Silanol-based pincer Pt(II) complexes: Synthesis, structure, and unusual reactivity

Article abstract of DOI:10.1021/ic800457u

Aiming at the generation of a silanone intramolecularly bound to platinum, we prepared pincer-type PSiP silanol Pt(II) complexes. While a stable silanone complex was not isolated, unusual reactivity modes, involving its possible intermediacy, were observed. Treatment of the new PSiH₂P-type ligand (o-iPr₂PC₆H₄)₂SiH₂ (7) with (Me₂S)₂Pt(Me)Cl yields the pincer-type hydrosilane complex [{(o- iPr₂PC₆H₄)₂SiH}PtCl] (8), which upon Ir(I)-catalyzed hydrolytic oxidation gives the structurally characterized silanol complex [{(o- iPr₂PC₆H ₄)₂SiOH}PtCl] (3). Complex 3, comprising in its structure the nucleophilic silanol fragment and electrophilic Pt(II)-Cl moiety, exhibits dual reactivity. Its reaction with the non-nucleophilic KB(C₆F ₅)₄ in fluorobenzene leads to the ionic complex [{(o- iPr₂PC₆H₄)₂SiOH}Pt]⁺ [(C₆F₅)₄B]^- (9), which reacts with CO to yield the structurally characterized [{(o- iPr₂PC ₆H₄)₂SiOH}PtCO]⁺ [(C ₆F₅)₄B]^- (10). Treatment of 3 with non-nucleophilic bases leads to unprecedented rearrangement and coupling, resulting in the structurally characterized, unusual binuclear complex 11. The structure of 11 comprises two different fragments: the original O-Si-Pt(II)-Cl pattern, and the newly formed silanolate Pt(II)-H pattern, which are connected via a disiloxane bridge. Complex 9 undergoes a similar hydrolytic rearrangement in the presence of iPr₂NEt to give the mononuclear silanolate Pt(II)-H complex 17. Both these rearrangement-coupling reactions probably involve the inner-sphere generation of an intermediate silanone 14, which undergoes nucleophilic attack by the starting silanol 3 to yield complex 11, or adds a water molecule to yield complex 17. X-ray diffraction studies of 3, 10, and 11 exhibit a very short Si-Pt bond length (2.27-2.28 A) in the neutral complexes 3 and 11 that elongates to 2.365 A in the carbonyl complex 10. A significantly compressed geometry of the silanolate platinum(II)-hydride fragment B of the binuclear complex 11 features a Pt(2)-O(2)-Si(2) angle of 100.4 (3)° and a remarkably short Pt(2)...Si(2) [2.884 (3) A] distance.

Full text of DOI:10.1021/ic800457u

Inorg. Chem. 2008, 47, 7177-7189
Silanol-Based Pincer Pt(II) Complexes: Synthesis, Structure, and
Unusual Reactivity
Edward E. Korshin,† Gregory Leitus,‡ Linda J. W. Shimon,‡ Leonid Konstantinovski,‡
and David Milstein*,†
Department of Organic Chemistry and Unit of Chemical Research Support, Weizmann Institute of
Science, 76100 RehoVot, Israel
Received March 12, 2008
Aiming at the generation of a silanone intramolecularly bound to platinum, we prepared pincer-type PSiP silanol
Pt(II) complexes. While a stable silanone complex was not isolated, unusual reactivity modes, involving its possible
intermediacy, were observed. Treatment of the new PSiH2P-type ligand (o-IPr2PC6H4)2SiH2 (7) with (Me2S)2Pt(Me)Cl
yields the pincer-type hydrosilane complex [{(o- iPr2PC6H4)2SiH}PtCl] (8), which upon Ir(I)-catalyzed hydrolytic oxidation
gives the structurally characterized silanol complex [{(o- iPr2PC6H4)2SiOH}PtCl] (3). Complex 3, comprising in its
structure the nucleophilic silanol fragment and electrophilic Pt(II)-Cl moiety, exhibits dual reactivity. Its reaction
with the non-nucleophilic KB(C6F5)4 in fluorobenzene leads to the ionic complex [{(o- iPr2PC6H4)2SiOH}Pt]+ [(C6F5)4B]-
(9), which reacts with CO to yield the structurally characterized [{(o- iPr2PC6H4)2SiOH}PtCO]+ [(C6F5)4B]- (10).
Treatment of 3 with non-nucleophilic bases leads to unprecedented rearrangement and coupling, resulting in the
structurally characterized, unusual binuclear complex 11. The structure of 11 comprises two different fragments:
the original O-Si-Pt(II)-Cl pattern, and the newly formed silanolate Pt(II)-H pattern, which are connected via
a disiloxane bridge. Complex 9 undergoes a similar hydrolytic rearrangement in the presence of iPr2NEt to give the
mononuclear silanolate Pt(II)-H complex 17. Both these rearrangement-coupling reactions probably involve the
inner-sphere generation of an intermediate silanone 14, which undergoes nucleophilic attack by the starting silanol
3 to yield complex 11, or adds a water molecule to yield complex 17. X-ray diffraction studies of 3, 10, and 11
exhibit a very short Si-Pt bond length (2.27-2.28 Å) in the neutral complexes 3 and 11 that elongates to 2.365
Å in the carbonyl complex 10. A significantly compressed geometry of the silanolate platinum(II)-hydride fragment
B of the binuclear complex 11 features a Pt(2)-O(2)-Si(2) angle of 100.4 (3)° and a remarkably short Pt(2) · · · Si(2)
[2.884 (3) Å] distance.
Introduction
ing blocks for practically important siloxane-type polymers.2
Metallosiloxanes, complexes of the type Si-O-M derived
from silanols, have also attracted considerable interest as
precursors for silicone polymers containing metal centers in
the polymer backbone, as well as catalysts which structurally
mimic metal-modified silica surfaces.1,3 In contrast, metal-
losilanols, M-Si-OH, represent a relatively new and
considerably less studied family of compounds.1a,4–7 In most
Organosilanols, silicon compounds of the general formula
RnSi(OH)4-n have been extensively studied.1 These com-
pounds have found various applications, especially as build-
* To whom correspondence should be addressed. E-mail: david.milstein@
weizmann.ac.il. Fax: 972-8-9344142.
†
Department of Organic Chemistry.
Unit of Chemical Research Support.
‡
(1) For recent general reviews on silanols, see (a) Chandrasekhar, V.;
Boomishankar, R.; Nagendran, S. Chem. ReV. 2004, 104, 5847. (b)
Lickiss, P. D. AdV. Inorg. Chem. 1995, 42, 147. (c) Lickiss, P. D. In
The Chemistry of Organic Silicon Compounds; Rapoport, Z.; Apeloig,
Y., Eds.; John Wiley: Chichester, 2001; Vol. 3, p 695. (d) Kliem, S.;
Reiche, C.; Klingebiel, U. Silicon Chemistry; Jutzi, P.; Schubert, U.,
Eds.; Wiley-VCH: Weinheim, 2003; p 338. (e) Tailor-Made Silicon-
Oxygen Compounds: From Molecules to Materials; Corriu, R.; Jutzi,
P., Eds.; Vieweg: Braunschweig/Wiesbaden, 1996.
(2) (a) Rochow, E. G. Silicon and Silicones; Springer: Berlin, Heidelberg,
1987. (b) Mark, J. E. Acc. Chem. Res. 2006, 39, 881. (c) Mark, J. E.
Acc. Chem. Res. 2004, 37, 946.
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Chem. ReV. 1996, 96, 2205. (b) Roesky, H. W.; Ananthamaran, G.;
Chandrasekhar, V.; Jancik, V.; Singh, S. Chem.sEur. J. 2004, 10,
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Heterosiloxanes; Academic Press: London, 1988.
10.1021/ic800457u CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 16, 2008 7177
Published on Web 07/19/2008

Korshin et al.
cases the preparations and structural characterizations of these
compounds were reported while very little is known about
their reactivity.
We reported the efficient and mild dehydrogenation of
i-Pr2SiHOH into transient i-Pr2SidO catalyzed by [(dmpe)-
PtH]2(OTf)2, giving the cyclic trimer (i-Pr2SiO)3.7 In this
catalytic cycle release of free silanone from a key intermedi-
ate, a platinum silanone complex (2′T 2′′) was suggested,
resulting from ꢀ-hydrogen elimination of a Pt(II)-silanol
precursor 1 (eq 1).7,8
silaurethane12a and silaformamide-borane complex,12b in-
tramolecularly supported by a NfSi donor interaction.
As predicted by calculations, binding of silanones to
transition metal centers could stabilize these short-living
species.13 Pincer-type complexes14 have been demonstrated
to be useful in the intramolecular stabilization of unusual
types of structures.15,16 It was reasonable to assume that upon
generation of silanone in the inner sphere of a pincer-type
complex, intramolecular binding would result in its kinetic
and thermodynamic stabilization.
Herein we describe the design and synthesis of the first
pincer-type silanol-Pt(II) framework, our attempts to convert
the latter into the corresponding silanone-platinum complex,
and an unexpected and unprecedented rearrangement and
coupling of silanol-Pt(II) complexes into silanolate-Pt(II)
hydrides. A number of rigid Ir(III) and Rh(III) pincer
complexes, derived from NSi(Me)N-type tridentate bis(8-
quinolyl)methylsilyl ligand, were recently reported by Tilley
et al.17 A single PSi(Me)P-type Pt(II)-Cl complex based
on the tridentate bis(ortho-diphenylphosphinobenzyl)meth-
ylsilyl ligand,18a and some PSi(Me)P-complexes of Pt(II),
Ru(II), and Ir(III) derived from the aliphatic tridentate
MeSiH[(CH2)nPR2]2 ligands (R ) Ph or c-Hex, n ) 2 or 3),
were described by Stobart et al.18b–d While the manuscript
was in preparation, rigid PSi(Me)P-type Ru(II), Rh(I), Pd(II),
and Pt(II) complexes supported by bis(ortho-diphenylphos-
phinophenyl)methylsilyl ligand were also reported.19
Such mild Pt-catalyzed generation of highly unstable
silanones (R2SidO)9,10 raised the question whether a sil-
anone-Pt complex, such as 2, can be stabilized. So far,
silanones with unambiguous sp2-hybridized silicon have not
been isolated except by low temperature matrix techniques.10
The major reason for the instability of silanones is the
extremely high polarization of the R2Siδ+dOδ- T R2Si+-O-
bond, which results in extraordinary reactivity, especially
toward oligomerization leading to cyclosiloxanes (R2SidO)n
and toward addition of external nucleophiles; both processes
are highly exothermic and, in the case of R ) H, proceed
with no barrier.11 Considerable progress in the chemistry of
silanone derivatives was reported in 2007 by Driess et al.,
who described the synthesis and characterization of
Results and Discussion
1. Synthesis of the Tridentate PSiH2P Ligand and
Pincer-Type Pt(II) Silanols. We previously reported the
synthesis of several Pt(II)-,7 Ir(III)-,6 and Rh(III)6b metalla-
silanols by the direct oxidative addition20 of nonfunctional-
(4) (a) Chang, L. S.; Johnson, M. P.; Fink, M. J. Organometallics 1991,
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M.; Schumacher, D.; Sohns, A.; Bera, H.; Jehle, H. In Silicon
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Kraatz, H.-B.; Milstein, D. J. Am. Chem. Soc. 1995, 117, 5865.
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Chem. Soc. 1996, 118, 10894.
(14) Reviews regarding transition metal pincer-type complexes: (a) Morales-
Morales, D.; Jensen, C. M. The Chemistry of Pincer Compounds;
Elsevier: Amsterdam, 2007. (b) Szabo, K. J. Synlett 2006, 811. (c)
van der Boom, M. E.; Milstein, D. Chem. ReV. 2003, 103, 1759. (d)
Rybtchinski, B.; Milstein, D. ACS Symp. Ser. 2004, 885, 70. (e)
Albrecht, M.; van Koten, G. Angew. Chem., Int. Ed. 2001, 40, 3750.
(f) Jensen, C. M. Chem. Commun. 1999, 2443. (g) Rybtchinski, B.;
Milstein, D. Angew. Chem., Int. Ed. 1999, 38, 870. (h) Singleton, J. T.
Tetrahedron 2003, 59, 1837.
(8) In contrast to the efficient catalytic dehydrogenation of i-Pr2SiHOH,
a related reaction of the bulkier t-Bu2SiHOH with (dmpe)PtMe(OTf)
resulted in platinum-silanol 1 formation. See ref 7 for more details.
(9) For recent reviews related to silanones, see: Tokitoh, N.; Okazaki, R.
In The Chemistry of Organic Silicon Compounds; Rapoport, Z.;
Apeloig, Y., Eds.; Wiley: Chichester, 1998; Vol. 2, p 1063. (b) Tokitoh,
N.; Okazaki, R. AdV. Organomet. Chem. 2001, 47, 121. (c) Brook,
M. A. Silicon in Organic, Organometallic and Polymer Chemistry;
Wiley: New York, 2000; pp 61-96.
(10) Selected recent papers on matrix isolation of silanones: (a) Maier, G.;
Meudt, A.; Jung, J.; Pahl, H. In The Chemistry of Organic Silicon
Compounds; Rapoport, Z.; Apeloig, Y., Eds., Wiley: Chichester, 1998;
Vol. 2, p 1143. (b) Khabashesku, V. N.; Kerzina, Z. A.; Kudin, K. N.;
Nefedov, O. M. J. Organomet. Chem. 1998, 566, 45.
(15) Reviews on transition metal pincer complexes emphasizing the
stabilization of commonly short-lived species: (a) Vigalok, A.;
Milstein, D. Acc. Chem. Res. 2001, 34, 798. (b) Milstein, D. Pure
Appl. Chem. 2003, 75, 2003.
(16) For recent examples, see (a) Vigalok, A.; Rybtchinski, B.; Gozin, Y.;
Koblenz, T. S.; Ben-David, Y.; Rozenberg, H.; Milstein, D. J. Am.
Chem. Soc. 2003, 125, 15692. (b) Gauvin, R. M.; Rozenberg, H.;
Shimon, L. J. W.; Ben-David, Y.; Milstein, D. Chem.sEur. J. 2007,
13, 1382.
(17) (a) Stradiotto, M.; Fujdala, K. L.; Tilley, T. D. Chem. Commun. 2001,
1200. (b) Sangtrirutnugul, P.; Tilley, T. D. Organometallics 2007, 26,
5557. (c) Sangtrirutnugul, P.; Stradiotto, M.; Tilley, T. D. Organo-
metallics 2006, 25, 1607.
(11) (a) Apeloig, Y. In The Chemistry of Organic Silicon Compounds; Patai,
S., Rapoport, Z., Eds., Wiley: Chichester, 1989; Vol. 1, p 57. (b) Kudo,
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Chem., Int. Ed. 2007, 46, 4159.
(18) (a) Gossage, R. A.; McLennan, G. D.; Stobart, S. R. Inorg. Chem.
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S. R. Organometallics 1997, 16, 5669. (c) Bushnell, G. W.; Casado,
M. A.; Stobart, S. R. Organometallics 2001, 20, 601. (d) Zhou, X.;
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(19) MacInnis, M. C.; MacLean, D. F.; Lundgren, R. J.; McDonald, R.;
Turculet, L. Organometallics 2007, 26, 6522.
7178 Inorganic Chemistry, Vol. 47, No. 16, 2008

Silanol-Based Pincer Pt(II) Complexes
satellites at δ ) 5.45 ppm (4JHP ) 8.7 Hz, 1JHSi ) 205 Hz).
The hydrosilane fragment in 7 is directly observed in the
IR-spectrum as a strong broad band at 2139 cm-1.
Scheme 1
The tridentate PSiH2P-ligand 7 readily reacts20 with
(Me2S)2Pt(Me)Cl to give the corresponding bicyclic hydrosi-
lane-Pt(II) chloride complex 8 in 85% yield according to
the 31P{1H} NMR spectra, and in 62% isolated yield after
flash chromatography (FC) (Scheme 1).24–27 For oxygenation
of metallo-hydrosilanes to metallo-silanols only a couple of
peroxidic reagents, namely, dimethyldioxirane5a,b,28 and urea-
hydroperoxide adduct in the presence of catalytic amounts
of MeReO3,29 have proved to be capable of chemoselective
transformations. We found that the hydrosilane complex 8
underwent slow (over one month) autoxidation upon stirring
its benzene solution without protection from air, yielding the
silanol-Pt(II) chloride complex 3 (65%). More efficient and
fast conversion of 8 to 3 in high yield (89% isolated) was
accomplished using the recently developed iridium-catalyzed
hydrolytic oxo-functionalization of silanes (Scheme 1).30
Both complexes 8 and 3, being stable colorless solids after
purification by chromatography, were fully characterized
using multinuclear NMR spectroscopy, IR, and ESI-MS
spectra as well as combustion analysis. A combination of
31P, 195Pt and 29Si NMR spectroscopy clearly evidenced the
connectivity of the heteroatoms and the highly symmetrical
structure of these complexes with trans arrangement of the
equivalent phosphine fragments. Indeed, a C6D6 solution of
complex 8 exhibits a singlet with 195Pt-satellites in the
31P{1H} NMR spectrum at δ ) 68.89 ppm (s, 195Pt satellites
1JPPt ) 2885 Hz), which is slightly shifted downfield to δ )
71.08 ppm (s, 195Pt satellites 1JPPt ) 3025 Hz) in the spectrum
of silanol 3. In the 195Pt{1H} NMR spectrum of complex 8,
a triplet at δ ) -5022 ppm (1JPtP ) 2885 Hz) was observed,
whereas the corresponding triplet in the spectrum of 3 is
slightly shifted to δ ) -4992 ppm (1JPtP ) 3025 Hz, with
29Si satellites 1JSiPt ) 1334 Hz). The very negative values of
195Pt chemical shifts for both complexes, which are near the
high field limit of the region of Pt(II) derivatives, are typical
ized secondary silanols (R2SiHOH, where R ) i-Pr or t-Bu)
to the corresponding low valent transition metal complexes.
This prompted us to construct the tridentate diphosphino-
silanol ligand 6, which, upon treatment with an appropriate
L2Pt(Me)Cl precursor, was expected to provide straightfor-
ward access to 3 (Scheme 1).
The synthetic route starts with the preparation of di-iso-
propyl(ortho-bromophenyl)phosphine (5)21 in 61.5% yield
from the known dichlorophosphine 1,22 as shown in Scheme
1. Our persistent attempts to prepare the diphosphino-silanol
6, through a bromide-to-lithium exchange in 5 followed by
a coupling with HSiCl3 [or with Et2NSi(H)Cl2] and subse-
quent hydrolysis, were unsuccessful.23 On the other hand,
one pot, well-controlled lithiation of 5 with tert-butyl lithium,
followed by coupling with silicon tetrachloride, and subse-
quent reduction of the intermediate silicon chlorides using
LiAlH4, afforded the diphosphino-dihydrosilane PSiH2P
ligand 7 in reasonable yield (63% isolated yield in 3 steps).
The dihydrosilane 7, which was isolated as a colorless oil,
indefinitely stable under inert atmosphere, was characterized
by multinuclear NMR-spectra, IR-spectrum, and electron
spray ionization (ESI) mass-spectra. The 31P{1H} NMR
spectrum of 7 exhibits a singlet at δ ) 3.0 ppm, whereas
the silicon nuclei exhibits in the 29Si-DEPT spectrum a triplet
at δ ) -39.95 ppm because of significant coupling with
the two phosphorus atoms (3JSiP ) 22.5 Hz). In the 29Si-
INEPT spectrum a large coupling constant with protons, 1JSiH
) 205 Hz, was additionally detected. In the 1H NMR spectra
of 7 the H2Si-fragment is observed as a triplet with 29Si-
(24) Even better (up to 95%) NMR yield of complex 8 was observed in
the reactions of ligand 7 with freshly prepared and purified by FC
(NBD)Pt(Me)Cl. However, this reaction is hardly reproducible.
Therefore, for preparative purposes the use of (Me2S)2Pt(Me)Cl is
preferable.
(25) To the best of our knowledge, this is the first reported application of
any dihydrosilane pincer ligands of type ESiH2E (E ) P, N, S, etc.)
for preparation of organometallic compounds. For additions of
NSiH(Me)N and PSiH(Me)P monohydrosilane tridentate ligands to
late transition metal complexes, see refs 17-19.
(26) For recent reviews on transition metal complexes based on (phosphi-
noalkyl)silanes as bidentate ligands, see. (a) Okazaki, M.; Ohshitanai,
S.; Iwata, M.; Tobita, H.; Ogino, H. Coord. Chem. ReV. 2002, 226,
167. (b) Balakrishna, M. S.; Chandrasekaran, P.; George, P. P. Coord.
Chem. ReV. 2003, 241, 87.
(20) For a comprehensive review regarding oxidative additions of hydrosi-
lanes to transition metal complexes, see Corey, J. Y.; Braddock-
Wilking, J. Chem. ReV. 1999, 99, 175.
(27) For a recently reported oxidative addition of tris(phosphino)hydrosilane
as a tetradentate ligand to Mes4Fe2, see Mankad, N. P.; Whited, M. T.;
Peters, J. C. Angew. Chem., Int. Ed. 2007, 46, 5768.
(21) It was mentioned that di-iso-propyl(ortho-bromophenyl)phosphine (5)
was prepared in good yield by monolithiation of ortho-dibromobenzene
followed by coupling with i-Pr2PCl. The suggested method gave only
poor results in our hands. Neither experimental details nor any
characterization of 5 was reported in this article. See Tamm, M.;
Drebel, B.; Baum, K.; Lu¨gger, T.; Pape, T. J. Organomet. Chem. 2003,
677, 1.
(28) (a) Adam, W.; Malisch, W.; Roschmann, K. J.; Saha-Moller, C. R.;
Schenk, W. A. J. Organomet. Chem. 2002, 661, 3. (b) Malisch, W.;
Voegler, M.; Schumacher, D.; Nieger, M. Organometallics 2002, 21,
2891. (c) Moeller, S.; Fey, O.; Malisch, W.; Seelbach, W. J.
Organomet. Chem. 1996, 507, 239.
(22) (a) Talay, R.; Rehder, D. Z. Naturforsch. 1981, 36B, 451. (b) Chiswell,
B.; Venanzi, L. M. J. Chem. Soc. (A) 1966, 417.
(29) Malisch, W.; Jehle, H.; Mitchel, C.; Adam, W. J. Organomet. Chem.
1998, 566, 259.
(23) As far as we are aware, there are no publications on synthesis of any
functionalized secondary silanols until now.
(30) Lee, Y.; Seomoon, D.; Kim, S.; Han, H.; Chang, S.; Lee, P. H. J.
Org. Chem. 2004, 69, 1741.
Inorganic Chemistry, Vol. 47, No. 16, 2008 7179

Korshin et al.
and constrained molecular structure, the Pt-Si distance in
3 [2.2773(10) Å] is about 0.02 Å shorter than the conven-
tional range of Pt-Si single bonds (2.30-2.40 Å)24,33,34 and
very similar to the value of the PtdSi bond in cationic
Fischer-type platinum silylene [2.270(2) Å].35 The strong
trans effect of the silyl ligand36 causes considerable elonga-
tion (0.04 Å) of the Pt(1)-Cl bond to 2.4694(9) Å in 3 as
compared with the corresponding bond length in the pincer-
type PCP-Pt(II) chlorides.37
In agreement with the X-ray data, the strong trans effect
of the silyl ligand labilizes the Pt(II)-Cl bond in complex
3. Indeed, exchange of the chloride ligand by less nucleo-
philic anions in pincer-type PCP complexes requires ap-
plication of the appropriate silver salts.37b–d In contrast to
that, treatment of the PSiP-type Pt(II) chloride complex 3
with the salt KB(C6F5)4 resulted in chloride abstraction by
the K+ cation and quantitative formation of the corresponding
cationic Pt(II)-silanol 9 (in 95% purity) bearing the non
nucleophilic (C6F5)4B- anion (eq 2).
Figure 1. Crystal structure of complex 3. Ellipsoids are at 50% probability
level. Hydrogen atoms except hydroxyl were omitted for clarity.
Table 1. Selected Bond Lengths (Å) and Bond Angles (Degrees) of
Complex 3
Pt(1)-Si(1)
Pt(1)-Cl
Pt(1)-P(1)
Pt(1)-P(2)
2.2773 (10)
2.4694 (9)
2.2892 (9)
2.2957 (9)
Si(1)-O(1)
Si(1)-C(1)
Si(1)-C(7)
1.652 (3)
1.883 (4)
1.880 (4)
Si(1)-Pt(1)-Cl
Si(1)-Pt(1)-P(1)
Si(1)-Pt(1)-P(2)
P(1)-Pt(1)-P(2)
P(1)-Pt(1)-Cl
P(2)-Pt(1)-Cl
175.08 (4)
84.35 (3)
84.12 (3)
161.70 (3)
95.50 (3)
97.18 (3)
O(1)-Si(1)-Pt(1)
O(1)-Si(1)-C(1)
O(1)-Si(1)-C(7)
C(1)-Si(1)-C(7)
Pt(1)-Si(1)-C(1)
Pt(1)-Si(1)-C(7)
112.70 (11)
105.99 (16)
108.08 (16)
114.53 (17)
108.76 (12)
106.92 (13)
Although formally a 14-electron complex with a nonco-
ordinating counteranion and solvent (C6H5F), compounds 9
is relatively stable in the solid state, as well as in CD2Cl2,
C6D6 or C6H5F solutions under standard anaerobic anhydrous
conditions. It may be stabilized by agostic interaction with
the i-Pr groups, although we have no evidence for that. The
31P{1H} NMR spectrum of 9 exhibits singlets with 195Pt
satellites at δ ) 73.12 ppm (1JPPt ) 3097 Hz) in CD2Cl2
and 72.84 ppm (1JPPt ) 3105 Hz) in C6H5F, which are
surprisingly little shifted downfield in comparison to the
parent Pt(II)-Cl complex 3 (δP ) 71.08 ppm in CD2Cl2).38
It should be mentioned that in the more studied pincer-type
PCP Pt(II) complexes the common differences ∆δP between
cationic and neutral Pt(II)-Cl complexes are as large as 10
for Pt(II)-silyl complexes31 and indicate high electron density
at the metal center.32 In the 29Si NMR spectra (obtained using
29Si-1H HMBC sequence) both complexes 8 and 3 give rise
to broadened singlets accompanied by one-bond coupling
195Pt satellites at δ ) 12.27 ppm (195Pt satellites 1JSiPt ) 1190
Hz) and δ ) 38.53 ppm (195Pt satellites JSiPt ) 1335 Hz),
1
respectively. In the 29Si-DEPT NMR (which is more sensitive
to small coupling constants) of the hydrosilane complex 8,
the mentioned above broadened singlet is resolved into a
2
triplet with JSiP ) 5.2 Hz and the same as before 195Pt
satellites, while a 29Si-INEPT experiment revealed addition-
ally the direct Si-H coupling constant, 1JSiH ) 183 Hz. The
diagnostic pattern of the Si-H proton of 8 was observed in
both 1H and 1H{31P} NMR spectra as a broadened singlet at
5.75 ppm with 195Pt and 29Si satellites 2JHPt ) 38.8 Hz, 1JHSi
) 183 Hz.
(33) Tilley T. D. In The Silicon-Heteroatom Bond; Patai, S., Rappoport,
Z. , Eds.; Wiley: New York, 1991, pp. 245-307, pp 309-364.
(34) Lukevics, E.; Arsenyan, P.; Pudova, O. Main Group Metal Chem. 2002,
25, 541.
(35) Grumbine, S. D.; Tilley, T. D.; Arnold, F. P.; Rheingold, A. L. J. Am.
Chem. Soc. 1993, 115, 7884.
The molecular structure of the first pincer-type metallo-
silanol complex 3 was defined by a single crystal X-ray
analysis (Figure 1, Table 1). The platinum center exhibits a
significantly distorted square planar geometry, while the
silicon center adopts a distorted tetrahedral structure, con-
siderably compressed toward planarity. Because of the rigid
(36) (a) Aizenberg, M.; Milstein, D. J. Am. Chem. Soc. 1995, 117, 6456.
(b) Eizen, M. S. In The Chemistry of Organic Silicon Compounds;
Rapoport, Z., Apeloig, Y., Eds.; Wiley: Chichester, 1998; Vol. 2, p
2037; and references therein.
(37) See, for example, (a) Poverenov, E.; Leitus, G.; Shimon, L. J. W.;
Milstein, D. Organometallics 2005, 24, 5937. (b) Schwartsburd, L.;
Poverenov, E.; Shimon, L. J. W.; Milstein, D. Organometallics 2007,
26, 2931. (c) Vuzman, D.; Poverenov, E.; Diskin-Posner, Y.; Leitus,
G.; Shimon, L. J. W.; Milstein, D. Dalton Trans. 2007, 5692. (d) Gorla,
F.; Venanzi, L. M.; Albinati, A. Organometallics 1994, 13, 43.
(38) For a few examples of CH2Cl2 coordination to cationic late transition
metal complexes, see (a) Taw, F. L.; White, R. C.; Bergman, R. G.;
Brookhart, M. J. Am. Chem. Soc. 2002, 124, 4192. (b) Gandelman,
M.; Konstantinovski, L.; Rosenberg, H.; Milstein, D. Chem.sEur. J.
2003, 9, 2595.
(31) See, for example, (a) Yamashita, H.; Tanaka, M.; Goto, M. Organo-
metallics 1997, 16, 4696. (b) Chan, D.; Duckett, S. B.; Heath, S. L.;
Khazal, I. G.; Perutz, R. N.; Sabo-Etienne, S.; Timmins, P. L.
Organometallics 2004, 23, 5744.
(32) (a) Still, B. M.; Kumar, P. G. A.; Aldrich-Wright, J. R.; Price, W. S.
Chem. Soc. ReV. 2007, 36, 665. (b) Pregosin, P. S. Coord. Chem. ReV.
1982, 44, 247.
7180 Inorganic Chemistry, Vol. 47, No. 16, 2008

Silanol-Based Pincer Pt(II) Complexes
Table 2. Selected Bond Lengths (Å) and Bond Angles (Degrees) of
Complex 10
Pt(1)-Si(1)
Pt(1)-P(1)
Pt(1)-P(2)
Pt(1)-C(25)
2.3650 (6)
2.3281 (6)
2.3225 (7)
1.994 (3)
Si(1)-O(1)
Si(1)-C(1)
Si(1)-C(7)
C(25)-O(2)
1.652 (2)
1.870 (3)
1.871 (3)
1.111 (3)
Si(1)-Pt(1)-C(25)
Si(1)-Pt(1)-P(1)
Si(1)-Pt(1)-P(2)
P(1)-Pt(1)-P(2)
P(1)-Pt(1)-C(25)
P(2)-Pt(1)-C(25)
Pt(1)-C(25)-O(2)
173.43 (8)
82.32 (2)
82.07 (2)
161.23 (2)
97.41 (8)
99.29 (8)
174.5 (3)
O(1)-Si(1)-Pt(1)
O(1)-Si(1)-C(1)
O(1)-Si(1)-C(7)
C(1)-Si(1)-C(7)
Pt(1)-Si(1)-C(1)
Pt(1)-Si(1)-C(7)
113.73 (7)
102.93 (11)
108.20 (11)
116.86 (12)
108.43 (8)
106.91 (8)
Pt-Si bond in the Pt(II)-carbonyl complex 10 is elongated
as compared to the Pt-Si bond in the platinum chloride
complex 3 [2.3650 (9) Å in 10 vs. 2.2773 (10) Å in 3]. This
elongation enlarges the distortion of the Pt(II) center from a
square planar arrangement. The Pt-CO bond length in the
silanol complex 10 is considerably longer than the corre-
sponding distances in the reported PCP-type Pt(II) carbonyls
(1.99 Å vs 1.89-1.93 Å).37b,c The C-O bond distance in
the Pt(II)-bound CO ligand in 10 is 1.111 (3) Å. This distance
is even shorter than the reported experimental bond length
of the free molecule of carbon monoxide (1.128 Å),39
indicating weak bonding of the carbonyl ligand to the Pt(II)
center.
2. Base-Induced Rearrangements of Neutral and
Cationic Pt(II)-Silanols. According to the structure com-
prising nucleophilic silanol and electrophilic Pt(II) chloride
centers, complex 3 was expected to exhibit dual reactivity.
While it did not react with of Et3N (in C6D6 and CD2Cl2) at
ambient temperature, upon treatment with strong non-
nucleophilic bases, complex 3 readily underwent unexpected
rearrangement and head-to-head dimerization to afford the
binuclear complex 11 as a major product rather than to give
the common head-to-tail type oligomerization products (eq
3). Thus, upon addition of 1 equiv of KN(SiMe3)2 to a
solution containing complex 3 and a catalytic amount of 18-
crown-6 (0.07 equiv) in ether-THF (conditions a), 31P NMR
monitoring of the reaction progress revealed that only about
10% of the starting 3 still remained after 12 h at -30 °C,
while the novel complex 11 formed in about 65% NMR
yield. Stirring the reaction mixture for an additional hour at
ambient temperature resulted in complete consumption of
complex 3 and simultaneous increase of the complex 11
content to about 75% yield. Running the reaction in the
absence of 18-crown-6 gave the product 11 in lower yield
(ca. 55%) after 12 h at -30 °C followed by 2.5 h at RT.
Practically the same yield of the binuclear complex 11 was
observed upon using potassium tert-butoxide in THF (condi-
tions b, eq 3). The yield values given in eq 3 are of the pure
complex 11 isolated as a colorless solid after anaerobic
chromatography on Florisil.
Figure 2. Crystal structure of complex 10. The (C6F5)4B-anion and all the
hydrogen atoms except hydroxyl were omitted for clarity. The thermal
ellipsoids are at 50% probability level.
ppm.37a–c Such a small ∆δP value in complexes 9 versus 3
might be a result of an efficient compensation of positive
charge by an increase of bonding from the silicon atom to
the positively charged platinum atom in cationic complex
9, although this is not supported by the observed NMR
shielding of the Si and Pt nuclei. Actually, the platinum
nucleus in 9 is observed as a triplet at -5075 ppm (1JPtP
)
3100 Hz) in the 195Pt{1H} NMR spectrum, and the silicon
nucleus is detected in the 29Si-1H HMBC spectrum as a
broadened singlet with characteristic 195Pt satellites at 25.24
ppm (1JSiPt ) 1478 Hz).
Complex 9 reacts rapidly with carbon monoxide to give
the Pt(II)-carbonyl complex 10 (eq 2). Because of the trans
influence of the silyl group, in addition to the cationic nature
of the complex, binding of CO is weak, and vacuum
treatment of the carbonyl complex 10 led to the recovered
precursor 9 (70% decarbonylation after 3 days at 1 mmHg).
The IR spectrum of complex 10 displays a distinctive band
at 2087 cm-1, corresponding to the CO ligand, and a very
broad band centered at 3470 cm-1 (ν O-H). The 31P{1H}
NMR spectrum of 10 exhibits a low-field shifted singlet at
82.24 ppm with a decreased value of the coupling constant
(1JPPt ) 2736 Hz). The same tendency was also observed in
PCP-type Pt(II) complexes.37a–c Rather unexpectedly, the Pt
nucleus is significantly shifted upfield to δ ) -5295 ppm (t
with 29Si satellites, 1JPtP ) 2736 Hz, 1JPtSi ) 980 Hz) in the
195Pt{1H} NMR spectra of 10, while the silicon nucleus is
deshielded and appears at 57.36 ppm (br s singlet with 195Pt
satellites, 1JSiPt ) 977 Hz). The decreased value of the 1JSiPt
coupling constant reflects considerable weakening of the
Pt-Si bond in 10.
The binuclear complex 11 is stable under neutral
anaerobic conditions and was fully characterized by a
combination of multinuclear NMR spectroscopy, IR, ESI
mass-spectroscopy, and by single-crystal X-ray crystal-
The molecular structure of complex 10 was confirmed by
an X-ray diffraction study (Figure 2, Table 2). Colorless
single crystals suitable for X-ray analysis were obtained upon
partial concentration of a C6D6 solution of 10 at RT. The
strong trans effects of both silicon and carbonyl ligands are
well reflected in the molecular structure of 10. Indeed, the
(39) Goldman, A. S.; Krogh-Jespersen, K. J. Am. Chem. Soc. 1996, 118,
12159.
Inorganic Chemistry, Vol. 47, No. 16, 2008 7181

Korshin et al.
lography. Complex 11 may be viewed as consisting of
two units: the original silanol-Pt(II)-chloride fragment
(A) and rearranged silanolate-Pt(II)-hydride fragment (B),
which are connected by a disiloxane bridge. While NMR,
IR, and X-ray patterns of the fragment A in complex 11
are similar to those of the parent complex 3, the corre-
sponding features of the fragment B are very distinctive.
Indeed, the 31P{1H} NMR spectrum of complex 11 in C6D6
shows a singlet at 69.75 ppm (195Pt satellites 1JPPt ) 3060
Hz, fragment A), and a broadened singlet in a higher field
Figure 3. Crystal structure of the binuclear complex 11. Hydrogen atoms
except Pt(II)-hydride were omitted for clarity. Ellipsoids are at 50%
probability level.
1
at 52.29 ppm (195Pt satellites JPPt ) 2844 Hz, fragment
Table 3. Selected Bond Lengths (Å) and Bond Angles (degrees) of the
Binuclear Complex 11
B). The broadening results from the incomplete decoupling
with the hydride ligand that appears in the 1H NMR spectra
as a triplet at -18.31 ppm (2JHP ) 12.4 Hz, with 195Pt
satellites 1JHPt ) 1180 Hz) or as the corresponding singlet
with the same 195Pt satellites in the 1H{31P} NMR spectra.
In the 29Si NMR spectra (29Si-1H HMBC) the silicon
nucleus of the fragment A appears as a broadened singlet
with 195Pt satellites at 23.64 ppm (1JSiPt ) 1416 Hz),
whereas a broad singlet of the silicon nucleus in the
fragment B appears in a higher field (δ ) -56.83 ppm)
and without pronounced 195Pt satellites (2JSiPt e 100 Hz).
The 195Pt{1H} NMR spectrum of complex 11 exhibits a
triplet at -4975 ppm (1JPtP ) 3060 Hz), which is
characteristic of the platinum nucleus of fragment A. The
platinum pattern in fragment B is observed using the more
sensitive and selective (for platinum hydrides) 195Pt-1H
HMQC experiment, which reveals a doublet of triplets at
fragment A
fragment B (bonding)
Pt(1)-Si(1)
2.269(3)
2.472(3)
2.286(2)
2.294(2)
1.884(9)
1.910(10)
Pt(2)-O(2)
2.131(6)
1.58(7)
Pt(1)-Cl
Pt(2)-H(2Pt)
Pt(1)-P(1)
Pt(1)-P(2)
Si(1)-C(1)
Si(1)-C(7)
Pt(2)-P(3)
2.271(2)
2.271(2)
1.596(7)
1.915(9)
1.902(9)
173(3)
87.97(17)
88.60(18)
162.02(11)
100.4(3)
114.5(4)
113.6(4)
111.9(3)
Pt(2)-P(4)
Si(2)-O(2)
Si(2)-C(25)
Si(2)-C(31)
Si(1)-Pt(1)-Cl
Si(1)-Pt(1)-P(1)
Si(1)-Pt(1)-P(2)
P(1)-Pt(1)-P(2)
P(1)-Pt(1)-Cl
176.15(9)
85.52(10)
82.14(9)
160.20(12)
96.33(9)
96.96(9)
109.4(3)
105.3(3)
113.8(4)
114.1(2)
107.5(3)
107.0(3)
O(2)-Pt(2)-H(2Pt)
O(2)-Pt(2)-P(3)
O(2)-Pt(2)-P(4)
P(3)-Pt(2)-P(4)
Pt(2)-O(2)-Si(2)
O(2)-Si(2)-C(25)
O(2)-Si(2)-C(31)
O(1)-Si(2)-O(2)
P(2)-Pt(1)-Cl
Pt(1)-Si(1)-C(1)
Pt(1)-Si(1)-C(7)
C(1)-Si(1)-C(7)
O(1)-Si(1)-Pt(1)
O(1)-Si(1)-C(1)
O(1)-Si(1)-C(7)
fragment B (nonbonding)
Pt(2) · · ·Si(2) 2.884(3)
O(2)-Pt(2)· · ·Si(2)
O(2)-Si(2)· · ·Pt(2)
32.97(18)
46.6(2)
1
-4558 ppm (1JPtH ) 1180 Hz, JPtP ) 2845 Hz). A broad
Disiloxane Bridge
medium intensity IR band at ν ) 2204 cm-1 is attributable
to the Pt-H bond. In the high resolution ESI-MS an
intensive protonated molecular ion m/z+ 1288.3162
[M + H+] is detected which corresponds to the composi-
tion C48H74ClO2P4195Pt196PtSi2. The less intensive positive
[M + H+] ions related to the correct isotope pattern are
also observed. The most intensive positive ions in the low-
resolution ESI mass-spectra are of m/z+ 1251 (65%) and
1252 (100%), both originating from [M+ - Cl] (the correct
isotope pattern), hence additionally confirming the com-
position of complex 11.
Si(1)-O(1)
Si(2)-O(1)
1.655(6)
1.638(6)
Si(1)-O(1)-Si(2)
137.8(4)
the Pt(1)-Cl bond to 2.472 (3) Å. The parameters of the
two bridging bonds Si(1)-O(1) and Si(2)-O(1), as well as
the Si(1)-O(1)-Si(2) angle, are typical for disiloxanes.40
In the newly formed Pt(II)-H fragment B the Pt(2) center
has a considerably distorted square planar geometry with a
P(3)-Pt(2)-P(4) angle of 162.02 (12)°, whereas the less
constrained Si(2) center in this fragment adopts a geometry
closer to tetrahedral than in both fragment A and in complex
3. The Pt(2)-O(2) bond in the fragment B of complex 11 is
lengthened by 0.04 Å (to 2.131 (6) Å) in comparison to the
corresponding bonds in the few reported acyclic Pt(II)-sila-
nolates (1.99-2.09 Å).41 A remarkably short Si(2)-O(2)
bond in complex 11 [1.596 (7) Å] is distinctive of
X-ray quality colorless crystals of complex 11 were
obtained upon cooling of a concentrated hexane solution at
-15 °C for two weeks. The X-ray diffraction data (Figure
3, Table 3) show a binuclear complex, containing two
different symmetrical fragments A and B, as discussed above,
linked to each other through a disiloxane bridge. The
geometry of the Pt(II)-Cl fragment A in the binuclear
complex 11 is very similar to the structure of the parent
Pt(II)-Cl complex 3, with a minor shortening of the
Pt(1)-Si(1) bond to 2.269 (3) Å, and a slight elongation of
(40) Kaftory, M.; Kapon, M.; Botoshansky, M. In The Chemistry of Organic
Silicon Compounds; Rappoport, Z., Apeloig, Y. , Eds.; Wiley:
Chichester, 1998; Vol. 2, p 181.
(41) (a) Mintcheva, N.; Nishihara, Y.; Mori, A.; Osakada, K. J. Organomet.
Chem. 2001, 629, 61. (b) Fukuoka, A.; Sato, A.; Kodama, K.; Hirano,
M.; Komiya, S. Inorg. Chim. Acta 1999, 294, 266.
7182 Inorganic Chemistry, Vol. 47, No. 16, 2008

Silanol-Based Pincer Pt(II) Complexes
Scheme 2
Pt(II)-silanolate complexes (1.56-1.59 Å).41 The unusual
geometry of the middle part fragment B in complex 11,
including the angle Pt(2)-O(2)-Si(2) of 100.4 (3)° and the
resulting rather short Pt(2) · · · Si(2) distance of 2.884 (3) Å
might lead to an impression of a Pt(2) · · · Si(2) bonding
interaction involving a Pt(2)-O(2)-Si(2) three-membered
ring, related to the calculated structure for a Pt-silanone
adduct.13a However, no spectroscopic indications for a
Pt(2)· · · Si(2) interaction have been found.
attack, as well as formation of the Pt-H fragment, can be
rationalized in terms of the mechanism shown in Scheme 2.
Taking into account a formal analogy with construction
of epoxides, the negatively charged oxygen atom in the
silanolate Pt(II)-chloride complex 13′′could attack intramo-
lecularly the electrophilic Pt(II) center to form a three-
membered cyclic intermediate 14′′. Although the X-ray data
for the neutral silanol complex 3 (Figure 1) indicated that
the geometry is not very favorable for such a direct
cyclization, in the silanolate complex 13 the negatively
charged oxygen could move more closely to the electrophilic
Pt(II) atom up to the auspicious bonding distance. Alterna-
tively, as shown in 13′, an electron density shift from
negatively charged oxygen to silicon atom could induce
cleavage of the Si-Pt σ-bond, with concomitant reduction
of the metal center, to form the silanone-type Pt(0) inter-
mediate 14′. The conversion 13f14 can be driven by the
irreversible extrusion of KCl from the ionic potassium
silanolate 13.42–44 The intramolecular binding of the silanone
moiety in the postulated intermediate 14′ (or 14′′) might
Although the mechanism of this unusual rearrangement
and head-to-head coupling has not been elucidated, the
intermediate generation of an intramolecularly coordinated
silanone looks like the most reasonable explanation of our
experimental results (Scheme 2). Indeed, generation of the
fragment B in the binuclear complex 11 ultimately requires
a nucleophilic attack of the silanolate-anion (or silanol
functionality itself) onto silicon atom, whereas its electro-
philicity in complex 3 is expected to be negligible. On the
other hand, the Pt(II) reaction center in the Pt(II)-Cl complex
3 is electrophilic in nature. In fact, the additionally labilized
chloride ligand in 3 is readily abstracted by K+B(C6F5)4 ,
-
(42) It looks like the ionic nature of the potassium silanolate 13 is essential
for the overall set of transformations 3f13f14fff11 (Scheme
2). For instance, our efforts to obtain the binuclear complex 11 by
deprotonation of 3 by t-BuLi (THF, -30 °C) via the lithium analogue
of 13 failed. Our attempts to induce release of di-tert-butylsilanone
from the silanol Pt(II)-OTf complex 1 (eq 1, R ) t-Bu) by
deprotonation with organolithium reagents were also unsuccessful:
Goikhman, R. ; Milstein, D. , unpublished results.
as described above (eq 2). Therefore, deprotonation of 3 to
13 was expected to result in a common intermolecular
nucleophilic substitution of chloride ligand at Pt(II) with the
silanolate moiety, leading to the head-to-tail type oligomer
12, unless the silicon atom is somehow activated toward
nucleophiles. Moreover, the conversion of the Pt-Cl to Pt-H
in the absence of an obvious hydride source is unexpected.
The significant activation of silicon atom toward nucleophilic
(43) A considerably covalent (vide infra) lithium silanolate, intermolecularly
bound to a Ir(III)-Cl complex, was found to undergo dimerization to
a Li-O-Li-O square-type dimer rather than release silanone and
LiCl, even in the presence of 12-crown-4 (ref 6).
Inorganic Chemistry, Vol. 47, No. 16, 2008 7183

Korshin et al.
provide the required additional thermodynamic stabilization
of these species. Although we are unaware of transformations
related to 13′f14′ in silicon- or in transition metal chemistry,
this process could be considered as a specific variant of a
base-induced Hoffmann elimination. Reactions of this type
proceed efficiently under very mild conditions, for instance,
in the case of R-hydroxyalkylphosphonium salts to give the
corresponding tertiary phosphines and the carbonyl
compounds.45a Few similar degradations of R-hydroxyalkyl-
sulfonium salts have been also reported.45b,c
Being reasonably stabilized toward oligomerization, the
silanone intermediate 14′/14′′ bearing a highly electrophilic
silicon atom could undergo intermolecular nucleophilic attack
by the silanolate 13 to form the binuclear siloxy-silanolate
intermediate 15. The latter can undergo an intramolecular
attack on the metal to give an anionic, formally Pt(0)/Pt(II)
binuclear intermediate 16. Finally, the anionic Pt(0) complex
16 is protonated by HN(SiMe3)2 (or t-BuOH) to give the
isolated binuclear Pt(II)-hydride product 11.46,47 Alterna-
tively, albeit being significantly less basic in comparison to
HN(SiMe3)2, the silanolate 15 could be reversibly protonated
by HN(SiMe3)2 to the corresponding silanol, which might
undergo probably irreversible oxidative addition to the neutral
Pt(0) center to yield the final Pt(II)-hydride 11.48
would undergo intramolecular transformation to the platinum-
silanone adduct 14 more effectively than the Pt-Cl silanolate
13, but would be at the same time a considerably weaker
nucleophile in the intermolecular processes. However, treat-
ment of the cationic complex 9 with various amounts of
KN(SiMe3)2 (from 0.4 to 1.1 equiv) in THF always afforded
a complex mixture of Pt products. In contrast, in the presence
of excess of the weaker base i-Pr2NEt (3.6 equiv) in the non-
coordinating solvent fluorobenzene, complex 9 was ef-
ficiently converted to complex 17 (g60% NMR yield) over
14 days at ambient temperature (eq 4).
The mononuclear hydroxysilanolate Pt(II)-hydride com-
plex 17 was isolated as a colorless waxy solid in about 35%
yield (>95% 31P NMR purity)49 by extraction from the
evaporated reaction mixture. The spectroscopic characteristics
(multinuclear NMR and IR spectra) of complex 17 are very
similar to the corresponding features of the fragment B in
the binuclear complex 11 (see above). Indeed, in the 31P{1H}
NMR spectrum of complex 17 in C6D6 a broadened singlet
Our efforts aimed at observation of the silanone-type
intermediates 14 prompted us to consider the option of
retarding the bimolecular nucleophilic attack of the silanolate
13 in the process leading to the binuclear complex 11. One
possibility is applying higher dilution. Indeed, reaction of
the silanol complex 3 with KN(SiMe3)2, upon 4.3 times
dilution (initial concentration 0.003 M vs 0.013 M), gave a
1
at 49.99 ppm with typical 195Pt satellites, JPPt ) 2857 Hz,
1
is observed. The hydride ligand appears in the H NMR
spectra as a triplet with 195Pt satellites at -19.32 ppm (2JHP
considerably lower amount of the binuclear 11 (ca. 30% 31
P
1
) 12.7 Hz, JHPt ) 1217 Hz), which is transformed to a
singlet with the corresponding 195Pt satellites in the 1H{31P}
NMR spectra. In the 195Pt-1H HMQC NMR spectra a doublet
NMR-yield), but a new Pt(II)-hydride, complex 17 (ca.
30%), was also formed. A further 3-fold dilution resulted in
a slightly higher yield of complex 17 (ca. 40%) at the expense
of the dimer 11 (ca. 10%). However, the insufficient content
of 17 and its instability toward chromatography still pre-
vented its isolation and characterization. Next, we employed
the cationic silanol Pt(II) complex 9, assuming that the
silanolate which would be obtained upon its deprotonation
1
of triplets at -4566 ppm (1JPtH ) 1220 Hz, JPtP ) 2858
Hz) is detected. The 29Si-1H HMBC spectra exhibit the
silicon nucleus resonance at -54.98 ppm as a broadened
singlet. A broad, medium intensity IR band at ν ) 2200 cm-1
is attributed to Pt-H bond, whereas a very broad band
centered at ν ) 3420 cm-1 corresponds to the O-H bond.
In the ESI mass-spectra of complex 17, the ions of m/z+
1287 (74%) and 1288 (100%) are detected, both related to
[2 M + H+] species (the correct isotope pattern).
(44) A lithium silanolate complex of Os(II) -Cl was recently isolated:
Albrecht, M.; Kwok, W.-H.; Lu, G.-L.; Rickard, C. E. F.; Roper,
W. R.; Salter, D. M.; Wright, L. J. Inorg. Chim. Acta 2005, 358, 1407.
(45) (a) Cristau, H. J., Ple´nat, F. In The Chemistry of Organophosphorus
Compounds; Hartley, F. R., Ed.; Wiley: Chichester, 1994; Vol. 3, p
45. (b) Knipe, A. C. In The Chemistry of Sulphonium Group; Stirling,
C. J. M., Ed.; Wiley: Chichester, 1981; Vol. 1, p 313. (c) Nenaidenko,
V. G.; Balenkova, E. S. Russ. J. Org. Chem. 2003, 39, 291.
(46) An unstable Pt(0) anionic complex was reported. It reacts with
electrophiles to form Pt(II) complexes. See Reger, D. L.; Ding, Y.
Organometallics 1994, 13, 1047.
Complex 17 was probably formed by nucleophilic attack
of adventitious water on the electrophilic silicon center in
the silanone-type intermediate 14 (eq 4), followed by a
sequence of steps as discussed above for formation of the
dimer 11. The mononuclear silanol complex 17 exhibits
considerable chemical lability in comparison to the structur-
ally related dimer 11. For example, the dimer 11 does not
reveal any changes upon chromatography on Florisil, whereas
its mononuclear counterpart 17 completely decomposed
under these conditions. Moreover, while the purified dimer
11 is stable at ambient temperature under anaerobic condi-
(47) We have recently prepared an anionic pincer-type Pt(0) complex that
undergoes facile protonation to give the corresponding Pt(II) hydride:
Schwartsburd, L.; Cohen, R.; Konstantinovski, L.; Milstein, D. Angew.
Chem., Int. Ed. 2008, 47, 3603.
(48) We are unaware of reported examples of O-H oxidative addition of
silanols to low-valent late transition metals. For oxidative addition of
water and alcohols to Pt(0) complexes, see (a) Yoshida, T.; Matsuda,
T.; Okano, T.; Kitani, T.; Otsuka, S. J. Am. Chem. Soc. 1979, 101,
2027. (b) Di Bugno, C.; Pasquali, M.; Leoni, P.; Sabatino, P.; Braga,
D. Inorg. Chem. 1989, 28, 1390. (c) For recent studies on addition of
water and alcohols to Ir(I) complexes, see Blum, O.; Milstein, D. J. Am.
Chem. Soc. 2002, 124, 11456. (d) Dorta, R.; Rosenberg, H.; Shimon,
L. J. W.; Milstein, D. Chem.sEur. J. 2003, 9, 5237.
(49) A small amount (2-3%) of i-Pr2NEt·HB(C6F5)4 impurity, as well as
residual traces of solvent, were observed in the 1H NMR spectrum of
complex 17. The i-Pr2NEt·HB(C6F5)4 contaminant was also detected
in both positive and negative modes ESI mass-spectra.
7184 Inorganic Chemistry, Vol. 47, No. 16, 2008

Silanol-Based Pincer Pt(II) Complexes
molecular sieves. The startings (ortho-bromophenyl)dihlorophos-
phine (4)22 and the metal complexes (Me2S)2Pt(Me)Cl51 and
[(COD)IrCl]252 were prepared according to the literature procedures.
Potassium tetra-kis(pentafluorophenyl)borate was prepared by the
essential modification (see below) of the previously reported
method.53
tions for weeks in a C6D6 solution and for months at -30
°C, the isolated monomer 17 partially decomposed (ca. 25%)
after 1 day in C6D6 at RT, and decomposed completely after
15 days at -30 °C (being kept as a solid or in frozen
C6D6).49,50
1
Analysis. H, 13C, and 31P NMR spectra were recorded at 500,
Summary
126, and 202 MHz, respectively, using a Bruker Avance-500 NMR
spectrometer, or at 400, 101, and 162 MHz, respectively, using a
Bruker Avance-400 NMR spectrometer. 29Si NMR spectra were
recorded at 99.5 MHz (Bruker Avance-500 NMR spectrometer) or
at 79.5 MHz (Bruker Avance-400 NMR spectrometer) using 29Si
DEPT, INEPT, and 29Si-1H HMBC experiments. 195Pt NMR spectra
were recorded at 107.5 MHz using a Bruker Avance-500 NMR
spectrometer; 195Pt{1H}- and 195Pt-1H HMQC NMR experiments
were conducted. 11B NMR spectra were measured on a Bruker
Avance-500 NMR spectrometer at 160.5 MHz, whereas 19F NMR
spectra were recorded on a Bruker Avance-250 NMR spectrometer
at 235.5 MHz. All measurements were done at ambient temperature.
1H, 13C, and 29Si NMR chemical shifts are reported in ppm relative
to tetramethylsilane (0 ppm). 1H NMR chemical shifts were
referenced to the residual hydrogen signal of the deuterated solvents
(δ ) 7.15 ppm for benzene, 5.32 ppm for dichloromethane, and
7.26 ppm for chloroform). In 13C NMR measurements the signals
of C6D6 (128.00 ppm), CD2Cl2 (53.80 ppm), or CDCl3 (77.00 ppm)
were used as internal references. 29Si chemical shifts were
referenced to an external CDCl3 solution of triphenylsilane (-17.8
ppm). 31P NMR chemical shifts are reported in ppm relative to
H3PO4 and were referenced to an external 85% solution of
phosphoric acid in D2O (0 ppm). 195Pt chemical shifts are reported
in ppm relative to Na2PtCl6 (0 ppm) and referenced to an external
concentrated solution of Na2PtCl4 in D2O (-1620 ppm). 11B
chemical shifts are reported in ppm relative to neat BF3 ·Et2O (0
ppm), which was used as an external standard. 19F chemical shifts
are reported in ppm relative CFCl3 and were referenced to an
external standard C6F6 (-163.0 ppm). Screw-cup 5 mm NMR tubes
were used in the NMR follow-up experiments. Abbreviations used
in the description of NMR data are as follows: Ar, aryl; br,
broad(ened); v, virtual; s, singlet; d, doublet; t, triplet; m, multiplet;
sym, symmetrical.
Exploring the possibility of generation of a silanone
stabilized by intramolecular coordination to platinum, pincer-
type silane- and silanol-Pt(II) complexes based on the new
PSiH2P tridentate ligand 7 were efficiently prepared. Treat-
ment of the structurally characterized platinum-silanol com-
plex 3 with a strong base resulted in an unprecedented
multistep rearrangement-coupling process leading finally to
thestructurallycharacterizedbinuclearsilanolatePt(II)-hydride
complex 11. We believe that a likely key intermediate in
the overall sequence of events is the postulated silanone 14,
being especially responsible for the coupling and rearrange-
ment steps. An analogous weak base-induced rearrangement
of the cationic Pt(II)-silanol complex 9 in the noncoordi-
nating fluorobenzene solvent to a mononuclear silanolate
Pt(II)-hydride 17 was also observed, and probably involved
water attack on the intermediate silanone complex 14.
Apparently, the intramolecular stabilization possibly allowed
the formation of the silanone 14 and protected it against the
expected cyclooligomerization. However, the currently
achieved stabilization is still unsatisfactory to exclude very
fast addition of external nucleophiles to the silicon center in
the silanone complex 14, which prevented its isolation. Thus,
the approach for stabilization through intramolecular binding
to transition metals in pincer-type complexes could open new
opportunities for the construction of more stable silanones
and related transients, but requires additional protection
against nucleophilic attack.
Experimental Section
Infrared spectra were recorded using a Nicolet Prote´ge´ 460 FT-
IR spectrometer in thin films on NaCl plates. Abbreviations used
in the description of IR data are as follows: br, broad; s, strong; m,
medium; v, very. Low resolution electrospray ionization (ESI) mass-
spectrometry was performed using Micromass Platform LCZ 4000
(Micromass, Manchester, U.K.) with sampling cone voltage of 43V,
extractor voltage of 4V, and desolvation temperature of 150 °C.
High resolution mass-spectra (HRMS) were recorded using SYN-
APT High Definition Q-TOF mass spectrometer (Waters Micro-
mass, Manchester, U.K.) with ESI positive mode, source temper-
ature 125 °C, desolvation temperature 275 °C, extractor voltage of
4 V, and sampling cone voltage of 24 V. Elemental analysis was
performed at H. Kolbe Mikroanalytisches Laboratorium, Germany.
Flash chromatography (FC) was commonly performed on Florisil
(Fluka), which was dried in the oven at 140 °C for a week at least,
and, upon introducing to the glovebox, was degassed by applying
vacuum at RT followed by addition of purified nitrogen (3 times
General Procedures. All experiments with the phosphine ligand
and the metal complexes were carried out under an atmosphere of
purified nitrogen in a Vacuum Atmospheres glovebox equipped with
MO 40-2 inert gas purifier or using common Schlenk techniques
under argon. All solvents were reagent grade or better. All
nondeuterated solvents except CH2Cl2 were refluxed over sodium/
benzophenone ketyl and distilled under argon atmosphere. Meth-
ylene chloride was refluxed for half a day over CaH2 and distilled
under argon. The distilled solvents were kept in the glovebox over
sodium (THF, benzene) or CaH2 (ether, CH2Cl2, toluene, pentane,
and hexane). Triethylamine and ethyl di-iso-propylamine were
distilled and stored over CaH2 under inert atmosphere. Fluoroben-
zene and silicon tetrachloride were stored over CaH2 in a glovebox
for at least 1 week before use. Commercial KN(SiMe3)2 (95%,
Fluka) was purified by dissolving in dry toluene, filtered through a
short plug of Celite followed by a thorough evaporation, and used
only freshly purified. Other commercially available reagents were
used as received. The deuterated solvents were dried over 4 Å
(51) Hill, G. S.; Irvin, M. J.; Levy, C. J.; Rendina, L. M.; Puddephatt,
R. J. Inorg. Synth. 1998, 32, 149.
(52) Herde, J. L.; Lambert, J. C.; Senoff, C. V. Inorg. Synth. 1974, 15, 18.
(53) (a) Massey, A. G.; Park, A. G. J. Organomet. Chem. 1964, 2, 245.
(b) Castellanos, F.; Fouassier, J. P.; Priou, C.; Cavezzan, J. J. Appl.
Polym. Sci. 1996, 60, 705.
(50) Such instability formally contradicts the stability of 17 in the reaction
mixture (prior to isolation). This could be rationalized by taking into
account the buffered nature of the reaction mixture and the presence
of an acidic i-Pr2NEt·HB(C6F5)4 impurity (ca. 2-3%) which might
be the cause of decomposition.
Inorganic Chemistry, Vol. 47, No. 16, 2008 7185

Korshin et al.
repeated cycle). TLC analysis was performed on E. Merck 0.25
mm precoated silica gel 60 F-254 plates.
) 16.0 Hz, 2P-CHMe2), 19.95 (d, JCP ) 18.7 Hz, 2CH3), 19.47 (d,
JCP ) 11.7 Hz, 2CH3).
(2) Preparation of PSiH2P Ligand 7. A pentane solution of
t-BuLi (5.30 mL of 1.7 M solution, 8.95 mmol) was added dropwise
(over 10 min) to an intensively stirred solution of bromophe-
nylphosphine 5 (2.32 g, 8.53 mmol) in dry Et2O (30 mL) at -60
°C under argon. The yellowish heterogeneous reaction mixture was
allowed to warm up to -10 °C over 2 h and was stirred for 1 h at
that temperature. The reaction mixture was cooled to -60 °C again,
and a solution of silicon tetrachloride (0.725 g, 4.265 mmol) in
ether (8 mL) was added rapidly (over 2 min). The reaction mixture
was allowed to warm up to ambient temperature over 3 h, stirred
at RT for 3 days, and after solid LiAlH4 (0.530 g, 13.25 mmol)
was added to the reaction mixture in small portions. After stirring
for 15 h at ambient temperature, the reaction was quenched by
cautious addition of acetone (in small portions; total 2.48 g, 42.65
mmol), stirred at RT for 4 h, diluted with pentane, and filtered
through a short plug of Celite. After evaporation, the residue was
subjected to vacuum distillation from a short vapor path distillation
flask to give the silane 7 (1.114 g, 63%) as a pale-greenish viscous
oil, b.p. 180-182 °C (0.33 mmHg).
X-ray Structure Determination and Refinement. General
Information. The crystals were mounted in a nylon loop and flash
frozen in a cold nitrogen stream (120 K) on a Nonius Kappa CCD
diffractometer with Mo KR radiation (λ ) 0.71071 Å), graphite
monochromator. Accurate unit cell dimensions were obtained from
20° of data. The data were processed with the Denzo-Scale pack
package. The structures were solved by direct methods (SHELXS-
97) and refined by full-matrix least-squares (SHELXL-97). Idealized
hydrogen atoms were placed and refined in the riding mode.
Potassium Tetrakis(pentafluorophenyl)borate. A solution of
KF (294 mg, 5.078 mmol) in dry methanol (6.0 mL) was added to
a clear solution of LiB(C6F5)4 ·2.5Et2O53a (2.868 g, 3.244 mmol)
in methanol (14 mL). The mixture that immediately became turbid
was stirred for 15 min and diluted with dry ether (50 mL). After
precipitation of LiF, the mixture was filtered and the solvent
evaporated. Two additional re-evaporations from benzene were
required for removal of methanol traces. The colorless solid residue
was extracted with hot dry ether (200 mL), the extract was filtered
through a glass cinter covered with Celite, and the solvent was
removed under vacuum to give colorless foam. Recrystallization
from dry benzene (15 mL) and CH2Cl2 (15 mL) afforded the major
portion of potassium tetrakis(pentafluorophenyl)borate (1.96 g,
84.5%) as heavy colorless plates. Concentration of the filtrate to
about 20 mL volume afforded an additional crop of the target
potassium salt (0.15 g, 6.5%) as a colorless solid. The combined
product was dried over P2O5 at 80 °C in vacuum (0.3 mmHg) for
2 days.
31P{1H} NMR (CDCl3, 162 MHz): δ 3.01 (s). 1H NMR (CDCl3,
400 MHz): δ 7.59 (br dvt, 2H, JHH ) 7.4 Hz, JHP ) 1.6 Hz, 2H
Ar), 7.52-7.46 (m, 2H, 2H Ar), 7.37 (2H, ddd, JHH ) JHH ) 7.4
Hz, JHP ) 1.4 Hz, 2H Ar), 7.26 (ddvt, 2H, JHH ) JHH ) 7.4 Hz,
4
JHP ) 1.3 Hz, 2H Ar), 5.45 (t with 29Si satellites, 2H, JHP ) 8.7
Hz, 1JHSi ) 205 Hz, H2Si), 2.14-2.03 (sym m, 4H, 4P-CHMe2),
1.09 [dd, JHP ) 14.3 Hz, JHH ) 7.0 Hz, 12H, 4PCH-(CH3)Me],
0.86 [dd, JHP ) 12.0 Hz, JHH ) 7.0 Hz, 12H, 4PCH-(CH3)Me].
The assignment of the coupling constants was confirmed by 1H{31P}
NMR. 13C{1H}/DEPT NMR (CDCl3, 100.6 MHz): δ 143.61 (d,
JCP ) 14.9 Hz, 2C Ar), 143.17 (dd, JCP ) 45.6 Hz, JCP ) 5.1 Hz,
2C Ar), 138.09 (dd, JCP ) 14.3 Hz, JCP ) 2.7 Hz, 2CH Ar), 131.53
19F NMR (acetone-d6, 235.4 MHz): δ -128.58 (br s, 8F, ortho-
3
F), -159.89 (t, JFF ) 20.0 Hz, 4F, para-F), -163.86 (sym m,
8F, meta-F). 11B NMR (acetone-d6, 160.5 MHz): δ -15.98 (br s).
Anal. for C24BF20K, Calcd: C, 40.14; F, 52.91; Found: C, 40.25;
F, 52.51.
(d, JCP ) 2.4 Hz, 2CH Ar), 128.95 (s, 2CH Ar), 127.86 (d, JCP
)
1.1 Hz, 2CH Ar), 24.70 (d, JCP ) 13.1 Hz, 4CH, 4PCHMe2), 20.04
(d, JCP ) 17.4 Hz, 4CH3), 19.70 (d, JCP ) 10.8 Hz, 4CH3). 29Si
NMR (CDCl3, 99.4 MHz, 29Si-DEPT/INEPT): δ -39.95 ppm (t in
DEPT or tt in INEPT, 3JSiP ) 22.5 Hz, 1JSiH ) 205 Hz). IR (film):
ν 2139 cm-1 (br s, Si-H). ESI MS (in MeOH/CH2Cl2, addition of
HCOOH/ HCOONa), found m/z (%): 439 (67) [MNa+], 417 (100)
[MH+] (both with the correct isotopic pattern). HRMS, calcd. m/z
for C24H39P2Si [MH+]: 417.2296; found: 417.2289.
Synthesis of Bis-[(2-di-iso-propylphosphanyl)phenyl]silane
(7). (1) Preparation of Di-iso-propyl(2-bromophenyl)-
phosphine (5). To a stirred cold (5 °C) solution of i-PrMgCl
[prepared in situ from i-PrCl (8.247 g, 105 mmol) and Mg-turnings
(2.45 g, 100.8 mmol)] in dry THF (50 mL) under argon was added
a solution of a freshly prepared dichlorophosphine 4 (10.186 g,
39.48 mmol) in THF (30 mL) dropwise with the rate not allowing
the exothermic reaction to exceed 20 °C. The reaction mixture was
stirred at RT overnight, heated at 50-60 °C for 1 h, and quenched
at RT with a powdered solid KH2PO4 (7.145 g, 52.5 mmol). The
mixture was stirred for 30 min at RT and for 30 min at 40-45 °C,
and diluted with a 20% solution of ethyl acetate in hexane (120
mL). Filtration, evaporation, followed by a vacuum distillation of
the residue afforded the phosphine 5 (6.618 g, 61.5%) as a colorless
liquid, bp 101-103 °C (0.4 mmHg).
Synthesis of [ClPt{HSi(2-C6H4PPr2-i)2}] (8). A solution of
ligand 7 (118.0 mg, 0.283 mmol) in dry benzene (2.5 mL) was
added to a yellow solution of trans-(Me2S)2Pt(Me)Cl (106.2 mg,
0.287 mmol) in benzene (2.5 mL). The reaction mixture, which
turned to pale yellow after a few minutes, was stirred for 1 h, filtered
through a plug of Celite, and evaporated to give a yellowish solid
residue. Complex 8 was purified by sequential FC on Florisil
(gradient elution, from 10% to 70% of ether in hexane). Totally
113.6 mg, (62%) of the pure complex 8 was isolated as a colorless
solid, Rf ) 0.52 (EtOAc /hexane 3:7).
1
31P{1H} NMR (C6D6, 162 MHz): δ 9.53 (s). H NMR (C6D6,
31P{1H} NMR (C6D6, 202.5 MHz): δ 68.89 (s with 195Pt satellites,
400 MHz): δ 7.47-7.42 (m, 1H; H Ar), 7.11 (br d, 1H, JHH ) 7.7
Hz, H Ar), 6.92 (ddd, 1H, JHH ) JHH ) 7.7 Hz, JHP ) 1.3 Hz, H
Ar), 6.72 (ddd, 1H, JHH ) JHH ) 7.7 Hz, JHP ) 1.4 Hz, H Ar),
1
1JPPt ) 2885 Hz). H NMR (C6D6, 500 MHz): δ 8.04 (d, 2H, JHH
) 7.3 Hz, 2 ortho-H ArSi), 7.30 (dvt, 2H, JHH ) 7.4 Hz, JHP ) 2.4
Hz, 2 ortho-H ArP), 7.21 (br dd, 2H, JHH ) JHH ) 7.3 Hz, 2H Ar),
7.10 (br dd, 2H, JHH ) JHH ) 7.3 Hz, 2H Ar), 5.75 (br s with 195Pt
1.94-1.84 (sym m, 2H, 2P-CHMe2); 1.075 (dd, ca. 4H, JHP
)
14.6 Hz, JHH ) 7.0 Hz) and 1.070 (dd, ca. 2H, JHP ) 14.6 Hz, JHH
) 7.0 Hz) [two rotamers, total 6H, 2PCH-(CH3)Me]; 0.865 (dd,
ca. 4H, JHP ) 12.2 Hz, JHH ) 6.9 Hz) and 0.860 (dd, ca. 2H, JHP
) 12.2 Hz, JHH ) 6.9 Hz) [two rotamers, total 6H, 2PCH-(CH3)Me].
13C{1H}/DEPT NMR (C6D6, 100.6 MHz): δ 137.98 (d, JCP ) 22.7
Hz, C Ar), 134.18 (s, CH Ar), 133.68 (d, JCP ) 32.3 Hz, C Ar),
133.61 (d, JCP ) 3.1 Hz, CH Ar), 126.70 (s, CH Ar), 24.34 (d, JCP
2
1
and 29Si satellites, 1H, JHPt ) 38.8 Hz, JHSi ) 183 Hz, HSi),
3.44-3.34 (sym m, 2H, 2P-CHMe2), 2.51-2.41 (sym m, 2H,
2P-CHMe2), 1.43 (dvt, 6H, JHH ) JHP ) 7.3 Hz, 2CH3), 1.39 (dvt,
6H, JHH ) JHP ) 7.5 Hz, 2CH3), 1.10 (dvt, 6H, JHH ) JHP ) 7.2
Hz, 2CH3), 0.92 (dvt, 6H, JHH ) JHP ) 7.4 Hz, 2CH3). The
1
assignment was confirmed by H{31P} and COSY NMR experi-
7186 Inorganic Chemistry, Vol. 47, No. 16, 2008

Silanol-Based Pincer Pt(II) Complexes
ments. 13C{1H}/DEPT NMR (C6D6, 125.8 MHz): δ 151.40 (vt, JCP
) 20.7 Hz, 2C Ar), 141.70 (vt, JCP ) 25.7 Hz, 2C Ar), 133.98 (vt,
JCP ) 9.6 Hz, 2CH Ar), 131.17 (vt, JCP ) 2.7 Hz, 2CH Ar), 130.35
(br s with 195Pt satellites, JCPt ) 9.2 Hz, 2CH Ar), 128.86 (vt, JCP
) 3.7 Hz, 2CH Ar), 27.69 (vt, JCP ) 13.9 Hz, 195Pt satellites JCPt
) 17.6 Hz, 2CHMe2), 25.92 (br vt, JCP ) 14.8 Hz, 2CHMe2), 19.20
(vt, JCP ) 2.1 Hz, 195Pt satellites JCPt ) 17.5 Hz, 2CH3), 19.04 (br
s with 195Pt satellites, JCPt ) 20.6 Hz, 2CH3), 18.61 (br s with 195Pt
satellites, JCPt ) 11.3 Hz, 2CH3), 18.19 (br s with 195Pt satellites,
JCPt ) 22.2 Hz, 2CH3). 29Si NMR (C6D6, 79.5 MHz, 29Si-DEPT/
94.9815(11)°, γ ) 90°, V ) 2586.8(1) Å3, Z ) 4, Fcalc ) 1.700 g
cm-3, µ ) 5.712 mm-1
.
Data Collection and Treatment. A total of 22636 reflections
were collected, -10 e h e 10, 0 e k e 23, 0 e l e 21, frame
scan with 1°, scan speed 1° per 30 s, 6096 independent reflections
(Rint ) 0.052, 2θmax ) 54.9°), final R ) 0.0281 (wR ) 0.0743) for
5233 reflections with I > 2σ(I), and R ) 0.0333 (wR ) 0.0771)
for all data.
Preparation of the Cationic Pt(II)-Silanol Complex
[{(2-C6H4PPr2-i)2SiOH}Pt]+ [(C6F5)4B]- (9). To a solid mixture
of complex 3 (6.9 mg, 0.0104 mmol) and KB(C6F5)4 (7.9 mg,
0.0110 mmol) was added dry fluorobenzene (0.7 mL), and the
reaction mixture was stirred at RT for 20 h. Complete consumption
of the neutral complex 3 and practically quantitative formation of
the cationic complex 9 was observed in the 31P NMR spectrum.
The reaction mixture was thoroughly evaporated, and the residue
was extracted with dry benzene (4.0 mL). The extract was filtered
through a fine Teflon filter (0.2 µm), evaporated and dried under
vacuum overnight at 0.5 mmHg to give the practically pure (95%
purity in 31P NMR) cationic complex 9 (13.7 mg, quantitative yield)
as a colorless light solid.
2
INEPT): δ 12.27 ppm (t with 195Pt satellites in DEPT, JSiP ) 5.2
Hz, 1JSiPt ) 1190 Hz; dt with 195Pt satellites in INEPT, 1JSiH ) 183
Hz). 195Pt{1H} NMR (C6D6, 107.5 MHz): δ -5022 (t with 29Si
1
1
satellites, JPtP ) 2885 Hz, JPtSi ) 1190 Hz). IR (film): ν 2040
cm-1 (br m, Si-H). ESI MS (in MeCN), found m/z (%): 651 (57)
[M+ - Cl + MeCN], 652 (95), 610 (58) [M+ - Cl], 611 (100)
(both sets of ions with the correct isotope pattern).
Anal. for C24H37ClP2PtSi, Calcd: C, 44.61; H, 5.77; Found: C,
44.85; H, 5.83.
Synthesis of [ClPt{HOSi(2-C6H4PPr2-i)2}] (3). To a solution
of complex 8 (28.0 mg, 0.0433 mmol) in a mixture of acetonitrile
(2.5 mL) and CH2Cl2 (0.5 mL) was added water (8.0 mg, 0.444
mmol) followed by a catalytic amount [(COD)IrCl]2 (0.5 mg), and
the yellow reaction mixture was stirred for 24 h under the common
aerobic conditions (without protection from atmospheric oxygen
and moisture). The reaction mixture was diluted with benzene and
evaporated. Sequential FC on Florisil (gradient elution, from 100%
pentane to 100% ether) afforded the silanol complex 3 (25.5 mg,
89%) as a colorless solid, Rf ) 0.14 (EtOAc /hexane 3:7).
31P{1H} NMR (C6D6, 202.5 MHz): δ 71.08 (s with 195Pt satellites,
31P{1H} NMR (CD2Cl2, 202.5 MHz): δ 73.12 (br s with 195Pt
1
satellites, 1JPPt ) 3097 Hz). H NMR (CD2Cl2, 500 MHz): δ 8.23
(d, 2H, JHH ) 7.3 Hz, 2 ortho-H ArSi), 7.78-7.71 (m, 2H, 2
ortho-H ArP), 7.65 (dd, 2H, JHH ) JHH ) 7.3 Hz, 2H Ar), 7.59
(dd, 2H, JHH ) JHH ) 7.3 Hz, 2H Ar), 3.38-3.21 (br sym m, 2H,
2P-CHMe2), 2.86-2.70 (br sym m, 2H, 2P-CHMe2), 1.38 (br
dvt, 6H, JHH ) 7.2 Hz, JHP ) 8.5 Hz, 2CH3), 1.36 (br dvt, 6H, JHH
) 7.4 Hz, JHP ) 8.3 Hz, 2CH3), 1.29 (br dvt, 6H, JHH ) 6.6 Hz,
JHP ) 7.6 Hz, 2CH3), 1.19 (dvt, 6H, JHH ) JHP ) 7.2 Hz, 2CH3).
The assignment was confirmed by 1H{31P} and COSY NMR
experiments. 13C{1H}/DEPT NMR (CD2Cl2, 125.8 MHz): δ 149.40
(br m, 2C Ar + C ArF), 147.45 (br m, C ArF), 139.60 (m, 2C Ar),
1
1JPPt ) 3025 Hz). H NMR (C6D6, 500 MHz): δ 8.14 (d, 2H, JHH
) 7.3 Hz, 2 ortho-H ArSi), 7.34 (dvt, 2H, JHH ) 7.5 Hz, JHP ) 2.3
Hz, 2 ortho-H ArP), 7.23 (br dd, 2H, JHH ) JHH ) 7.3 Hz, 2H Ar),
7.12 (br dd, 2H, JHH ) JHH ) 7.3 Hz, 2H Ar), 3.43-3.31 (sym m,
2H, 2P-CHMe2), 2.57-2.44 (sym m, 2H, 2P-CHMe2), 1.42 (dvt,
6H, JHH ) JHP ) 7.5 Hz, 2CH3), 1.36 (dvt, 6H, JHH ) JHP ) 7.5
Hz, 2CH3), 1.08 (dvt, 6H, JHH ) JHP ) 7.2 Hz, 2CH3), 0.93 ppm
(dvt, 6H, JHH ) JHP ) 7.4 Hz, 2CH3). 13C{1H}/DEPT NMR (C6D6,
125.8 MHz): δ 155.47 (vt, JCP ) 21.9 Hz, 2C Ar), 141.23 (vt, JCP
137.61 (br m, C ArF), 135.68 (br m, C ArF), 132.96 (br vt, JCP
)
9.5 Hz, 2CH Ar), 131.75 (br s, 2CH Ar), 131.33 (br s, 2CH Ar),
130.95 (m, 2CH Ar), 28.10 (vt, JCP ) 13.5 Hz, 2CHMe2), 26.73
(br vt, JCP ) 12.2 Hz, 2CHMe2), 19.97 (br s, 2CH3), 18.87 (br s,
2CH3), 18.64 (br s, 4CH3). 11B{1H} NMR (CD2Cl2, 160.5 MHz):
δ -16.03 ppm (s). 19F NMR (CD2Cl2, 235.4 MHz): δ -133.45 (br
s, 8F, ortho-F ArF), -163.45 (t, 3JFF ) 20.5 Hz, 4F, para-F ArF),
-167.44 (sym m, 8F, meta-F ArF). 29Si NMR (CD2Cl2, 99.4 MHz,
) 25.3 Hz, 2C Ar), 132.99 (vt, JCP ) 9.8 Hz, 195Pt satellites JCPt
44.0 Hz, 2CH Ar), 130.81 (vt, JCP ) 3.0 Hz, 195Pt satellites JCPt
)
)
1
29Si-1H HMBC): δ 25.24 (br s with 195Pt satellites, JSiPt ) 1478
38.2 Hz, 2CH Ar), 130.44 (br s with 195Pt satellites, JCPt ) 10.8
Hz, 2CH Ar), 129.50 (vt, JCP ) 3.5 Hz, 195Pt satellites JCPt ) 16.2
1
Hz). 195Pt{1H} NMR (CD2Cl2, 107.5 MHz): δ -5075 (t, JPtP
)
Hz, 2CH Ar), 27.51 (br vt, JCP ) 13.9 Hz, 195Pt satellites JCPt
)
3100 Hz).
13.8 Hz, 2CHMe2), 25.86 (br vt, JCP ) 14.9 Hz, 195Pt satellites
Preparation of the Silanol-Pt(II)-carbonyl complex [{(2-
C6H4PPr2-i)2SiOH}PtCO]+[(C6F5)4B]- (10). Through a solution
of 9 (13.7 mg, 0.0104 mmol) in CD2Cl2 (0.7 mL) in a screw-cap
NMR tube equipped with a Teflon septum CO gas was mildly
bubbled for 5 min, resulting in quantitative formation of the
platinum carbonyl complex 10. After NMR and IR characterizations,
the solution was evaporated followed by re-evaporation from C6D6
and vacuum drying for 3 h under oil pump vacuum, to give complex
10 as a colorless solid (13.7 mg, quantitative yield, g95% purity
according to 31P and 1H NMR spectra). The analytically pure
complex could not be obtained because of some CO loss under
prolonged vacuum drying
JCPt ) 9.0 Hz, 2CHMe2), 19.52 (br s with 195Pt satellites, JCPt
20.2 Hz, 2CH3), 19.34 (vt, JCP ) 2.0 Hz, 195Pt satellites JCPt
)
)
12.1 Hz, 2CH3), 18.69 (br s with 195Pt satellites, JCPt ) 12.3 Hz,
2CH3), 18.29 (br s with 195Pt satellites, JCPt ) 23.6 Hz, 2CH3).
1
1
The assignment was confirmed by H{31P}, COSY, and H-13C
HSQC NMR experiments. 29Si NMR (C6D6, 99.4 MHz, 29Si-1H
HMBC): δ 38.53 (br s with 195Pt satellites, JSiPt ) 1335 Hz).
1
195Pt{1H} NMR (C6D6, 107.5 MHz): δ -4992 (t, 1JPtP ) 3025 Hz,
29Si satellites JPtSi ) 1334 Hz). IR (film): ν 3404 cm-1 (v br, m,
1
O-H).
Anal. for C24H37ClOP2PtSi, Calcd: C, 43.54; H, 5.63; Found: C,
43.68; H 5.61.
X-ray Structural Analysis of 3. The X-ray quality single crystals
of 3 were formed upon cooling of a hexane/benzene solution (5:1)
at -15 °C for 2 weeks.
31P{1H} NMR (CD2Cl2, 202.5 MHz): δ 82.24 (s with 195Pt
1
satellites, 1JPPt ) 2736 Hz). H NMR (CD2Cl2, 500 MHz): δ 8.27
(d, 2H, JHH ) 7.3 Hz, 2 ortho-H ArSi), 7.82 (dvt, 2H, JHH ) 7.6
Hz, JHP ) 3.0 Hz, 2 ortho-H ArP), 7.77 (br dd, 2H, JHH ) JHH
)
Crystal Data. C24H37ClOP2PtSi, fw ) 662.21, colorless prism,
0.6 × 0.3 × 0.3 mm3, monoclinic, space group P21/c (No. 14), a
) 8.4654(1), b ) 18.2462(3), c ) 16.8102(3) Å, R ) 90°, ꢀ )
7.3 Hz, 2H Ar), 7.70 (ddvt, 2H, JHH ) JHH ) 7.5 Hz, JHP ) 1.4
Hz, 2H Ar), 3.23-3.08 (sym m, 2H, 2P-CHMe2), 2.87-2.74 (sym
m, 2H, 2P-CHMe2), 1.32 (br dvt, 6H, JHH ) 6.7 Hz, JHP ) 10.0
Inorganic Chemistry, Vol. 47, No. 16, 2008 7187

Korshin et al.
Hz, 2CH3), 1.27 (br dvt, 6H, JHH ) 8.4 Hz, JHP ) 10.8 Hz, 2CH3),
1.23 (br dvt, 6H, JHH ) 6.7 Hz, JHP ) 9.0 Hz, 2CH3), 1.00 (dvt,
6H, JH,H ) 6.7 Hz, JH,P ) 9.0 Hz, 2CH3). The assignment of the
coupling constants was confirmed by 1H{31P} NMR. 13C{1H}/DEPT
NMR (CD2Cl2, 125.8 MHz): δ 190.81 (vt, JCP ) 7.0 Hz, Pt-CO),
151.86 (vt, JCP ) 21.0 Hz, 2C Ar), 149.40 (br m, C ArF), 147.49
(br m, C ArF), 139.55 (br vt, JCP ) 17.0 Hz, 2C Ar), 137.60 (br
m, C ArF), 135.68 (br m, C ArF), 134.24 (vt, JCP ) 9.8 Hz, 195Pt
satellites JCPt ) 20.0 Hz, 2CH Ar), 133.32 (br s, 2CH Ar), 132.29
(vt, JCP ) 3.7 Hz, 195Pt satellites JCPt ) 15.2 Hz, 2CH Ar), 131.54
(vt, JCP ) 3.2 Hz, 195Pt satellites JCPt ) 36.4 Hz, 2CH Ar), 30.11
(br vt, JCP ) 15.1 Hz, 195Pt satellites JCPt ) 16.2 Hz, 2CHMe2),
28.18 (br vt, JCP ) 16.3 Hz, 195Pt satellites JCPt ) 6.0 Hz, 2CHMe2),
20.12 (br s with 195Pt satellites, JCPt ) 17.3 Hz, 2CH3), 19.40 (s
with 195Pt satellites, JCPt ) 22.4 Hz, 2CH3), 19.00 (s with 195Pt
satellites, JCPt ) 18.5 Hz, 2CH3), 18.67 (br s, 2CH3). 19F NMR
(CD2Cl2, 235.4 MHz): δ -134.00 (br s, 8F, ortho-F ArF), -164.30
(t, 3JFF ) 20.3 Hz, 4F, para-F ArF), -168.22 (sym m, 8F, meta-F
ArF). 29Si NMR (CD2Cl2, 99.4 MHz, 29Si-1H HMBC): δ 57.36
(br s with 195Pt satellites, 1JSiPt ) 977 Hz). 195Pt{1H} NMR (CD2Cl2,
107.5 MHz): δ -5295 (t, 1JPtP ) 2736 Hz, with 29Si satellites, 1JPtSi
) 980 Hz). IR (film): ν 3470 cm-1 (br m, O-H), 2087 cm-1 (m,
Pt-CO). ESI MS (in MeOH/CH2Cl2), found m/z+ (%): 625 (72),
626 (100) [M+ - CO], 627 (87) (the correct isotopic pattern); m/z-
(%): 678 (22), 679 (100) [Anion-], 680 (24) (the correct isotope
pattern). HRMS, calcd. m/z+ for C24H37OP2195PtSi [M+ - CO]:
626.1738; found: 626.1749.
The reaction mixture was evaporated, and extracted with pentane
(6.0 mL). Evaporation of the extract followed by chromatography
of the residue on Florisil as described above afforded the dimer 11
(4.6 mg, 36%).
31P{1H} NMR (C6D6, 202.5 MHz): δ 69.75 (s with 195Pt satellites,
1
1JPPt ) 3060 Hz, 2PPt1), 52.29 (br s with 195Pt satellites, JPPt
)
2844 Hz, 2PPt2). H NMR (C6D6, 500 MHz): δ 8.17 (d, 2H, JHH
) 7.3 Hz, 2ortho-H ArSi1), 8.11 (d, 2H, JHH ) 7.4 Hz, ortho-H
ArSi2), 7.33 (dvt, 2H, JHH ) 7.5 Hz, JHP ) 3.6 Hz, 2ortho-H
ArPPt1), 7.13 (dd, 2H, JHH ) JHH ) 7.1 Hz, 2H Ar), 7.08-7.02
(m, 4H, 4H Ar), 6.97 (dd, 2H, JHH ) JHH ) 7.7 Hz, 2H Ar),
6.97-6.91 (m, 2H, 2H Ar), 3.42-3.28 (sym m, 2H,
2Pt1P-CHMe2), 2.76-2.64 (sym m, 2H, 2Pt1P-CHMe2), 2.22-1.99
(m, 4H, 4Pt2P-CHMe2), 1.55 (dvt, 6H, JHH ) JHP ) 7.4 Hz, 2CH3),
1
1.39 (dvt, 6H, JHH ) JHP ) 7.3 Hz, 2CH3), 1.29 (dvt, 6H, JHH
)
JHP ) 7.3 Hz, 2CH3), 1.27 (br dvt, 6H, JHH ≈ JHP ) 8.0 Hz, 2CH3),
1.15 (dvt, 6H, JHH ) JHP ) 7.6 Hz, 2CH3), 1.11 (br dvt, 6H, JHH
≈ JHP ) 7.7 Hz, 2CH3), 1.01 (dvt, 6H, JHH ) JHP ) 7.0 Hz, 2CH3),
0.83 (dvt, 6H, JHH ) JHP ) 7.3 Hz, 2CH3), -18.31 (t with 195Pt
1
2
satellites, JHP ) 12.4 Hz, JHPt ) 1180 Hz, 1H; HPt2). 13C{1H}/
DEPT NMR (C6D6, 125.8 MHz): δ 155.77 (vt, JCP ) 23.0 Hz, 2C
Ar), 151.77 (vt, JCP ) 10.8 Hz, 2C Ar), 142.31 (vt, JCP ) 26.3 Hz,
2C Ar), 137.92 (vt, JCP ) 6.6 Hz, 2CH Ar), 137.45 (vt, JCP ) 22.8
Hz, 2C Ar), 133.75 (br vt, JCP ) 9.9 Hz, 2CH Ar), 130.04 (br s,
2CH Ar), 129.98 (m, 2CH Ar), 129.43 (br s, 2CH Ar), 127.46 (br
s, 2CH Ar), 28.50 (vt, JCP ) 13.7 Hz, 2PCHMe2), 26.65 (vt, JCP
)
13.6 Hz, 2PCHMe2), 25.70 (vt, JCP ) 14.5 Hz, 2PCHMe2), 21.34
(br s, 2CH3), 20.82 (br s, 2CH3), 20.67 (vt, JCP ) 16.6 Hz,
2PCHMe2), 19.57 (br s, 2CH3), 19.36 (vt, JCP ) 4.1 Hz, 2CH3),
18.77 (br s, 2CH3), 18.71 (br s, 2CH3), 18.69 (br s, 2CH3), 17.14
ppm (br s, 2CH3). The assignment was confirmed by 1H{31P},
X-ray Structural Analysis of 10. The X-ray quality single
crystals of 10 grew from a concentrated benzene solution at RT.
Crystal Data. C25 H37O2P2PtSi·BC24F20, fw ) 1333.72, colorless
3
j
prism, 0.4 × 0.3 × 0.1 mm , triclinic, space group P1 (No. 2), a )
1
13.6579(1), b ) 15.0983(3), c ) 15.2010(2) Å, R ) 112.5430(7)°,
COSY, and H-13C HSQC NMR experiments. 29Si NMR (C6D6,
ꢀ ) 94.5989(6)°, γ ) 116.8269(3)°, V ) 2458.58(7) Å3, Z ) 2,
99.4 MHz, 29Si-1H HMBC): δ 23.64 (br s with 195Pt satellites,
1JSiPt ) 1416 Hz, Si1), -56.83 ppm (br s, Si2). 195Pt NMR (C6D6,
F
calc) 1.802 g cm-3, µ ) 3.060 mm-1
.
1
1
Data Collection and Treatment. A total of 51413 reflections
107.5 MHz): δ -4558 (dt, JPtP ) 2845 Hz, JPtH ) 1180 Hz in
195Pt-1H HMQC, Pt2), -4975 ppm (t, 1JPtP ) 3060 Hz in 195Pt{1H},
Pt1). IR (film): ν 2204 cm-1 (br m, Pt-H). ESI MS (in MeOH/
CH2Cl2), found m/z (%): 1251 (65), 1252 (100) [M+ - Cl] (the
were measured, -17 e h e 17, -19 e k e 18, 0 e l e 19, frame
scan width 1°, scan speed 1° per 80 s, 11206 independent reflections
(Rint) 0.040, 2θmax ) 54.9°), final R ) 0.0244 (wR ) 0.0543) for
10076 reflections with I > 2σ(I), and R ) 0.0302 (wR ) 0.0516)
for all data.
correct
isotope
pattern).
HRMS,
calcd.
m/z
for
C48H74ClO2P4195Pt196PtSi2 [MH+]: 1288.3164; found: 1288.3162.
X-ray Structural Analysis of 11. The X-ray quality single
crystals of 11 grew from a solution in hexane at -20 °C over 1
month.
Base-Induced Rearrangement-Coupling of [ClPt{HOSi(2-
C6H4PPr2-i)2}] (3). Synthesis of the binuclear complex 11. (a)
A cold solution of KN(SiMe3)2 (3.8 mg, 0.0191 mmol) in dry ether
(1.0 mL) and dry THF (0.5 mL) was added dropwise to a cold
(-30 °C) stirred solution of complex 3 (12.8 mg, 0.0193 mmol)
and a catalytic amount of 18-crown-6 (0.7 mg, 0.0014 mmol) in a
mixture of ether (1.0 mL) and THF (0.5 mL). The slightly turbid
reaction mixture was left at -30 °C for 12 h and was stirred for
1 h at RT. At that time, 31P NMR monitoring revealed complete
consumption of the starting complex 3 and formation of the dimer
11 in about 75% yield. The reaction mixture was evaporated, and
the brownish solid residue was extracted with ether (4.0 mL). The
ethereal extract was filtered through a plug of Celite, evaporated,
and the residue subjected to chromatography on Florisil (gradient
elution, from 5% ether in hexane to 100% ether) to give the dimer
11 (7.2 mg, 58% yield, eluted with 50-60% ether in hexane) as a
colorless solid.
Crystal Data. C48H73ClO2P4Pt2Si2, fw ) 1287.75, colorless plate,
0.3 × 0.1 × 0.1 mm3, orthorhombic, space group Pca21 (No. 29),
a ) 22.827(5), b ) 12.115(2), c ) 18.502(4) Å, V ) 5116.7(18)
Å3, Z ) 4, Fcalc ) 1.672 g cm-3, µ ) 5.722 mm-1
.
Data Collection and Treatment. A total of 38094 reflections
were measured, 0 e h e 29, 0 e k e 15, 0 e l e 23, frame scan
width 1°, scan speed 1° per 240 s, 7104 independent reflections
(Rint ) 0.130, 2θmax ) 54.9°), final R ) 0.0378 (wR ) 0.0635) for
5466 reflections with I > 2σ(I), and R ) 0.0458 (wR ) 0.0656)
for all data.
Base-Induced Hydrolytic Rearrangement of [{(2-C6H4PPr2-
i)2SiOH}Pt]+ [(C6F5)4B]- (9). Isolation of the Monomeric Hy-
droxysilanolate Pt(II)-Hydride 17. To a mixture of complex 3
(9.0 mg, 0.0136 mmol) and KB(C6F5)4 (10.7 mg, 0.0150 mmol)
was added dry fluorobenzene (1.0 mL), and the reaction mixture
was stirred for 15 h at RT. At that time 31P NMR monitoring
revealed complete consumption of the starting platinum chloride
complex 3 and clean formation of the cationic complex 9. Dry
i-Pr2NEt (6.3 mg, 0.0488 mmol) was added to the reaction mixture
to induce slow conversion of 9 to the platinum hydride complex
(b) To a stirred cold (-30 °C) solution of 3 (13.0 mg, 0.0196
mmol) in dry THF (0.8 mL) was added a solution of t-BuOK (2.8
mg, 0.0250 mmol) in THF (1.0 mL). The mixture was stirred for
4 h at ambient temperature, at which time 31P NMR monitoring
revealed disappearance of the starting complex 3 and formation of
the dimer 11 in about 55% yield along with several byproducts.
7188 Inorganic Chemistry, Vol. 47, No. 16, 2008

Silanol-Based Pincer Pt(II) Complexes
17 (ca. 60% 31P NMR yield after 14 d at RT). All the volatiles
were evaporated; the residue was dissolved in a minimal amount
of benzene (0.3 mL) and diluted with hexane (5.0 mL) upon
shaking. After sedimentation of the colorless solid, the colorless
solution was filtered through a fine (0.2 µm) Teflon filter. Evapora-
tion of the filtrate followed by vacuum drying of the residue
afforded the complex 17 (3.3 mg, 38%, g95% purity in 31P NMR)
as a colorless waxy mass. An additional amount of less pure
compound 17 could be obtained by a repetition of the extraction
procedure.
127.47 (br s, 2CH Ar), 27.14 (vt, JCP ) 13.2 Hz, 2PCHMe2), 22.96
(vt, JCP ) 16.7 Hz, 2PCHMe2), 19.96 (br s, 2CH3), 19.08 (br s,
2CH3), 18.82 (vt, JCP ) 3.8 Hz, 2CH3), 17.98 (br s, 2CH3). 29Si
NMR (C6D6, 99.4 MHz, 29Si-1H HMBC): δ -54.98 ppm (br s).
195Pt NMR (C6D6, 107.5 MHz, 195Pt-1H HMQC): δ ) -4566 ppm
(dt, 1JPtP ) 2858 Hz, 1JPtH ) 1220 Hz). IR (film): ν 3420 (v br m,
O-H), 2200 cm-1 (br m, Pt-H). ESI MS (in MeCN), found m/z
(%): 1287 (74), 1288 (100) [2 M + H+] (the correct isotope pattern).
Acknowledgment. This work was supported by the Israel
Science Foundation, Jerusalem, Israel, and by the MINERVA
foundation, Munich, Germany. We thank Dr. Arye Tishbee
for carrying out mass spectroscopy measurements. E.E.K.
thanks the Israel Ministry of Absorption for the Kamea
Excellence Fellowship. D.M. is the holder of the Israel Matz
Professorial Chair of Organic Chemistry.
31P{1H} NMR (C6D6, 202.5 MHz): δ 49.99 (br s with 195Pt
satellites, 1JPPt ) 2857 Hz). 1H NMR (C6D6, 500 MHz): δ 8.19 (d,
2H, JHH ) 7.4 Hz, 2 ortho-H ArSi), 7.07 (dd, 2H, JHH ) JHH
)
7.4 Hz, 2H Ar), 6.99 (dd, 2H, JHH ) JHH ) 7.4 Hz, 2H Ar), 6.90
(dvt, 2H, JHH ) 7.4 Hz, JHP ) 3.3 Hz, 2 ortho-H ArP), 2.11-2.00
(sym m, 2H, 2P-CHMe2), 2.03-1.93 (sym m, 2H, 2P-CHMe2),
1.01-0.91 (m, 18H, 6CH3), 0.65 (dvt, JHH ) JHP ) 7.7 Hz, 6H,
2CH3), -19.32 (t with 195Pt satellites, 2JHP ) 12.7 Hz, 1JHPt ) 1217
Hz, 1H, HPt). The assignment was confirmed by 1H{31P} and
COSY NMR experiments. 13C{1H}/DEPT NMR (C6D6, 125.8
Supporting Information Available: CIF files containing X-ray
crystallographic data for compounds 3, 10 and 11. This material is
available free of charge via the Internet at http://pubs.acs.org.
MHz): δ 150.04 (m, 2C Ar), 138.06 (m, 2C Ar), 137.11 (vt, JCP
)
6.8 Hz, 2CH Ar), 136.16 (br s, 2CH Ar), 130.95 (br s, 2CH Ar),
IC800457U
Inorganic Chemistry, Vol. 47, No. 16, 2008 7189