the cis and trans phosphorus resonances (see the
Supporting Information). In addition, 31P VT experiments revealed the
same coalescence temperature and activation parameters within
experimental error as observed in the 1H VT NMR study. These data
support the mechanism shown in Scheme 2.
(20) Kiffen, A. A.; Masters, C.; Visser, J . P. J . Chem. Soc., Dalton
Trans. 1975, 1311.
(21) For example, the 29Si resonance for 4 appeared at - 69.8 ppm
(C6D6) (Braddock-Wilking, J .; Levchinsky, Y. Unpublished results) and
-78.5 ppm for 1.10

5504 Organometallics, Vol. 19, No. 25, 2000
Braddock-Wilking et al.
Initially, the reaction of (Ph3P)2Pt(η2-C2H4) with 1
equiv of ArSiH3 (4 or 5) at room temperature afforded
the mononuclear species cis-(Ph3P)2Pt(H)[SiH2Ar] (11
and 12, respectively) in quantitative yield by NMR
spectroscopy (eq 2). The room-temperature conversions
of 11 to 9 and of 12 to 10 occurred with vastly different
rates. For example, the conversion of 11 to 9 took place
over approximately 3-4 h at room temperature (low
yield) but was rapid at +78 °C in part due to the
increased solubility of 11. No Pt-Si-containing species
other than 11 and 9 were observed in the reaction
mixture. However, the formation of 10 took several
months at room temperature (see below). No other
intermediates, apart from complex 12, were observed
in the formation of 10. Attempts to react (Ph3P)2Pt(η2-
C2H4) with excess RFSiH3 (5) in order to produce the
bis(silyl) complex (Ph3P)2Pt[SiH2(RF)]2 resulted in ex-
clusive formation of 12.
F igu r e 3. Selected 1H NMR data (500 MHz, C6D6) for
(Ph3P)2Pt(H)[SiH2(RF)] (12).
The formation of 11 and 12 was unexpected, due to
the fact that complexes of the type L2Pt(H)(SiH2R) are
quite rare, and in general primary silanes react with
phosphine-platinum precursors to give either bis(silyl)
or dimeric species of the type [(R3P)2Pt(µ-SiHR)]2.1
Surprisingly, there are no reports in the literature that
describe the reactivity of (Ph3P)2Pt(η2-C2H4) with pri-
mary silanes.1 Complexes of this structural type are
rare, and only a few examples are known, such as trans-
(Cy3P)2Pt(H)(SiH2Cl) and trans-(Cy3P)2Pt(H)(SiH3).23
Complexes 11 and 12 were characterized by 1H,
29Si{1H}, and 31P{1H} NMR and IR spectroscopy. In
addition, solutions of 12 were analyzed by 19F NMR,
several 2D COSY and EXSY experiments, and elemen-
tal analyses. Complexes 11 and 12 exhibited similar
spectroscopic features, as discussed below.
In contrast to 12, which exhibited a Si-H resonance
in the 1H NMR spectrum (Figure 3) as a complex
multiplet (δ 5.03) due to long-range fluorine coupling,
the Si-H resonance of 11 appeared as a pseudo triplet
1
centered at 4.26 ppm. The H{31P} NMR spectrum for
11 showed the Si-H resonance as a sharp singlet
without any observed coupling to platinum. This was
unusual, because the Si-H resonance of 12 did couple
to the Pt center (2J PtH ) 20 Hz) but did not exhibit any
1
coupling to phosphorus (confirmed by a H-31P COSY
experiment). These observations could be due to the
difference in the electronic and steric effects between
the RF and PPP systems.
The 31P{1H} NMR spectrum of 11 and 12 exhibited
two doublets with Pt satellites near 30 ppm with similar
Pt-P coupling (1J PtP ) 1713 Hz for 11 and 1896 Hz for
1
The upfield region of the H NMR spectrum (Figure
3) for 11 and 12 exhibited a doublet of doublets near
-2 ppm flanked by 195Pt satellites which arises from
coupling to phosphorus nuclei cis and trans to the
hydride (part of an AXX′ system). Upon decoupling of
the 31P nuclei, the doublet of doublets collapsed to a
singlet with Pt-H coupling in the typical range for
complexes of the type24 (R3P)2(H)PtSiR3 (1J PtH ≈ 950
Hz). The multiplicity pattern of the hydride, as well as
the inequivalent coupling to the two phosphorus nuclei,
indicated that the phosphines occupy mutually cis
positions on the Pt center.
1
12 (P trans to Si); J PtP ) 2422 Hz for 11 and 2282 Hz
for 12 (P trans to H)). The 29Si NMR spectrum of 11
and 12 showed a doublet of doublets upfield of TMS at
-45 ppm flanked by platinum satellites. The resonance
for 12 was broadened due to coupling to both 31P and
19F nuclei, and the coupling was not resolved, due to
overlapping peaks. The magnitude of the downfield
29Si shift for 11 and 12 is substantially smaller than
the range seen for complexes 6-10 relative to the free
silane.
The presence of both terminal Si-H (2089 cm-1 for
11; 2126 cm-1 for 12) and Pt-H groups (2068 cm-1 for
11; 2072 cm-1 for 12) was observed in the infrared
spectrum. The higher energy Si-H stretching vibration
for 12 can be explained on the basis of a higher
concentration of “s” character in the Si-H bond.25
In an effort to probe the mechanism of formation of
6-10, we investigated the reactivity of a less hindered
arylsilane, (p-Tol)SiH3. Reaction of 2 equiv of (p-Tol)-
SiH3 with 1 equiv of (Ph3P)2Pt(η2-C2H4) proceeded
(22) These bands are related by a factor of 1.38, which is in good
agreement with the theoretical value of 1.39: (a) Shoemaker, D. P.;
Garland, C. W.; Nibler, J . W. In Experiments in Physical Chemistry,
6th ed.; McGraw-Hill: New York, 1996; p 400. (b) Ebsworth, E. A. V.;
Rankin, D. W. H.; Cradock, S. In Structural Methods In Inorganic
Chemistry, 2nd ed.; CRC Press: Boca Raton, FL, 1991; p 228.
(23) Ebsworth, E. A. V.; Marganian, V. M.; Reed, F. J . S.; Gould, R.
O. J . Chem. Soc., Dalton Trans. 1978, 1167.
(24) (a) Koizumi, T.; Osakada, K.; Yamamoto, T. Organometallics
1997, 16, 6014. (b) Latif, L. A.; Eaborn, C.; Pidcock, A.; Weng, N. S. J .
Organomet. Chem. 1994, 474, 217. (c) Packett, D. L.; Syed, A.; Trogler,
W. C. Organometallics 1988, 7, 159. (d) Paonessa, R. S.; Prigano, A.
L.; Trogler, W. C. Organometallics 1985, 4, 647. (e) Ciriano, M.; Green,
M.; Howard, J . A. K.; Proud, J .; Spencer, J . L.; Stone, F. G. A.; Tsipis,
C. J . Chem. Soc., Dalton Trans. 1978, 801.
(25) Bent, H. A. Chem. Rev. 1961, 61, 275.

Diplatinum Complexes Containing µ-η2-H-SiHAr Ligands
Organometallics, Vol. 19, No. 25, 2000 5505
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
Deta ils for 9 a n d 10
9
10
formula
fw
C
72H62PPtSi
C36H28F9PPtSi
885.73
223(2)
1181.37
223(2)
temp (K)
cryst dimens (mm)
cryst syst
space group
a (Å)
0.40 × 0.18 × 0.04 0.08 × 0.14 × 0.3
triclinic
P1h
triclinic
P1h
12.3883(2)
14.9728(2)
17.0647(2)
82.05(1)
74.747(1)
67.47(1)
2818.15(7)
2
8.3309(1)
13.9395(2)
15.5969(2)
74.832(1)
82.811(1)
82.184(1)
1724.29(4)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
dcalcd (Mg/m3)
1.392
2.582
1.008
1.706
4.224
1.029
µ (mm-1
)
F igu r e 4. 1H NMR spectrum (300 MHz, C6D6) showing
the Si-H region of 13.
GOF
R1 (obsd data)
0.0561
0.1407
2.423
0.0356
0.0674
1.261
wR2 (all data)
largest diff peak (e Å-3
)
rapidly with vigorous gas evolution to give cis-(Ph3P)2-
Pt[SiH2(p-Tol)]2 (13) (quantitative yield by NMR) as a
yellow solid (eq 3). Changing the ratio of starting
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 6a , 9, a n d 10
6a 10
9
10
Bond Distances
Pt-P
2.2485(8)
2.3248(9)
2.4280(9)
2.7021(2)
1.593
2.258(2)
2.321(2)
2.428(2)
2.7144(6)
2.2635(10)
2.2998(11)
2.4051(11)
2.7181(3)
1.445
Pt-Si
Pt-Pt#1
Si-H (terminal)
Si‚‚‚H (bridging)
Pt‚‚‚H
materials to 1:1 afforded 13 in 50% yield (based on the
platinum precursor; all silane was consumed). The
monosubstituted platinum complex (Ph3P)2Pt(H)[SiH2-
(p-Tol)] was not observed by NMR spectroscopy. Inter-
estingly, reaction of PhSiH3 with (Ph3P)2Pt(η2-C2H4)
gave several products.26 J ust after mixing, a short-lived
species was observed by 1H and 31P{1H} NMR that was
assigned to (Ph3P)2Pt(SiH2Ph)2. In addition, a minor
resonance was observed that was assigned to a di-
nuclear species analogous to 6-10, [(Ph3P)Pt(µ-η2-H-
SiPh2)]2. No other Pt-Si-containing species were iden-
tified in the reaction mixture.
1.669
1.799
1.647
1.738
Bond Angles
Si-Pt-Si
Pt-Si-Pt
P-Pt-Si
110.74(3)
69.26(3)
105.08(3)
143.89(3)
161.78(2)
53.57(2)
57.17(2)
110.32(6)
69.68(6)
105.10(8)
144.58(7)
162.10(5)
53.32(5)
57.00(6)
109.46(3)
70.54(3)
106.63(4)
143.47(4)
162.39(3)
52.92(3)
56.54(3)
P-Pt-Pt
Si-Pt-Pt
seem to convert to the dimeric µ-silylene complex
{(Ph3P)2Pt[µ-HSi(p-Tol)]}2, in contrast to {(Et3P)2Pt-
[SiH2(p-Tol)]2.28 Complex 13 appears to be fairly stable
in the solid state when stored in the dark.
Complex 13 was characterized by 1H and 31P{1H}
NMR spectroscopy. The 31P{1H} spectrum exhibited a
singlet centered at 35.5 ppm (1J PtP ) 1887 Hz) flanked
by platinum satellites. The value of the platinum-
phosphorus coupling constant is consistent with a cis
configuration for 13.
X-r a y Cr ysta llogr a p h y. The molecular structures
of 6a ,10 9, and 10 were determined by X-ray crystal-
lography. Crystal data and structure refinement for 9
and 10 are given in Table 2. For comparison, selected
bond distances and angles for 6a 10 and 9 and 10 are
given in Table 3. The molecular structures of 9 and 10
are shown in Figures 5 and 6, respectively. The central
core structure of 6a is shown in Figure 7. Both the
terminal and bridging hydrides on silicon and platinum
were located and refined for 6a , but only the bridging
hydrides for 9 and terminal hydrides for 10 were found.
All three complexes exhibited a planar Pt2Si2 core with
the substituents at silicon lying directly above and below
the plane of the ring. The phenyl groups on the penta-
phenylphenyl moiety in complex 9 are oriented in a
propeller type arrangement. Several similarities in the
structures are observed between 6a and complexes 9
and 10 and are summarized below.
1
The H NMR spectrum of 13 exhibited a triplet Si-H
resonance (with 195Pt satellites) centered at 5.08 ppm
1
with J SiH ) 177 Hz (Figure 4), a downfield shift of 0.8
1
ppm and a decrease by 22 Hz in J SiH for the free silane.
The triplet arises from coupling to phosphorus, and
platinum satellites overlap with the outer component
of this triplet to give an overall appearance of a septet.
The multiplet collapsed to a singlet flanked by Pt
satellites upon decoupling of the 31P nuclei. The upfield
region of the 1H spectrum of 13 did not exhibit any
platinum-hydride resonances, thus confirming the bis-
(silyl) structure.
Complex 13 was found to be exceptionally light
sensitive and underwent decomposition in toluene,
hexane, and ether solutions. Bis(silyl)platinum com-
plexes have been reported to decompose in benzene
solutions.27 It should be noted that complex 13 did not
A notable feature in the X-ray structures of 6a and
complexes 9 and 10 are two different Pt-Si distances
(27) Eaborn, C.; Ratcliff, B.; Pidcock, A. J . Organomet. Chem. 1974,
65, 181.
(26) Braddock-Wilking, J .; Levchinsky, Y. Unpublished results.
(28) Heyn, R. H.; Tilley, T. D. J . Am. Chem. Soc. 1992, 114, 1917.

5506 Organometallics, Vol. 19, No. 25, 2000
Braddock-Wilking et al.
distances in 6a and complexes 9 and 10 fall in the range
of known Pt-Si bonds (mean value 2.368 Å).1a Slightly
shorter Pt-Si distances in 10 relative to 6a and 9 are
probably due to the stronger Pt-Si bonds found in
complexes where a Si center contains electronegative
substituents, such as the RF ligand.1
The Pt-Pt distances in 9 and 10 were found to be
slightly longer than in 6a (2.7144(6), 2.7181(3), and
2.7021(2) Å, respectively). Despite the fact that the Pt-
Pt distances are longer than the sum of the covalent
radii (2.62 Å), they fall within the range of known values
for two Pt(I) atoms bound to each other.29 Each platinum
atom in 6a and in 9 and 10 has a distorted (due to the
bridging hydride) square planar environment and a
nonlinear P-Pt-Pt#1 angle of ∼162°. The obtuse Si-
Pt-Si angles in 6a and in 9 and 10 (ca. 110°) are
consistent with a Pt-Pt bond. Consequently, the Pt-
Si-Pt angles are acute (∼70°).
F igu r e 5. Molecular structure of {(Ph3P)Pt[µ-η2-H-SiH-
(PPP)]}2 (9) with thermal ellipsoids drawn at 50% prob-
ability. Phenyl hydrogen atoms have been omitted for
clarity.
Direct comparison of the terminal Si-H and bridging
Si‚‚‚H distances was only possible for compound 6a
(1.593 vs 1.669 Å, respectively), where both types of
hydrides were located. The elongated Si-H bridging vs
terminal distance supports the presence of a nonclas-
sical 3c-2e interaction. The bridging Si‚‚‚H distance in
9 and terminal Si-H distance in 10 are in good
agreement with the values found for 6a (Table 3). In
addition, the Pt‚‚‚H distances in 6a and 9 are slightly
longer than normal.30
Discu ssion
The present work has shown that bulky primary
arylsilanes containing ortho substituents on the aro-
matic ring react with (Ph3P)2Pt(η2-C2H4) to provide
dinuclear complexes 6-10. Spectroscopic and crystal-
lographic data indicate that the same structure is
present both in solution and in the solid state. Several
notable features are found in solution and are discussed
below. Many of these features are also found with the
related derivatives prepared by Stone,6 Tessier,7 and
Osakada.8 Chart 1 shows the general structures for the
complexes described in the present work (I), and related
complexes prepared by Stone (II), Tessier (III), and
Osakada (IV). Table 4 summarizes key features ob-
served in the spectroscopic and crystallographic data for
I-IV.
F igu r e 6. Molecular structure of {(Ph3P)Pt[µ-η2-H-SiH-
(RF)]}2 (10) with thermal ellipsoids drawn at 50% prob-
ability. Phenyl hydrogen atoms have been omitted for
clarity. The p-CF3 groups are disordered.
1
The H NMR data for 6-10 show unusually low field
resonances for the terminal Si-H moiety and a high
1
field shift for the bridging hydrides. The J SiH coupling
of 48 Hz for the nonclassical interaction in 9 falls within
the range of values reported for other systems contain-
ing a nonclassical type interaction.2 For comparison, the
bridging hydrogens in the related complex III (R′ ) Et)
1
were found at 1.03-1.05 ppm in C6D6 with J SiH ) 30
F igu r e 7. Partial molecular structure of 6a showing the
central core (thermal ellipsoids drawn at 50% probability).
Hz.7 In addition, the presence of the bridging hydride
was confirmed by IR spectroscopy and the ν(Pt‚‚‚H‚‚‚
Si) stretching values are in a close agreement with the
values reported for II6 (∼1645 cm-1) and III7 (∼1630
cm-1). The fluxional behavior found in complexes 6-8
is unusual and was not observed in the related com-
(Table 3) with the shorter Pt-Si distance corresponding
to the unbridged Pt-Si bond (∼2.3 vs 2.4 Å). This is
consistent with what is observed for complexes contain-
ing nonclassical interactions for M‚‚‚H‚‚‚Si, where elon-
gated M‚‚‚H, Si‚‚‚H, and M‚‚‚Si distances are expected,
compared to normal 2c-2e bonds between these ele-
ments.1a,2 In addition, two different Pt-Si distances are
(29) Green, M.; Howard, J . A. K.; Proud, J .; Spencer, J . L.; Stone,
F. G. A.; Tsipis, C. J . Chem. Soc., Chem. Commun. 1976, 671.
(30) The mean value for terminal (1.61 Å) and bridging Pt-H (1.69
Å) distances were determined by neutron diffraction: Bau, R.; Drabnis,
M. H. Inorg. Chim. Acta 1997, 259, 27.
2
consistent with the two distinct values of J PtSiH that
were observed in the 1H NMR spectrum. The Pt-Si

Diplatinum Complexes Containing µ-η2-H-SiHAr Ligands
Organometallics, Vol. 19, No. 25, 2000 5507
Ta ble 4. Selected Sp ectr oscop ic a n d X-r a y
and Si‚‚‚H distances are expected in complexes contain-
ing a nonclassical M‚‚‚H‚‚‚Si interaction, and indeed this
was found in complexes 6 and 9. These distances are in
close agreement with the structure reported by Stone
et al. for II (R′ ) Cy; R ) Me) (Pt‚‚‚H ) 1.78 Å and
Si‚‚‚H ) 1.72 Å).6 The palladium analogues IV also
revealed elongated Pd‚‚‚H and Si‚‚‚H bond lengths.8
Cr ysta llogr a p h ic Da ta for I-IV
Ia
IIa,b
IIIa,c
IVa,d
1H NMRe
terminal Si-H 8.4-8.9
bridging Si-H
0.4-2.4
1.89
1.03-1.05 1.07-1.77
1J SiH (bridging) 48 (for 9)
1J PtH (bridging) 650
30
77-78
608
Other prominent features found in the structures of
6, 9, and 10 are the angles associated with the ring Pt
and Si atoms. Acute Pt-Si-Pt and obtuse Si-Pt-Si
angles were found in all three of these structures. These
angles are in agreement with those observed by Tessier
and co-workers for III (R′ ) Et), which displayed Si-
Pt-Si angles of 113-114° and Pt-Si-Pt angles of 66-
67°.7 Stone et al. found Si-Pt-Si values of 110.4(3)° and
Pt-Si-Pt angles of 69.5(3)° for II (R′ ) Cy; R ) Me).6
The related Pd analogues IV displayed Si-Pt-Si angles
of ∼110° and Pd-Si-Pd values of ∼69°.8
31P NMRe
35.8-57.8
4250-4389 3971-4237 2465
37.7-41.2
23.6
-34 to +15
1J PtP
2J PtP
216-305
231-319
29Si NMRe
1346
125-175
194
707
1J PtSi
IRf
terminal Si-H 2102-2158
bridging Si-H
1618-1686 1625-1655 1630
X-rayg
2.32-2.42
Pt-Si
Pt-Pt
Pt‚‚‚H
2.29-2.43
2.70-2.71
1.74-1.80
2.34-2.44 2.33-2.39
(Pd-Si)
2.68
Mech a n istic Stu d ies. The arylsilanes 1-3 reacted
instantaneously with (Ph3P)2Pt(η2-C2H4) to afford
{(Ph3P)Pt[µ-η2-H-SiH(Ar)]}2 (6-8). No intermediates
were observed, even when an attempt was made to
monitor the reaction at low temperature by NMR
spectroscopy. Presumably, the first step involves the
oxidative addition of the silane to the Pt center to give
a complex of the type (Ph3P)2Pt(H)(SiH2Ar). A subse-
quent reaction then occurs to give the observed products
6-8. Tetrakis(triphenylphosphine)platinum was intro-
duced as an alternative Pt(0) precursor to (Ph3P)2Pt-
(η2-C2H4), with the expectation that the reaction with
the silane would proceed at a slower rate, allowing the
possibility of monitoring the stages of reaction by NMR
spectroscopy. However, when silane 1 was treated with
Pt(PPh3)4 at room temperature and the reaction was
monitored by 31P NMR spectroscopy, only peaks due to
free Ph3P and product 6 (observed as a broad hump
centered around 38 ppm) were detected.10
2.70
2.69-2.70
(Pd-Pd)
1.85-2.04
(Pd‚‚‚H)
1.60-1.75
69-70
1.78
Si‚‚‚H
Pt-Si-Pt
Si-Pt-Si
1.65-1.67
69-70
109-110
1.72
69
110
68
111-112
110
a
b
See Chart 1 for structure. X-ray data for R′ ) Cy, R ) Me.
d
c Data are listed for R′ ) Et. Data are listed for R′ ) Ph, R′ )
Me, Et; SiR2 ) SiMePh, R′ ) Me; spectra obtained in CD2Cl2.
e Chemical shifts are given in ppm, and coupling constants are
given in Hz. Spectra were obtained in C6D6 unless otherwise noted.
f Si-H stretching frequency reported in cm-1
.
Distances are in
g
angstroms; angles are in degrees.
plexes II and III. However, the unsymmetrical Pd
complex [(L)Pd(µ-η2-H-SiR2)Pd(L)n] (L ) PMe3; R2Si )
Ph2Si; n ) 2) was fluxional by 31P NMR spectroscopy
(involving the dissociation of one PMe3 ligand).8
The 31P NMR data for 6-10 exhibit a typical pattern
for a diplatinum system containing one phosphorus
atom at each metal center. Similar data were observed
by Stone et al. for the related derivatives II, where the
chemical shifts ranged from ∼36 to 58 ppm and the
In contrast, arylsilanes 4 and 5 exhibited slower
reactivity with (Ph3P)2Pt(η2-C2H4) at room temperature,
initially resulting in the formation of 11 and 12,
respectively. Complex 12 was found to be stable in the
solid state but decomposes in benzene and toluene
solutions over time (to unidentified products). Signifi-
cantly slower decomposition of 12 occurs in the reaction
mixture, whereas the decomposition process is fairly
rapid for a solution of the pure complex.24d The reaction
1
measured coupling constants were J PPt ≈ 4100 Hz and
2J PPt ≈ 270 Hz.6 In contrast, remarkably different
couplings were seen for III (23.6 ppm for P bound to
1
2
the ring Pt; J PPt ) 2465 Hz; J PPt was not resolved).7
The 29Si NMR spectra for 6-10 show resonances that
are consistent with data for complexes containing bridg-
ing silylene moieties (including those with M‚‚‚H‚‚‚Si
interactions) which exhibit resonances in the range of
60-290 ppm.5a,31 The nonclassical complex III exhibited
1
mixture of 12 was monitored by H and 31P NMR over
several weeks, and after several days dissociation of a
phosphine ligand trans to silicon was observed. The 31P
NMR spectrum of an aged solution of the reaction
mixture containing 12 exhibited broadened peaks due
to the trans phosphine, whereas the resonance due to
the cis phosphine did not change its appearance relative
to the freshly prepared solution. A 31P-31P EXSY
experiment indicated that the free phosphine exchanged
with both platinum-bound phosphines. Eventually, the
peaks for the trans phosphine disappeared; however, no
new Pt-Si-containing products were observed. Simi-
larly, proton NMR spectra of aged solutions of 12
revealed much broader aromatic resonances for the
trans phosphine and the fine structure in the hydride
resonance was no longer observed. It should be noted
that while the hydride resonance became very broad,
the Si-H resonance was completely unaffected. Thus,
a
29Si resonance at much lower field than complexes
6-8 and 10 with a resonance at 195 ppm.7
Several diagnostic features are seen in the solid-state
structures of 6, 9, and 10. All three of these complexes
show a pattern of two alternating Si-Pt distances. This
trend was also observed in the molecular structure of
II (R′ ) Cy; R ) Me), which exhibited similar Pt-Si
bond distances (2.324(2) and 2.420(2) Å).6 Four different
ring Pt-Si distances were observed in III (R′ ) Et) with
alternating shorter and longer distances in the range
of 2.347(3)-2.441(4) Å.7 In addition, the related Pd
analogues IV exhibited alternating Si-Pd bond lengths
in the range of 2.318(2)-2.411(2) Å.8 Elongated M‚‚‚H
(31) (a) Lickiss, P. D. Chem. Soc. Rev. 1992, 21, 271. (b) Zybill, C.
Top. Curr. Chem. 1991, 160, 1.

5508 Organometallics, Vol. 19, No. 25, 2000
Braddock-Wilking et al.
(4 Å) before use. Pt(PPh3)4 (Strem Chemical) and (Ph3P)2Pt-
(η2-C2H4) (Aldrich Chemical Co.) were used as received.
{(Ph3P)Pt[µ-η2-H-SiH(IMP)]}2 (6) was previously prepared by
reaction of IMPSiH3 (1) with (Ph3P)2Pt(η2-C2H4).10 (p-Tol)SiH3
was prepared by reduction of commercially available (p-Tol)-
SiCl3 (Aldrich Chemical Co.) with LiAlH4 in Et2O at 0 °C.34
The syntheses of the hydrosilanes TMPSiH3,11 MesSiH3,12
it appears that the reason for the greater stability of
12 in the reaction mixture in comparison to pure 12 is
the presence of excess silane, which presumably slows
down the decomposition process.32,33 Additionally, no
signs of decomposition were observed when complex 12
was heated to 100 °C in toluene-d8 for several days in
the reaction mixture, in contrast to rapid decomposition
of pure 12 at room temperature.
The slow formation of complex 10 is most likely
attributed to the extraordinary stability of the initial
product, cis-(Ph3P)2Pt(H)[SiH2(RF)]) (12), in contrast to
cis-(Ph3P)2Pt(H)(SiH2Ar) (Ar ) IMP, TMP, Mes), which
were not observed even at low temperatures. Even
though slightly aged solutions of 12 (ca. 12 h) exhibited
small resonances attributed to free Ph3P and 10 (by 31P-
{1H} NMR), the conversion of 12 to 10 by NMR to any
significant extent was not observed. The results de-
scribed above suggest that phosphine loss from a species
analogous to 11 and 12 may be the initial step in the
mechanism of formation of the dinuclear complexes
6-10. The precise mechanism of formation of 6-10 is
unknown at the present time.
PPPSiH3,13 and RFSiH3 were reported elsewhere.
14
All NMR data were recorded on either a Bruker ARX-500
MHz spectrometer or Varian Unity Plus 300 MHz WB spec-
trometer at ambient temperature (unless noted otherwise).
Chemical shifts (δ) are reported in ppm and coupling constants
(J ) in hertz. Because of the low solubility of 6-10, fairly long
NMR acquisition times were required which prevented deter-
mination of all coupling constants. The solution 29Si spectra
1
were acquired using the DEPT pulse sequence35 or a 2D H-
29Si HMQC36 experiment. Infrared spectra were recorded on
a Perkin-Elmer 1600 series FT-IR spectrometer. High-resolu-
tion mass spectra were measured at the Washington Univer-
sity Resource for Biomedical and Bioorganic Mass Spectrom-
etry, and parent ion or highest mass peaks are reported.
Elemental analyses were obtained from Atlantic Microlab, Inc.,
Norcross, GA. X-ray crystal structure determinations were
performed on a Bruker SMART diffractometer equipped with
a CCD area detector at 233 K.
Va r ia ble-Tem p er a tu r e NMR Sp ectr oscop y of 6. A
sample of 6 (4 mg, 3.2 × 10-6 mol) was dissolved in 1 mL of
Su m m a r y
1
toluene-d8 and analyzed by H NMR from room temperature
The formation of complexes of the type {(Ph3P)Pt[µ-
η2-H-SiH(Ar)]}2 (6-10) was observed only in those
cases where the aryl group contains ortho substituents
(Ar ) IMP, TMP, Mes, PPP, RF). A different structural
motif is observed when the ortho substituents are
removed (Ar ) p-Tol), resulting in the formation of a
bis(silyl)platinum complex (13). On the other hand,
removal of the para substituents (i.e., IMP vs Mes) did
not seem to influence the reactivity of the silane
precursor or the nature of the product formed. These
initial results found with the RF ligand system at silicon
suggest that the electronic character of the groups on
the silane (and possibly Pt) have a significant impact
on the formation of the dinuclear complexes 6-10. The
current study has shown that altering the substituents
at the silane results in the formation of Pt-Si complexes
of differing structural types. Recent work has also
shown that alteration of the phosphine substituents at
the Pt center influences the outcome of the reaction of
bulky monoarylsilanes with platinum phosphine pre-
cursors.5b Further studies are needed to resolve the
mode of formation of complexes 6-10 (such as steric
and/or electronic effects at silicon and platinum).
(25 °C) to 75 °C in 10 °C increments and from 66 to 75 °C in
1 °C increments to determine the coalescence temperature for
the terminal Si-H resonances of 6a and 6b (8-9 ppm). The
coalescence temperature (Tc) was found to be 69 °C.
P r ep a r a tion of {(P h 3P )P t[µ-η2-H-SiH(TMP )]}2 (7). A
solution of (TMP)SiH3 (2; 30 mg, 0.15 mmol) was added to a 7
mL vial containing (Ph3P)2Pt(η2-C2H4) (98 mg, 0.13 mmol) in
1 mL of C6H6. Vigorous evolution of gas was observed, and
the color of the reaction mixture turned from yellow to amber.
After 1 h precipitation of a microcrystalline white solid (7) was
observed. After 24 h the solid was filtered, washed with Et2O
(6 × 0.5 mL), and then dried in vacuo to give {(Ph3P)Pt[µ-η2-
H-SiH(TMP)]}2 (7; 68 mg, 79% yield) as a mixture of trans
1
(7a ) and cis (7b) isomers (ratio 3:2 by NMR). H NMR (C6D6,
2
1
300 MHz) for 7a : δ 2.44 (bd, 2H, J PtH ) 118 Hz, J PtH not
resolved, Pt‚‚‚H‚‚‚Si), 3.03 (s, 12H, o-ArOCH3), 3.40 (s, 6H,
p-ArOCH3),37 5.94 (s, 4H, Ar H), 6.95 [m, 18H, P(m-C6H5)3 and
P(p-C6H5)3], 7.79 [m, 12H, P(o-C6H5)3], 8.95 (s, 2H, 2J PtH ) 159
Hz, 2J PtH ) 74 Hz, SiH). 29Si{1H} NMR (C6D6, 1H-29Si HMQC,
500 MHz): δ 125. IR (KBr, cm-1): ν 2102.0 (Si-H), ∼1634
(Pt-H, partially overlaps with CdC stretching). Anal. Calcd
for C54H56O6 P2Pt2Si2: C, 49.54; H, 4.31. Found: C, 49.12; H,
1
4.34. H NMR (C6D6, ppm, 300 MHz) for 7b: δ 2.38 (bd, 2H,
Pt‚‚‚H‚‚‚Si, coupling constants not resolved), 3.00 (s, 12H,
o-ArOCH3), 3.40 (s, 6H, p-ArOCH3), 5.88 (s, 4H, Ar H), 6.95
[m, 18H, P(m-C6H5)3 and P(p-C6H5)3], 7.79 [m, 12H, P(o-
Exp er im en ta l Section
2
2
C6H5)3], 8.65 (s, 2H, SiH, J PtH ) 160 Hz, J PtH ) 79 Hz).
29Si{1H} NMR (C6D6, 1H-29Si HMQC, 500 MHz): δ 126. IR
(KBr, cm-1): ν 2102.0 (Si-H), ∼1634 (Pt-H, partially overlaps
with CdC stretching).
Gen er a l Ma ter ia ls a n d P r oced u r es. All reactions and
manipulations were performed in dry glassware under an
argon atmosphere in an inert-atmosphere drybox or on a
double-manifold Schlenk line. All solvents were distilled under
an atmosphere of N2 and dried before use: pentanes, hexanes,
and C6H6 (CaH2); Et2O and DME (sodium/benzophenone ketyl);
THF (CaH2, then sodium/benzophenone ketyl). Solvents were
degassed by freeze-pump-thaw degassing (liquid N2) before
being brought into the drybox. Toluene-d8, CD2Cl2, and C6D6
were dried over activated alumina and Linde molecular sieves
Va r ia ble-Tem p er a tu r e NMR Sp ectr oscop y of 7. A
sample of 7 (4 mg, 3.1 × 10-6 mol) was dissolved in 1 mL of
toluene-d8 and analyzed by VT-NMR. The sample was ana-
1
lyzed by H NMR from room temperature (25 °C) to 75 °C in
10 °C increments and from 68 to 70 °C in 1 °C increments to
determine the coalescence temperature for the terminal Si-H
(34) Banovets, J . P.; Suzuki, H.; Waymouth, R. M. Organometallics
1993, 12, 4700.
(35) Blinka, T. A.; Helmer, B. J . Adv. Organomet. Chem. 1984, 23,
193.
(36) Bax, A.; Subramanian, S. J . Magn. Reson. 1986, 67, 565.
(37) Overlaps with the cis isomer 7b.
(32) Several reports show examples of transition-metal-silyl species
that are stable only in the presence of excess silane. See, for example,
ref 24d.
(33) An 1H-1H EXSY experiment revealed that 12 undergoes
exchange when excess RFSiH3 is present.

Diplatinum Complexes Containing µ-η2-H-SiHAr Ligands
Organometallics, Vol. 19, No. 25, 2000 5509
resonances of 7a and 7b (8-9 ppm). The coalescence temper-
ature (Tc) was found to be 70 °C (343 K).
was washed with 5 mL of C6H6 and 10 mL of hexanes and
then dried in vacuo to afford 9 as a cream-colored solid (75
1
1
P r ep a r a tion of {(P h 3P )P t[µ-η2-H-SiH(Mes)]}2 (8). In a
7 mL vial containing (Mes)SiH3, (3; 24 mg, 0.16 mmol) were
added (Ph3P)2Pt(η2-C2H4) (98 mg, 0.13 mmol) and 3 mL of
C6H6. Vigorous gas evolution was observed, and the solution
turned bright yellow. After approximately 24 h a small amount
of off-white solid, {(Ph3P)Pt[µ-η2-H-SiH(Mes)]}2 (8), had formed,
which was washed with Et2O (2 × 1 mL) and dried in vacuo.
Additional solid was obtained from the mother liquor and
washed with Et2O and dried. Total yield of 8: 56 mg, 71% as
a mixture of trans (8a ) and cis (8b) isomers (ratio 3:2 by NMR).
1H NMR (C6D6, 300 MHz) for 8a : δ 2.14 (s, 6H, p-ArCH3), 2.27
mg, 97%). H NMR (CD2Cl2, 500 MHz): δ 0.35 (d, 2H, J SiH
)
2
1
2
2
48 Hz, J SiH ) 25 Hz J PtH ) 650 Hz, J PtH ) 112 Hz, J PH ) 7
Hz, Pt-H-Si), 5.89-7.83 [m, 80H, P(C6H5)3 and Si[C6(C6H5)5]],
7.48 (s, 2H, Si-H). 29Si{1H} NMR (CD2Cl2, 1H-29Si HMQC,
500 MHz): δ 174.5. IR (KBr, cm-1): ν 2118.1 (Si-H), 1654.0
(Pt-H-Si). Anal. Calcd for C108H84P2Pt2Si2: C, 68.63; H, 4.48.
Found: C, 68.05; H, 4.52.
P r ep a r a tion of tr a n s-{(P h 3P )P t[µ-η2-H-SiH(RF)]}2 (10).
A solution of (RF)SiH3 (5; 22 mg, 0.07 mmol) in 1 mL C6H6
was added to (Ph3P)2Pt(η2-C2H4) (52 mg, 0.07 mmol) to give a
clear amber solution. Vigorous bubbling was observed initially
for approximately 5 min. The reaction mixture was set aside
in the drybox for 2 months, after which evaporation of the
solvent had occurred to give a dark amber oily residue. The
residue was extracted with Et2O (2 mL), and the washings
were stored at -35 °C for several days, after which pale yellow
microcrystals of trans-{(Ph3P)Pt[µ-η2-H-SiH(RF)]}2 (10) suit-
able for X-ray analysis had formed. The solid was washed with
cold hexanes (3 × 1 mL) and dried in vacuo to give 10 mg (19%
1
2
2
(bd, 2H, J PtH ) 650 Hz, J PH ) 5 Hz, J PtH not resolved, Pt‚‚‚
H‚‚‚Si), 2.38 (s, 12H, o-ArCH3), 6.61 (s, 4H, Ar H), 6.89 [m,
18H, P(m-C6H5)3 and P(p-C6H5)3], 7.61 [m, 12H, P(o-C6H5)3],
8.95 (s, 2H, 2J PtH ) 136 Hz, 2J PtH ) 75 Hz, SiH). 29Si{1H} NMR
(C6D6, 1H-29Si HMQC, 500 MHz): δ 131. IR (KBr, cm-1):
ν 2122.3 (Si-H), 1618.0 (Pt-H). Anal. Calcd for C54H56P2Pt2-
Si2: C, 53.46; H, 4.65. Found: C, 52.99; H, 4.69. 1H NMR
(C6D6, ppm, 300 MHz) for 8b: δ 2.17 (s, 6H, p-ArCH3), 2.34
(s, 12H, o-ArCH3), 6.68 (s, 4H, Ar H), 6.89 [m, 18H, P(m-C6H5)3
1
yield) of 10. H NMR (C6D6, 300 MHz) for 10: δ 2.10 (b, 2H,
2
and P(p-C6H5)3], 7.61 [m, 12H, P(o-C6H5)3], 8.52 (s, 2H, J PtH
coupling constants not resolved, Pt‚‚‚H‚‚‚Si), 6.81 [m, 18H,
P(m-C6H5)3 and P(p-C6H5)3], 7.57 [m, 12H, P(o-C6H5)3], 7.68
(bs, 4H, Ar H), 8.41 (m, 2H, coupling constants not resolved,
SiH). 29Si{1H} NMR (C6D6, 1H-29Si HMQC, 500 MHz): δ 135.
IR (KBr, cm-1): ν 2158.4 (Si-H), 1686.0 (Pt-H). Anal. Calcd
for C54H38F18 P2Pt2Si2: C, 42.19; H, 2.49. Found: C, 39.65; H,
2.38.
2
) 135 Hz, J PtH ) 73 Hz, SiH).38 31P{1H} NMR (C6D6, 121
2
3
MHz): 38.2 (1J PtP ) 4264 Hz, J PtP ) 252 Hz, J PP ) 60 Hz).
29Si{1H} NMR (C6D6, 1H-29Si HMQC, 500 MHz): δ 129. IR
(KBr, cm-1): ν 2116.1 (Si-H), 1618.0 (Pt-H).
Va r ia ble-Tem p er a tu r e NMR Sp ectr oscop y of 8. A
sample of 8 (4 mg, 5.8 × 10-6 mol) was dissolved in 1 mL of
1
toluene-d8 and analyzed by H NMR spectroscopy from room
P r ep a r a tion of cis-(P h 3P )2P t(H)[SiH2(P P P )] (11). A
solution of (PPP)SiH3 (4; 84 mg, 0.17 mmol) in 1.0 mL of C6D6
was added to (Ph3P)2Pt(η2-C2H4) (131 mg, 0.17 mmol) to give
a clear amber solution with vigorous bubbling for approxi-
mately 5 min. Analysis of the reaction mixture by 1H and 31P-
{1H} NMR indicated quantitative formation of cis-(Ph3P)2Pt-
(H)[SiH2(PPP)] (11). After 1 h an off-white solid began to
precipitate. The solution was filtered, and the solid was washed
with 4 mL of C6H6 and dried in vacuo to give 157 mg (76%) of
11. 1H NMR (C6D6, 300 MHz): δ - 1.81 [dd, 1H, 2J PH ) 21 Hz
temperature (25 °C) to 95 °C in 10 °C increments and from 77
to 83 °C in 2 °C increments to determine the coalescence
temperature for the terminal Si-H resonances of 8a and 8b
(8-9 ppm). The coalescence temperature (Tc) was found to be
83 °C (356 K).
P r ep a r a tion of {(P h 3P )P t[µ-η2-D-SiD(Mes)]}2 (8-d 4). In
a 7 mL vial containing 52 mg (0.07 mmol) of (Ph3P)2Pt(η2-C2H4)
was placed a solution of MesSiD3 (3-d 3; 13 mg, 0.08 mmol) in
C6H6 (1 mL). Rapid gas evolution was observed, the solution
turned pale yellow, and a solid precipitate formed after 3 h.
After 24 h the solid was filtered, washed with Et2O (8 × 1
mL), and then dried in vacuo to give 28 mg of {(Ph3P)Pt[µ-η2-
D-SiD(Mes)]}2 (8-d 4), (67% yield) as a mixture of trans (8a -
d 4) and cis (8b-d 4) isomers (ratio 3:2 by NMR). 1H NMR (C6D6,
300 MHz) for 8a -d 4: δ 2.14 (s, 6H, p-ArCH3), 2.38 (s, 12H,
o-ArCH3), 6.62 (s, 4H, Ar H), 6.89 [m, 18H, P(m-C6H5)3 and
P(p-C6H5)3], 7.60 [m, 12H, P(o-C6H5)3]. 2H NMR (C6H6/C6D6,
2
1
(cis), J PH ) 156 Hz (trans), J PtH ) 984 Hz, Pt-H], 4.26 (pt,
1
3
2H, J SiH ) 182 Hz, J PH ) 7 Hz, Si-H), 6.65-7.60 [m, 55H,
P(C6H5)3 and Si[C6(C6H5)5]. 31P{1H} NMR (C6D6, 121 MHz):
1
2
31.7 (d, J PtP ) 1713 Hz, J PP ) 14 Hz, PtP trans to Si), 32.9
(d, 1J PtP ) 2422 Hz, 2J PP ) 14 Hz, PtP cis to Si). 29Si{1H} NMR
1
2
(C6D6, DEPT, 99 MHz): δ -45.7 [dd, J PtSi ) 1155 Hz, J PSi
)
155 Hz (trans), J PSi ) 12 Hz (cis)]. IR (KBr, cm-1): ν 2088.8
(Si-H), 2067.6 (Pt-H). Anal. Calcd for C72H58P2PtSi: C, 71.57;
H, 4.84. Found: C, 69.77; H, 4.72.
2
1
2
77 MHz): δ 2.28 (b, 2D, J PtD ) 102 Hz, J PtD not resolved,
Pt‚‚‚D‚‚‚Si), 8.93 (s, 2D, 1J PtD not resolved, SiD). 31P{1H} NMR
(C6D6, ppm, 121 MHz): 39.0 (1J PtP ) 4251 Hz, 2J PtP ) 263 Hz,
3J PP ) 56 Hz). IR (KBr, cm-1): ν 1541.5 (Si-D), 1157.4 (Pt-
D). Anal. Calcd for C54H52D4P2Pt2Si2: C, 53.29; H, 4.28.
Found: C, 52.91; H, 4.67. 1H NMR (C6D6, 300 MHz) for 8b-
d 4: δ 2.17 (s, 6H, p-ArCH3), 2.33 (s, 12H, o-ArOCH3), 6.68 (s,
4H, Ar H), 6.89 [m, 18H, P(m-C6H5)3 and P(p-C6H5)3], 7.60 [m,
12H, P(o-C6H5)3]. 2H NMR (C6H6/C6D6, 77 MHz): δ 1.49 (b,
P r ep a r a tion of cis-(P h 3P )2P t(H)[SiH2(RF )] (12). A solu-
tion of (RF)SiH3 (5; 22 mg, 0.07 mmol) in 1 mL of C6H6 was
added to (Ph3P)2Pt(η2-C2H4) (48 mg, 0.06 mmol) to give a clear
yellow solution. Vigorous bubbling was observed initially for
approximately 5 min, and then hexanes (ca. 5 mL) were added
to the reaction mixture. The solution was stored at -35 °C for
several days, after which pale yellow microcrystals of cis-
(Ph3P)2Pt(H)[SiH2(RF)]) (12) had formed. The solid was washed
with hexanes (3 × 3 mL) and dried in vacuo to give 36 mg
1
2
2
2D, J PtD and J PtD not resolved, Pt‚‚‚D‚‚‚Si), 8.51 (s, 2D, J PtH
not resolved, SiD). 31P{1H} NMR (C6D6, 121 MHz): 38.6 (1J PtP
1
(54% yield)39 of 12. H NMR (C6D6, 500 MHz): δ - 2.39 [dd,
) 4249 Hz, J PtP ) 251 Hz, J PP ) 56 Hz). IR (KBr, cm-1):
2
3
2
2
1
1H, J PH ) 20 Hz (cis), J PH ) 156 Hz (trans), J PtH ) 930 Hz,
1
2
5
ν 1541.5 (Si-D), 1157.4 (Pt-D).
Pt-H], 5.03 (m, 2H, J SiH ) 187 Hz, J PtH ) 20 Hz, J FH ) 8
Hz, Si-H), 6.86 [m, 9H, P(m-C6H5)3 and P(p-C6H5)3 trans to
Si], 6.89 [m, 9H, P(m-C6H5)3 and P(p-C6H5)3 cis to Si], 7.44
[m, 6H, P(o-C6H5)3 trans to Si], 7.52 [m, 6H, P(o-C6H5)3 cis to
Si], 7.86 (s, 2H, Ar H). 19F NMR (C6D6, 471 MHz): δ -63.3 (s,
P r ep a r a t ion of tr a n s-{(P h 3P )P t [µ-η2-H -SiH (P P P )]}2
(9). A sample of (Ph3P)2Pt(η2-C2H4) (61 mg, 0.08 mmol) was
dissolved in C6H6 (1.5 mL), and a solution of (PPP)SiH3 (4; 41
mg, 0.08 mmol, 1.5 mL C6H6) was added. The reaction mixture
turned yellow, and slow evolution of gas was observed. The
solution was heated to 78 °C, and vigorous bubbling was
observed immediately, followed by precipitation of trans-
{(Ph3P)Pt[µ-η2-H-SiH(PPP)]}2 (9) within minutes. The solid
3F, 7J PtF ) 11 Hz, p-CF3), -57.2 (dt, 6F, 5J SiHF ) 8 Hz, 5J PtF
)
64 Hz, J PtHF ) 2 Hz, o-CF3). 29Si{1H} NMR (C6D6, DEPT, 99
6
1
2
MHz): δ - 45.1 [dm, J PtSi ) 1326 Hz, J PSi ) 175 Hz (trans),
(39) The reaction was quantitative by 1H and 31P NMR spectroscopy.
A low isolated yield of 12 is probably due to loss of product during
workup.
(38) Only terminal Si-H could be observed for 8b. The bridging
Si-H resonance was obscured by the ArMe group.

5510 Organometallics, Vol. 19, No. 25, 2000
Braddock-Wilking et al.
2J PSi (cis), J SiF are not resolved]. 31P{1H} NMR (C6D6, 121
Information). Structure solution and refinement were carried
out using the SHELXTL-PLUS software package.40 The struc-
tures were solved by direct method and refined successfully
in the space group P1h. Full-matrix least-squares refinement
1
2
MHz): 30.3 (d, J PtP ) 1896 Hz, J PP ) 16 Hz, PtP trans to
1
2
Si), 30.6 (d, J PtP ) 2282 Hz, J PP ) 16 Hz, PtP cis to Si). IR
(KBr, cm-1): ν 2125.5 (Si-H), 2071.6 (Pt-H). Anal. Calcd for
45H35F9P2PtSi: C, 52.38; H, 3.39. Found: C, 51.82; H, 3.41.
2
was carried out by minimizing ∑w(Fo - Fc2)2. The non-
C
P r epar ation of cis-(P h 3P )2P t[SiH2(p-Tol)]2 (13). A sample
hydrogen atoms were refined anisotropically to convergence.
The hydrogen atoms were treated using the appropriate riding
model. One and a half molecules of benzene were found in the
crystal lattice for compound 10. One of the CF3 groups is also
disordered, which was resolved to be in the ratio of 75:25. In
both cases the bridging H atom was located and refined
successfully. Structure refinement parameters are listed in
Table 2 for 10. A projection view of the molecules with non-
hydrogen atoms represented by 50% probability ellipsoids,
showing the atom labeling, is presented in Figures 5 and 6.
of (Ph3P)2Pt(η2-C2H4) (53 mg, 0.07 mmol) was treated with a
solution of (p-Tol)SiH3 (22 mg, 0.18 mmol) in toluene-d8 (1 mL)
to give a yellow solution. Bubbling was observed for about 5
min, and analysis of the sample by 1H and 31P{1H} NMR
indicated quantitative formation of cis-(Ph3P)2Pt[SiH2(p-Tol)]2
(13). Precipitation of 13 was achieved by addition of hexanes
(2.5 mL), followed by storage at - 35 °C (2.5 h in the dark).
The solution was filtered, and the yellow solid was dried in
vacuo to give 58 mg (88%) of 13. The clear yellow decantate
was found to be light sensitive. Upon exposure to light for 10
min, the color of the decantate changed to a dark amber. In
addition, the yellow solid was sensitive to light and changed
from yellow to orange upon exposure for 5 min. 1H NMR (C6D6,
Complete listings of the atomic coordinates for the non-
hydrogen atoms and the geometrical parameters, positional
and isotropic displacement coefficients for hydrogen atoms, and
anisotropic displacement coefficients for the non-hydrogen
atoms have been submitted as Supporting Information.
1
300 MHz): δ 2.20 (s, 6H, ArCH3), 5.08 (m, 4H, J SiH ) 177
2
3
Hz, J PtSiH ) 53 Hz, J PSiH ) 14 Hz, SiH), 6.87 [m, 18H, P(m-
3
C6H5)3 and P(p-C6H5)3], 7.07 (d, 4H, J HH ) 7 Hz, Ar H), 7.39
[m, 12H, P(o-C6H5)3], 7.77 (d, 4H, 3J HH ) 7 Hz, Ar H). 31P{1H}
NMR (C6D6, 121 MHz): δ 35.5 [1J PtP ) 1887 Hz, 2J PSi ) 21 Hz
Ack n ow led gm en t. This work was supported by a
University of MissourisSt. Louis Research Award. The
NSF (Grant No. CHE-9318696) and the University of
Missouri Research Board are gratefully acknowledged
for support of the purchase of Varian Unity Plus 300
and Bruker ARX-500 NMR spectrometers. The UMs
St. Louis X-ray Crystallography Facility is funded in
part by a NSF Instrumentation Grant (Grant No. CHE-
9309690) and a UMsSt. Louis Research Award. J .B.-
W. is also grateful to Professors Claire Tessier, J oyce
Y. Corey, and Peter P. Gaspar for stimulating discus-
sions.
2
(cis), J PSi ) 62 Hz (trans)].
X-r a y Cr ysta llogr a p h y. Crystals of 9 were grown from a
dilute C6D6 solution by slow evaporation over several days.
Crystals of 10 were grown from Et2O at -35 °C over a period
of several days. Preliminary examination and data collection
were performed using a Bruker SMART CCD detector system.
Preliminary unit cell constants were determined with a set of
45 narrow frames (0.3° in $) scans. The data sets collected
consisted of 4028 frames with a frame width of 0.3° in $ and
counting time of 15 s/frame at a crystal to detector distance of
4.930 cm. The double-pass method of scanning was used to
exclude any noise. SMART and SAINT software packages40
were used for data collection and data integration. Analysis
of the integrated data did not show any decay. Final cell
constants were determined by a global refinement of xyz
centroids. Collected data were corrected for systematic errors
using SADABS41 based on the Laue symmetry using equiva-
lent reflections.
Su p p or tin g In for m a tion Ava ila ble: Tables giving ad-
ditional crystallographic data for 9 and 10 and figures giving
2D NMR data for 7, IR spectra for 8 and 8-d 4, 1D and 2D NMR
data for 12, and the molecular structure of 9 showing full atom
labeling. This material is available free of charge via the
Internet at http://pubs.acs.org.
Crystal data and intensity data collection parameters are
listed in Table 1 (see also Tables S1 and S6 in the Supporting
OM000602R
(40) Sheldrick, G. M. Bruker Analytical X-ray Division, Madison,
WI, 1999.
(41) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.