Formation and X-ray crystal structure determination of the novel triplatinum cluster [(Ph3P)Pt(μ-SiC12H8)]3 from reaction of silafluorene with (Ph3P)2Pt(η2-C2H4</

Article abstract of DOI:10.1021/om020565z

The formation and x-ray crystal structure determination of the novel triplatinum cluster were studied. The trinuclear platinum complex containing bridging silylene units was formed from mononuclear silicon and platinum precursors. Dinuclear and especially

Full text of DOI:10.1021/om020565z

Organometallics 2002, 21, 5467-5469
5467
F or m a tion a n d X-r a y Cr ysta l Str u ctu r e Deter m in a tion of
th e Novel Tr ip la tin u m Clu ster [(P h 3P )P t(µ-SiC12H8)]3
fr om Rea ction of Sila flu or en e w ith (P h 3P )2P t(η2-C2H4)
J anet Braddock-Wilking,* J oyce Y. Corey, Kimberly Dill, and Nigam P. Rath
Department of Chemistry and Biochemistry, University of MissourisSt. Louis,
St. Louis, Missouri 63121
Received J uly 16, 2002
Summary: Reaction of silafluorene (H2SiC12H8) with
(Ph3P)2Pt(η2-C2H4) in C6D6 (or C7D8) provided the tri-
nuclear complex [(Ph3P)Pt(µ-SiC12H8)]3 (3). The structure
of 3, which exhibits a nonplanar Pt3Si3 core, was
confirmed by X-ray crystallography.
Oxidative addition reactions of primary and secondary
hydrosilanes with late-transition-metal precursors have
provided a variety of structural motifs.1 Formal inser-
tion of the metal center into the Si-H bond initially
provides a complex with the general formula LnM(H)-
SiR3. With primary and secondary hydrosilanes, re-
sidual protons at the bound silicon center (SiR3, where
R can be H) provide additional sites of reactivity that
can give rise to dinuclear or higher order metal clusters.
Examples of different complexes that can be gener-
F igu r e 1. Examples of complexes formed from Si-H bond
activation reactions involving primary and secondary hy-
drosilanes with Pt-phosphine precursors.
ated from Si-H bond activation reactions involving
primary and secondary hydrosilanes with platinum
centers are shown in Figure 1. Mononuclear complexes
containing one silyl group (A)2 or two silyl groups at
platinum (B)3 where only one Si-H bond has been
reacted with a metal have been reported. In addition,
dinuclear complexes containing bridging silylene moi-
eties (C)3a,b,4 as well as dinuclear species having non-
classical Pt‚‚‚H‚‚‚Si interactions (D)2b,4g,5 have been
prepared. More recently, a trinuclear platinum cluster
containing a bridging silylene group has been isolated
(E).6 Dinuclear and especially trinuclear complexes
containing Pt and Si are quite rare.
Herein, we report the synthesis of a triplatinum
cluster containing a bridging silafluorenyl unit (SiC12H8)
by starting from the secondary arylhydrosilane silafluo-
rene (H2SiC12H8)7 and the Pt(0) precursor (Ph3P)2Pt-
(η2-C2H4). To the best of our knowledge, this is the first
example of a trinuclear platinum complex containing
bridging silylene units formed from mononuclear silicon
and platinum precursors.
Reaction of (Ph3P)2Pt(η2-C2H4) with (H2SiC12H8) (ca.
1:1 ratio) initially provided the oxidative addition
product (Ph3P)2Pt(H)[Si(H)C12H8] (1) in quantitative
1
yield by H and 31P{1H} NMR spectroscopy. Complex 1
* To whom correspondence should be addressed. E-mail: jwilking@
umsl.edu. Fax: (314) 516-5342. Tel: (314) 516-6436.
was characterized in solution only (C6D6 or C7D8).8 After
approximately 15 min the NMR signals for 1 disap-
peared. During the initial 15 min period a new broad
resonance (ca. 20 ppm) intensified in the 31P{1H}
spectrum. Low-temperature NMR experiments suggest
that this species is the dinuclear complex 2, which will
be described in more detail in a full paper.9
(1) Corey, J . Y.; Braddock-Wilking, J . Chem. Rev. 1999, 99, 175.
(2) (a) Simons, R. S.; Sanow, L. M.; Galat, K. J .; Tessier, C. A.;
Youngs, W. J . Organometallics 2000, 19, 3994. (b) Braddock-Wilking,
J .; Levchinsky, Y.; Rath, N. P. Organometallics 2000, 19, 5500.
(3) (a) Heyn, R. H.; Tilley, T. D. J . Am. Chem. Soc. 1992, 114, 1917.
(b) Shimada, S.; Tanaka, M.; Honda, K. J . Am. Chem. Soc. 1995, 117,
8289. (c) Michalczyk, M. J .; Recatto, C. A.; Calabrese, J . C.; Fink, M.
J . J . Am. Chem. Soc. 1992, 114, 7955.
(4) (a) Zarate, E. A.; Tessier-Youngs, C. A.; Youngs, W. J . J . Chem.
Soc., Chem. Commun. 1989, 577. (b) Tessier, C. A.; Kennedy, V. O.;
Zarate, E. A. In Inorganic and Organometallic Oligomers and Poly-
mers; Harrod, J . F., Laine, R. M., Eds.; Kluwer Academic: Dordrecht,
The Netherlands, 1991; p 13. (c) Anderson, A. B.; Shiller, P.; Zarate,
E. A.; Tessier-Youngs, C. A.; Youngs, W. J . Organometallics 1989, 8,
2320. (d) Zarate, E. A.; Tessier-Youngs, C. A.; Youngs, W. J . J . Am.
Chem. Soc. 1988, 110, 4068. (e) Levchinksy, Y.; Rath, N. P.; Braddock-
Wilking, J . Organometallics 1999, 18, 2583. (f) Braddock-Wilking, J .;
Levchinsky, Y.; Rath, N. P. Organometallics 2001, 20, 474. (g) 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. (h)
Braddock-Wilking, J .; Levchinksy, Y.; Rath, N. P. Inorg. Chim. Acta
2002, 330, 82.
The reaction mixture was continuously monitored by
NMR spectroscopy over a period of several hours. After
(6) Osakada, K.; Tanabe, M.; Tanase, T. Angew. Chem., Int. Ed.
2000, 39, 4053.
(7) (a) Chang, L. S.; Corey, J . Y. J . Organomet. Chem. 1986, 307, 7.
(b) For a recent report on the synthesis of dichlorosilafluorene, see:
Liu, Y.; Stringfellow, T. C.; Ballweg, T.; Guzei, I. A.; West, R., J . Am.
Chem. Soc. 2002, 124, 49.
(8) Complex 1 was not isolated. Selected spectroscopic data for 1:
1
31P{1H} NMR (C7D8, 202 MHz) δ 34.2 (d with Pt satellites, J PtP
)
1877 Hz, 2J PtP ) 7 Hz, P trans to Si), 33.9 (br s with Pt satellites, 1J PtP
(5) 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.
) 2533 Hz); 1H NMR (C7D8, 500 MHz) δ 5.1 (m, 1H, SiH), -1.72 (dd
1
2
with Pt satellites, 1H, Pt-H, J PtH ) 956 Hz, J PH (trans) ) 156 Hz,
2J PH (cis) ) 21 Hz).
10.1021/om020565z CCC: $22.00 © 2002 American Chemical Society
Publication on Web 11/06/2002

5468 Organometallics, Vol. 21, No. 25, 2002
Communications
Sch em e 1
approximately 2.5-3 h an additional new resonance
appeared in the 31P{1H} NMR spectrum at ca. 70 ppm
as a singlet with a complex Pt satellite pattern.10 This
resonance was assigned to the trinuclear Pt complex 3.11
Scheme 1 summarizes the products observed from
reaction of silafluorene with (Ph3P)2Pt(η2-C2H4).
The structure of 3 was confirmed by X-ray crystal-
lography (Figure 2).12 Although the quality of the
structural data for 3 does not permit a detailed discus-
sion, it provides information for the basic features of
the molecule. Each Pt in the triangular Pt core is
bridged by a silafluorenylidene moiety, and one PPh3
ligand is bound to each Pt center. The central Pt3Si3
F igu r e 2. (a, top) Top view of the molecular structure of
[(Ph3P)Pt(µ-SiC12H8)]3 (3) (50% probability). (b, bottom)
Side view of the molecular structure of 3 showing core
P3Pt3Si3 atoms only. Selected bond distances (Å) and angles
(deg): Pt(1)-Pt(2) ) 2.7080(11), Pt(1)-Pt(3) ) 2.7114(11),
Pt(2)-Pt(3) ) 2.7033(11), Pt(1)-P(1) ) 2.240(6), Pt(2)-P(2)
) 2.238(5), Pt(3)-P(3) ) 2.277(5), Pt(1)-Si(1) ) 2.374(6),
Pt(1)-Si(3) ) 2.388(6), Pt(2)-Si(1) ) 2.348(6), Pt(2)-
Si(2) ) 2.346(6), Pt(3)-Si(2) ) 2.344(6), Pt(3)-Si(3) )
2.355(6); Pt(2)-Pt(1)-Pt(3) ) 59.84(3), Pt(2)-Pt(3)-Pt(1)
) 60.02(3), Pt(3)-Pt(2)-Pt(1) ) 60.14(3), Pt(2)-Si(1)-
Pt(1) ) 69.99(17), Pt(3)-Si(2)-Pt(2) ) 70.44(17), Pt(3)-
Si(3)-Pt(1) ) 69.74(17).
(9) Two distinct resonances were observed in the 31P{1H} NMR
spectrum at 17 (d) and 31 (t) ppm in a 2:1 ratio, each with two sets of
Pt satellites. The 29Si{1H} NMR spectrum showed two peaks at 146
(t) and 154 (d) ppm, indicating two different silicon sites. In addition,
the 1H NMR spectrum exhibited two hydride signals at ca. -5 (t, with
Pt satellites) and 2 ppm (d, Pt satellites not resolved). The data were
obtained at 223 K and are consistent with an unsymmetrical environ-
ment about the two Pt centers in 2. Precedence for a directly related
unsymmetrical palladium dimer has recently been published; see: Kim,
Y.-J .; Lee, S.-C.; Park, J .-I.; Osakada, K.; Choi, J .-C.; Yamamoto, T.
Organometallics 1998, 17, 4929.
core is nonplanar (Figure 2b). One silicon (Si2) lies above
the plane defined by the remaining Pt3Si2 atoms by
approximately 1 Å. In addition, one phosphorus atom
(P1) also lies above that plane by nearly 0.4 Å, whereas
the other two phosphorus centers lie in the same
plane as the Pt3Si2 atoms. The unsymmetrical nature
found in the solid-state structure of 3 may be due to
packing forces. The Pt-Pt-Pt angles are acute, as a
result of the triangular arrangement of the Pt3 core
(59-60°). The Pt-Si distances (2.34-2.38 Å) fall in
the range1 for other known Pt-Si complexes and are
similar to those in the related structure [(Me3P)Pt-
(µ-SiPh2)]3.6 The Pt-Pt distances are in the expected
range (2.70-2.71 Å) for Pt-Pt single bonds in triangular
platinum systems.13,14 Due to the quality of the crystal-
lographic data, the presence of a terminal or bridging
(10) The satellite pattern observed in the 31P{1H} NMR spectrum
for 3 is in good agreement with a calculated spectrum for the related
triplatinum complex Pt3(µ-CO)3(PCy3)3; see: Moor, A.; Pregosin, P. S.;
Venanzi, L. M. Inorg. Chim. Acta 1981, 48, 153.
(11) Silafluorene (73 mg, 0.40 mmol) and (Ph3P)2Pt(η2-C2H4) (250
mg, 0.33 mmol) were added to C6D6 (1.5 mL) and C6H6 (3.5 mL),
resulting in a clear, amber red solution. After several hours, red
crystals of 3 had precipitated, which were separated. Addition of
hexane (8 mL) to the mother liquor resulted in precipitation of an
additional crop of 3. The solid was dried under vacuum for 2 h to give
3 (64 mg, 30%). Selected NMR data for 3: 31P{1H} NMR (C7D8, 202
1
2
MHz) δ 70.5 (s with Pt satellites, J PtP ) 3338 Hz, J PtP ) 421 Hz,
3J PP ) 80 Hz); 1H NMR (CD2Cl2, 500 MHz) δ 7.40 (d, J HH ) 7.6 Hz),
3
3
3
7.06 (t, J HH ) 7.3 Hz), 6.95-6.87 (m), 6.07 (t, J HH ) 7.6 Hz) ArH;
29Si{1H} NMR (C7D8, 99 MHz) δ 269 (1J PtSi ) 934 Hz). Anal. Calcd for
C
90H69P3Pt3Si3‚2C6H6: C, 59.21; H, 3.95. Found: C, 59.32; H, 4.11.
(12) Crystals of 3 were obtained by slow evaporation from d8-toluene
solution. Crystallographic data for 3: C90H69P3Pt3Si3‚C7D8, monoclinic,
space group P21/n, T ) 223(2) K, a ) 9.8929(2) Å, b ) 14.4094(2) Å, c
) 55.0754(9) Å, â ) 92.649(1)°, V ) 7842.7 (2) Å3, Z ) 4, µ ) 8.834
mm-1, F(000) ) 3920, Fcalcd ) 1.698 g cm-3. Final residual values: RF
) 11.2% for 11 672 reflections (I > 2σ(I)) and Rw(F2) ) 21.6% for 13 184
reflections and 919 parameters. Crystallographic data for structure 3
have been be deposited with the Cambridge Structural Data Base dep
#CCDC 196309.
(13) For a recent review see: Imhof, D.; Venanzi, L. M. Chem. Soc.
Rev. 1994, 23, 185.
(14) See for example: Bender, R.; Braunstein, P.; Dedieu, A.; Ellis,
P. D.; Huggins, B.; Harvey, P. D.; Sappa, E.; Tiripicchio, A. Inorg.
Chem. 1996, 35, 1223.

Communications
Organometallics, Vol. 21, No. 25, 2002 5469
hydride could not be confirmed. When d2-silafluorene
was utilized as the reactant, the H NMR spectrum did
not show resonances for either bridging or terminal
metal deuterides.
Further studies are in progress with other constrained
secondary hydrosilanes to determine if such silicon
systems will generate trinuclear or higher order poly-
nuclear clusters as well as their mechanism of forma-
tion.
2
Trinuclear complexes of Pt containing bridging car-
bonyl,13 nitrile, or phosphido14 ligands are well-known,
but those that incorporate silyl substituents are uncom-
mon. For example, Osakada et al. recently prepared the
triplatinum complex [(Me3P)Pt(µ-SiPh2)]3 in 28% yield
from thermolysis of the preformed mononuclear complex
(Me3P)2Pt(SiPh2H)2 at 100 °C.6 Unlike Osakada’s Pt3-
Si3 system, the current triplatinum-µ-silylene complex
(3) was generated at room temperature. To the best of
our knowledge, the only other known Pt3 system incor-
porating a silicon-containing substituent is a triplati-
num complex with a terminal silyl group, -Si(OSiMe3)3,
which was synthesized by reaction of the preexisting
triplatinum cluster [Pt3(Ph)(µ-PPh2)3(PPh3)2] with HSi-
(OSiMe3)3.15 Both complexes were structurally charac-
terized by X-ray crystallography. Trinuclear complexes
of other transition metals with bridging silylene units
are particularly rare.16
Ack n ow led gm en t. We are thankful for a University
of MissourisSt. Louis Small Grants Award for the
purchase of chemicals. The support of an NSF grant (No.
CHE-9974801) and an UM-Research Board grant for the
purchase of a Bruker Avance 300 NMR spectrometer
are gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Figures giving se-
lected NMR spectroscopic data and tables giving crystal-
lographic data for 3, including crystal data and structure
refinement details, atomic coordinates, and bond distances and
angles. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM020565Z
(15) Bender, R.; Braunstein, P.; Bouaoud, S.-E.; Merabet, N.; Rouag,
D.; Zanello, P.; Fontani, M. New J . Chem. 1999, 23, 1045.
(16) Ogino, H.; Tobita, H. Adv. Organomet. Chem. 1998, 42, 223.