Alkyl and hydrido complexes of platinum(IV) supported by the bis(8-quinolyl)methylsilyl ligand

Article abstract of DOI:10.1021/om701162h

The Pt(II) complex (NSiN)PtCl (2; NSiN = bis(8-quinolyl)methylsilyl) was prepared from reaction of (COD)PtCl₂, Qn₂SiHMe (1) and excess NEt₃ in dichloromethane. The X-ray structure of 2 confirms a square-planar geometry abo

Full text of DOI:10.1021/om701162h

Organometallics 2008, 27, 2223–2230
2223
Alkyl and Hydrido Complexes of Platinum(IV) Supported by the
Bis(8-quinolyl)methylsilyl Ligand
Preeyanuch Sangtrirutnugul and T. Don Tilley*
Department of Chemistry, UniVersity of California, Berkeley, Berkeley, California 94720
ReceiVed NoVember 19, 2007
The Pt(II) complex (NSiN)PtCl (2; NSiN ) bis(8-quinolyl)methylsilyl) was prepared from reaction of
(COD)PtCl2, Qn2SiHMe (1) and excess NEt3 in dichloromethane. The X-ray structure of 2 confirms a
square-planar geometry about platinum and a highly distorted tetrahedral geometry at Si. A series of
thermally stable (NSiN)Pt(IV) compounds including (NSiN)PtH2(X) [X ) Cl (5), OTf (10)] and
(NSiN)PtMe2(X) [X ) I (6), OTf (7)] were also synthesized. Five-coordinate Pt(IV) complexes of the
type [(NSiN)PtR2][B(C6F5)4] (X ) Me (9), H (11)] were generated by treatment of the corresponding
triflato derivatives with 1 equiv of Li(Et2O)3[B(C6F5)4] in dichloromethane. A crystal structure of 9 reveals
a square-pyramidal structure with an empty coordination site trans to silicon. Initial reactivity studies
have shown that complex 9 is thermally and chemically robust.
sp3-hybridized Si, the NSiN ligand prefers binding to the metal
in a facial manner.11–13 As a result, square-planar Pt(II)
complexes of the type (NSiN)PtX (X ) halide, H, and alkyl)
are expected to possess ring strain that may be relieved by
bond activation reactions to produce octahedral Pt(IV)
products (eq 1).
Introduction
Organoplatinum compounds are known to mediate a number
of important and interesting chemical transformations, including
homogeneous C-H bond activation,1,2 alkene hydrosilylation,3
and hydroformylation.4 Many of these complexes feature
chelating ligands, which provide higher thermal stability to the
resulting platinum complexes as a result of the chelate effect.1,5–7
Despite extensive research in this field, there are few reports of
platinum complexes containing a multidentate ligand framework
based on silicon donor atoms.8–10 Because of their strong
electron donor and trans-labilizing properties, silyl groups may
facilitate bond activation processes, while enforcing coordinative
unsaturation at the platinum center. Within this context, explora-
tion of the chemistry of platinum complexes of the bis(8-
quinolyl)methylsilyl (NSiN) ligand was of interest. With the
(1)
Platinum(IV) complexes containing alkyl and/or hydride
ligands have often been prepared via protonation of the
corresponding Pt(II) complexes.14,15 Other synthetic methods
are based on oxidative additions of R3E-H (R3E ) Me3Sn,16
Et3Si17) or C-H18 bonds to platinum(II) complexes. Elegant
mechanistic studies by Puddephatt19 and Goldberg20,21 have
* Address correspondence to this author. E-mail: tdtilley@berkeley.edu.
(1) Labinger, J. A.; Bercaw, J. E. Nature 2002, 417, 507.
(2) (a) Shilov, A. E.; Shul’pin, G. B. ActiVation and Catalytic Reations
of Saturated Hydrocarbons in the Presence of Metal Complexes; Kluwer:
Boston, 2000. (b) Shilov, A. E. ActiVation of Saturated Hydrocarbons by
Transition Metal Complexes; Dordrecht: The Netherlands, 1984. (c) Periana,
R. A.; Taube, D. J.; Gamble, S.; Taube, H.; Satoh, T.; Fujii, H. Science
1998, 280, 560.
(3) (a) Chalk, A. J.; Harrod, J. F. J. Am. Chem. Soc. 1965, 87, 16. (b)
Marciniec, B.; Gulinski, J.; Urbaniak, W.; Kornetka, Z. W. ComprehensiVe
Handbook on Organosilicon Chemistry; Pergamon: Oxford, 1992. (c) Ojima,
I. In The Chemistry of Organic Silicon Compounds; Patai, S., Rappaport,
Z.,. Eds.; J. Wiley: Chichester, UK, 1989.
(4) (a) van Duren, R.; van der Vlugt, J. I.; Kooijman, H.; Spek, A. L.;
Vogt, D. Dalton Trans. 2007, 1053. (b) Slaugh, L. H.; Mullineaux, R. D.
(Shell Oil Company) U.S. Patent 3 239 571, 1966. (c) Schwager, I.; Knifton,
J. F. J. Catal. 1976, 45, 256. (d) Wilkinson, M. G. (Johnson Matthey Co.
Ltd.) Fr. Patent, 1 459 643, 1966. (e) Haelg, P.; Consiglio, G.; Pino, P. J.
Organomet. Chem. 1985, 296, 281. (f) Agbossou, F.; Mortreux, A. Chem.
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13, 1200.
(12) Sangtrirutnugul, P.; Stradiotto, M.; Tilley, T. D. Organometallics
2006, 25, 1607.
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(14) (a) Canty, A. J.; Fritsche, S. D.; Jin, H.; Patel, J.; Skelton, B. W.;
White, A. H. Organometallics 1997, 16, 2175. (b) O’Reilly, S. A.; White,
P. S.; Templeton, J. L. J. Am. Chem. Soc. 1996, 118, 5684. (c) Reinartz,
S.; White, P. S.; Brookhart, M.; Templeton, J. L. Organometallics 2000,
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Organometallics 1999, 18, 2861. (e) Vedernikov, A. N.; Fettinger, J. C.;
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Kreuzfeld, H.-J. J. Organomet. Chem. 1989, 370, 343.
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Organometallics 1996, 15, 2845.
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2000, 19, 4193.
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(8) Stobart, S. R.; Brost, R. D.; Bruce, G. C.; Joslin, F. L. Organome-
tallics 1997, 16, 5669.
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10.1021/om701162h CCC: $40.75
2008 American Chemical Society
Publication on Web 04/10/2008

2224 Organometallics, Vol. 27, No. 10, 2008
Sangtrirutnugul and Tilley
shown that reductive elimination from octahedral Pt(IV) com-
plexes involves dissociation of a ligand to afford an intermediate,
five-coordinate species. Complexes of the latter type have also
been isolated, and a few of these have been crystallographically
characterized.22–24 Given the known properties of the NSiN
ligand, as outlined above, it should be possible to access a range
of (NSiN)Pt(IV) complexes. Additionally, the strong trans-
labilizing ability of silicon should make coordinatively unsatur-
ated, five-coordinate complexes of the type [(NSiN)PtR2]+ (R
) H, alkyl) reasonable synthetic targets. Initial investigations
of such systems are described in this paper.
Results and Discussion
Figure 1. ORTEP diagram of the square-planar complex 2 with
thermal ellipsoids shown at the 50% probability level. Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å): Pt-Cl )
2.528(2), Pt-Si ) 2.225(2). Selected bond angles (deg): C8-Pt-C17
) 126.1(3), N1-Pt-N2 ) 166.7(2), Pt-Si-C19 ) 120.8(2).
Synthesis of (NSiN)Pt(II) Complexes. Treatment of 1 with
25
1 equiv of (COD)PtCl2 (COD ) 1,5-cyclooctadiene) and an
excess of NEt3 (ca. 3 equiv) in dichloromethane afforded the
chelate-assisted, Si-H bond activation product (NSiN)PtCl (2),
along with NEt3 · HCl and COD (eq 2). Complex 2 was
crystallized as a fine yellow powder from CH2Cl2 solution.
Despite successive washings and crystallizations, 2 inevitably
contained a small amount of COD, according to 1H NMR
spectroscopy. An analytically pure sample of 2, free of COD,
was obtained in relatively low yield (32%) by evaporating a
toluene suspension of 2 to dryness at 100 °C.
this distance is comparable to that reported for Stobart’s Pt(II)
complex (PSiP)PtCl (2.44 Å)8 [PSiP ) -SiMe(CH2CH2PPh2)2].
A further apparent consequence of the chelate ring strain in 2
is a significant deviation of the C(8)-Si-C(17) angle (126.1(3)°)
from the ideal tetrahedral value. In comparison, the crystal
structure of the related octahedral Pt(IV) complex (NSiN)-
PtMe2OTf (7) reveals a smaller C(8)-Si-C(17) angle of
109.4(3)° (Vide infra).
Syntheses of more electron-rich, square-planar complexes of
the type (NSiN)PtR (R ) H, alkyl, aryl) were also attempted.
Efforts to generate these platinum(II) complexes focused on
25
reactions of platinum compounds such as (COD)PtMe2 and
(COD)PtPh227 with 1, as it was anticipated that Si-H oxidative
addition would be followed by rapid elimination of hydrocarbons
(e.g., CH4 or C6H6). However, 1H NMR spectroscopy indicated
that conversions did not occur even at a reaction temperature
of 80 °C (in benzene or dichloromethane solvent). Prolonged
heating of the reaction mixtures at this temperature eventually
resulted in decomposition of the platinum starting materials. In
addition, reactions of 1 with various Pt(0) complexes such as
Pt(PPh3)2(C2H4),28 Pt(PPh3)4,29 and Pt(dba)2 (dba ) diben-
zylideneacetone)30 in benzene-d6 resulted in intractable mixtures
of products.
(2)
The H and 13C{1H} NMR spectra of 2 contain one set of
quinolyl resonances, indicating mirror symmetry for the mol-
1
1
ecule. In the H NMR spectrum of 2, the silyl methyl group
(3JPtH ) 45 Hz) and the ortho protons of both quinolyl rings
(3JPtH ) 22 Hz) display platinum satellites. Despite the
preference for facial binding of the NSiN ligand, the NMR data
indicate the presence of a square-planar structure, with the NSiN
ligand coordinated to the Pt(II) center in a tridentate fashion
and a chloride ligand occupying a position trans to Si.
Similar observations regarding the lower reactivity of
(COD)PtR2 dialkyl compounds, compared to that of
(COD)PtCl2, toward Si-H bond oxidative addition were previ-
ously noted for the syntheses of dimeric Pt(II) complexes (µ-
Cl)2[(η2-COD)Pt(SiR3)]2 (SiR3 ) SiEt3, SiMe2Cl, SiMeCl2,
Si(OEt)3, SiPhMe2, SiMe2OSiMe3).31 A possible explanation
for this difference is that COD binds more strongly to the
platinum center in (COD)PtR2 (when R ) alkyl or phenyl).25
On the basis of this reasoning, platinum complexes containing
a more labile ligand such as tetramethylethylenediamine (tmeda)
were expected to be more reactive toward Si-H bond activation.
Indeed, treatment of 1 with (tmeda)PtMe2 in benzene at 80
°C afforded a new platinum complex (3) via CH4 elimination.
X-ray quality crystals were obtained from a dichloromethane
solution of 2 at -30 °C. Crystallographic data reveal a distorted
square-planar geometry about the Pt(II) center, and the sum of
the angles around platinum is essentially 360° (359.7(3)°; Figure
1). The N(1)-Pt-N(2) angle (166.7(2)°) is reduced from 180°
as a result of ligand rigidity and the constraint imposed by the
sp3-hybridized silicon. As expected, the Pt-Cl bond distance
(2.528(2) Å) is long compared to distances involving Pt-Cl
bonds that are trans to ligands with a trans influence weaker
than silicon (e.g., nitrogen and carbon, 2.28–2.39 Å).26 However,
1
Although the H NMR spectrum of 3 in dichloromethane-d2
1
contains one set of quinolyl protons, no H NMR resonance
(21) (a) Goldberg, K. I.; Yan, J.; Breitung, E. M. J. Am. Chem. Soc.
1995, 117, 6889. (b) Goldberg, K. I.; Yan, J.; Winter, E. L. J. Am. Chem.
Soc. 1994, 116, 1573.
assignable to a Pt-CH3 group is observed. Multinuclear NMR
spectroscopy combined with elemental analysis identify 3 as
(22) Reinartz, S.; White, P. S.; Brookhart, M.; Templeton, J. L. J. Am.
Chem. Soc. 2001, 123, 6425.
(23) Fekl, U.; Kaminsky, W.; Goldberg, K. I. J. Am. Chem. Soc. 2001,
123, 6423.
(27) Kistner, C. R.; Hutchinson, J. H.; Doyle, J. R.; Storlie, J. C. Inorg.
Chem. 1963, 2, 1255.
(24) Kloek, S. M.; Goldberg, K. I. J. Am. Chem. Soc. 2007, 129, 3460.
(25) Clark, H. C.; Manzer, L. E. J. Organomet. Chem. 1973, 59, 411.
(26) (a) Kleij, A. W.; Gebbink, R. J. M. K.; Lutz, M.; Spek, A. L.; van
Koten, G. J. Organomet. Chem. 2001, 621, 190. (b) Davies, M. S.; Diakos,
C. I.; Messerle, B. A.; Hambley, T. W. Inorg. Chem. 2001, 40, 3048.
(28) Cook, C. D.; Jauhal, G. S. J. Am. Chem. Soc. 1968, 90, 1404.
(29) Ugo, R.; Cariati, F.; Lamonic, G. Inorg. Synth. 1990, 28, 123.
(30) Cherwinski, W. J.; Johnson, B. F. G.; Lewis, J. J. Chem. Soc.,
Dalton Trans. 1974, 1405.
(31) Roy, A. K.; Taylor, R. B. J. Am. Chem. Soc. 2002, 124, 9510.

Alkyl and Hydrido Complexes of Platinum(IV)
Organometallics, Vol. 27, No. 10, 2008 2225
strain of the NSiN ligand. Thus, this alkyl platinum(II) in-
termediate is not observed, presumably because it rapidly adds
another equivalent of 1 to yield the final product 3.
Reactions of Complex 2. Attempts were also made to prepare
alkyl and aryl complexes of the type (NSiN)PtR via reaction
of 2 with various reagents including MeLi, EtMgCl, PhMgBr,
and Mg(CH2Ph)2(THF)2. However, the 1H NMR spectra of the
resulting reaction mixtures reveal a complex mixture of products,
and no pure products were isolated.
It was also of interest to generate 14-electron complexes of
the type [(NSiN)Pt][X], since such three-coordinate Pt(II)
species are believed to be key intermediates in C-H bond
activations.34 Given the strong trans-labilizing ability of Si, it
seemed that chloride displacement of 2 by more weakly
coordinating anions should readily take place. In related Rh
complexes, it has been found that the NSiN ligand promotes
lability in ligands trans to Si and stabilizes five-coordinate
Rh(III) complexes.12
Figure 2. ORTEP diagram of the square-planar complex cis-(κ2-
NSiN)2Pd with thermal ellipsoids shown at the 50% probability
level. Hydrogen atoms and solvent molecules are omitted for clarity.
Selected bond lengths (Å): Pd-N1 ) 2.231(5), Pd-Si ) 2.276(2).
Selected bond angles (deg): Si-Pd-N1 ) 83.9(1), Si-Pd-SiA
) 90.66(10), N1-Pd-N1A ) 101.8(3).
Reaction of 2 with either 0.5 or 1 equiv of Li(Et2O)3[B-
(C6F5)4] in dichloromethane afforded a yellow solid (4), which
was crystallized from diethyl ether at room temperature. The
1H NMR spectrum of 4 (dichloromethane-d2) contains one set
the bidentate complex cis-(κ2-NSiN)2Pt (eq 3). An analogous
palladium complex, cis-(κ2-NSiN)2Pd,32 was synthesized from
reaction of 1 with (tmeda)PdMe2.33 The X-ray crystal structure
of cis-(κ2-NSiN)2Pd reveals a distorted square-planar structure
with each NSiN ligand binding through only one quinolyl
nitrogen and the silyl group, in a bidentate manner (Figure 2).
Observation of only one set of quinolyl protons in the spectrum
of the related Pt complex 3 at room temperature suggests a
fluxional process that rapidly interconverts the quinolyl groups.
At -80 °C, the 1H NMR resonances of 3 (dichloromethane-d2)
are broader, but no decoalescence was apparent.
of quinolyl protons and a singlet resonance at δ 0.24 (3JPtH
)
35 Hz), corresponding to the SiCH3 group. In addition, no
1
diethyl ether ligand was observed by H NMR spectroscopy.
Elemental analysis of 4 is consistent with a dinuclear, chloro-
bridged platinum structure (eq 4). A related chloride-bridged
structure has previously been observed for the cationic Ir(III)
complex (µ-Cl)[(NSiN)Ir(H)(coe)]2[B(C6F5)4]11 (coe ) cy-
clooctene).
(4)
Synthesis of (NSiN)Pt(IV) Complexes. The square -planar
complex 2 was expected to readily undergo oxidative addition
reactions to afford Pt(IV) complexes in which the NSiN ligand
is facially bonded to platinum. Heating a dichloromethane-d2
solution of 2 under 1–2 atm of H2 at 60 °C resulted in formation
of a new product (5) in approximately 15% yield after 2 days
(by 1H NMR, with Si(SiMe3)4 as an internal standard). The 1H
NMR spectrum of the reaction mixture reveals unreacted 2 as
a major species, and a hydride resonance for 5 at δ -18.3 (1JPtH
) 1274 Hz). Prolonged heating of the reaction mixture did not
result in an increase in the amount of 5. Notably, although
platinum is involved in both heterogeneous35 and homoge-
(3)
Complex 3 results from Si-H bond activations of 2 equiv
of 1 by (tmeda)PtMe2. A plausible mechanism involves the
formation of a transient intermediate, (NSiN)PtMe, which adds
another equivalent of 1 via methane loss. Given the reactive
nature of (tmeda)PtMe2, it is reasonable to assume that
(NSiN)PtMe would also react rapidly with 1, especially given
the more electron-rich Pt center and the expected chelate ring
(32) Crystal data: C49H46N4Si2O3Pd, Pbcn (#60), a ) 8.8297(2) Å, b )
27.9592(6) Å, c ) 18.1044(4) Å, V ) 4469.5(2) Å3, Z ) 4, R1 ) 0.047,
wR2 ) 0.061. See Supporting Information for more detailed crystallographic
parameters.
(33) de Graaf, W.; Boersma, J.; Smeets, W. J. J.; Spek, A. L.; van Koten,
G. Organometallics 1989, 8, 2907.
(34) Lersch, M.; Tilset, M. Chem. ReV. 2005, 105, 2471.
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A. O. I. Appl. Catal. A: Gen. 2004, 276, 129. (b) Arai, M.; Usui, K.;
Nishiyama, Y. J. Chem. Soc., Chem. Commun. 1993, 1853.

2226 Organometallics, Vol. 27, No. 10, 2008
Sangtrirutnugul and Tilley
neous36 hydrogenation catalysis, few examples of H-H oxida-
tive additions to Pt(II) complexes have previously been re-
ported.37
Complex 5 was independently synthesized by heating a
dichloromethane solution of (COD)PtCl2 and 2 equiv of 1 at
60 °C for 36 h (eq 5). A second equivalent of 1 serves as a
reducing agent, to produce the byproduct Qn2Si(Cl)Me. Crystal-
lization of 5 from a 1:1 mixture of dichloromethane and diethyl
ether at -30 °C afforded the pure product in 56% yield.
Figure 3. ORTEP diagram of the triflato complex 7 with thermal
ellipsoids shown at the 50% probability level. Hydrogen atoms are
omitted for clarity. Selected bond lengths (Å): Pt-O1 ) 2.425(4),
Pt-Si ) 2.244(2), Pt-C20 ) 2.043(7). Selected bond angles (deg):
C8-Pt-C17 ) 109.4(3), N1-Pt-N2 ) 87.0(2), Si-Pt-O1 )
172.1(1).
(5)
The related dimethyl Pt(IV) complexes (NSiN)PtMe2(X) [X
) I (6), OTf (7)] were obtained in high yields from addition of
1 to 0.25 equiv of [Me3PtX]4 (X ) I, OTf) in dichloromethane
solution (eq 6). Alternatively, 7 was generated from reaction
of 6 with 1 equiv of AgOTf in dichloromethane. Formation of
6 and 7 involves an interesting Si-H activation at a Pt(IV)
center, for which the mechanism (e.g., oxidative addition vs
σ-bond metathesis) is currently unknown.
methyl ligand trans to nitrogen in a Pt(IV) complex.38,39 The
Pt-O bond distance (2.425(4) Å) is longer than corresponding
distances in Pt-OTf complexes with the triflate group trans to
amido or methyl ligands (2.099–2.320 Å).38,40
Five-Coordinate (NSiN)Pt(IV) Complexes. Given the un-
usual stability of five-coordinate (NSiN)Rh(III) complexes,12
and the ability of silyl ligands to stabilize high oxidation
states,9,15,22,23,41 it seemed that coordinatively unsaturated dialkyl
complexes of the type (NSiN)PtR2+ might be unusually stable
toward the reductive elimination of alkane. Treatment of 6 with
either 0.5 or 1.0 equiv of Li(Et2O)3[B(C6F5)]4 in dichlo-
romethane resulted in the same product (8), which was isolated
in 85% yield from a mixture of dichloromethane and diethyl
1
ether. The H NMR spectrum of 8 contains resonances at δ
1.28 (2JPtH ) 62 Hz) and 1.13 (3JPtH ) 25 Hz), corresponding
to Pt-CH3 and Si-CH3 groups, respectively. The combustion
analysis of 8 is consistent with the iodo-bridged diplatinum
complex shown in eq 7.
(6)
The 1H NMR spectra of 6 and 7 (dichloromethane-d2) contain
single resonances at δ 1.17 (2JPtH ) 63 Hz) and 0.844 (2JPtH
)
The displacement of triflate from 7 is a more efficient process
for synthesis of a five-coordinate Pt(IV) complex. Reaction of
7 with 1 equiv of Li(Et2O)3[B(C6F5)]4 in dichloromethane
afforded the cationic complex [(NSiN)PtMe2][B(C6F5)4] (9),
isolated in 91% yield by vapor diffusion of pentane into a
dichloromethane solution of 9 at room temperature (eq 8).
Although 9 was generated in the presence of diethyl ether,
no ether coordination to platinum was observed for the isolated,
60 Hz), respectively, which can be assigned to the Pt-CH3
groups. Consistently, the 13C{1H} resonances for the methyl
groups in 6 and 7 appear at δ -13.3 (1JPtC ) 640 Hz) and -9.80
(1JPtC ) 645 Hz), respectively. X-ray quality crystals of 7 were
obtained by slow vapor diffusion of diethyl ether into a
dichloromethane solution of 7 at room temperature. The crystal
structure reveals a distorted octahedral complex with an inner-
sphere triflate anion bonded to the platinum center trans to the
quinolylsilyl group (Figure 3). The Pt-C bond distances of
2.043(7) and 2.052(7) Å are within the expected range for a
(40) (a) Harkins, S. B.; Peters, J. C. Organometallics 2002, 21, 1753.
(b) Schlecht, S.; Dehnicke, K.; Magull, J.; Fenske, D. Angew. Chem., Int.
Ed. Engl. 1997, 36, 994.
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1973.
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A. H. J. Organomet. Chem. 1995, 490, C18. (b) Brookhart, M.; Grant, B. E.;
Lenges, C. P.; Prosenc, M. H.; White, P. S. Angew. Chem., Int. Ed. 2000,
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Klei, S. R.; Tilley, T. D.; Bergman, R. G. J. Am. Chem. Soc. 2000, 122,
1816. (e) Prokopchuk, E. M.; Puddephatt, R. J. Organometallics 2003, 22,
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metallics 2006, 25, 1583.
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Acta 1998, 270, 363.
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15, 2108.

Alkyl and Hydrido Complexes of Platinum(IV)
Organometallics, Vol. 27, No. 10, 2008 2227
(7)
Figure 4. ORTEP diagram of the cationic complex 9 with thermal
ellipsoids shown at the 50% probability level. Hydrogen atoms and
the B(C6F5)4 anion are omitted for clarity. Selected bond lengths
(Å): Pt-Si ) 2.256(1), Pt-N1 ) 2.142(3), Pt-C20 ) 2.036(5).
Selected bond angles (deg): C20-Pt-C21 ) 90.9(2), N1-Pt-N2
) 91.4(1), Si-Pt-C20 ) 95.5(2).
such as isotopically labeled 13CH4 and C6H6 were investigated.
Treatment of the dichloromethane-d2 solution of 9 with 1–2 atm
of 13CH4 did not result in the incorporation of 13C into the
platinum methyl groups at 90 °C over 2 days. Similarly, heating
a dichloromethane-d2 solution of 9 with an excess of C6H6 (ca.
20 equiv) at 115 °C resulted in no reaction after 2 days,
according to 1H NMR spectroscopy. This unusual stability of 9
is believed to be due to the preference of the NSiN ligand for
binding facially to the platinum center and its ability to stabilize
a coordinatively unsaturated, high oxidation state Pt(IV) complex.
Given the observed stability of (NSiN)Pt(IV) complexes, it
was of interest to examine the ability of this fragment to support
alkyl hydride complexes, especially given the generally high
tendency for such species to undergo reductive elimination. In
addition, alkyl hydrides such as (NSiN)PtMe2(H) might offer
an intriguing route to Pt(II) square-planar complexes of the type
(NSiN)PtMe, if methane elimination was to cleanly occur.
However, treatment of 6 and 7 with various hydride sources
such as LiBH4, LiBEt3H, and NaH under various reaction
conditions resulted in no conversion of the starting materials.
Heating a PhF/benzene-d6 (1:1) solution of 7 and 1 equiv of
NEt3 under 1–2 atm of H2 at 60 °C yielded the Si-C reductive
(8)
crystalline product, according to NMR spectroscopy and
elemental analysis. A single crystal of 9 suitable for X-ray
crystallographic analysis was obtained from vapor diffusion of
pentane into a dichloromethane solution of 9 at room temper-
ature. The X-ray data reveal a square-pyramidal structure for
the platinum molecule, with the silyl group in an apical position
trans to an empty coordination site (Figure 4). The B(C6F5)4
counterion is not in the vicinity of the platinum center (the
shortest Pt · · · F distance is 5.16 Å).
Although five-coordinate platinum(IV) species are proposed
as intermediates in bond activation chemistry,19,21,42 only a few
X-ray structures of complexes of this type have been reported.22–24
The crystallographically characterized complex [κ2-((Hpz*)-
BHpz*2)PtH2(SiEt3)][BAr′4] (BHpz*3 ) hydridotris(3,5-dim-
ethylpyrazolyl)borate) decomposes slowly in dichloromethane
to form (BHpz*3)PtH3 via a heterolytic Pt-Si cleavage.22
Similarly, in the presence of light, the five-coordinate Pt(IV)
complex (nacnac′)PtMe3 [nacnac′ ) {(o-iPr2C6H3)NC(CH3)}2-
CH-] converts to the corresponding Pt(II) dimethyl complex,
44
coupling product Qn2SiMe2 and CH4, based on 1H NMR
spectroscopy.
The successful synthesis of 9, and its remarkable stability,
prompted us to investigate the synthesis of a cationic Pt(IV)
dihydride complex. The reactivity of [(NSiN)PtH2][B(C6F5)4]
was of interest, given the known bond activation chemistry of
the electronically analogous complex (PCP)IrH2.5 Reaction of
5 with 1 equiv of AgOTf in dichloromethane readily afforded
the corresponding triflato complex (NSiN)PtH2(OTf) (10) as an
off-white solid in 88% yield (eq 9). The 1H NMR spectrum of
10 in dichloromethane-d2 is similar to that of 5, with a hydride
+
as a result of a CH3 transfer from platinum to the central
anionic carbon of the diimine ligand.23 Thermal decomposition
of (nacnac′)PtMe3 occurs in benzene at 150 °C in the absence
of light, with elimination of ethane and methane.7
Notably, 9 is thermodynamically stable, as no reaction was
observed upon heating a dichloromethane-d2 solution of 9 to
90 °C for 3 days (by H NMR spectroscopy). In the presence
1
resonance at δ -17.3 (1JPtH ) 1312 Hz; for 5: δ -18.3, JPtH
1
of an atmosphere of C2H4, 9 does not react to form an ethylene
adduct or insertion product, as no conversion was observed at
90 °C after 3 days. Given the exceptional C-H bond activation
chemistry of the electronically related complex [Cp*(PMe3)Ir-
(Me)(CH2Cl2)][BArf4],43 reactions of 9 with small molecules
(44) Qn2SiMe2 was independently synthesized from lithiation of 8-bro-
moquinoline using BuLi, followed by addition of 0.5 equiv of Cl2SiMe2 in
THF at-78 °C. 1H NMR (C6D6, 500 MHz): δ 8.63 (d, JHH ) 4.1 Hz, of d,
JHH ) 1.8 Hz, 2 H, ArH), 7.94 (d, JHH ) 6.7 Hz, of d JHH ) 1.4 Hz, 2 H,
ArH), 7.52 (d, JHH ) 8.2 Hz, of d, JHH ) 1.8 Hz, 2 H, ArH), 7.44 (d, JHH
) 8.2 Hz, of d JHH ) 1.5 Hz, 2 H, ArH), 7.19 (d, JHH ) 8.2 Hz, of d, JHH
) 6.7 Hz, 2 H, ArH), 6.70 (d, JHH ) 8.2 Hz, of d, JHH ) 4.1 Hz, 2 H,
ArH), 1.32 (s, 6 H, SiCH3). 13C{1H} NMR (C6D6, 125 MHz): δ 153.3,
149.2, 141.4, 137.9, 136.0, 129.2, 126.3, 120.6 (aryl carbons), 0.47 (SiCH3).
29Si{1H} NMR (C6D6, 99 MHz): δ-5.9. Anal. Calcd (%) for C20H18N2Si:
C, 76.39, H, 5.77, N, 8.91. Found: C, 76.11, H, 5.73, N, 8.62.
(42) (a) Hill, G. S.; Rendina, L. M.; Puddephatt, R. J. Organometallics
1995, 14, 4966. (b) Williams, B. S.; Holland, A. W.; Goldberg, K. I. J. Am.
Chem. Soc. 1999, 121, 252.
(43) Arndtsen, B. A.; Bergman, R. G. Science 1995, 270, 1970.

2228 Organometallics, Vol. 27, No. 10, 2008
Sangtrirutnugul and Tilley
) 1274 Hz). In addition, the IR spectrum of 10 contains a strong
Pt-H band at 2231 cm-1. The structure of 10 is believed to be
similar to that of 7, with the triflate bound to platinum. Both
NMR spectroscopy and elemental analysis reveal no solvent in
the isolated product, and this is also consistent with an inner-
sphere triflate structure.
(NSiN)Pt(IV) complexes should generally be substitutionally
labile. This lability appears to play a role in the clean, facile
formation of 9 and 11.
Further investigations of (NSiN)Pt complexes will attempt
to establish reaction pathways for the activation of substrate
molecules and incorporation of observed reactivity into catalytic
cycles involving Pt(II)/Pt(IV) interconversions.
Experimental Sections
General Procedures. Manipulations involving air-sensitive
compounds were conducted using standard Schlenk techniques
under a purified N2 atmosphere or in a Vacuum Atmospheres
drybox. In general, solvents were distilled under N2 from appropriate
drying agents and stored in PTFE-valved flasks. Deuterated solvents
were purchased from Cambridge Isotopes, dried with appropriate
drying agents, and vacuum-transferred before use. NEt3, tetram-
ethylethylene diamine (tmeda), and COD (Aldrich) were dried with
CaH2 and distilled prior to use. Dihydrogen (Praxair), ethylene
(Airgas), and 13CH4 (Aldrich) were used as received.
The reagents bis(8-quinolyl)methylsilane (1),12 (COD)PtCl2,25
(tmeda)PtMe2,25 (tmeda)PdMe2,33 [PtMe3X]4 (X ) I,45 OTf 46),
8-bromoquinoline,47 and Li(Et2O)3[B(C6F5)4]48 were prepared ac-
cording to literature procedures. AgOTf and BuLi (1.6 M in
hexanes) were purchased from Aldrich and used without further
purification.
1H (500.1 MHz), 13C{1H} (124.7 MHz), and 29Si{1H} (99.3
MHz) NMR spectra were acquired on Bruker DRX-500, AV-500,
or AVB-400 spectrometers. The DRX-500 and AVB-400 spec-
trometers are each equipped with a 5 mm Z-gradient proton/
broadband probe, while the AV-500 instrument features a 5 mm
TBI (triple inverse broadband) probe with Z-gradient. 19F (376.5
MHz) NMR spectra were obtained from an AVQ-400 spectrometer
containing a 5 mm QNP probe. Unless otherwise noted, NMR
spectra were recorded at room temperature and were referenced to
protic impurities in the deuterated solvent for 1H, solvent
peaks for 13C{1H}, CFCl3 for 19F, or SiMe4 for 29Si{1H}. The
1H,29Si{1H} HMBC experiments were carried out to determine the
29Si-195Pt coupling constants. The 13C{1H} resonances corre-
sponding to the B(C6F5)4 anion or the CF3 group of the triflate are
not reported. Elemental analyses were performed by the University
of California, Berkeley College of Chemistry Microanalysis Facility.
Infrared spectra were recorded as Nujol mulls on a Nicolet Nexus
6700 FT-IR spectrometer with a liquid nitrogen cooled MCT-B
detector.
(9)
Treatment of 10 with 1 equiv of Li(Et2O)3[B(C6F5)4] in
dichloromethane yielded a new complex (11), which was
crystallized from dichloromethane as a white microcrystalline
solid in 58% yield. Elemental analysis and the 1H NMR
spectrum of 11 are consistent with its formulation as the cationic
Pt(IV) complex [(NSiN)PtH2][B(C6F5)4]. The 1H NMR spectrum
of 11 in dichloromethane-d2 contains a broad resonance at δ
-16.1 (1JPtH ) 1314 Hz) corresponding to two hydride ligands.
The Pt-H vibrational stretch appears as a broad band at 2228
cm-1 in the IR spectrum. Once isolated, 11 is only sparingly
soluble in dichloromethane. In addition, 11 slowly decomposes
in dichloromethane to give intractable products over several days
at room temperature.
Concluding Remarks. Despite its strong tendency to bind
to metal centers in a facial manner, the NSiN ligand has been
found to form a square-planar complex of platinum (NSiN)PtCl
(2). However, initial investigations indicate that related Pt(II)
derivatives with more electron-donating ligands (e.g., X ) H,
alkyl, aryl) are highly reactive and difficult to isolate. Several
reactions described in this paper have shown that the NSiN
ligand is readily installed via reactions of the Si-H bond of
Qn2SiHMe (1) at a Pt(II) center. A related reaction of note
involves addition of 1 to [PtMe3X]4 (X ) I, OTf), which
involves a particularly unusual activation of an Si-H bond at
a Pt(IV) center, to form (NSiN)PtMe2(X) complexes. In addition,
reaction of 1 with (COD)PtCl2 in dichloromethane to afford
(NSiN)PtH2Cl (5) represents a convenient, new synthetic route
to a Pt(IV) hydride complex.
(NSiN)PtCl (2). A 100 mL Schlenk flask equipped with a
magnetic stir bar was charged with (COD)PtCl2 (0.200 g, 0.532
mmol) and 1 (0.160 g, 0.533 mmol). To this solid mixture,
approximately 60 mL of CH2Cl2 was added, followed by neat NEt3
(0.21 µL, 1.73 mmol). After 8 h of stirring at room temperature,
the reaction solution was evaporated to dryness. The remaining
orange residue was dissolved in approximately 8 mL of CH2Cl2.
At -30 °C, a yellow precipitate was obtained. Drying a 5 mL
toluene suspension of this solid at 100 °C under vacuum afforded
1
the COD-free product 2 in 32% yield (0.090 g, 0.170 mmol). H
NMR (CD2Cl2, 500 MHz): δ 10.2 (d JHH ) 4.0 Hz, of d JHH ) 2.0
Hz, 2 H, ArH, 3JPtH ) 45 Hz), 8.44 (d JHH ) 8 Hz, of d JHH ) 1.5
Hz, 2 H, ArH), 8.31 (d JHH ) 7.0 Hz, of d JHH ) 1.5 Hz, 2 H,
ArH), 7.92 (d JHH ) 8 Hz, of d JHH ) 1.5 Hz, 2 H, ArH), 7.66 (d
JHH ) 8 Hz, of d JHH ) 6.5 Hz, 2 H, ArH), 7.44 (d JHH ) 5.8 Hz,
of d JHH ) 5 Hz, 2 H, ArH), 0.405 (s, 3 H, SiCH3, 3JPtH ) 22 Hz).
13C{1H} NMR (CD2Cl2, 125 MHz): δ 158.5, 155.4, 141.6, 138.2,
135.0, 129.8, 128.8, 127.8, 122.2 (aryl carbons), 2.75 (SiCH3).
The structural and electronic properties of the NSiN ligand
promote the formation of five-coordinate complexes, as seen
in the isolation of [(NSiN)PtR2][B(C6F5)4] [R ) Me (9), H (11)].
This observation is consistent with earlier investigations of
(NSiN)Ir11,13 and (NSiN)Rh12 complexes and suggests that
(45) Baldwin, J. C.; Kaska, W. C. Inorg. Chem. 1975, 14, 2020.
(46) Baldwin, J. C.; Kaska, W. C. Inorg. Chem. 1978, 18, 686.
(47) Butler, J. L.; Gordon, M. J. Heterocycl. Chem. 1975, 12, 1015.
(48) Massey, A. G.; Park, A. J. J. Organomet. Chem. 1964, 2, 245.

Alkyl and Hydrido Complexes of Platinum(IV)
Organometallics, Vol. 27, No. 10, 2008 2229
1
29Si{1H} NMR (CD2Cl2, 99 MHz): δ 14.9 (s, JPtSi ) 1414 Hz).
Anal. Calcd (%) for C19H15N2SiClPt: C, 43.06, H, 2.85, N, 5.29.
Found: 42.77, H, 2.81, N, 5.01.
added a 20 mL CH2Cl2 solution of 1 (0.246 g, 0.819 mmol). The
yellow reaction mixture was stirred at room temperature for 24 h,
after which the CH2Cl2 solution was reduced to a volume of
approximately 8 mL. Vapor diffusion of diethyl ether into this
CH2Cl2 solution at room temperature afforded a yellow crystalline
solid in 82% yield (0.436 g, 0.669 mmol). 1H NMR (CD2Cl2, 500
MHz): δ 11.0 (m, 2 H, ArH), 8.28 (d JHH ) 8 Hz, of d JHH ) 1.5
Hz, 2 H, ArH), 8.16 (d JHH ) 6.5 Hz, of d JHH ) 1.5 Hz, 2 H,
ArH), 7.84 (d JHH ) 8 Hz, of d JHH ) 1 Hz, 2 H, ArH), 7.59 (d
JHH ) 8 Hz, of d JHH ) 7 Hz, 2 H, ArH), 7.46 (d JHH ) 8 Hz, of
cis-(K2-NSiN)2Pt (3). A PTFE-valved heavy-walled sealable
reaction flask equipped with a micromagnetic stir bar was charged
with (tmeda)PtMe2 (0.055 g, 0.161 mmol), 1 (0.100 g, 0.333 mmol),
and 10 mL of benzene. The flask was sealed, and the reaction
solution was stirred in a temperature-controlled oil bath at 80 °C
for 12 h, resulting in a color change from yellow to dark red. Then,
the solution was concentrated to a volume of approximately 3 mL
and filtered through Celite. Slow evaporation of this benzene
solution at room temperature afforded a yellow microcrystalline
solid in 64% yield (0.081 g, 0.103 mmol). 1H NMR (CD2Cl2, 500
MHz): δ 8.79 (d JHH ) 4.4 Hz, of d JHH ) 1.7 Hz, 4 H, ArH), 8.16
(m, 8 H, ArH), 7.63 (d JHH ) 8.0 Hz, of d JHH ) 1.4 Hz, 4 H,
ArH), 7.33 (d JHH ) 8.2 Hz, of d JHH ) 4.6 Hz, 4 H, ArH), 7.27
(d JHH ) 8.0 Hz, of d JHH ) 6.9 Hz, 4 H, ArH), 0.915 (s, 6 H,
2
d JHH ) 5 Hz, 2 H, ArH), 1.17 (s, 6 H, PtCH3, JPtH ) 63 Hz),
1.00 (s, 3 H, SiCH3, 3JPtH ) 22 Hz). 13C{1H} NMR (CD2Cl2, 125
MHz): δ 158.7, 151.0, 142.6, 139.4, 137.2, 130.3, 130.2, 128.0,
123.9 (aryl carbons), -9.3 (SiCH3, 2JPtC ) 57.5 Hz), -13.3 (PtCH3,
1JPtC ) 640 Hz). 29Si{1H} NMR (CD2Cl2, 99 MHz): δ 9.3 (1JPtSi
) 1143 Hz). Anal. Calcd (%) for C21H21N2SiIPt: C, 38.71, H, 3.25,
N, 4.30. Found: C, 39.04, H, 3.33, N, 4.11.
(NSiN)PtMe2(OSO2CF3) (7). (1) To a 10 mL CH2Cl2 solution
of [PtMe3OTf]4 (0.100 g, 0.062 mmol) was added a 5 mL CH2Cl2
solution of 1 (0.078 g, 0.260 mmol). After 10 h of stirring at room
temperature, the reaction mixture was filtered through Celite. The
yellow filtrate was concentrated to a volume of approximately 3
mL. Vapor diffusion of diethyl ether into this CH2Cl2 solution at
room temperature afforded a yellow crystalline solid in 83% yield
(0.138 g, 0.205 mmol).
SiCH3, JPtH ) 45 Hz). 13C{1H} NMR (CD2Cl2, 125 MHz): δ
3
153.3, 148.7, 148.4, 138.2, 137.3, 128.7, 127.5, 126.7, 120.7 (aryl
carbons), 2.24 (SiCH3). 29Si{1H} NMR (CD2Cl2, 99 MHz): δ -6.0
(1JPtSi ) 1670 Hz). Anal. Calcd (%) for C38H30N4Si2Pt: C, 57.48,
H, 3.81, N, 7.06. Found: C, 57.69, H, 3.92, N, 7.09.
(µ-Cl)[(NSiN)Pt]2[B(C6F5)4] (4). To a 10 mL CH2Cl2 solution
of 2 (0.090 g, 0.170 mmol) was slowly added a 5 mL CH2Cl2
solution of Li(Et2O)3[B(C6F5)4] (0.085 g, 0.0935 mmol). The
reaction mixture was stirred at room temperature for 4 h, after which
it was filtered through Celite and evaporated to dryness, resulting
in a yellow foamy residue. The resulting solid was stirred in
approximately 10 mL of diethyl ether for 15 min, and then a yellow
precipitate started to form. The yellow supernatant was decanted,
leaving a yellow solid (4) in 68% yield (0.098 g, 0.0575 mmol).
1H NMR (CD2Cl2, 400 MHz): δ 9.51 (d JHH ) 6 Hz, 2 H, ArH,
(2) Complex 7 can be alternatively synthesized from addition
of approximately 50 mL of CH2Cl2 to a solid mixture of 6 (0.217
g, 0.333 mmol) and AgOTf (0.090 g, 0.350 mmol). The reaction
flask was covered with aluminum foil, and the reaction mixture
was stirred for 4 h at room temperature. Cannula filtration afforded
a clear yellow filtrate, which was concentrated to ca. 5 mL. Vapor
diffusion of diethyl ether into this CH2Cl2 solution produced 7 in
3JPtH ) 59 Hz), 8.18 (d JHH ) 8.4 Hz, 2 H, ArH), 8.04 (d JHH
)
1
89% yield (0.199 g, 0.296 mmol). H NMR (CD2Cl2, 500 MHz):
11 Hz, 2 H, ArH), 7.73 (d JHH ) 10 Hz, 2 H, ArH), 7.64 (m, 2 H,
ArH), 6.71 (d JHH ) 11 Hz, of d JHH ) 6.8 Hz, 2 H, ArH), 0.239
(s, 3 H, SiCH3, 3JPtH ) 35 Hz). 13C{1H} NMR (CD2Cl2, 125 MHz):
δ 157.6, 155.3, 140.1, 138.8, 135.8, 130.0, 129.9, 128.8, 122.6 (aryl
carbons), 2.80 (SiCH3). 19F NMR (CD2Cl2, 376.5 MHz): -132.3
(br s), -162.8 (t JFF ) 21 Hz), -166.7 (br t JFF ) 17 Hz).
29Si{1H} NMR (CD2Cl2, 99 MHz): δ 14.8 (1JSiPt ) 1378 Hz). Anal.
Calcd (%) for C62H30N4Si2ClBF20Pt2: C, 43.71, H, 1.77, N, 3.29.
Found: 43.99, H, 1.85, N, 3.21.
δ 9.72 (m, 2 H, ArH), 8.34 (d JHH ) 8.4 Hz, 2 H, ArH), 8.20 (d
JHH ) 6.8 Hz, 2 H, ArH), 7.92 (d JHH ) 8 Hz, 2 H, ArH), 7.64 (m,
3
4H, ArH), 1.12 (s, 3 H, SiCH3, JPtH ) 28 Hz), 0.844 (s, 6 H,
2
PtCH3, JPtH ) 60 Hz). 13C{1H} NMR (CD2Cl2, 125 MHz): δ
151.7, 150.3, 139.8, 139.6, 136.7, 130.5, 130.3, 128.3, 123.7 (aryl
3
3
2
1
carbons), -7.7 (SiCH3, JPtC ) 71.2 Hz), -9.8 (PtCH3, JPtC
)
645 Hz). 19F{1H} NMR (CD2Cl2, 376.5 MHz): δ -79.2. 29Si{1H}
NMR (CD2Cl2, 99 MHz): δ 7.4 (1JPtSi ) 1223 Hz). Anal. Calcd
(%) for C22H21N2O3F3SiSPt: C, 39.22, H, 3.14, N, 4.16. Found: C,
39.25, H, 3.03, N, 4.00.
(NSiN)PtH2(Cl) (5). A PTFE-valved heavy-walled sealable
reaction flask equipped with a small magnetic stir bar was charged
with (COD)PtCl2 (0.150 g, 0.401 mmol), 1 (0.253 g, 0.842 mmol),
and approximately 15 mL of CH2Cl2. The reaction mixture was
stirred at 60 °C for 36 h, after which all volatiles were removed
under vacuum. The remaining pale yellow solid was washed with
benzene (2 × 3 mL) and dissolved in 10 mL of CH2Cl2, and the
resulting solution was filtered through Celite. The resulting filtrate
was concentrated to a volume of approximately 3 mL and layered
with 3 mL of diethyl ether. A yellow microcrystalline solid was
obtained at room temperature in 54% yield (0.115 g, 0.216 mmol).
(µ-I)[(NSiN)PtMe2]2[B(C6F5)4] (8). To a 3 mL CH2Cl2 solution
of Li(Et2O)3[B(C6F5)4] (0.074 g, 0.0849 mmol) was added a 5 mL
CH2Cl2 solution of 6 (0.100 g, 0.153 mmol). After 4 h of stirring
at room temperature, the reaction mixture was concentrated to ca.
3 mL and filtered through Celite. The resulting filtrate was then
layered with 3 mL of diethyl ether at room temperature to afford
a pale yellow solid in 85% yield (0.121 g, 0.0650 mmol). 1H NMR
(CD2Cl2, 500 MHz): δ 10.6 (br m, 2 H, ArH), 8.37 (d JHH ) 8.5
Hz, of d JHH ) 1.5 Hz, 2 H, ArH), 8.23 (d JHH ) 7.0 Hz, of d JHH
) 1.5 Hz, 2 H, ArH), 7.93 (d JHH ) 8.0 Hz, d JHH ) 1.0 Hz, 2 H,
ArH), 7.67 (d JHH ) 8.0 Hz, of d JHH ) 7.0 Hz, 2 H, ArH), 7.49
(d JHH ) 8.0 Hz, of d JHH ) 5.0 Hz, 2 H, ArH), 1.28 (s, 6 H,
3
1H NMR (CD2Cl2, 500 MHz): δ 10.3 (m, 1 H, ArH, JPtH ) 17
Hz), 8.28 (d JHH ) 8.0 Hz, of d JHH ) 1.5 Hz, 2 H, ArH), 8.18 (d
JHH ) 6.5 Hz, of d JHH ) 1.0 Hz, 2 H, ArH), 7.81 (d JHH ) 8.5
Hz, of d JHH ) 1.0 Hz, 2 H, ArH), 7.62 (d JHH ) 8.0 Hz, of d JHH
) 7.0 Hz, 2 H, ArH), 7.55 (d JHH ) 8.0 Hz, of d JHH ) 5.0 Hz, 2
H, ArH), 1.31 (s, 3 H, SiCH3, 3JPtH ) 36 Hz), -18.3 (s, 2 H, PtH,
1JPtH ) 1274 Hz). 13C{1H} NMR (CD2Cl2, 125 MHz): δ 152.4,
152.1, 143.7, 139.3, 136.2 (JPtC ) 18 Hz), 129.6, 129.4, 127.9,
122.7 (JPtC ) 10 Hz) (aryl carbons), -3.85 (s, SiCH3). 29Si{1H}
NMR (CD2Cl2, 99 MHz): δ 6.7 (s, SiCH3, 1JPtSi ) 982 Hz). Anal.
Calcd (%) for C19H17N2SiClPt: C, 42.89, H, 3.22, N, 5.27. Found:
C, 42.58, H, 3.23, N, 5.01. IR (cm-1): 2243 (PtH).
2
3
PtCH3, JPtH ) 62 Hz), 1.13 (s, 3 H, SiCH3, JPtH ) 25 Hz).
13C{1H} NMR (CD2Cl2, 125 MHz): δ 156.4, 150.2, 140.2, 140.0,
137.4, 130.7, 130.3, 128.3, 123.6 (aryl carbons), -8.2 (SiCH3),
-10.8 (PtCH3). 19F NMR (CD2Cl2, 376.4 MHz): δ -132.3 (br m),
-162.9 (t 3JFF ) 18.8 Hz), -166.8 (br t 3JFF ) 18.8 Hz). 29Si{1H}
NMR (CD2Cl2, 99 MHz): δ 12.6 (s, 1JPtSi ) 1168 Hz). Anal. Calcd
(%) for C66H42N4BF20Si2IPt2: C, 42.73, H, 2.28, N, 3.02. Found:
C, 42.66, H, 2.43, N, 2.75.
[(NSiN)PtMe2][B(C6F5)4] (9). To a 5 mL CH2Cl2 solution of
Li(Et2O)3[B(C6F5)4] (0.126 g, 0.145 mmol) was added a 5 mL
CH2Cl2 solution of 7 (0.090 g, 0.134 mmol). After 2 h of stirring
at room temperature, the reaction mixture was concentrated to 4
(NSiN)PtMe2(I) (6). To a 100 mL Schlenk flask charged with a
40 mL CH2Cl2 solution of [PtMe3I]4 (0.300 g, 0.204 mmol) was

2230 Organometallics, Vol. 27, No. 10, 2008
Sangtrirutnugul and Tilley
mL and filtered through Celite. The resulting yellow filtrate was
layered with approximately 4 mL of pentane. At room temperature,
a colorless microcrystalline solid was obtained in 91% yield (0.146
g, 0.121 mmol). 1H NMR (CD2Cl2, 500 MHz): δ 9.17 (br m, 2 H,
ArH), 8.47 (d JHH ) 8.5 Hz, of d JHH ) 1.5 Hz, 2 H, ArH), 8.27
(d JHH ) 7.0 Hz, of d JHH ) 1.0 Hz, 2 H, ArH), 8.05 (d JHH ) 8.0
(d JHH ) 8.0 Hz, of d JHH ) 2.0 Hz, 2 H, ArH), 6.62 (d JHH ) 8.0
Hz, of d JHH ) 4.0 Hz, 2 H, ArH), 1.04 (s, 3 H, SiCH3). 13C{1H}
NMR (C6D6, 125 MHz): δ 153.0, 150.4, 148.2, 137.0, 136.2, 128.1,
126.7, 126.2, 119.5 (aryl carbons), 2.67 (SiCH3). 29Si{1H} NMR
(C6D6, 99 MHz): δ 13.2 (s). Anal. Calcd (%) for C36H30N4Si2Pd:
C, 57.07, H, 4.31, N, 6.66. Found: C, 56.68, H, 4.17, N, 6.35.
X-ray Crystallography. General Considerations. The single-
crystal X-ray analyses of compounds 2, 7, 9, and cis-(κ2-NSiN)2Pd
were carried out at the UC Berkeley CHEXRAY crystallographic
facility. All measurements were made on a Bruker SMART or
APEX CCD area detector with graphite-monochromated Mo KR
radiation (λ ) 0.71069 Å). Crystals were mounted on capillaries
or a Kapton loop with Paratone N hydrocarbon oil and held in a
low-temperature N2 stream during data collection. Frames were
collected using ω scans at 0.3° increments, using exposures of 10 s
(7 and cis-(κ2-NSiN)2Pd) or 20 s (2 and 9). Cell constants and an
orientation matrix for data collection were obtained from a least-
squares refinement using the measured positions of reflections in
the range 3.5° < 2θ < 49.4°. The frame data were integrated by
the program SAINT (SAX Area-Detector Integration Program;
V4.024; Siemens Industrial Automation, Inc.: Madison, WI, 1995)
and corrected for Lorentz and polarization effects. Data were
analyzed for agreement and possible absorption using XPREP.
Empirical absorption corrections based on comparison of redundant
and equivalent reflections were applied using SADABS. The
structures were solved using the teXsan crystallographic software
package of Molecular Structure Corporation, using direct methods
or Patterson methods, and expanded with Fourier techniques. Unless
stated otherwise, all non-hydrogen atoms were refined anisotropi-
cally, and the hydrogen atoms were placed in calculated positions
but not refined. The function minimized in the full-matrix least-
squares refinement was ∑w(Fo - Fc).2 The weighting scheme was
based on counting statistics and included a p-factor to downweight
the intense reflections. Crystallographic data are summarized in the
Supporting Information.
Hz, d JHH ) 1.0 Hz, 2 H, ArH), 7.73 (d JHH ) 8.0 Hz, of d JHH
)
7.0 Hz, 2 H, ArH), 7.70 (d JHH ) 8.0 Hz, of d JHH ) 5.0 Hz, 2 H,
3
ArH), 1.31 (s, 3 H, SiCH3, JPtH ) 32 Hz), 1.03 (s, 6 H, PtCH3,
2JPtH ) 60 Hz). 13C{1H} NMR (CD2Cl2, 125 MHz): δ 150.4, 149.0,
141.0, 137.1, 136.1, 131.4, 130.5, 128.8, 123.7 (aryl carbons), -5.0
(PtCH3, 1JPtC ) 645 Hz), -5.1 (SiCH3, 2JPtC ) 71.2 Hz). 19F NMR
(CD2Cl2, 376.4 MHz): δ -132.3 (br m), -162.9 (t 3JFF ) 18.8 Hz),
-166.8 (br t 3JFF ) 18.8 Hz). 29Si{1H} NMR (CD2Cl2, 99 MHz): δ
22.8 (s, 1JPtSi ) 1126 Hz). Anal. Calcd (%) for C45H21N2BF20SiPt: C,
44.90, H, 1.76, N, 2.33. Found: C, 45.20, H, 1.88, N, 2.33.
(NSiN)PtH2(OTf) (10). To an aluminum foil-covered reaction
flask was added a 3 mL CH2Cl2 solution of AgOTf (0.036 g, 0.140
mmol) and a 8 mL CH2Cl2 solution of 5 (0.070 g, 0.132 mmol).
The reaction mixture was stirred at room temperature for 12 h,
after which it was filtered through Celite. The pale green filtrate
was evaporated to dryness, leaving an analytically pure pale green
solid in 88% yield (0.075 g, 0.116 mmol). 1H NMR (CD2Cl2, 500
MHz): δ 9.56 (m, 2 H, ArH), 8.34 (d JHH ) 8.2 Hz, of d JHH ) 1.4
Hz, 2 H, ArH), 8.18 (d JHH ) 7.0 Hz, of d JHH ) 1.4 Hz, 2 H,
ArH), 7.88 (d JHH ) 8.2 Hz, of d JHH ) 1.0 Hz, 2 H, ArH),
3
7.66–7.61 (m, 4 H, ArH), 1.30 (s, 3 H, SiCH3, JPtH ) 42 Hz),
1
-17.3 (s, 2 H, PtH, JPtH ) 1312 Hz). 13C{1H} NMR (CD2Cl2,
125 MHz): δ 151.3, 151.2, 141.0, 139.9, 136.5, 129.9, 129.8, 128.2,
123.1 (aryl carbons), -4.03 (s, SiCH3). 19F NMR (CD2Cl2, 376.4
MHz): δ -77.0. 29Si{1H} NMR (CD2Cl2, 99 MHz): δ 2.3 (s, SiCH3,
1JPtSi ) 1029 Hz). Anal. Calcd (%) for C20H17N2SiO3SF3Pt: C,
37.20, H, 2.65, N, 4.34. Found: C, 36.83, H, 2.65, N, 4.68. IR
(cm-1): 2231 (PtH).
[(NSiN)PtH2][B(C6F5)4] (11). To a 3 mL CH2Cl2 solution of
Li(Et2O)3[B(C6F5)4] (0.071 g, 0.082 mmol) was added a 5 mL
CH2Cl2 solution of 10 (0.050 g, 0.077 mmol). After 1 h of stirring,
the reaction mixture was concentrated under vacuum to a volume
of approximately 2 mL and filtered through Celite and a glass fiber
filter. The resulting filtrate was then layered with ca. 2 mL of diethyl
ether. After 3 h at room temperature, a white microcrystalline solid
was collected in 58% yield (0.052 g, 0.045 mmol). 1H NMR
(CD2Cl2, 500 MHz): δ 9.19 (br m, 2 H, ArH), 8.44 (d JHH ) 8.0
Hz, 2 H, ArH), 8.21 (d JHH ) 7.0 Hz, of d JHH ) 1.0 Hz, 2 H,
ArH), 7.95 (d JHH ) 8.0 Hz, 2 H, ArH), 7.70 (t JHH ) 7.0, 2 H,
ArH), 7.66 (d JHH ) 8.5 Hz, of d JHH ) 5.0 Hz, 2 H, ArH), 1.33
For 2: Crystals were grown from a concentrated dichloromethane
solution of 2 at -30 °C.
For 7: Crystals were grown by a vapor diffusion of diethyl ether
into a dichloromethane solution of 7 at room temperature.
For 9: Crystals were grown by a vapor diffusion of pentane into
a dichloromethane solution of 9 at room temperature.
For cis-(κ2-NSiN)2Pd: Crystals were grown by layering diethyl
ether onto a THF solution of cis-(κ2-NSiN)2Pd at -30 °C.30 Each
asymmetric unit contains one palladium molecule and three THF
molecules. A disordered THF molecule lying on the crystallographic
C2 axis was assigned half-occupancy of O(2), C(24)-C(26), and
refined isotropically.
3
1
(s, 3 H, SiCH3, JPtH ) 43 Hz), -16.1 (s, 2 H, PtH, JPtH ) 1314
Hz). 13C{1H} NMR (CD2Cl2, 125 MHz): δ 150.6, 147.5, 141.0, 137.6,
137.3, 130.5, 130.1, 128.2, 123.2 (aryl carbons), -3.8 (SiCH3). 19F
NMR (CD2Cl2, 376.4 MHz): δ -132.3 (br m), -162.9 (t 3JFF ) 18.8
Hz), -166.8 (br t 3JFF ) 18.8 Hz). 29Si{1H} NMR (CD2Cl2, 99 MHz):
δ 14.9 (s). Anal. Calcd (%) for C43H17N2BF20SiPt: C, 43.93, H, 1.46,
N, 2.38. Found: C, 44.23, H, 1.30, N, 2.22. IR (cm-1): 2228 (PtH).
cis-(K2-NSiN)2Pd. To a stirred 5 mL C6H6 solution of (tmeda)P-
dMe2 (0.060 g, 0.237 mmol) was added a 5 mL C6H6 solution of
1 (0.143 g, 0.477 mmol). After 8 h at room temperature, the reddish
reaction solution was filtered through Celite and dried under
vacuum. The resulting solid was redissolved in approximately 3
mL of THF. Crystallization from a 1:1 mixture of THF/diethyl ether
at -30 °C afforded cis-(κ2-NSiN)2Pd in 44% yield (0.074 g, 0.104
Acknowledgment. We thank Dr. Fred Hollander and Dr.
Alan Oliver of the UC Berkeley CHEXRAY facility for
assistance with X-ray crystallography, Jennifer McBee for
technical assistance, Dr. Urs Burckhardt, Dr. Rudi Nunlist,
and Dr. Herman van Halbeek for implementation of 29Si
NMR experiments, and Dr. Ulla Andersen for carrying out
mass spectroscopy measurements. This work was supported
by the National Science Foundation under Grant No. CHE-
0649583.
Supporting Information Available: X-ray experimental details
and structural data for 2, 7, 9, and cis-(κ2-NSiN)2Pd. This material
is available free of charge via the Internet at http://pubs.acs.org.
1
mmol). H NMR (C6D6, 500 MHz): δ 8.48 (d JHH ) 4.0 Hz, of d
JHH ) 1.5 Hz, 2 H, ArH), 8.04 (d JHH ) 6.5 Hz, of d JHH ) 1.5
Hz, 2 H, ArH), 7.49 (d JHH ) 8.0 Hz, of d JHH ) 2.0 Hz, 2 H,
ArH), 7.29 (d JHH ) 6.5 Hz, of d JHH ) 1.5 Hz, 2 H, ArH), 7.11
OM701162H