Facile intramolecular silicon-carbon bond activation at Pt0 and PtII centers

Article abstract of DOI:10.1016/j.poly.2012.07.072

The compound (2-Cy₂PC₆H₄) ₂SiMe₂ (1) reacted readily with Pt(PPh₃) ₄ to undergo Si-C(sp³) bond cleavage and form the Pt ^II species (Cy-PSiP)PtMe (2, Cy-PSiP = κ³-(2-Cy ₂PC₆H₄)₂SiMe^-). The silane 1 also undergoes Si-C(sp³) bond activation with the Pt ^II precursor [(Me₂S)PtMe₂]₂ to generate 2. Two intermediate species were observed in situ during the reaction of 1 with [(Me₂S)PtMe₂]₂. One intermediate was tentatively assigned as the bis(phosphino) Pt^II species (κ²-Cy-PSiP)PtMe₂ (4), which was crystallographically characterized. A second intermediate (5) was tentatively assigned as the Pt^IV species (Cy-PSiP)PtMe₃ resulting from Si-C(sp³) bond cleavage in 4. In an effort to prepare a (Cy-PSiP)Pt^IV species that may serve as a model for 5, complex 2 was reacted with MeI and I₂, respectively; both reactions resulted in the quantitative formation of (Cy-PSiP)PtI (6), which could also be independently prepared by the reaction of (COD)PtI₂ with (Cy-PSiP)H. The reaction of (Cy-PSiP)H with PtMe₃I resulted in the formation of a Pt ^IV species (7) as the major product. Complex 7 was tentatively assigned as (Cy-PSiP)PtMe₂I, and undergoes relatively facile elimination of ethane to form 6.

Full text of DOI:10.1016/j.poly.2012.07.072

Polyhedron 52 (2013) 750–754
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Facile intramolecular silicon–carbon bond activation at Pt0 and PtII centers
Samuel J. Mitton a, Robert McDonald b, Laura Turculet a,
⇑
a Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J3
b X-Ray Crystallography Laboratory, Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
a r t i c l e i n f o
a b s t r a c t
The compound (2-Cy2PC6H4)2SiMe2 (1) reacted readily with Pt(PPh3)4 to undergo Si–C(sp3) bond cleavage
Article history:
Available online 1 August 2012
and form the PtII species (Cy-PSiP)PtMe (2, Cy-PSiP = 3-(2-Cy2PC6H4)2SiMeÀ). The silane 1 also undergoes
j
Si–C(sp3) bond activation with the PtII precursor [(Me2S)PtMe2]2 to generate 2. Two intermediate species
were observed in situ during the reaction of 1 with [(Me2S)PtMe2]2. One intermediate was tentatively
Dedicated to Alfred Werner on the 100th
Anniversary of his 1913 Nobel prize in
Chemistry.
assigned as the bis(phosphino) PtII species ( 2-Cy-PSiP)PtMe2 (4), which was crystallographically charac-
j
terized. A second intermediate (5) was tentatively assigned as the PtIV species (Cy-PSiP)PtMe3 resulting
from Si–C(sp3) bond cleavage in 4. In an effort to prepare a (Cy-PSiP)PtIV species that may serve as a
model for 5, complex 2 was reacted with MeI and I2, respectively; both reactions resulted in the quanti-
tative formation of (Cy-PSiP)PtI (6), which could also be independently prepared by the reaction of
(COD)PtI2 with (Cy-PSiP)H. The reaction of (Cy-PSiP)H with PtMe3I resulted in the formation of a PtIV spe-
cies (7) as the major product. Complex 7 was tentatively assigned as (Cy-PSiP)PtMe2I, and undergoes rel-
atively facile elimination of ethane to form 6.
Keywords:
Platinum
Pincer
Bond activation
Silyl
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Si–C(sp3) bond cleavage involving both Pt0 and PtII precursors to
ultimately form the known PtII complex (Cy-PSiP)PtMe (2) [5].
The activation of chemical bonds (e.g. Si–H, B–H, C–H) at tran-
sition metal centers is a fundamental area of inquiry in organome-
tallic chemistry, and has been shown to be a key step in numerous
catalytic processes [1]. In this context, examples of Si–C(sp3) bond
activation by transition metals are exceedingly rare [2,3], due in
part to the high bond dissociation energy and low polarity associ-
ated with Si–C linkages. The study of metal complexes that readily
undergo Si–C(sp3) bond cleavage processes is anticipated to play
an important role in furthering our understanding of Si–C bond
activation and may have utility in the development of new metal
catalyzed reactions for the functionalization of organosilanes [4].
We have recently reported on the facile and reversible cleavage
of Si–C(sp2) and Si–C(sp3) bonds in Ni and Pd silyl pincer com-
We also report our attempts to observe (Cy-PSiP)PtIV species that
are proposed as intermediates in the formation of 2 via Si–C(sp3)
oxidative addition to PtII.
2. Results and discussion
2.1. Si–C(sp3) bond activation at Pt0
In an effort to observe Si–C bond cleavage mediated by Pt0, the
silane (2-Cy2PC6H4)2SiMe2 (1) was reacted with Pt(PPh3)4
(Scheme 1) in room temperature benzene-d6 solution and the reac-
tion was monitored by use of 1H and 31P NMR spectroscopy. Over
the course of 48 h, complete conversion to the previously reported
[5] PtII complex (Cy-PSiP)PtMe (2; 31P NMR: 57.9 ppm,
1JPPt = 2938 Hz) was observed, and complex 2 was isolated in 86%
yield from this reaction. No intermediates were observed by use
of 1H or 31P NMR spectroscopy during the course of the reaction.
The mechanism of Si–C(sp3) bond activation by Pt0 complexes
has been previously investigated. Hofmann and co-workers have
demonstrated that Si–C bond activation of tetramethylsilane by
(dtbpm)Pt0 (dtbpm = tBu2PCH2PtBu2) proceeds via an initial C–H
bond activation of the silane, followed by a rearrangement to give
the Si–C bond activation product [2c]. As such, it is possible that
the formation of 2 proceeds via an initial C–H bond activation of
a SiMe group in 1, which is followed by a rearrangement to provide
2 as the final product. However, we do not currently have mecha-
plexes of the type (Cy-PSiP)MMe (Cy-PSiP = j
3-(2-Cy2-
PC6H4)2SiMeÀ; M@Ni, Pd; Fig. 1) [2a]. We proposed that
complexes of the type (Cy-PSiP)MMe serve as a source of the M0
species [j
2-(2-Cy2PC6H4)2SiMe2]M, which undergoes subsequent
Si–C(sp2) or Si–C(sp3) bond cleavage. In accordance with this
hypothesis, we observed that the silane (2-Cy2PC6H4)2SiMe2 (1) re-
acted quantitatively with Pd2(dba)3 (dba = dibenzylidene acetone)
to form [(j j
2-Cy2PC6H4SiMe2)Pd( 2-Cy2PC6H4)] via Si–C(sp2) bond
cleavage in 1 (Scheme 1) [2a]. In an effort to expand this Si–C bond
activation chemistry to Pt, we report herein that 1 undergoes facile
⇑
Corresponding author. Tel.: +1 902 494 6414; fax: +1 902 494 1310.
E-mail address: laura.turculet@dal.ca (L. Turculet).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.07.072

S.J. Mitton et al. / Polyhedron 52 (2013) 750–754
751
nance at 23.1 ppm (1JPPt = 934 Hz). The magnitude of the coupling
constant observed for complex 5 suggests that this complex likely
corresponds to a PtIV species.
PCy2
PCy2
M
M = Pd
M = Ni
MeSi
M
Me
Me2Si
PCy2
Despite exhaustive efforts, we have thus far not been able to
isolate either of 4 or 5 in pure form; rather, mixtures of 2, 4, and
5 were invariably obtained. However, crystallization attempts en-
abled the isolation of a minute quantity of crystalline material
(from a Et2O solution at À35 °C) that proved suitable for single
crystal X-ray diffraction analysis. The crystallographically charac-
PCy2
Fig. 1. Cleavage of Si–C(sp2) and Si–C(sp3) bonds in silyl pincer complexes of the
type (Cy-PSiP)MMe (M@Ni, Pd).
terized material (Fig. 2 and Table 1) corresponds to [j
2-(2-Cy2-
PC6H4)2SiMe2]PtMe2, the product of phosphine coordination in 1
to the PtMe2 fragment. We tentatively assign this compound as
complex 4, a putative intermediate in the formation of 2 via Si–
C(sp3) bond activation in 1 at a PtII center. The solid state structure
of 4 features approximate square planar geometry at Pt, with cis-
disposed phosphino groups (P1–Pt–P2 = 102.491(14)°). The eight-
membered metallacycle resulting from coordination of the phos-
phino groups in 1 to Pt adopts a ‘‘boat-boat’’-type configuration,
such that a Si-Me group is oriented directly above the square plane
defined by the Pt center (PtÁ Á ÁC(1) = 3.35 Å; PtÁ Á ÁSi = 3.53 Å). The
structure of 4 is related to that of (bps)PtMe2 (bps = bis(2-pyri-
dyl)dimethylsilane), which adopts a similar orientation of a Si-
Me substituent (PtÁ Á ÁSi = 3.25 Å) [2g]. Interestingly, the structurally
related complex (bps)PtMe2 has been reported to undergo Si–
C(sp3) bond cleavage only under oxidizing conditions to afford PtIV
species of the type [j3N,N,O-(2-C5H4N)2SiMeO]PtMe3 [2g]. No Si–C
bond activation was reported for (bps)PtMe2 in the absence of oxi-
dants such as oxygen, hydrogen peroxide, or dibenzoyl peroxide, in
contrast to the system presented herein. Mechanistic studies in the
(bps)PtMe2 system suggested that oxidation to PtIV preceded
methyl transfer from Si to Pt.
nistic data to favor this mechanism over direct insertion of the Pt
center into a Si–C bond.
Surprisingly, Si–C bond activation in 1 involving Pt0 differs from
the previously reported reaction of 1 with Pd2(dba)3, which also
proceeds quantitatively in room temperature benzene-d6 solution
to provide complex 3, the product of Si–C(sp2) bond cleavage
(Scheme 1); as in the case of the Pt(PPh3)4 reaction, no intermedi-
ates were observed by use of 1H or 31P NMR spectroscopy during
the course of this reaction [2a]. In contrast, our previous report
of reversible Si–C(sp2) and Si–C(sp3) bond cleavage involving (Cy-
PSiP)NiMe suggests that Ni0 species of the type
PC6H4)2SiMe2]Ni are able to access both Si–C(sp2) bond cleavage
(to form the Ni analog of 3, [(
2-Cy2PC6H4SiMe2)Ni( 2-Cy2PC6H4)])
[j
2-(2-Cy2-
j
j
and Si–C(sp3) bond cleavage to reform (Cy-PSiP)NiMe [2a]. Thus it
appears that the choice of metal influences the outcome of Si–C
bond cleavage in this system, such that Pt favors the formation
of products resulting from Si–C(sp3) bond cleavage, while Pd favors
the formation of products resulting from Si–C(sp2) bond cleavage,
and Ni is able to access both types of products in a reversible
fashion.
In the case of Si–C activation in 1 involving an LnPtMe2 precur-
sor, we propose that
j
2-coordination of 1 to Pt occurs initially to
2.2. Si–C(sp3) bond activation involving PtII
form the bis(phosphino) complex 4. In previously reported exam-
ples of Si–C(sp3) activation at PtII centers, it has been proposed that
such transformations proceed via an initial C–H bond activation
step [2e,f], followed by a subsequent concerted migration process
that leads to the formation of the net Si–C bond cleavage product
[2f]. Although such a mechanism is plausible in the case of 4, we
also cannot discount a process involving direct insertion of Pt into
a Si–C bond. The product of such Si–C bond cleavage is the PtIV spe-
cies (Cy-PSiP)PtMe3, which we tentatively assign as complex 5, and
which was observed in situ during the course of the formation of 2
(vide supra) [6]. Reductive elimination of ethane from the putative
We further investigated the reactivity of 1 with [(Me2S)PtMe2]2
in order to determine if Si–C bond activation could also be
achieved by use of PtII precursors. Thus, treatment of a benzene-
d6 solution of 1 with half an equiv. of [(Me2S)PtMe2]2 led to the for-
mation of three products (1:1:1 ratio by 31P NMR) upon standing at
room temperature for 5 days (Scheme 1). One of the three reaction
products was identified as complex 2 on the basis of its 31P NMR
1
chemical shift (57.9 ppm, JPPt = 2938 Hz). A second product (4)
features a 31P NMR resonance at 27.7 ppm (1JPPt = 2050 Hz), while
the third species in solution (5) features a broad 31P NMR reso-
Si-C(sp2) activation
Si-C(sp3) activation
PCy2
PCy2
PCy2
0.5 Pd2(dba)3
Pt(PPh3)4
RT, 48 h
MeSi
Me
MeSi
Pt Me
Me2Si
Pd
PCy2
PCy2
PCy2
3
1
2
0.5 [(Me2S)PtMe2]2
− C2H6
Me
Si
SiMe
Me
Me
Me
Cy2P
Cy2P
Pt
Me
Me
Cy2P
Cy2P
Pt
4
Me
5
Scheme 1. Reaction of 1 with Pt0, Pd0, and PtII complexes.

752
S.J. Mitton et al. / Polyhedron 52 (2013) 750–754
PCy2
PCy2
Pt
PCy2
MeI or I2
(COD)PtI2
Et3N
MeSi
Pt Me
MeSi
I
MeSi
H
PCy2
PCy2
PCy2
2
6
PtMe3I
− CH4
− C2H6
SiMe
Me
Me
Cy2P
Cy2P
Pt
I
7
Scheme 2. Attempted synthesis of a (Cy-PSiP)PtIV species.
2.3. Attempted synthesis of a (Cy-PSiP)PtIV species
In an effort to synthesize a (Cy-PSiP)PtIV species that may serve as
a model for the proposed PtIV intermediate (5) in the Si–C(sp3) bond
activation process observed for 1 at PtII, complex 2 was reacted with
one equiv each of either MeI or I2 (Scheme 2). No reaction was ob-
served (by 31P NMR) upon treatment of 2 with one equiv of MeI at
room temperature in benzene-d6 solution. Subsequent heating of
the reaction mixture at 75 °C for 1 h resulted in quantitative (by
Fig. 2. ORTEP diagram for 4 shown with 50% displacement ellipsoids; all H-atoms
have been omitted for clarity. Selected interatomic distances (Å) and angles (°) for
4: Pt–P1 2.3078(4); Pt–P2 2.3106(4); Pt–C3 2.1032(16); Pt–C4 2.1051(16); PtÁ Á ÁC(1)
3.35; PtÁ Á ÁSi 3.53; P1–Pt–P2 102.491(14); C3–Pt–C4 81.82(7); P1–Pt–C4 170.50(5);
P2–Pt–C3 163.33(5).
1
31P NMR) formation of (Cy-PSiP)PtI (6; 58.9 ppm, JPPt = 2948 Hz),
which was independently synthesized by the reaction of (Cy-PSiP)H
with (COD)PtI2 (COD = 1,5-cyclooctadiene) in the presence of Et3N.
Treatment of 2 with one equiv of I2 resulted in the immediate and
quantitative (by 31P NMR) formation of 6. No intermediates were
observed in the reaction of 1 with either MeI or I2.
Table 1
Crystal data and refinement parameters for 4.
4
Alternatively, treatment of (Cy-PSiP)H with one equiv of PtMe3I
in benzene-d6 solution resulted in the formation of a mixture of
two products (2:1 ratio by 31P NMR) upon heating for 3.5 h at
75 °C. The major product (7) gives rise to a broad 31P NMR reso-
nance at 19.3 ppm (1JPPt = 1187 Hz), while the minor product corre-
sponds to the PtII iodo complex 6 (Scheme 2). The magnitude of the
Pt–P one bond coupling in 7 is consistent with a PtIV species of the
Empirical formula
Formula weight
Crystal dimensions
Crystal system
Space group
a (Å)
C40H64P2PtSi
830.03
0.63 Â 0.44 Â 0.31
C2/c (No. 15)
monoclinic
38.7504(13)
9.3925(3)
20.8598(7)
90
b (Å)
c (Å)
1
type (Cy-PSiP)PtMe2I (7; cf. JPPt = 1112 Hz for (dppe)PtMe3I;
a
(°)
dppe = Ph2PCH2CH2PPh2 [7b]). The 1H NMR spectrum of the reac-
tion mixture features resonances for both methane (0.15 ppm)
and ethane (0.80 ppm), which is consistent with initial Si–H activa-
tion in (Cy-PSiP)H to liberate methane and form complex 7, fol-
lowed by C–C reductive elimination in 7 to give 6. Further
heating of the reaction mixture for 12 h at 95 °C resulted in the
quantitative formation of 6. Unfortunately, attempts to isolate
the PtIV species 7 were not successful, as 6 was always observed
as a contaminant. However, the in situ observation of putative 7
would appear to suggest that (Cy-PSiP)PtIV species of this type
are synthetically accessible and readily undergo reductive elimina-
tion of ethane.
b (°)
96.2086(4)
90
7547.7(4)
8
1.461
3.861
0.3759–0.1940
55.12
À49 6 h 6 50
À12 6 k 6 12
À26 6 l 6 27
32378
8699
0.0123
7991
8699/0/401
1.053
0.0154
0.0400
0.684, À0.723
c
(°)
V (Å3)
Z
qcalc (gcmÀ3
)
l
(mmÀ1
)
Range of transmission
2h limit (°)
Total data collected
Independent reflections
Rint
Observed reflections
Data/restraints/parameters
Goodness-of-fit
3. Summary and conclusions
R1 [Fo2 P 2
wR2 [Fo2 P –3
Largest peak, hole (eÅÀ3
r
(Fo2)]
r
(Fo2)]
Examples of Si–C(sp3) bond activation in the silane (2-Cy2-
PC6H4)2SiMe2 (1) involving both Pt0 and PtII precursors have been
described. In the case of Si–C cleavage involving Pt0, 1 reacted read-
ily with Pt(PPh3)4 to form the PtII complex (Cy-PSiP)PtMe (2) with no
evidence of intermediate species. Interestingly, this example of
Si–C(sp3) bond activation differs from the previously reported,
analogous reaction of 1 with the Pd0 source Pd2(dba)3, which
led to formation of the Si–C(sp2) bond activation product
)
intermediate 5 provides the final observed product of this reaction,
complex 2 [7]. The 1H NMR spectrum of the reaction mixture con-
taining 4, 5, and 2 indeed indicates the evolution of ethane
(0.80 ppm, benzene-d6).

S.J. Mitton et al. / Polyhedron 52 (2013) 750–754
753
[(
j
2-Cy2PC6H4SiMe2)Pd(
j
2-Cy2PC6H4)] (3). Previous results involv-
4.2.1. Synthesis of 2 via Si–C(sp3) bond cleavage involving Pt0
ing Ni are consistent with the formation of an equilibrium mixture
containing both Si–C(sp3) and Si–C(sp2) bond activation products
derived from 1. Thus it is evident that the choice of metal (Ni versus
Pd versus Pt) directs the outcome of Si–C bond cleavage involving 1.
The silane 1 also reacted with [(Me2S)PtMe2]2 to generate 2.
Two intermediate species were observed in situ during the course
of this reaction. One intermediate was tentatively assigned as the
A solution of 1 (0.10 g, 0.17 mmol) in ca. 5 mL of benzene was
added to Pt(PPh3)4 (0.21 g, 0.17 mmol). The resulting pale yellow
solution was allowed to stand at room temperature over the course
of 48 h. The volatile components of the reaction mixture were sub-
sequently removed in vacuo and the remaining residue was
washed with cold (À30 °C) pentane (5 Â 3 mL) and dried under
vacuum to afford 2 as a pale yellow solid (0.12 g, 86% yield). The
spectroscopic characterization of the product obtained was in full
agreement with previously published data [5].
bis(phosphino) PtII species ( 2-Cy-PSiP)PtMe2 (4), which was crys-
j
tallographically characterized, and is structurally related to the
bis(2-pyridyl) dimethylsilane complex (bps)PtMe2. The latter com-
plex was also reported to undergo Si–C(sp3) bond cleavage, how-
ever only upon treatment with oxidants. As such, the mechanism
of Si–C(sp3) cleavage in 4 is different, as no oxidants are required
for the transformation. This disparity likely results from a ligand
effect, as the electronic character of the bis(phosphino) PtII center
is likely quite different from that of a bis(pyridyl) PtII center. We
propose that Si–C(sp3) cleavage in 4 leads to the formation of the
PtIV species (Cy-PSiP)PtMe3 (5), which undergoes subsequent elim-
ination of ethane to generate 2. The second intermediate observed
in situ during the course of the reaction of 1 with [(Me2S)PtMe2]2
indeed appears to be a PtIV species, and was thus tentatively as-
signed as 5. As we were unable to isolate complex 5, we attempted
to prepare a model species that featured Cy-PSiP coordination to
PtIV. Indeed, the reaction of (Cy-PSiP)H with PtMe3I led to the for-
mation of a PtIV complex (7), which we tentatively assign as (Cy-
PSiP)PtMe2I. Complex 7 features a 31P NMR chemical shift and 1JPPt
that are very similar to those observed for the proposed intermedi-
ate 5, and it also undergoes relatively facile reductive elimination
of ethane to generate (Cy-PSiP)PtI (6). This data would appear to
provide indirect evidence for the viability of the intermediate 5
and for C–C reductive elimination from 5 to generate a PtII species.
4.2.2. Generation of 2 via Si–C(sp3) bond cleavage involving PtII
A solution of 1 (0.030 g, 0.050 mmol) in ca. 1 mL of benzene-d6
was added to [Pt(SMe2)Me2]2 (0.014 g, 0.025 mmol). The resulting
yellow solution was allowed to stand at room temperature over
the course of 5 days and was monitored by 31P and 1H NMR spec-
troscopy. After standing at room temperature for 18 h, 31P NMR
analysis of the reaction mixture indicated 80% consumption of 1
and the formation of
a product mixture consisting of 4
1
1
(27.7 ppm, JPPt = 2050 Hz) and 5 (23.1 ppm, br s, JPPt = 934 Hz)
in a 1:3 ratio. After standing at room temperature for 5 days, 31P
NMR analysis of the reaction mixture indicated complete con-
sumption of 1 and the formation of a product mixture consisting
1
1
of 2 (57.9 ppm, JPPt = 2938 Hz), 4 (27.7 ppm, JPPt = 2050 Hz) and
1
5 (23.1 ppm, br s, JPPt = 934 Hz) in a 1:1:1 ratio. Although 1H
NMR analysis of the resulting product mixtures was complicated
by the overlap of aryl and cyclohexyl proton resonances, a reso-
nance at 0.80 ppm corresponding to ethane was observed.
4.3. (Cy-PSiP)PtI (6)
4.3.1. Synthesis of 6 via (COD)PtI2
A solution of (Cy-PSiP)H (0.10 g, 0.17 mmol) in. ca 2 mL of ben-
zene was added to (COD)PtI2 (0.095 g, 0.17 mmol). The resulting
reaction mixture was treated with NEt3 (0.026 mL, 0.19 mmol).
The reaction mixture was subsequently allowed to stand at room
temperature for 1 h, and was then filtered through Celite. The vol-
atile components of the filtrate solution were removed under vac-
uum. The remaining yellow residue was washed with ca. 3 mL of
cold (À30 °C) pentane and dried under vacuum to afford 6 as a pale
yellow solid (0.15 g, 96% yield). The spectroscopic data obtained for
6 is in good agreement with the previously reported analogous
complexes (Cy-PSiP)PtCl and (Cy-PSiP)PtOTf [5]. 1H NMR
(500 MHz, benzene-d6): d 8.07 (d, 2H, Harom, J = 7 Hz), 7.51 (m,
2H, Harom), 7.31 (t, 2H, Harom, J = 7 Hz), 7.19 (t, 2H, Harom, J = 7 Hz),
3.43 (m, 2H, PCH), 2.77 (m, 2H, PCH), 2.40 (m, 2H, PCy), 2.24–
2.09 (overlapping resonances, 6H, PCy), 1.75–0.82 (overlapping
resonances, 32H, PCy), 0.68 (s with Pt satellites, 3H, SiMe,
3JHPt = 26 Hz). 13C{1H} NMR (125.8 MHz, benzene-d6): d 156.4
(apparent t, Carom, J = 22 Hz), 141.1 (apparent t, Carom, J = 25 Hz),
133.3 (CHarom), 131.8 (CHarom), 130.9 (CHarom), 129.4 (CHarom),
4. Experimental
4.1. General
All experiments were conducted under nitrogen in an MBraun
glovebox or using standard Schlenk techniques. Dry, oxygen-free
solvents were used throughout. All non-deuterated solvents were
deoxygenated and dried by sparging with nitrogen and subsequent
passage through a double-column solvent purification system pur-
chased from MBraun Inc. Tetrahydrofuran and diethyl ether were
purified over two activated alumina columns, while benzene, tolu-
ene, and pentane were purified over one activated alumina column
and one column packed with activated Q-5. All purified solvents
were stored over 4 Å molecular sieves. Benzene-d6 was degassed
via three freeze–pump–thaw cycles and stored over 4 Å molecular
sieves. The compounds Pt(PPh3)4 and PtMe3I were purchased from
Strem and used as received. The compounds (2-Cy2PC6H4)2SiMe2
[2a], (2-Cy2PC6H4)2SiHMe [8], (COD)PtI2 [9], [(Me2S)PtMe2]2 [10],
and (Cy-PSiP)PtMe [5] were prepared according to literature proce-
dures. All other reagents were purchased from Aldrich and used
without further purification. Unless otherwise stated, 1H, 13C, 31P,
and 29Si characterization data were collected at 300 K on a Bruker
AV-500 spectrometer operating at 500.1, 125.8, 202.5, and
99.4 MHz (respectively) with chemical shifts reported in parts
per million downfield of SiMe4 (for 1H, 13C, and 29Si), or 85%
H3PO4 in D2O (for 31P). 29Si NMR assignments are based on
1H–29Si HMQC and 1H–29Si HMBC experiments.
39.5 (apparent t, CHCy
, J = 15 Hz), 37.9 (apparent t, CHCy,
J = 13 Hz), 31.6–26.3 (overlapping resonances, CH2Cy), 8.4 (SiMe).
31P {1H} NMR (202.5 MHz, benzene-d6): d 59.0 (s with Pt satellites,
1JPPt = 2948 Hz). 29Si NMR (99.4 MHz, benzene-d6): d 39.8 (s with Pt
1
satellites, JSiPt = 1155 Hz).
4.3.2. Generation of 6 via the reaction of 2 with MeI
A solution of 2 (0.015 g, 0.019 mmol) in ca. 1 mL of benzene-d6
was treated with MeI (1.2 ll, 0.019 mmol). The resulting pale yel-
low reaction mixture was heated at 75 °C for 1 h, at which point 31
NMR analysis indicated quantitative conversion to 6.
P
4.2. (Cy-PSiP)PtMe (2)
4.3.3. Generation of 6 via the reaction of 2 with I2
The synthesis of this compound by an alternate route and its full
characterization have been previously reported [5].
A solution of 2 (0.010 g, 0.013 mmol) in ca. 1 mL of benzene-d6
was treated with I2 (0.003 g, 0.013 mmol). The resulting purple

754
S.J. Mitton et al. / Polyhedron 52 (2013) 750–754
reaction mixture was allowed to stand at room temperature over
the course of 10 min, at which point 31P NMR analysis indicated
quantitative conversion to 6.
Appendix A. Supplementary data
CCDC 879358 contains the supplementary crystallographic data
for 4. These data may be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223–336-033; or e-mail: deposit@ccdc.cam.ac.uk.
4.3.4. Generation of 6 via PtMe3I
A solution of (Cy-PSiP)H (0.015 g, 0.025 mol) in ca. 1 mL of ben-
zene-d6 was added to PtMe3I (0.009 g, 0.025 mmol). The reaction
mixture was subsequently heated at 75 °C over the course of
3.5 h, at which point 31P NMR analysis indicated complete con-
sumption of (Cy-PSiP)H and the formation of a product mixture
consisting of 6 and 7 (19.3 ppm, br s, 1JPPt = 1187 Hz) in a 1:2 ratio.
Subsequent heating of the reaction mixture at 95 °C for 12 h re-
sulted in the quantitative formation of 6. 1H NMR (500 MHz) anal-
ysis of the reaction mixture after heating at 75 °C for 3.5 h revealed
several resonances that could be unambiguously assigned to 7 (as
References
[1] J.F. Hartwig, Organotransition Metal Chemistry. From Bonding to Catalysis,
University Science Books, Sausalito, CA, 2010.
[2] For selected examples of Si–C(sp3) bond activation involving platinum group
metals, see:
(a) S.J. Mitton, R. McDonald, L. Turculet, Angew. Chem., Int. Ed. 48 (2009)
8568;
(b) J. Takaya, N. Iwasawa, Organometallics 28 (2009) 6636;
(c) P. Hofmann, H. Heiss, P. Neiteler, G. Müller, J. Lachmann, Angew. Chem., Int.
Ed. Engl. 29 (1990) 880;
(d) S.K. Thomson, G.B. Young, Organometallics 8 (1989) 2068;
(e) A.F. Heyduk, J.A. Labinger, J.E. Bercaw, J. Am. Chem. Soc. 125 (2003) 6366;
(f) C.M. Ong, T.J. Burchell, R.J. Puddephatt, Organometallics 23 (2004) 1493;
(g) M. Safa, M.C. Jennings, R.J. Puddephatt, Organometallics 31 (2012) 3539;
(h) B.C. Fullmer, H. Fan, M. Pink, J.C. Huffman, N.P. Tsvetkov, K.G. Caulton, J.
Am. Chem. Soc. 133 (2011) 2571;
well as the formation of ethane and methane): d 7.65 (d, 2H, Harom
,
J = 7 Hz). 7.46 (m, 2H, Harom), 7.12 (t, 2H, Harom, J = 7 Hz), 7.03 (t, 2H,
Harom, J = 7 Hz), 0.35–0.86 (overlapping resonances corresponding
to PCy and PtMe protons in 6 and 7), 0.61 (s with Pt satellites,
3
3H, SiMe, JHPt = 17 Hz).
4.4. X-ray crystallography
(i) D.E. Hendriksen, A.A. Oswald, G.B. Ansell, S. Leta, R.V. Kastrup,
Organometallics 8 (1989) 1153;
Crystallographic data for 4 were obtained at 173( 2) K on a Bru-
ker D8/APEX II CCD diffractometer using graphite-monochromated
(j) W. Lin, S.R. Wilson, G.S. Girolami, Organometallics 13 (1994) 2309;
(k) R. Hua, M. Akita, Y. Moro-oka, Chem. Commun. (1996) 541.
[3] For selected examples of Si–C(sp) and Si–C(sp2) bond activation, see:
(a) P. Steenwinkel, R.A. Gossage, T. Maunula, D.M. Grove, G. van Koten, Chem.
Eur. J. 4 (1998) 763;
MoKa (k = 0.71073 Å) radiation, employing a sample that was
mounted in inert oil and transferred to a cold gas stream on the dif-
fractometer. Programs for diffractometer operation, data collec-
(b) K. Temple, A.J. Lough, J.B. Sheridan, I. Manners, J. Chem. Soc., Dalton Trans.
(1998) 2799;
tion, and data reduction (including SAINT) were supplied by
(c) H. Gilges, U. Schubert, Organometallics 17 (1998) 4760;
(d) N. Mintcheva, Y. Nishihara, M. Tanabe, K. Hirabayashi, A. Mori, K. Osakada,
Organometallics 20 (2001) 1243;
(e) R. Beck, S.A. Johnson, Organometallics 31 (2012) 3599;
(f) D. Huang, R.J. Heyn, J.C. Bollinger, K.G. Caulton, Organometallics 16 (1997)
292;
Bruker. Gaussian integration (face-indexed) was employed as the
absorption correction method. The structure was solved by use of
the Patterson search/structure expansion and were refined by use
of full-matrix least-squares procedures (on F2) with R1 based on
Fo2 P 2
r
(Fo2) and wR2 based on Fo2 P À3
r
(Fo2). Anisotropic dis-
(g) B.L. Edelbach, R.J. Lachicotte, W.D. Jones, Organometallics 18 (1999) 4660;
(h) C. Müller, R.J. Lachicotte, W.D. Jones, Organometallics 21 (2002) 1190.
[4] I. Ojima, in: S. Patai, Z. Rappoport (Eds.), The Chemistry of Organosilicon
Compounds, Wiley, Chichester, 1989.
placement parameters were employed for all the non-hydrogen
atoms of 4. Hydrogen-atoms were added at calculated positions
and refined by use of a riding model employing isotropic displace-
ment parameters based on the isotropic displacement parameter of
the attached atom. Additional crystallographic information is pro-
vided in Table 1.
[5] S.J. Mitton, R. McDonald, L. Turculet, Organometallics 28 (2009) 5122.
[6] Although we cannot discount the possibility of C–C reductive elimination in 4
to afford a bis(phosphino)Pt0 species that undergoes subsequent Si–C(sp3)
bond cleavage, the observation of a putative PtIV species (5) in the reaction
mixture would appear to suggest that a PtIV intermediate is involved in the
observed bond cleavage process.
[7] For a discussion of C–C reductive elimination from PtIV species, see:
(a) M.P. Brown, R.J. Puddephatt, C.E.E. Upton, J. Chem. Soc., Dalton Trans.
(1974) 2457;
Acknowledgements
We are grateful to the Natural Sciences and Engineering Research
Council (NSERC) of Canada (including a Discovery Grant for L.T.), the
Canada Foundation for Innovation, the Nova Scotia Research and
Innovation Trust Fund, and Dalhousie University for their generous
support of this work. We also thank Dr. Michael Lumsden (NMR3,
Dalhousie) for his assistance in the acquisition of NMR data.
(b) K.I. Goldberg, J. Yan, E.M. Breitung, J. Am. Chem. Soc. 117 (1995) 6889;
(c) D.M. Crumpton-Bregel, K.I. Goldberg, J. Am. Chem. Soc. 125 (2003) 9442.
[8] D.F. MacLean, R. McDonald, M.J. Ferguson, A.J. Caddell, L. Turculet, Chem.
Commun. (2008) 5146.
[9] H.C. Clark, L.E. Manzer, J. Organomet. Chem. 59 (1973) 411.
[10] G.S. Hill, M.J. Irwin, C.J. Levy, L.M. Rendina, R.J. Puddephatt, Inorg. Synth. 32
(1998) 149.