Trimethylsilylplatinum(IV) complexes as reaction intermediates

Article abstract of DOI:10.1016/j.ica.2010.11.018

The oxidative addition of I₂, PhCH₂Br and MeI with [Pt(CH₂SiMe₃)₂(DPK)], 1, DPK = di-2-pyridyl ketone, occurred with trans stereochemistry to give [PtI₂(CH ₂SiMe₃)₂(DPK)], [PtBr(CH₂Ph)(CH ₂SiMe₃)₂(DPK)] and [PtIMe(CH ₂SiMe₃)₂(DPK)], respectively. Complex 1 reacted with acids HX (X = Cl or CF₃CO₂) to give initially the hydridoplatinum complexes [PtHX(CH₂SiMe₃) ₂(DPK)], but these complexes were thermally unstable and decomposed largely by α-silyl migration to give compounds such as [PtX(SiMe ₃)Me₂(DPK)], as determined by monitoring the reactions by NMR at low temperature. With excess acid, HX, at room temperature, the products were largely [PtX₂(DPK)], CH₄ and Me₃SiX with Me₄Si as a minor product only. The mechanism of the easy Si-CH ₂ bond cleavage is discussed.

Full text of DOI:10.1016/j.ica.2010.11.018

Inorganica Chimica Acta 369 (2011) 190–196
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Trimethylsilylplatinum(IV) complexes as reaction intermediates
⇑
Michael J. Hamilton, Richard J. Puddephatt
Department of Chemistry, University of Western Ontario, London, Canada N6A 5B7
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 21 November 2010
The oxidative addition of I2, PhCH2Br and MeI with [Pt(CH2SiMe3)2(DPK)], 1, DPK = di-2-pyridyl ketone,
occurred with trans stereochemistry to give [PtI2(CH2SiMe3)2(DPK)], [PtBr(CH2Ph)(CH2SiMe3)2(DPK)]
and [PtIMe(CH2SiMe3)2(DPK)], respectively. Complex 1 reacted with acids HX (X = Cl or CF3CO2) to give
initially the hydridoplatinum complexes [PtHX(CH2SiMe3)2(DPK)], but these complexes were thermally
Dedicated to Robert G. Bergman.
unstable and decomposed largely by a-silyl migration to give compounds such as [PtX(SiMe3)Me2(DPK)],
Keywords:
Platinum
Organometallic
Trimethylsilyl
Trimethylsilylmethyl
as determined by monitoring the reactions by NMR at low temperature. With excess acid, HX, at room
temperature, the products were largely [PtX2(DPK)], CH4 and Me3SiX with Me4Si as a minor product only.
The mechanism of the easy Si–CH2 bond cleavage is discussed.
Ó 2010 Elsevier B.V. All rights reserved.
R
1. Introduction
R
M
M
CH2
ð2Þ
Me
Me
M
M
CH2SiMe2R
Trimethylsilylmethyl derivatives of transition metals played an
important role in developing the present understanding of the nat-
ure of the alkyl-transition metal bond [1,2]. The compounds with
MCH2SiMe3 groups contain no b-hydrogen atom and so they are
stabilized with respect to the most common mechanism of decom-
position, namely the b-hydride elimination reaction [1,2]. The tri-
methylsilylmethyl complexes, and related compounds which have
no b-hydrogen atom, must therefore decompose by other mecha-
nisms, and there are well-defined examples of decomposition
CH2SiMe3
SiMe2
- RH
R
R
M CHSiMe3
M
H
ð3Þ
ð4Þ
CH2SiMe3
C
SiMe3
H
through
[Eq. (1)] [3–7], b-methyl migration to give a methyl derivative
[Eq. (2)] [8,9], -hydride elimination to give an alkylidene complex
[Eq. (3)] [10,11], or -trimethylsilyl migration to give a trimethyl-
silyl derivative [Eq. (4)] [12–17]. In many cases the reactions are
facilitated by the presence of a second group R, which may be an
alkyl, hydride or halide ligand, and the C–H or C–Si bond activa-
tion step may involve oxidative addition or metathesis (Eqs.
(1)–(4)) [1–17].
c-hydride elimination to give a metallasilacyclobutane
a
R
R
a
M
M
M
CH2R
CH2
Me3Si
Me3Si
CH2SiMe3
As part of a project on the mechanism of C–H bond activation at
platinum(II) [18–25], the protonolysis of complexes containing
PtCH2SiMe3 groups has been studied [19] and, while this work
was in progress, an independent study of related complexes was
published [18]. Thus, the protonolysis of trimethylsilylmethyl–
platinum(II) bonds in a diimine complex was shown to occur
according to Eq. (5) (R = CF3CD2, S = solvent, Ar = 3,5-Me2C6H3)
[18]. No tetramethylsilane, the expected product of simple proton-
olysis, was formed. Also, there was no deuterium incorporation
into the MeSi groups of the product Me3SiOR, while all possible
isotopomers of methane (CHnD4ꢀn) and methylplatinum groups
(PtCHnD3ꢀn) were present (Eq. (5)) [18].
- RH
H
R
R
M
Si
Me
M
M
ð1Þ
CH2SiMe3
Si
Me
Me
Me
⇑
Corresponding author.
E-mail address: icarjp@uwo.ca (R.J. Puddephatt).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.11.018

M.J. Hamilton, R.J. Puddephatt / Inorganica Chimica Acta 369 (2011) 190–196
191
ð6Þ
2.2. Reactions with iodine and alkyl halides
In order to monitor the stereochemistry of oxidative addition to
complex 1, the reactions with iodine, benzyl bromide and methyl
iodide were studied (Scheme 2). The reaction with iodine gave
the product of trans oxidative addition 2 (Scheme 2). Complex 2
has effective C2v symmetry and it, like complex 1, gave a single res-
onance in the 1H NMR spectrum for the Me3Si groups [d = 0.11] and
for the PtCH2 groups [d = 2.70, 2J(PtH) = 86 Hz].
Scheme 1.
The reaction of complex 1 with benzyl bromide occurred to give
the product of trans oxidative addition 3 in about 90% selectivity.
Complex 3 has effective Cs symmetry and the 1H NMR spectrum
contained a single resonance for the Me3Si groups [d = ꢀ0.06]
and for the methylene protons of the PtCH2Ph groups [d = 3.44,
2J(PtH) = 88 Hz]. The methylene protons of the PtCH2SiMe3 groups
are diastereotopic and gave an [AB] multiplet in the 1H NMR
spectrum [d = 1.25, 2J(HH) = 14 Hz, 2J(PtH) = 84 Hz; 1.42, 2J(HH) =
14 Hz, 2J(PtH) = 79 Hz]. A minor product in the initial reaction is
likely to be the isomeric complex formed by overall cis oxidative
addition, but many of the NMR resonances were too weak to allow
positive identification. Recrystallization gave complex 3 in pure
form.
In contrast, the reaction of complex 1 with methyl iodide
occurred to give the product of cis oxidative addition 5 in about
95% selectivity. Complex 5 has no symmetry so the 1H NMR spec-
trum contains two resonances for the Me3Si protons [d = ꢀ0.39,
+0.20] and one for the methylplatinum group [d = 1.71, 2J(PtH) =
73 Hz]. The two Me3SiCH2 groups in 5 are non-equivalent and each
has diastereotopic methylene protons, so four resonances were
ð5Þ
These observations were interpreted in terms of a mechanism
(A), Scheme 1, which involves nucleophilic attack at silicon to cleave
the Si–CH2 bond in a cationic 16-electron hydridoplatinum(IV)
intermediate. It was argued that mechanism (B), involving reduc-
a-migration of the Me3Si group, would
lead to formation of some tetramethylsilane and probably to deute-
tive coupling followed by
rium incorporation into the methyl groups of the product Me3SiOR,
and that mechanism (C), involving earlier a-migration would give a
high energy carbene intermediate [18]. There are no well defined
platinum(IV) complexes with simple carbene (Pt@CH2) groups,
though organoplatinum(IV) complexes with stabilized NHC-carb-
enes are now known [26,27]. Once the product containing the
PtCH2D group is formed, it can undergo H/D exchange with D+ to
give isotopomers containing PtCHnD3ꢀn groups and then slower
cleavage to give isotopomers of methane CHnD4ꢀn [18].
In an earlier communication, it was noted that intermediates
containing PtSiMe3 groups could be detected in analogous
reactions of H+ or D+ with [Pt(CH2SiMe3)2(bu2bipy)], bu2bipy =
4,40-di-t-butyl-2,20-bipyridine, which appeared inconsistent with
mechanism A in Scheme 1 [19]. This article describes a study of
the reactivity of the related complex [Pt(CH2SiMe3)2(DPK)], DPK =
di-2-pyridyl ketone. The research connects to a broader theme of
Si–C bond activation at transition metal centers [28–30] as well
as providing new examples of
a-silyl migration of the type illus-
trated in Eq. (4) [12–17]. Some chemistry of the methylplatinum
complex [PtMe2(DPK)] has been described earlier [25,31,32].
2. Results
2.1. The complex [Pt(CH2SiMe3)2(DPK)], 1
The complex [Pt(CH2SiMe3)2(DPK)], 1, was prepared by reaction
of the complex [Pt2(CH2SiMe3)4(l-SMe2)2] with di-2-pyridyl ke-
tone (DPK), as shown in Eq. (6). It was readily characterized by
its 1H NMR spectrum, which contained single resonances for the
Me3Si groups [d = ꢀ0.19] and for the PtCH2 groups [d = 0.54,
2J(PtH) = 94 Hz], by comparison to related compounds [18,19].
Scheme 2.

192
M.J. Hamilton, R.J. Puddephatt / Inorganica Chimica Acta 369 (2011) 190–196
Scheme 3. Reagents: (i) CD3l; (ii) –CD3CN.
observed for the PtCHaHbSi protons. The minor product was iden-
tified as the product of trans oxidative addition 4, identified from
its Me3Si [d = 0.00] and MePt resonances [d = 0.08, 2J(PtH) = 76 Hz]
(see below).
Scheme 4.
The formation of 5 as major product was unexpected because
oxidative addition of alkyl halides to platinum(II) usually occurs
with trans stereochemistry [31–36], so the reaction of CD3I with
[Pt(CH2SiMe3)2(DPK)], 1, in CD3CN or in (CD3)2CO solution was
monitored by low temperature NMR to search for intermediates.
The initial product in CD3CN at ꢀ40 °C was identified as trans-
[Pt(CD3)(CH2SiMe3)2(DPK)(NCCD3)]I, 6 (Scheme 3), as expected in
an SN2 mechanism of oxidative addition [37]. The 1H NMR spectrum
contained a single resonance for the Me3Si group [d = ꢀ0.03] and an
[AB] multiplet for the PtCH2Si protons [d = 1.06, 2J(HH) = 14 Hz,
2J(PtH) = 84 Hz; 1.13, 2J(HH) = 14 Hz, 2J(PtH) = 74 Hz]. At ꢀ20 °C,
these resonances decayed slowly and new resonances for trans-
[PtI(CD3)(CH2SiMe3)2(DPK)], 40, were identified. The symmetry is
Cs for both 6 and 40 so the NMR spectra are similar, though with sig-
nificant differences in chemical shifts. Thus, 40 gives d(1H) = 0.06 for
the SiMe3 protons and 1.37, 1.59 for the PtCHaHb protons. The final
product was identified at 20 °C as cis-[PtI(CD3)(CH2SiMe3)2(DPK)],
50, whose NMR spectrum is like 5 but without the methylplatinum
resonance. A similar result was obtained in acetone-d6 solvent,
though the cationic intermediate was less stable. These results
show that the normal trans-oxidative addition occurs but that the
kinetic product then undergoes isomerization to the product of cis
oxidative addition. The isomerization is expected to require a
5-coordinate intermediate, as shown in Scheme 3 [38–40].
indicated by the presence of a single Me3Si resonance [d = ꢀ0.23]
and an [AB] multiplet for the PtCH2 protons [d = 0.50,
2J(PtH) = 88 Hz; 0.83, 2J(PtH) = 80 Hz]. At ꢀ20 °C, the resonances
for 8a had decayed and the major product was [PtClMe(Si-
Me3)(CH2SiMe3)(DPK)], 9a. In the 1H NMR spectrum, complex 9a
gave a methylplatinum resonance at d = 1.02, 2J(PtH) = 61 Hz, a
trimethylsilylplatinum resonance at d = ꢀ0.41, 3J(PtH) = 18 Hz,
and resonances for the PtCH2SiMe3 group at d = 0.25 [Me3Si] and
0.60, 2J(PtH) = 85 Hz; 0.94, 2J(PtH) = 80 Hz [PtCHaHb].
A similar reaction with four equivalents of HCl gave the same
initial products as above. However, at ꢀ20 °C, resonances assigned
to [PtClMe2(SiMe3)(DPK)], 12a, were observed and 12a became the
major product at ꢀ5 °C. The Cs symmetry of 12a was indicated by
the presence of
a
single Me3SiPt resonance [d = ꢀ0.24,
3J(PtH) = 18 Hz,] and a single methylplatinum resonance [d = 1.18,
2J(PtH) = 60 Hz] [19,42]. The formation of complex 12a was accom-
panied by formation of Me3SiCl [d1Y = 0.40, d29Si = 30], as well as
by smaller amounts of methane [d1Y = 0.24], Me4Si [d1Y = 0.00,
d
29Si = 0] and [PtClMe(DPK)], 14a [d(MePt) = 1.04, 2J(PtH) = 77 Hz].
At room temperature, 14a had reacted further with HCl to give
complete conversion to [PtCl2(DPK)], with formation of more
methane [32]. The methylsilicon products were characterized ini-
tially by their 1H and 29Si chemical shifts and confirmed by ‘‘spik-
ing’’ samples with the authentic compounds [43–45].
2.3. Reaction of [Pt(CH2SiMe3)2(DPK)], 1, with HCl
When the similar reaction was carried out with DCl, the TMS
was formed very largely as Me3SiCH2D [d(MeSi) = ꢀ0.002, 9H;
d(CH2D) = ꢀ0.02, 2H, 1:1:1 triplet, 2J(HD) = 2 Hz]. No SiCHD2 reso-
nance was detected and the integration of Me:CH2D = 9:2 indi-
cated that no significant amount of Me2Si(CH2D)2 was present. A
minor amount of Me4Si was also formed and its 1H resonance
was just resolved at d(MeSi) = 0.00. No deuterium incorporation
into the product Me3SiCl was detected.
The reaction of complex 1 with anhydrous HCl in dichlorometh-
ane solution occurred to a major extent according to Scheme 4
(X = Cl).
The reaction of complex 1 with one equivalent of HCl at ꢀ80 °C
gave the complex [PtHCl(CH2SiMe3)2(DPK)], 8a, as major product.
The hydride was characterized by
a singlet resonance at
d = ꢀ20.9, with 1J(PtH) = 1595 Hz [19,41]. The Cs symmetry was

M.J. Hamilton, R.J. Puddephatt / Inorganica Chimica Acta 369 (2011) 190–196
193
Table 1
Selected NMR data.
present and at ꢀ30 °C the reaction was complete to give methane
and 14b [d(MePt) = 0.82, 2J(PtH) = 76 Hz]. Complex 15b gives a sin-
gle methylplatinum resonance [d(MePt) = 0.86, 2J(PtH) = 70 Hz],
while complex 16b gives two [d(MePt) = 1.00, 2J(PtH) = 76 Hz, trans
to CF3CO2; 1.24, 2J(PtH) = 70 Hz, trans to DPK]. The coupling con-
stant 1J(PtH) is higher for 15b [d(PtH) = ꢀ25.85, 1J(PtH) = 1730 Hz]
than for 16b [d(PtH) = ꢀ20.12, 1J(PtH) = 1435 Hz]. These hydride
complexes 15b and 16b are presumed to be formed as intermedi-
ates in the conversion of 13 to 14b in the reactions of trifluoroacetic
acid with complex 1 (Scheme 4), but they were not identified di-
rectly in those reactions. It is likely that, under the conditions under
which they are formed, they are too shortlived to be characterized
directly.
Complex
d(PtCH2)
d(SiMe)
d(PtH)
d(PtMe)
d(Si)
1
8a
0.54 (94)
0.50 (88)
0.83 (80)
0.22 (88)
0.55 (80)
0.60 (85)
0.94 (80)
ꢀ0.19
ꢀ0.23
3.0
2.1
ꢀ20.9 (1595)
ꢀ25.3 (1680)
8b
9a
ꢀ0.35
1.5
ꢀ0.24
1.02 (60)
6.1
0.2
0.25
12a
12b
15b
ꢀ0.24 (18)
1.18 (60)
1.14 (60)
0.86 (70)
ꢀ3.0
ꢀ0.17 (20)
1.0
ꢀ25.8 (1730)
3. Discussion
The reactions of [Pt(CH2SiMe3)2(DPK)], 1, with acids occur in a
similar way to those reported earlier for [Pt(CH2SiMe3)2(bu2bipy)]
[19]. Overall, the main reaction converts HX + Pt(II)–CH2SiMe3 first
to Pt(IV)HX(CH2SiMe3), then to Pt(IV)XMe(SiMe3) and finally to
Me3SiX + Pt(II)Me. A minor reaction (typically ca. 10%) converts
the intermediate Pt(IV)HX(CH2SiMe3) to Me4Si + Pt(II)X. This min-
or reaction is absent in the otherwise similar reaction with the dii-
mine stabilizing ligand described by Eq. (5) [18]. Of the
mechanisms (Scheme 1) considered in the original report [18],
the preferred mechanism A can be eliminated based on the present
work because it does not allow the formation of Me3Si–Pt bonds at
intermediate stages of reaction [19]. Remaining potential mecha-
nisms for the first steps of the reactions are summarized in Scheme
6, based on initial formation of a cationic 16-electron complex 17a,
and some relevant calculated energies using DFT theory for the
case with NN = DPK are shown in Fig. 1. There is good precedent
for expecting the key rearrangements to occur from the 5-coordi-
nate platinum(IV) intermediates [18–25,38–40]. The potential
Scheme 5.
mechanism involving
c-CH activation analogous to Eq. (1) [3–7]
2.4. Reaction of [Pt(CH2SiMe3)2(DPK)], 1, with CF3CO2H
is not considered because it would require a 7-coordinate plati-
num(VI) intermediate, which would surely lie at very high energy.
Two of the possible mechanisms can be eliminated based on re-
sults from isotope labeling or calculated energies. Thus, the mech-
anism involving initial b-methyl migration to give 23 should be
considered based on precedents of Eq. (2) [8,9], but it predicts sub-
sequent deuterium incorporation into the trimethylsilylplatinum
group in 24, and hence into the final product Me3SiX, which was
not observed (note that 24 would be expected to isomerize very
easily to the isomer with axial silyl group, analogous to the iso-
topomer 22). It has previously been suggested that carbene inter-
mediates such as 19 would be too high in energy to be viable
reaction intermediates [18], and this is now supported by the cal-
culations (Fig. 1). Thus, complex 19 is calculated to be 203 kJ molꢀ1
higher in energy than the less stable cis-isomer of the hydride
derivative, 17b (Fig. 1). The mechanism involving initial reductive
coupling to give the TMS complex 20 is analogous to mechanism B
of Scheme 1 [18]. It was initially rejected because it should lead to
formation of TMS and because easy switching of the alkane–plati-
num interaction between all C–H/C–D bonds of the TMS ligand
would be expected to occur and would lead to deuterium incorpo-
ration into the product Me3SiX [18]. In the present work, TMS is
formed, albeit as a minor product, and the calculations indicate
that 20 is thermodynamically more stable than the precursor 17a
or 17b and is easily formed from them (Fig. 1). If complex 20 is
an intermediate in formation of Me3SiX, it is necessary that SiC
bond activation via 21 to give the trimethylsilylplatinum complex
22 should be faster than either displacement of TMS from 20 or
switching between coordinated methyl groups of the TMS ligand
[18]. The final mechanism involves a concerted reaction in which
The reaction of complex 1 with trifluoroacetic acid took place in
a similar way (Scheme 4, Table 1) but the intermediates were more
transient. With three equivalents of CF3CO2H in CD2Cl2 solution at
ꢀ80 °C, the hydride complex 8b was detected. The hydride reso-
nance was at d = ꢀ25.3, with 1J(PtH) = 1680 Hz. The Cs symmetry
was indicated in the 1H NMR spectrum by the presence of a single
Me3Si resonance [d = ꢀ0.35] and an [AB] multiplet for the PtCH2
protons [d = 0.22, 2J(PtH) = 88 Hz; 0.55, 2J(PtH) = 80 Hz]. The reso-
nances for 8b decayed slowly even at ꢀ80 °C and, by ꢀ60 °C, the
major product was characterized as 12b (Scheme 4). In the 1H
NMR spectrum, complex 12b gave a single Me3SiPt resonance
[d = ꢀ0.17, 3J(PtH) = 20 Hz] and a single methylplatinum resonance
[d = 1.14, 2J(PtH) = 60 Hz]. As complex 12b was formed,
a
resonance for Me3SiO2CCF3 [d1Y = 0.34, d29Si = 34], as well as by
smaller amounts of methane [d = 0.24], Me4Si [d = 0.00] and
[Pt(O2CCF3)Me(DPK)], 14b [d(MePt) = 1.00, 2J(PtH) = 76 Hz]. With
a larger excess (8 equivalents) of trifluoroacetic acid, complex
14b was the major product even at ꢀ80 °C.
2.5. Reaction of [PtMe2(DPK)], 13, with CF3CO2H
The reaction of complex 13 with HCl has been described previ-
ously (Scheme 5) [32]. Complex 15a is sufficiently stable to be iso-
lated at ꢀ30 °C but, at higher temperatures, it equilibrates with the
product 16a of cis oxidative addition, and then eliminates methane
to give 14a. The hydride intermediates on reaction of 13 with excess
CF3CO2H are much less stable and they equilibrate much faster. At
ꢀ80 °C in CD2Cl2 solution, the hydrides 15b and 16b are both

194
M.J. Hamilton, R.J. Puddephatt / Inorganica Chimica Acta 369 (2011) 190–196
Scheme 6.
The reaction can be initiated by easy reductive coupling to give
26 or by silyl migration to give 27, and 27 is also easily accessible
from 26. Once the Pt–Si bond formation begins, the reaction to give
28 is steeply downhill (Fig. 2) and irreversible under mild condi-
tions. It can be considered that 26 and 27 are
plexes, respectively, analogous to the
2- and
which are also of very similar energy [20,22,23], and it is noted that
there are several well-characterized SiC -complexes which can be
considered as analogs of Si–C -interaction intermediate complex
g
2- and
g
g
3-TMS com-
g
3-CH4 complexes
r
r
27 and which are clearly significant in Si–C bond activation [46,47].
4. Experimental
All syntheses were carried out under a dry nitrogen atmosphere
by using standard Schlenk techniques. 1H and 29Si NMR spectra
were recorded by using a Varian Inova 400 spectrometer. The
Fig. 1. Relative energies (kJ molꢀ1, based on 17b = 0) for some of the complexes in
Scheme 6.
complexes [Pt2Me4(l-SMe2)2], [Pt2(CH2SiMe3)4(l-SMe2)2] and
[PtMe2(DPK)] were prepared according to literature methods
[19,31,48]. DFT calculations were carried out using the Becke–
Perdew exchange-correlation functional in the Amsterdam Density
Functional program [49], including first-order scalar relativistic
corrections and standard parameters used in previous studies of
organoplatinum compounds [33].
4.1. [Pt(CH2SiMe3)2(DPK)], 1
To a solution of [Pt2(CH2SiMe3)4(l-SMe2)2] (0.5 g) in Et2O
(50 mL) was added a solution of di-2-pyridyl ketone (DPK, 0.22 g)
in Et2O (10 mL). The mixture was stirred for 2 h and the volume
of the solvent was reduced. The product precipitated as a dark red
powder, which was filtered, washed with ether and dried under
vacuum. Yield: 74%. Anal. Calc. for C19H30N2OPtSi2: C, 41.21; H,
5.46; N, 5.06. Found: C, 40.87; H, 5.25; N, 4.72%. NMR in (CD3)2CO:
Scheme 7.
a
-trimethylsilyl migration is accompanied by transfer of the
d
(1H) = ꢀ0.19 [s, 18H, SiMe3]; 0.54 [s, 4H, 2J(PtH) = 94 Hz, PtCH2];
hydride group to the methylene group to give 18 and then the
complex 22. The overall reaction of 17a or 17b to give 22 is
strongly exothermic, driven by formation of the strong Pt–SiMe3
bond [42], and is therefore irreversible under the mild conditions
used. Hence, the mechanism naturally accounts for both the forma-
tion of the complexes with Pt–SiMe3 groups and the absence of
deuterium in the products Me3SiX [19].
7.78 [m, 2H, H5]; 8.02 [m, 2H, H3]; 8.25 [m, 2H, H4]; 8.88 [m, 2H,
3J(PtH) = 32 Hz, H6]; d(13C) = ꢀ10.3 [s, PtCH2]; 2.8 [s, SiMe3];
125.5, 129.2, 138.4, 151.0, 155.0 [DPK]; d(29Si) = 3.0 [s, SiMe3].
4.2. [PtI2(CH2SiMe3)2(DPK)], 2
Calculations have also been carried out with the simpler model
system in which two ammine ligands are substituted for DPK, and
in which only one trimethylsilylmethyl group is present. The re-
sults are summarized in Scheme 7 and Fig. 2.
To a solution of [Pt(CH2SiMe3)2(DPK)] (0.10 g) in CH2Cl2 (10 mL)
was added I2 (0.048 g). The color of the solution changed from red
to deep yellow. After 1 h, the volume of the solution was reduced
and the product was precipitated as a yellow powder by addition

M.J. Hamilton, R.J. Puddephatt / Inorganica Chimica Acta 369 (2011) 190–196
195
Fig. 2. The calculated structures of intermediate cationic complexes 25–27 of Scheme 7 (only H-atoms involved in bonding to platinum are shown for clarity) and their
relative energies.
of pentane (10 mL), washed with ether and pentane and dried un-
der vacuum. Yield: 64%. Anal. Calc. for C19H30I2N2OPtSi2: C, 28.26;
H, 3.74; N, 3.47. Found: C, 28.43; H, 3.91; N, 3.54%. NMR in
(CD3)2CO: d(1H) = 0.11 [s, 18H, SiMe3]; 2.70 [s, 4H, 2J(PtH) = 86 Hz,
PtCH2]; 8.04 [m, 2H, H5]; 8.37 [m, 2H, H3]; 8.48 [m, 2H, H4]; 9.54
[m, 2H, 3J(PtH) = 20 Hz, H6].
14 Hz, 2J(PtH) = 74 Hz, PtCHaHb]; 8.00 [m, 2H, H5]; 8.29 [m, 2H,
H3]; 8.42 [m, 2H, H4]; 8.83 [m, 2H, H6]. At ꢀ20 °C, trans-
[PtI(CD3)(CH2SiMe3)2(DPK)] was also identified. NMR: d(1H) =
0.06 [s, 18H, SiMe3]; 1.37 [m, 2H, 2J(HH) = 14 Hz, 2J(PtH) = 84 Hz,
PtCHaHb]; 1.59 [m, 2H, 2J(HH) = 14 Hz, 3J(PtH) = 86 Hz, PtCHaHb];
7.82 [m, 2H, H5]; 8.21 [m, 2H, H3]; 8.30 [m, 2H, H4]; 9.40 [m, 2H,
H6]. The final product was identified at 20 °C as cis-[PtI(CD3)(CH2Si-
Me3)2(DPK)]. d(1H) = ꢀ0.34 [s, 9H, SiMe3]; 0.24 [s, 9H, SiMe3]; 1.01
[m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 88 Hz, PtCHaHb trans to I]; 1.17
[m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 88 Hz, PtCHaHb trans to I]; 1.32
[m, 1H, 2J(HH) = 13 Hz, 3J(PtH) = 80 Hz, PtCHaHb trans to N]; 1.47
[m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 92 Hz, PtCHaHb trans to N]; 7.86–
9.30 [m, 8H, DPK].
4.3. [PtBr(CH2Ph)(CH2SiMe3)2(DPK)], 3
To
a solution of [Pt(CH2SiMe3)2(DPK)] (0.10 g) in acetone
(12 mL) was added PhCH2Br (0.15 mL). The color of the solution
changed from red to pale yellow. After 1 h, the volume of the solu-
tion was reduced and the product was precipitated as a yellow
powder by addition of pentane (10 mL), washed with ether and
pentane and dried under vacuum. Yield: 72%. Anal. Calc. for
4.6. Reaction of CD3I and MeI with [Pt(CH2SiMe3)2(DPK)]
C26H37BrN2OPtSi2: C, 43.09; H, 5.15; N, 3.87. Found: C, 42.70; H,
4.94; N, 3.71%. NMR in (CD3)2CO: d(1H) = ꢀ0.06 [s, 18H, SiMe3];
1.25 [m, 2H, 2J(HH) = 14 Hz, 2J(PtH) = 84 Hz, PtCHaHbSi]; 1.42 [m,
2H, 2J(HH) = 14 Hz, 2J(PtH) = 79 Hz, PtCHaHbSi]; 3.44 [s, 2J(PtH) =
88 Hz, PtCH2Ph]; 6.66–8.49 [m, 13H, DPK and Ph].
To an NMR tube charged with
a solution of [Pt(CH2Si-
Me3)2(DPK)] (0.005 g, 0.010 mmol) in (CD3)2CO at ꢀ60 °C was
added CD3I (0.10 mmol) by microsyringe. The initial product at
ꢀ60 °C was identified as mostly trans-[Pt(CD3)(CH2SiMe3)2(DP-
K){OC(CD3)2}]I. NMR: d(1H) = ꢀ0.12 [s, 18H, SiMe3]; 0.92 [m, 2H,
2J(HH) = 14 Hz, 2J(PtH) = 83 Hz, PtCHaHb]; 1.02 [m, 2H, 2J(HH) =
14 Hz, 2J(PtH) = 75 Hz, PtCHaHb]; 7.88 [m, 2H, H5]; 8.25 [m, 2H,
H3]; 8.40 [m, 2H, H4]; 8.79 [m, 2H, H6]. At ꢀ40 °C, the major prod-
uct was trans-[PtI(CD3)(CH2SiMe3)2(DPK)]. NMR: d(1H) = ꢀ0.02 [s,
18H, SiMe3]; 1.21 [m, 2H, 2J(HH) = 14 Hz, 2J(PtH) = 83 Hz, PtCHaHb];
1.53 [m, 2H, 2J(HH) = 14 Hz, 3J(PtH) = 84 Hz, PtCHaHb]; 7.95 [m, 2H,
H5]; 8.21 [m, 2H, H3]; 8.38 [m, 2H, H4]; 9.40 [m, 2H, H6]. The final
product was identified at 20 °C as cis-[PtI(CD3)(CH2SiMe3)2(DPK)].
d(1H) = ꢀ0.40 [s, 9H, SiMe3]; 0.20 [s, 9H, SiMe3]; 0.99 [m,
1H, 2J(HH) = 13 Hz, 2J(PtH) = 86 Hz, PtCHaHb trans to I]; 1.09
[m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 87 Hz, PtCHaHb trans to I]; 1.25
[m, 1H, 2J(HH) = 13 Hz, 3J(PtH) = 80 Hz, PtCHaHb trans to N]; 1.35
[m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 92 Hz, PtCHaHb trans to N]; 7.86–
9.30 [m, 8H, DPK].
4.4. cis-[PtIMe(CH2SiMe3)2(DPK)], 5
To
a solution of [Pt(CH2SiMe3)2(DPK)] (0.10 g) in acetone
(12 mL) was added MeI (0.15 mL). The color of the solution chan-
ged from red to yellow. After 1 h, the volume of the solution was
reduced and the product was precipitated as a yellow powder by
addition of pentane (10 mL), washed with ether and pentane and
dried under vacuum. Yield: 64%. Anal. Calc. for C20H33IN2OPtSi2:
C, 34.53; H, 4.78; N, 4.03. Found: C, 35.01; H, 4.89; N, 3.87%.
NMR in (CD3)2CO: d(1H) = ꢀ0.39 [s, 9H, SiMe3]; 0.20 [s, 9H, SiMe3];
0.92 [m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 88 Hz, PtCHaHb trans to I];
1.07 [m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 88 Hz, PtCHaHb trans to I];
1.25 [m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 80 Hz, PtCHaHb trans to N];
1.37 [m, 1H, 2J(HH) = 13 Hz, 2J(PtH) = 92 Hz, PtCHaHb trans to N];
1.71 [s, 3H, 2J(PtH) = 73 Hz, PtMe]; 7.90–9.40 [m, 8H, DPK]. A trace
of the trans isomer was detected by resonances at: d(1H) = 0.00 [s,
18H, SiMe3]; 0.08 [s, 3H, 2J(PtH) = 76 Hz, PtMe].
A similar reaction was carried out using MeI (12 equivalents) to
identify the methylplatinum resonances. trans-[PtMe(CH2Si-
Me3)2(DPK){OC(CD3)2}]I: d(MePt) = 0.05 [s, 3H, 2J(PtH) = 79 Hz];
trans-[PtIMe(CH2SiMe3)2(DPK)]: d(MePt) = 0.08 [s, 3H, 2J(PtH) =
76 Hz]; cis-[PtIMe(CH2SiMe3)2(DPK)]: d(MePt) = 1.71 [s, 3H, 2J(PtH)
= 73 Hz].
4.5. Reaction of CD3I with [Pt(CH2SiMe3)2(DPK)]
To an NMR tube charged with
a solution of [Pt(CH2Si-
Me3)2(DPK)] (0.005 g, 0.010 mmol) in CD3CN (0.5 mL) at ꢀ40 °C
was added CD3I (0.10 mmol) by microsyringe. The initial product
was identified at ꢀ40 °C as trans-[Pt(CD3)(CH2SiMe3)2(DPK)-
(NCCD3)]I. NMR: d(1H) = ꢀ0.03 [s, 18H, SiMe3]; 1.06 [m, 2H,
2J(HH) = 14 Hz, 2J(PtH) = 84 Hz, PtCHaHb]; 1.13 [m, 2H, 2J(HH) =
5. Reactions with acids
A typical reaction is described, with details of product identifi-
cation given in the text. To an NMR tube charged with a solution of
[Pt(CH2SiMe3)2(DPK)] (0.005 g, 0.010 mmol) in CD2Cl2 at ꢀ78 °C

196
M.J. Hamilton, R.J. Puddephatt / Inorganica Chimica Acta 369 (2011) 190–196
[19] C.M. Ong, T.J. Burchell, R.J. Puddephatt, Organometallics 23 (2004) 1493.
[20] A.N. Vedernikov, Curr. Org. Chem. 11 (2007) 1401.
[21] N.M. West, J.L. Templeton, Canad. J. Chem. 87 (2009) 288.
[22] M. Lersch, M. Tilset, Chem. Rev. 105 (2005) 2471.
[23] U. Fekl, K.I. Goldberg, Adv. Inorg. Chem. 54 (2003) 259.
[24] J.A. Labinger, J.E. Bercaw, Nature 417 (2002) 507.
[25] F. Zhang, C.W. Kirby, D.W. Hairsine, M.C. Jennings, R.J. Puddephatt, J. Am.
Chem. Soc. 127 (2005) 14196.
was added CF3CO2H (0.0.03 mmol) by microsyringe. The tube was
shaken to ensure mixing, then inserted into the pre-cooled probe
of the NMR spectrometer at ꢀ80 °C. The NMR spectra were re-
corded at ꢀ80 °C and then at 20 °C intervals to room temperature.
Reactions with HCl and DCl were carried out by using standard
solutions in CD2Cl2.
[26] E.M. Prokopchuk, M.C. Jennings, R.J. Puddephatt, Organometallics 22 (2003)
563.
Acknowledgment
[27] R. Lindner, C. Wagner, D. Steinborn, J. Am. Chem. Soc. 131 (2009) 8861.
[28] H. Gilges, U. Schubert, Organometallics 17 (1998) 4760.
[29] C. Muller, R.J. Lachicotte, W.D. Jones, Organometallics 21 (2002) 1190.
[30] N. Tokitoh, M. Kawai, N. Takeda, T. Sasamori, Heterocycles 79 (2009) 311.
[31] F. Zhang, M.E. Broczkowski, M.C. Jennings, R.J. Puddephatt, Canad. J. Chem. 83
(2005) 595.
We thank the NSERC (Canada) for financial support.
References
[32] F. Zhang, E.M. Prokopchuk, M.E. Broczkowski, M.C. Jennings, R.J. Puddephatt,
Organometallics 25 (2006) 1583.
[33] R.H.W. Au, L.J. Findlay-Shirras, N.M. Woody, M.C. Jennings, R.J. Puddephatt,
Canad. J. Chem. 87 (2009) 904.
[1] C.S. Cundy, B.M. Kingston, M.F. Lappert, Adv. Organomet. Chem. 11 (1973) 253.
[2] B. Wozniak, J.D. Ruddick, G. Wilkinson, J. Chem. Soc. A (1971) 3116.
[3] R.A. Anderson, R.A. Jones, G. Wilkinson, J. Chem. Soc., Dalton (1978) 446.
[4] T.H. Tulip, D.L. Thorn, J. Am. Chem. Soc. 103 (1981) 2448.
[5] G.M. Smith, J.D. Carpenter, T.J. Marks, J. Am. Chem. Soc. 108 (1986) 6805.
[6] L. Andreucci, P. Diversi, G. Ingrosso, A. Lucherini, F. Marchetti, V. Adovasio, M.
Nardelli, J. Chem. Soc. Dalton (1986) 477.
[7] P.W. Jennings, L.L. Johnson, Chem. Rev. 94 (1994) 2241.
[8] B.C. Ankianiec, V. Christou, D.T. Hardy, S.K. Thomson, G.B. Young, J. Am. Chem.
Soc. 116 (1994) 9963.
[9] N. Mintcheva, Y. Nishihara, M. Tanabe, K. Hirabayashi, A. Mori, K. Osakada,
Organometallics 20 (2001) 1243.
[10] M.K. Galakhov, M. Gomez, P. Gomez-Sal, P. Velasco, Eur. J. Inorg. Chem. (2006)
4242.
[11] F. Basuli, D. Adhikari, J.C. Huffman, D.J. Mindiola, J. Organomet. Chem. 692
(2007) 3115.
[12] P. Hofmann, H. Heiss, P. Neiteler, G. Mueller, J. Lachmann, Angew. Chem., Int.
Ed. 29 (1990) 880.
[34] P.K. Monaghan, R.J. Puddephatt, J. Chem. Soc., Dalton Trans. (1988) 595.
[35] R.H. Hill, R.J. Puddephatt, J. Am. Chem. Soc. 107 (1985) 1218.
[36] L.M. Rendina, R.J. Puddephatt, Chem. Rev. 97 (1997) 1735.
[37] M.C. Crespo, R.J. Puddephatt, Organometallics 6 (1987) 2548.
[38] R.J. Puddephatt, Angew. Chem., Int. Ed. 41 (2002) 261.
[39] S. Reinartz, P.S. White, M. Brookhart, J.L. Templeton, J. Am. Chem. Soc. 123
(2001) 6425.
[40] J.L. McBee, T.D. Tilley, Organometallics 28 (2009).
[41] R.J. Puddephatt, Coord. Chem. Rev. 219–221 (2001) 195.
[42] C.J. Levy, R.J. Puddephatt, J. Am. Chem. Soc. 119 (1997) 10127.
[43] H. Schmidbaur, H. Chem. Ber. 97 (1964) 830.
[44] H. Schmidbaur, J. Am. Chem. Soc. 85 (1963) 2336.
[45] T. Ostdick, P.A. McCusker, Inorg. Chem. 6 (1967) 98.
[46] H. Fan, B.C. Fullmer, M. Pink, K.G. Caulton, Angew. Chem., Int. Ed. 47 (2008)
9112.
[13] K. Itoh, T. Fuakhori, J. Organomet. Chem. 349 (1988) 227.
[14] W. Lin, S.R. Wilson, G.S. Girolami, J. Am. Chem. Soc. 115 (1993) 3022.
[15] H. Ogini, Chem. Record 2 (2002) 291.
[16] Q.D. Shelby, W. Lin, G.S. Girolami, Organometallics 18 (1999) 1904.
[17] Y.K. Sau, H.-K. Lee, I.D. Williams, W.-H. Leung, Chem. Eur. J. 12 (2006) 9323.
[18] A.F. Heyduk, J.A. Labinger, J.E. Bercaw, J. Am. Chem. Soc. 125 (2003) 6367.
[47] S. Sasaki, N. Mizoe, Y. Musashi, B. Biswas, M. Sugimoto, J. Phys. Chem. A 102
(1998) 8027.
[48] J.D. Scott, R.J. Puddephatt, Organometallics 2 (1983) 1643.
[49] A. Becke, Phys. Rev. A 38 (1988) 3098.