Hydrodealkoxylation reactions of silyl ligands at platinum: Reactivity of SiH3 and SiH2Me complexes

Article abstract of DOI:10.1039/c5dt04923g

The platinum(ii) complex [Pt(H)₂(dcpe)] (1; dcpe = 1,2-bis(dicyclohexylphosphino)ethane) reacts with an excess of the dialkoxymethylsilanes (HSiMe(OR)₂; R = Me, Et) to give the bis(silyl) complex [Pt(SiH₂Me)₂(dcpe)] (3) and trialkoxymethylsilanes by hydrodealkoxylation reactions. These rearrangements of the silyl ligands involve Si-O bond activations. The exchange of the alkoxy moieties against silicon-bound hydrogen atoms occurs stepwise. The intermediate complexes [Pt(H){SiMe(OEt)₂}(dcpe)] (5), [Pt{SiMe(OEt)₂}₂(dcpe)] (6), [Pt{SiHMe(OEt)}₂(dcpe)] (7) and [Pt{SiHMe(OMe)}₂(dcpe)] (8) were detected. Treatment of the complex 1 with an excess of dichloromethylsilane yields the bis(silyl) complex [Pt(SiMeCl₂)₂(dcpe)] (9). The hydrido silyl complex [Pt(H)(SiMeCl₂)(dcpe)] (10) was identified as an intermediate. The reactions of the complexes [Pt(SiH₃)₂(dcpe)] (2) and [Pt(SiH₂Me)₂(dcpe)] (3) with iodomethane lead to a transfer of the SiH₃ and SiH₂Me ligands. Methylsilane and dimethylsilane, respectively, as well as the platinum diiodo complex [Pt(I)₂(dcpe)] (11) were identified as main products.

Full text of DOI:10.1039/c5dt04923g

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Hydrodealkoxylation reactions of silyl ligands
at platinum: reactivity of SiH3 and SiH2Me
Cite this: DOI: 10.1039/c5dt04923g
complexes†
Cathérine Mitzenheim, Thomas Braun,* Reik Laubenstein, Beatrice Braun and
Roy Herrmann
The platinum(II) complex [Pt(H)2(dcpe)] (1; dcpe = 1,2-bis(dicyclohexylphosphino)ethane) reacts with an
excess of the dialkoxymethylsilanes (HSiMe(OR)2; R = Me, Et) to give the bis(silyl) complex [Pt(SiH2Me)2-
(dcpe)] (3) and trialkoxymethylsilanes by hydrodealkoxylation reactions. These rearrangements of the
silyl ligands involve Si–O bond activations. The exchange of the alkoxy moieties against silicon-bound
hydrogen atoms occurs stepwise. The intermediate complexes [Pt(H){SiMe(OEt)2}(dcpe)] (5), [Pt{SiMe-
(OEt)2}2(dcpe)] (6), [Pt{SiHMe(OEt)}2(dcpe)] (7) and [Pt{SiHMe(OMe)}2(dcpe)] (8) were detected. Treatment
of the complex 1 with an excess of dichloromethylsilane yields the bis(silyl) complex [Pt(SiMeCl2)2(dcpe)]
(9). The hydrido silyl complex [Pt(H)(SiMeCl2)(dcpe)] (10) was identified as an intermediate. The reactions
of the complexes [Pt(SiH3)2(dcpe)] (2) and [Pt(SiH2Me)2(dcpe)] (3) with iodomethane lead to a transfer of
the SiH3 and SiH2Me ligands. Methylsilane and dimethylsilane, respectively, as well as the platinum diiodo
complex [Pt(I)2(dcpe)] (11) were identified as main products.
Received 17th December 2015,
Accepted 22nd February 2016
DOI: 10.1039/c5dt04923g
www.rsc.org/dalton
(Cp*)] (R′ = OMe).14 Again the reaction steps for these
rearrangements of the silyl ligand are unclear. Note also that
Introduction
The oxidative addition of silicon–hydrogen bonds to tran- Schmidbaur et al. reported a transition-metal-free conversion
sition-metal complexes and the formation of silyl complexes of aryl trialkoxysilanes into hydrogen rich arylsilanes ArSiH3
and/or silylene complexes are considered to be important key and interesting RO/H ligand redistributions were found.15,16
steps in transition-metal-mediated silylations, like hydrosilyl- Beck and Benkeser reported a metal-mediated redistribution
ation1,2 and bis(silylation)3 reactions as well as the redistribu- at silanes which involves an exchange of chloro and methyl
tion of substituents at silanes.4–9 In particular, the groups.17 Thus, chloroplatinic acid can catalyse the redistribu-
redistribution reactions can involve the cleavage of fairly stable tion of SiMeR′3 and HSiCl3 yielding SiR′3Cl and HSiMeCl2
Si–C, Si–O or Si–N bonds. For instance, titanocene complexes (R′ = alkyl) via Si–C bond cleavage reactions.
are reported to catalyse the redistribution of alkoxysilanes.10
We reported on remarkable hydrodealkoxylation reactions
The reaction of dimethyltitanocene with tertiary alkoxysilanes which involve the formation of [Pt(SiH3)2(dcpe)] (2) after treat-
to give the binuclear complex [Cp4Ti2(µ-HSiH2)2] involves the ment of [Pt(H)2(dcpe)] (1) with an excess of trialkoxysilanes
redistribution of silicon-bound alkoxy groups and hydrogen (HSi(OR)3; R = Me, Et) at room temperature.18 The identifi-
atoms at silyl ligands.11–13 Though mechanistically, the reac- cation of intermediate silyl complexes by NMR spectroscopy
tion pathway of this conversion is speculative. Comparable gave an insight into the rearrangement reactions at silyl
rearrangement reactions of alkoxysilanes are known at ligands and revealed a repetitive activation of Si–O bonds at
hafnium and zirconium complexes.14 The addition of alkoxysi- silyl ligands and the generation of free tetraalkoxysilane. The
lanes HSiR′(OMe)2 to the hafnium silyl chlorido complex two SiH3 ligands are formed stepwise. Intermediate complexes
[Hf{Si(SiMe3)3}(Cl)(Cp)(Cp*)] proceeds via a metal-mediated bearing Si(OR)3, SiH(OR)2 and SiH2(OR) ligands were detected.
redistribution of the alkoxysilane and yields the complexes
Herein we present the synthesis of [Pt(SiH2Me)2(dcpe)] (3)
[Hf(SiH2Me)(Cl)(Cp)(Cp*)] (R′ = Me) and [Hf(SiH3)(Cl)(Cp) by hydrodealkoxylation reactions of dialkoxymethylsilanes
(HSiMe(OR)2; R = Me, Et). The methyl moiety of the dialkoxy-
methylsilyl ligands does not undergo any exchange reactions like
the alkoxy moiety. Treatment of the complexes [Pt(SiH3)2(dcpe)]
(2) and [Pt(SiH2Me)2(dcpe)] (3) with iodomethane led to the
Humboldt-Universität zu Berlin, Department of Chemistry, Brook-Taylor-Str. 2,
D-12489 Berlin, Germany. E-mail: thomas.braun@chemie.hu-berlin.de
†CCDC 1439201–1439203. For crystallographic data in CIF or other electronic
formation of methylsilane and dimethylsilane, respectively.
format see DOI: 10.1039/c5dt04923g
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1
coupling constant of JH,Si = 161 Hz proves the presence of a
Results and discussion
Synthesis of [Pt(SiH2Me)2(dcpe)] (3) by hydrodealkoxylation
3
SiH unit. The hydrogen–hydrogen coupling constant of JH,H
=
4.5 Hz is also found for the signal at δ = 0.31 ppm for the
reactions
hydrogen atoms of the methyl groups. The chemical shifts in
1
Treatment of the platinum dihydrido complex [Pt(H)2(dcpe)] the H NMR spectrum are comparable to those of other com-
(1), which was generated in situ by a reaction of [Pt(Cl)2(dcpe)] plexes with SiH2Me or SiHMe2 ligands.11,32–34 The 29Si{1H}
(4) with lithium triethylborohydride,18–21 with an excess of NMR spectrum displays
a doublet of doublets at δ =
dimethoxymethyl- or diethoxymethylsilane at room tempera- −40.1 ppm due to the coupling of the silicon atoms to the
ture yielded solely the platinum bis(silyl) complex [Pt(SiH2- phosphorus atoms in the trans and cis position. The data are
Me)2(dcpe)] (3) and trimethoxymethylsilane or triethoxy- in accordance with the cross-peaks found in the 1H,
1
methylsilane, respectively (Scheme 1). The generation of SiMe- 29Si HMBC NMR and H, 31P HMBC NMR spectra. The LIFDI
(OR)3 (R = Me, Et) was confirmed by 29Si{1H} and 1H,29Si MS spectra reveals a peak at m/z = 707 which can be assigned
HMBC NMR spectroscopy.22
to the molecular ion [M]+ and a peak at m/z = 662 which corres-
This reaction pattern is in contrast to well-known Si–H ponds to the fragment ion [M − {SiH2Me}]+.
bond activation reactions at platinum complexes which involve
The molecular structure of 3 was confirmed by single-
the formation of hydrido silyl complexes after elimination of crystal X-ray analysis (Fig. 1). Selected bond lengths and angles
H2.1,2,23–28 Note that the reaction of [Pt(PEt3)3] with an excess are summarized in Table 1. The structure reveals a distorted
of triethoxysilane yields the isomeric compounds trans- and square-planar arrangement of the chelating phosphine ligand
cis-[Pt(H){Si(OEt)3}(PEt3)2].24
and the two silyl ligands at the platinum centre. The silicon-
Complex 3 is soluble in tetrahydrofuran and insoluble in bound hydrogen atoms were located in the difference Fourier
hexane. In benzene or toluene complex 3 precipitates after one map and were refined isotropically. The platinum–silicon
day as a solid powder or crystallizes. Compound 3 was charac- bond lengths of 2.3724(14) Å and 2.3539(13) Å are comparable
terized by NMR spectroscopy, LIFDI mass spectroscopy, single- to those in the complex [Pt(SiHMe2)2(dcpe)] [2.3741(9) Å,
crystal X-ray analysis and elemental analysis.
2.3654(10) Å],32 which was synthesized by the reaction of
Complex 3 has been synthesized before by Fink et al. on a [Pt(η2-C2H4)(dcpe)] with 1,1,2,2-tetramethyldisilane, but are
different route.29 Reaction of [Pt(H)2(dcpe)] with 1,2-dimethyl- longer compared to those in the complex [Pt(SiH3)2(dcpe)] (2)
disilane at −25 °C leads initially to a hydrido disilanyl complex [2.3500(7) Å, 2.3408(6) Å].18 The Pt–P bond lengths of 2.3152(13)
by Si–H bond activation. After warming up to room tempera- Å and 2.3181(12) Å are similar to those of [Pt(SiHMe2)2(dcpe)]
ture the silyl ligand migrates and the complex 3 is formed. The [2.3125(8) Å, 2.3213(8) Å]32 and slightly longer as the
NMR data of 3 were reported, but some values differ from our corresponding bonds in the complex
2 [2.3045(5) Å,
data significantly due to a different solvent which was used 2.3075(6) Å].18 The bite angle of the chelating phosphine
and some coupling constants were missing.29
ligand P1–Pt1–P2 is 86.76(4)° and compares well with those
The 31P{1H} NMR spectrum of 3 shows a singlet with 195Pt reported for [Pt(SiHMe2)2(dcpe)] [85.94(3)°]32 and for complex
satellites at δ = 73.8 ppm. The phosphorus–platinum coupling 2 [86.992(19)°].18
constant of 1JP,Pt = 1558 Hz is in accordance with a platinum(II)
The conversion of 1 into 3 with dimethoxymethylsilane is
metal centre.30,31 The silicon-bound hydrogen atoms give rise finished within one hour at room temperature. With diethoxy-
to a multiplet with satellites in the 1H NMR spectrum at δ = methylsilane the reaction needs 24 hours to be completed and
4.04 ppm which transforms into a quartet with 29Si and 195Pt in this case it was possible to detect the three intermediates
satellites upon phosphorus decoupling. The hydrogen–silicon [Pt(H){SiMe(OEt)2}(dcpe)] (5), [Pt{SiMe(OEt)2}2(dcpe)] (6) and
Scheme 1 Reactions of [Pt(H)2(dcpe)] (1) with an excess of dialkoxymethylsilane and dichloromethylsilane; R = Me, Et.
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[Pt{SiHMe(OEt)}2(dcpe)] (7) by monitoring the reaction by
NMR spectroscopy (Scheme 2). Such varying reaction times for
various alkoxysilanes were also observed for the zirconium-
mediated redistribution of dialkoxymethylsilane to methyl-
silane and trialkoxymethylsilane.14
The 31P{1H} NMR spectrum of 5 displays two doublets with
195Pt satellites at δ = 83.3 ppm (1JP,Pt = 1403 Hz) and δ =
73.7 ppm (1JP,Pt = 2044 Hz) for the two inequivalent phos-
phorus atoms. The phosphorus–phosphorus coupling con-
2
stant of JP,P = 2 Hz is fairly small when compared to typical
coupling constants for square-planar coordinated hydrido silyl
platinum complexes.23,24,32,35 The difference in the P–Pt coup-
ling constants arises from the strong trans influence of the
silyl ligand.36 For the phosphorus atom in the trans position to
1
the silicon atom the JP,Pt coupling constant is smaller
(1403 Hz) than for the phosphorus atom in the trans position
to the hydrido ligand (2044 Hz). The hydrido ligand gives rise
to a doublet of doublets with 195Pt satellites in the 1H NMR
spectrum at δ = −1.12 ppm. The hydrogen–platinum coupling
Fig. 1 An ORTEP diagram of 3. The ellipsoids are drawn to 50% prob-
ability level. The hydrogen atoms, except the silicon-bound, are omitted
for clarity.
1
constant of JH,Pt = 1020 Hz indicates the presence of a
platinum-bound hydrogen atom.
The 31P{1H} NMR spectrum for the platinum bis(silyl)
complex 6 shows a singlet with 195Pt satellites at δ = 74.4 ppm
1
(1JP,Pt = 1342 Hz). The H NMR spectrum displays a signal at δ
= 0.36 ppm for the hydrogen atoms of the methyl groups.
These signals are in accordance with the cross-peaks found in
the 1H, 29Si HMBC and the 31P, 29Si HMBC NMR spectra. Fig. 2
depicts part of the 1H, 29Si HMBC NMR spectrum displaying
the cross-peak connecting the signal for the silicon atoms and
the signal for the OCH2 units. The 1JSi,Pt and 2JSi,P-trans coupling
constants are also revealed.
Table 1 Selected bond lengths (Å) and angles (°) for 3·C6H6 with esti-
mated standard deviations in parentheses
Bond lengths [Å]
Bond angles [°]
Pt1–Si1
Pt1–Si2
Pt1–P1
Pt1–P2
Si1–C27
Si2–C28
2.3724(14)
2.3539(13)
2.3152(13)
2.3181(12)
1.905(5)
P1–Pt1–P2
P1–Pt1–Si1
P1–Pt1–Si2
P2–Pt1–Si1
P2–Pt1–Si2
Si1–Pt1–Si2
C27–Si1–Pt1
C28–Si2–Pt1
86.76(4)
97.21(5)
172.46(4)
174.84(5)
95.22(5)
80.43(5)
115.05(18)
118.45(19)
The platinum bis(silyl) complex 7 with two SiHMe(OEt)
ligands is chiral and one diastereomer gives rise to a singlet
with 195Pt satellites in the 31P{1H} NMR spectrum at δ =
1.887(5)
1
76.4 ppm (1JP,Pt = 1445 Hz). The H NMR spectrum displays a
Scheme 2 Detected intermediates during the formation of [Pt(SiH2Me)2(dcpe] (3).
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Fig. 2 Part of the 1H, 29Si HMBC NMR spectrum of [Pt{SiMe-
(OEt)2}2(dcpe)] (6).
Scheme 3 Postulated mechanism for the hydrodealkoxylation steps for
the generating of complex 7.
multiplet with satellites at δ = 6.05 ppm for the silicon-bound
hydrogen atoms. Upon phosphorus decoupling the signal
again transforms into a quartet with satellites. The hydrogen–
constants which might be assigned to complexes with two
different silyl ligands such as B (Scheme 3).
1
silicon coupling constant of JH,Si = 202 Hz indicates a Si–H
moiety. The 29Si{1H} NMR spectrum shows a doublet of doub-
lets at δ = 39.7 ppm due to the coupling to the phosphorus
atoms. The cross-peaks found in the 1H, 29Si HMBC NMR
spectrum are in accordance with these signals. A second
diastereomer of 7 shows in the 31P{1H} NMR spectrum a signal
with 195Pt satellites at δ = 73.4 ppm. The 29Si{1H} NMR
spectrum reveals a doublet of doublet at δ = 38.8 ppm.
Similar intermediates are supposed for the formation of 3
with HSiMe(OMe)2 for which the reaction time is much
shorter. However, the addition of only four equivalents
dimethoxymethylsilane to the dihydrido complex 1 gave the
bis(silyl) complex [Pt{SiHMe(OMe)}2(dcpe)] (8), which is
comparable to the intermediate 7 formed during the reaction
with HSiMe(OEt)2 (Scheme 2). The reaction solution did not
contain any complex 3, but 8 reacts with more dimethoxy-
methylsilane to yield 3. The NMR data of 8 are comparable to
those of complex 7. The LIFDI data of 8 reveal a peak at m/z =
767 which can be assigned to the molecular ion [M]+
and a peak at m/z = 692 which corresponds to the fragment
ion [M − {SiHMe(OMe)}]+.
The following reaction pathway can be illustrated based on
these observations (Scheme 2). The activation of the Si–H
bond of diethoxymethylsilane gives the hydrido silyl complex 5
and the release of dihydrogen. Another equivalent of the
silane yields the bis(silyl) complex 6 and dihydrogen again.
Further addition of silane leads to a rearrangement of the sub-
stituents at the silyl ligands and an exchange of the alkoxy
moieties to silicon-bound hydrogen atoms which is associated
with the formation of trialkoxymethylsilane. These rearrange-
ments involve repetitive Si–O bond activations. The complexes
This mechanism sequence is comparable to the stepwise
formation of [Pt(SiH3)2(dcpe)] (2).18 It is conceivable that the
hydrodealkoxylation steps involve a migration of an ethoxy
group resulting in the generation of the silylene complex A
(Scheme 3). Alternatively a dissociation of the OEt− group
might lead to the cationic silyl(silylene) platinum complex
[Pt{SiMe(OEt)2}{vSiMe(OEt)}(dcpe)]OEt. The addition of
diethoxymethylsilane across a MvSi bond would then give a
silicon-bound hydrogen atom at the silyl ligand of the complex
B and trialkoxymethylsilane. Note that Berry et al. suggested
comparable rearrangement steps at silyl ligands.37 For the
redistribution of methyl groups and X in the complexes [Cp2W
(SiMe3)(SiR2X)] (R = iPr, CH3, CD3; X = Cl, OSO2CF3) a dis-
sociation of X− and the formation of a cationic silyl(silylene)
tungsten intermediate was proposed. A dissociation of a triflat
group of a silyl ligand by cleavage of a Si–O bond to form a
silylene ligand was also postulated by Tilley et al.38 A silylene
ligand might in addition be stabilized by an intramolecular
interaction of an alkoxy group of the neighboring silyl ligand
with the silylene ligand.5,8,39–41 We have no indication for
reaction steps which involve an α-hydrogen abstraction from a
silyl ligand.38,42 The methyl groups bound at the silyl ligands
also do not rearrange and remain at the silicon atom.
Studies on hydrodechlorination reactions of
dichloromethylsilane at complex 1
To investigate potential hydrodechlorination reactions at
silyl ligands, the dihydrido complex [Pt(H)2(dcpe)] (1) was
treated with an excess of dichloromethylsilane at room
temperature. This yielded the platinum bis(silyl) complex
[Pt(SiMeCl2)2(dcpe)] (9) and dihydrogen (Scheme 1). The
hydrido silyl complex [Pt(H)(SiMeCl2)(dcpe)] (10) was identi-
fied as an intermediate.
7,
8 and 3 are generated by such hydrodealkoxylation
reactions. Note that the 31P{1H} NMR spectra of the reaction
2
solutions reveal additional small doublets with JP,P coupling
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The complex 9 was characterized by NMR spectroscopy, silicon bond lengths of 2.3435(19) Å and 2.344(2) Å are longer
LIFDI mass spectroscopy and single-crystal X-ray analysis. The than those in the comparable complex [Pt(SiMeCl2)2(cod)]
31P{1H} NMR spectrum shows a singlet with 195Pt satellites at [2.3090(11) Å]43 and shorter than of those in the complex 3
δ = 68.8 ppm. The phosphorus–platinum coupling constant of [2.3724(14) Å, 2.3539(13) Å]. The platinum–phosphorus bond
1JP,Pt = 1628 Hz indicates a platinum(II)metal centre.30,31 The lengths of 2.3374(17) Å and 2.3406(17) Å are longer than those
29Si{1H} NMR spectrum reveals a doublet of doublets at δ = of complex 3 [2.3152(13) Å, 2.3181(12) Å].
61.3 ppm for the two silicon atoms in the trans and cis posi-
As mentioned above, NMR spectroscopic investigations
tion to phosphorus atoms. The H, 29Si HMBC NMR spectrum revealed the formation of [Pt(H)(SiMeCl2)(dcpe)] (10) as an
displays a cross-peak connecting the signal for the silicon intermediate (Scheme 1). An independent reaction of the di-
atoms and the signal for the hydrogen atoms of the methyl hydrido complex 1 with one equivalent of dichloromethyl-
groups. The LIFDI data reveal a peak at m/z = 794 which can be silane also yielded the complex 10. Addition of another
1
assigned to the fragment ion [M − Cl − CH3]+.
equivalent of dichloromethylsilane to 10 gave the bis(silyl)
The molecular structure of 9 was confirmed by single- complex 9. Both reactions might occur via σ-bond metathesis
crystal X-ray analysis and is illustrated in Fig. 3. Selected bond steps or via an oxidative addition of the Si–H bond of the
lengths and angles are listed in Table 2. The asymmetric cell silane and the reductive elimination of dihydrogen from an
unit includes two crystallographically independent molecules, intermediate platinum(IV) complex.
which show only minor differences in bond lengths and
The 31P{1H} NMR spectrum of 10 displays two doublets
angles. Therefore, only one of the molecules is shown and with 195Pt satellites at δ = 84.6 ppm (1JP,Pt = 1546 Hz) and δ =
discussed. The platinum atom is coordinated by two silyl 70.7 ppm (1JP,Pt = 1924 Hz). The P–Pt coupling constants varies
ligands and the chelating phosphine ligand. The platinum– because of the strong trans influence of the silyl ligand.36 The
hydrido ligand gives rise to a doublet of doublets with
1
195Pt satellites in the H NMR spectrum at δ = 0.26 ppm. The
chemical shift is in an unusual range compared to the data for
comparable complexes.23,44–46 The complex cis-[Pt(H)(SiMeCl2)
(PCy3)2], synthesized by reaction of [Pt(PCy3)2] with dichloro-
methylsilane at 260 K, exhibits in the 1H NMR spectrum for
the hydrido ligand a doublet of doublets at δ = −4.5 ppm.23
The hydrido ligand of trans-[Pt(H)(SiMeCl2)(PEt3)2] gives rise to
1
1
a signal in the H NMR spectrum at δ = −3.32 ppm.44 The H,
29Si HMBC NMR spectrum of 10 displays cross-peaks between
the signal for the silicon atoms and the signals for the hydrido
ligands as well as for the methyl groups.
Platinum-mediated hydrodechlorination reactions of the
chloro silyl ligands were not observed. Neither the reaction of
an excess of dichloromethylsilane with the complex 1 nor with
the complex 9, even by heating up the reaction solution to
70 °C over several days, did result in any rearrangement reac-
tions (Scheme 1). We also did not observe any formation of
platinum chlorido complexes by Si–Cl bond activation.44,47–50
The complex 9 is very stable, even in solution and at higher
temperatures. However, rearrangement reactions of silyl chloro
ligands are known.4 Berry et al. reported the thermic isomeri-
zation of [W(SiMe3)(SiR2Cl)(Cp)2] to give [W(SiMe2Cl)(SiR2Me)
(Cp)2] which includes a migration of Cl−.37 Note that treatment
of [Ru(H)2(η2-H2)2(PCy3)2] with ten equivalents of HSiMeCl2
results in the formation of the three ruthenium silyl complexes
[Ru(H)2(η2-H2)(η2-HSiMeCl2)(PCy3)2], [Ru(H)2(η2-HSiMeCl2)(PCy3)2]
and [Ru(Cl)(SiMeCl2)(η2-H2)(PCy3)2], which are stabilised by SISHA
interactions (SISHA = Secondary Interactions between Silicon and
Hydrogen Atoms).45,46,51
Fig. 3 An ORTEP diagram of 9. The ellipsoids are drawn to 50% prob-
ability level. The hydrogen atoms are omitted for clarity. The asymmetric
unit cell contains two crystallographically independent molecules; only
one of them is shown. Both molecules show disorder of the methyl and
chlorine substituents.
Table 2 Selected bond lengths (Å) and angles (°) for 9·C6H6 with esti-
mated standard deviations in parentheses
Bond lengths [Å]
Bond angles [°]
Reactivity of the complexes 2 and 3 towards iodomethane
176.35(6) After the successful synthesis of [Pt(SiH3)2(dcpe)] (2)18 and
Pt1–Si1
Pt1–Si2
Pt1–P1
Pt1–P2
2.3435(19)
2.344(2)
2.3374(17)
2.3406(17)
P1–Pt1–P2
P1–Pt1–Si1
P1–Pt1–Si2
P2–Pt1–Si1
P2–Pt1–Si2
Si1–Pt1–Si2
84.30(6)
93.58(7)
94.00(6)
175.22(7)
88.36(7)
[Pt(SiH2Me)2(dcpe)] (3) we focused on their reactivity towards a
possible cleavage of the Pt–Si bonds. The reaction of complex
3 with hydrochloric acid led to a protonation of the Pt–Si bond
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and gave SiH3Me and [Pt(Cl)2(dcpe)] (4). Complex 2 showed a
similar reactivity.18 Treatment of the complexes 2 and 3 with
iodomethane led to the transfer of the silyl groups to the
carbon atom by formation of Si–C bonds. Methylsilane or di-
methylsilane, respectively, and the platinum diiodo complex
[Pt(I)2(dcpe)] (11) were identified as main products (Scheme 4).
Small amounts of methane were also detected. The ratio of
methylsilane to methane is approximately 10 : 1. Methyl-
silane52 and dimethylsilane53,54 were identified by comparison
with literature NMR data. To support the observed transfer of
the SiH3 moiety to the methyl group of iodomethane, the
complex 2 was treated with 13C-labelled iodomethane and
deuterated iodomethane which resulted in the formation of
SiH313CH3 or SiH3CD3, respectively, and the diiodo complex 11
(Scheme 4).
The NMR data of 11 are comparable to literature data.55,56
The LIFDI data reveal a peak at m/z = 871 which can be
assigned to the molecular ion [M]+ and a peak at m/z = 744
which corresponds to the fragment ion [M − I]+. Furthermore
the molecular structure of 11 was determined by single-crystal
X-ray analysis (Fig. 4). Selected bond lengths and angles are
summarized in Table 3. The structure shows a distorted
square-planar arrangement of the two cis-orientated iodine
ligands and the chelating phosphine ligand. The platinum–
Fig. 4 An ORTEP diagram of 11·C6H6. The ellipsoids are drawn to 50%
probability level. The hydrogen atoms are omitted for clarity.
Table 3 Selected bond lengths (Å) and angles (°) for 11 with estimated
standard deviations in parentheses
Bond lengths [Å]
Bond angles [°]
I1–Pt1
2.6306(5)
2.6647(5)
2.2463(11)
2.2431(11)
P1–Pt1–I1
P1–Pt1–I2
P2–Pt1–I1
P2–Pt1–I2
P1–Pt1–P2
I1–Pt1–I2
174.65(3)
92.42(3)
90.62(3)
173.36(3)
87.85(4)
89.694(16)
iodine bond lengths of 2.6306(5) Å and 2.6647(5) Å are com- I2–Pt1
P1–Pt1
P2–Pt1
parable to those of the complex [Pt(I)2(dppe)] [2.6533(9) Å,
2.6684(9) Å; dppe = 1,2-bis(diphenylphosphino)ethane].57,58
The Pt–P bonds of 2.2463(11) Å and 2.2431(11) Å are compar-
able with those of [Pt(I)2(dppe)] [2.240(3) Å, 2.246(3) Å].
To the best of our knowledge there might be only one
example for a metal-mediated transfer of a SiH3 ligand onto a
Scheme 5 Cyclic process for the formation of SiH3Me or SiH2Me2 from
HSi(OR)3 or HSiMe(OR)2 (R = Me, Et; 2: SiR’3 = SiH3, with HSi(OR)3; 3:
SiR’3 = SiH2Me, with HSiMe(OR)2).
carbon atom.59 Reaction of the samarium complex [Cp*2Sm-
(SiH3)(OPPh3)] with iodomethane leads to [Cp*2Sm(I)(OPPh3)]
and methylsilane.59 The formation of the latter was only postu-
lated without any spectroscopic evidence.
Scheme 4 Reactivity of the complex 2 towards iodomethane, 13C-
labelled iodomethane and deuterated iodomethane and the reactivity of
complex 3 towards iodomethane.
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The conversion of 2 or 3 into the complex 11 completes a Synthesis of [Pt(SiH2Me)2(dcpe)] (3)
cyclic process for the formation of SiH3Me or SiH2Me2 from
HSi(OR)3 or HSiMe(OR)2, respectively (Scheme 5), since the (a) A toluene solution (2 mL) of in situ prepared [Pt(H)2(dcpe)]
complex 11 can be converted into the dihydrido complex 1 by (1) (0.19 mmol) was treated with dimethoxymethylsilane
treatment with lithium triethylborohydride.60
A catalytic (0.14 mL, 1.14 mmol) at room temperature. After stirring for
conversion is not possible due to interferences between the an hour the solution was filtered through a cannula and all
reagents. However, the used platinum complex can be volatile compounds were removed in vacuo. The residue was
recovered because each individual reaction can be performed washed twice with hexane (3 mL) and was dried in vacuo.
in high yield.
Yield: 107 mg (0.15 mmol, 79%). Colourless crystals were
grown from a concentrated benzene solution at 298 K.
(b) To a benzene-d6 solution (0.5 mL) of in situ prepared
[Pt(H)2(dcpe)] (1) (0.12 mmol) diethoxymethylsilane (0.12 mL,
0.72 mmol) was added at room temperature. NMR spectra
Conclusions
In conclusion, treatment of [Pt(H)2(dcpe)] (1) with an excess of reveal the intermediate formation of [Pt(H){SiMe(OEt)2}(dcpe)]
dialkoxymethylsilanes HSiMe(OR)2 (R = Me, Et) at room temp- (5), [Pt{SiMe(OEt)2}2(dcpe)] (6) and [Pt{SiHMe(OEt)}2(dcpe)] (7).
erature leads to hydrodealkoxylation reactions and gives the After 24 h the solution was filtered through a cannula and all
bis(silyl) complex [Pt(SiH2Me)2(dcpe)] (3) and trialkoxymethyl- volatile compounds were removed in vacuo. The residue was
silane. The stepwise exchange of alkoxy moieties to silicon- washed twice with hexane (2 mL) and was dried in vacuo.
bound hydrogen atoms at the silyl ligands by Si–O bond Yield: 61 mg (86 µmol, 72%).
activation was monitored by NMR spectroscopy and three
Analytical data for [Pt(SiH2Me)2(dcpe)] (3). Elemental analy-
intermediates were detected. We did not observe any migration sis (%) for C28H58P2PtSi2·C4H8O (780.08): calcd C 49.27, H 8.53;
of the methyl groups. For the synthesis of the bis(silyl) found C 49.02, H 8.57. The sample for the elemental analysis
complex [Pt(SiMeCl2)2(dcpe)] (9) by Si–H bond activation was obtained by recrystallization in THF. 1H NMR (300.1 MHz,
of HSiMeCl2 at complex 1 the intermediate hydrido silyl THF-d8): δ = 4.04 (m + satellites, q + satellites in the 1H{31P}
1
2
3
complex
[Pt(H)(SiMeCl2)(dcpe)]
(10)
was
identified. NMR spectrum, JH,Si = 161 Hz, JH,Pt = 46 Hz, JH,H = 4.5 Hz,
1
Moreover, treatment of the complex 3 and [Pt(SiH3)2(dcpe)] (2) 4H, SiH; the coupling constants were determined from the H
with iodomethane leads to the transfer of the SiH3 or SiH2Me {31P} NMR spectrum), 1.8–1.0 (m, 48H, CH2, CH), 0.31 ppm (m
ligands onto the methyl group and the formation of + satellites, t + satellites in the H{31P} NMR spectrum, JH,H
=
1
3
3
methylsilane and dimethylsilane, respectively, as well as 4.5 Hz, JH,Pt = 33 Hz, 6H, SiCH3; the coupling constants were
[Pt(I)2(dcpe)] (11).
determined from the 1H{31P} NMR spectrum). 1H NMR
(300.1 MHz, C6D6): δ = 4.91 (m + satellites, q + satellites in the
1H{31P} NMR spectrum, JH,Si = 161 Hz, JH,Pt = 46 Hz, JH,H
=
1
2
3
4.5 Hz, 4H, SiH; the coupling constants were determined from
Experimental
the 1H{31P} NMR spectrum), 1.8–1.0 (m, 48H, CH2, CH),
The synthetic work was carried out on a Schlenk line or in a 0.58 ppm (m + satellites, t + satellites in the 1H{31P} NMR spec-
3
3
glove box under an atmosphere of argon. Toluene, hexane, trum, JH,H = 4.5 Hz, JH,Pt = 32 Hz, 6H, SiCH3; the coupling
1
benzene-d6 and tetrahydrofuran-d8 were purified by distillation constants were determined from the H{31P} NMR spectrum).
from Na/K and stored under argon over molecular sieves. The 31P{1H} NMR (121.5 MHz, THF-d8): δ = 73.8 ppm (s + satellites,
NMR spectra were recorded on a Bruker DPX 300, a Bruker 1JP,Pt = 1558 Hz). 31P{1H} NMR (121.5 MHz, C6D6): δ =
Avance 300 or a Bruker Avance 400 spectrometer. 1H NMR 75.1 ppm (s + satellites, JP,Pt = 1542 Hz). H, 31P HMBC NMR
chemical shifts were referenced to residual C6D5H at δ = (400.1/162.0 MHz, C6D6): δ = 4.9/75.1, 1.8/75.1, 1.5/75.1, 1.1/
7.15 ppm or C4D7HO at δ = 3.58 ppm. The 31P{1H} NMR and 75.1, 0.6/75.1 ppm. 29Si{1H} NMR (59.6 MHz, C6D6): δ =
1
1
2
2
29Si{1H} NMR spectra were referenced externally to H3PO4 at −40.1 ppm (dd, JSi,P-trans = 152 Hz, JSi,P-cis = 14 Hz; 195Pt satel-
δ = 0.0 ppm and to SiMe4 at δ = 0.0 ppm, respectively. Micro- lites were not observed). 1H, 29Si HMBC NMR (300.1/59.6 MHz,
analyses were performed with a HEKAtech Euro EA Elemental THF-d8): δ = 4.0/−40.6 (d/d, JH,Si = 161 Hz, JSi,P-trans = 152 Hz,
Analyzer. Mass spectra were recorded on a Micromass Q-Tof-2 SiH), 0.3/−40.6 ppm (s + satellites/d + satellites, JSi,Pt = 1172
1
2
1
2
3
instrument equipped with a Linden LIFDI source (Linden CMS Hz, JSi,P-trans = 152 Hz, JH,Pt = 33 Hz, SiCH3). LIFDI-TOF-MS:
GmbH). GC-MS mass spectra were recorded with an Agilent calcd for C28H58P2PtSi2 [M]+: m/z = 707, found 707; calcd for
6890N gas chromatograph and an Agilent 5973 Network mass C27H53P2PtSi [M − {SiH2Me}]+: m/z = 662, found 662.
selective detector. The compounds [Pt(Cl)2(cod)]61 and
Analytical data for [Pt(H){SiMe(OEt)2}(dcpe)] (5). 1H NMR
[Pt(Cl)2(dcpe)] (4)55 were prepared according to the literature. (300.1 MHz, C6D6): δ = 3.66 (q, 3JH,H = 7 Hz, 4H, OCH2), 1.8–1.0
The platinum dihydrido complex [Pt(H)2(dcpe)] (1) was syn- (m, CH, CH2; no integration possible because of overlapping
3
thesized from [Pt(Cl)2(dcpe)] (4) and lithium triethyl- signals), 1.06 (t, JH,H = 7 Hz, OCH2CH3; no integration poss-
borohydride.18 The complex 1 was prepared in situ for the ible because of overlapping signals), 0.31 (s, 3H, SiCH3),
further conversions to prevent the formation of the binuclear −1.12 ppm (dd + satellites, 1JH,Pt = 1020 Hz, 2JH,P-trans = 152 Hz,
complex [Pt2(H)3(dcpe)2]+.62
2JH,P-cis = 13 Hz, 1H, PtH). 31P{1H} NMR (121.5 MHz, C6D6): δ =
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1
2
83.3 (d + satellites, JP,Pt = 1403 Hz, JP,P = 2 Hz, 1P, P trans to 41.7 ppm (s + satellites/d + satellites, 1JSi,Pt = 1537 Hz, 2JSi,P-trans
1
2
3
Si), 73.7 ppm (d + satellites, JP,Pt = 2044 Hz, JP,P = 2 Hz, 1P, = 179 Hz, JH,Pt = 26 Hz, SiCH3). LIFDI-TOF-MS: calcd for
P trans to H).
C30H62O2P2PtSi2 [M]+: m/z
= 767, found 767; calcd for
Analytical data for [Pt{SiMe(OEt)2}2(dcpe)] (6). 1H NMR C28H55OP2PtSi [M − {SiHMe(OMe)}]+: m/z = 692, found 692.
(300.1 MHz, C6D6): δ = 3.74 (q, 3JH,H = 7 Hz, 8H, OCH2), 1.8–1.0
(m, CH, CH2; no integration possible because of overlapping
signals), 1.07 (t, JH,H = 7 Hz, OCH2CH3; no integration poss- (a) Dichloromethylsilane (37 µL, 0.36 mmol) was added to a
Formation of [Pt(SiMeCl2)2(dcpe)] (9)
3
ible because of overlapping signals), 0.36 ppm (s, 6H, SiCH3). toluene solution (1.5 mL) of in situ prepared [Pt(H)2(dcpe)] (1)
31P{1H} NMR (121.5 MHz, C6D6): δ = 74.4 ppm (s + satellites, (90 µmol) at room temperature. After 10 min the NMR spectro-
1JP,Pt = 1342 Hz). 29Si{1H} NMR (59.6 MHz, C6D6): δ = 36.7 ppm scopic data of the reaction solution reveal the intermediate
2
2
(dd, JSi,P-trans = 193 Hz, JSi,P-cis = 16 Hz; 195Pt satellites were formation of [Pt(H)(SiMeCl2)(dcpe)] (10). After stirring for 3 h
not observed). H, 29Si HMBC NMR (300.1/59.6 MHz, C6D6): δ the solution was filtered through a cannula and all volatile
1
1
2
= 3.7/36.7 (s/d + satellites, JSi,Pt = 1577 Hz, JSi,P-trans = 193 Hz, compounds were removed in vacuo. The residue was washed
SiOCH2), 0.4/36.7 ppm (s + satellites/d + satellites, 1JSi,Pt = 1578 twice with hexane (2 mL) and was dried in vacuo. Yield: 48 mg
2
3
Hz, JSi,P-trans = 193 Hz, JH,Pt = 17 Hz, SiCH3). 31P, 29Si HMBC (57 µmol, 63%). Colourless crystals were grown from a concen-
NMR (162.0/79.5 MHz): δ = 74.4/36.7 ppm (d + satellites/s + trated benzene solution at 298 K.
satellites, 1JP,Pt = 1342 Hz, 2JP,Si-trans = 193 Hz, 1JSi,Pt = 1577 Hz).
(b) A benzene-d6 solution (0.5 mL) of [Pt(H)(SiMeCl2)(dcpe)]
Analytical data for the diastereomeric mixture of [Pt{SiHMe (10) (70 µmol) was treated with dichloromethylsilane (8 µL,
(OEt)}2(dcpe)] (7). 1H NMR (300.1 MHz, C6D6): δ = 6.05 (m + 70 µmol) at room temperature. After 3 h the quantitative for-
1
1
satellites, q + satellites in the H{31P} NMR spectrum, JH,Si
=
mation of 9 was revealed by NMR spectroscopy.
202 Hz, JH,Pt = 58 Hz, 3JH,H = 4 Hz, 2H, SiH; the coupling con-
Analytical data for [Pt(SiMeCl2)2(dcpe)] (9). 1H NMR
2
stants were determined from the 1H{31P} NMR spectrum), 3.72 (300.1 MHz, C6D6): δ = 1.8–1.0 (m, CH2, CH, no integration
3
(q, JH,H = 7 Hz, 4H, OCH2), 1.8–1.0 (m, CH, CH2; no inte- possible because of overlapping signals), 1.60 ppm (s + satel-
gration possible because of overlapping signals), 1.14 (t, JH,H lites, JH,Pt = 14 Hz, SiCH3, no integration possible because of
= 7 Hz, OCH2CH3; no integration possible because of overlap- overlapping signals). 31P{1H} NMR (121.5 MHz, C6D6): δ =
3
3
3
3
1
ping signals), 0.47 ppm (d + satellites, JH,H = 4 Hz, JH,Pt
27 Hz, 6H, SiCH3). 31P{1H} NMR (121.5 MHz, C6D6): δ = 76.4 (59.6 MHz, C6D6): δ = 61.3 ppm (dd, 2JSi,P-trans = 210 Hz, 2JSi,P-cis
(s + satellites, 1JP,Pt = 1445 Hz), 73.4 ppm (br + satellites, 1JP,Pt = 15 Hz; 195Pt satellites were not observed). 1H, 29Si HMBC
=
68.8 ppm (s + satellites, JP,Pt = 1628 Hz). 29Si{1H} NMR
=
1408 Hz). 29Si{1H} NMR (59.6 MHz, C6D6): δ = 39.7 (dd, 2JSi,P-trans NMR (300.1/59.6 MHz, C6D6): δ = 1.6/61.3 ppm (s + satellites/d
= 162 Hz, JSi,P-cis = 16 Hz; 195Pt satellites were not observed), + satellites, JSi,Pt = 1617 Hz, JSi,P-trans = 210 Hz, JH,Pt = 14 Hz,
38.8 ppm (dd, 2JSi,P-trans = 172 Hz, 2JSi,P-cis = 10 Hz; 195Pt satellites SiCH3). LIFDI-TOF-MS: calcd for C27H51Cl3P2PtSi2 [M − Cl − CH3]+:
were not observed). 1H, 29Si HMBC NMR (300.1/59.6 MHz, m/z = 794, found 794.
2
1
2
3
1
2
C6D6): δ = 6.0/39 (d/d, JH,Si = 202 Hz, JSi,P-trans = 162 Hz, SiH),
3.7/39 (s/d + satellites, JSi,Pt = 1592 Hz, JSi,P-trans = 177 Hz,
SiOCH2), 0.5/39 ppm (s + satellites, d + satellites, JSi,Pt
1311 Hz, 2JSi,P-trans = 162 Hz, 2JH,Pt = 27 Hz, SiCH3).
1
2
Formation of [Pt(H)(SiMeCl2)2(dcpe)] (10)
1
=
To a benzene-d6 solution (0.5 mL) of in situ prepared
[Pt(H)2(dcpe)] (1) (70 µmol) dichloromethylsilane (7 µL, 70 µmol)
was added at room temperature. After 10 min the quantitative
formation of 10 was confirmed by NMR spectroscopy.
Formation of [Pt{SiHMe(OMe)}2(dcpe)] (8)
Dimethoxymethylsilane (80 µL, 0.64 mmol) was added to a
Analytical data for [Pt(H)(SiMeCl2)(dcpe)] (10). 1H NMR
tetrahydrofuran-d8 solution (0.5 mL) of in situ prepared (300.1 MHz, C6D6): δ = 1.8–1.0 (m, 48H, CH2, CH), 0.87 (s +
3
[Pt(H)2(dcpe)] (1) (0.16 mmol) at room temperature. The satellites, JH,Pt = 14 Hz, 3H, SiCH3), 0.26 ppm (dd + satellites,
2
2
formation of 8 was confirmed by NMR spectroscopic data and 1JH,Pt = 1032 Hz, JH,P-trans = 163 Hz, JH,P-cis = 15 Hz, 1H, PtH).
1
MS data.
31P{1H} NMR (121.5 MHz, C6D6): δ = 84.6 (d + satellites, JP,Pt
=
Analytical data for [Pt{SiHMe(OMe)}2(dcpe)] (8). 1H NMR 1546 Hz, 2JP,P = 3 Hz, 1P, P trans to Si), 70.7 ppm (d + satellites,
2
1
(300.1 MHz, THF-d8): δ = 6.01 (m + satellites, q + satellites in 1JP,Pt = 1924 Hz, JP,P = 3 Hz, 1P, P trans to H). H, 29Si HMBC
the 1H{31P} NMR spectrum, 1JH,Si = 310 Hz, 2JH,Pt = 138 Hz, 3JH,H NMR (300.1 MHz/59.6 MHz, C6D6): δ = 0.9/−48.6 (s/d, 2JSi,P-trans
2
= 3.6 Hz, 2H, SiH; the coupling constants were determined = 159 Hz, SiCH3), 0.2/−48.6 ppm (dd/d, JH,P-trans = 163 Hz,
from the H{31P} NMR spectrum), 3.74 (s, 6H, OCH3), 1.8–1.0 2JH,P-cis = 15 Hz, 2JSi,P-trans = 159 Hz, PtH).
1
(m, 48H, CH, CH2), 0.55 ppm (m + satellites, d + satellites in
1
3
3
Treatment of [Pt(SiH3)2(dcpe)] (2) with iodomethane
the H{31P} NMR spectrum, JH,H = 3.6 Hz, JH,Pt = 26 Hz, 6H,
SiCH3; the coupling constants were determined from the A Young NMR tube with [Pt(SiH3)2(dcpe)] (2) (36 mg, 53 µmol)
1H{31P} NMR spectrum). 31P{1H} NMR (121.5 MHz, THF-d8): in a benzene-d6 solution (0.5 mL) was treated with iodo-
1
δ = 78.5 (s + satellites, JP,Pt = 1413 Hz), 77.7 ppm (s for a methane (7 µL, 0.11 mol) at room temperature. After 3 days
second diastereomer, 195Pt satellites were not observed). 1H, the NMR spectroscopic data revealed the quantitative for-
29Si HMBC NMR (300.1/59.6 MHz, THF-d8): δ = 3.7/41.7 (s/d + mation of [Pt(I)2(dcpe)] (11) and SiH3CH3. Complex 1155,56 and
1
2
satellites, JSi,Pt = 1537 Hz, JSi,P-trans = 179 Hz, SiOCH3), 0.5/ methylsilane52 were identified by comparison with literature
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NMR data. As a minor product methane was detected.63 Treatment of [Pt(SiH2Me)2(dcpe)] (3) with iodomethane-13C
The ratio of methylsilane to methane was approximately 10 : 1.
Colourless crystals of 11 were grown from a concentrated
A benzene-d6 solution of [Pt(SiH2Me)2(dcpe)] (3) (48 mg, 68 µmol)
in a Young NMR tube was treated with iodomethane-13C (9 µL,
benzene solution at 298 K.
0.14 mmol) at room temperature. NMR spectroscopic data revealed
Analytical data for [Pt(I)2(dcpe)] (11): 31P{1H} NMR
the quantitative formation of [Pt(I)2(dcpe)] (11) and SiH3CH313CH3
(121.5 MHz, C6D6): δ = 66.3 ppm (s + satellites, 1JP,Pt = 3350 Hz).
after 3 days. Complex 11 55,56 and dimethylsilane53,54 were identi-
LIFDI-TOF-MS: calcd for C26H48I2P2Pt [M]+: m/z = 871, found
fied by comparison with literature NMR data.
871; calcd for C26H48IP2Pt [M − I]+: m/z = 744, found 744.
Treatment of [Pt(I)2(dcpe)] (11) with lithium
triethylborohydride
Treatment of [Pt(SiH3)2(dcpe)] (2) with iodomethane-13C
To
a benzene-d6 solution of [Pt(I)2(dcpe)] (11) (34 mg,
A benzene-d6 solution of [Pt(SiH3)2(dcpe)] (2) (29 mg, 43 µmol)
in a Young NMR tube was treated with iodomethane-13C (6 µL,
86 µmol) at room temperature. The NMR spectroscopic data
revealed the quantitative formation of [Pt(I)2(dcpe)] (11) and
0.04 mmol) lithium triethylborohydride (0.08 ml, 0.08 mmol,
1 M solution in tetrahydrofuran) was added. The reaction pro-
ceeds within minutes. [Pt(H)2(dcpe)] (1) was identified as
product by comparison with literature NMR data.18–20
SiH313CH3 after
3
days. Complex 11 55,56 and methyl-
silane-13C52 were identified by comparison with literature
NMR data. As a minor product methane-13C was detected.63
The ratio of methylsilane-13C to methane-13C was approxi-
mately 10 : 1.
Structure determination of the complexes 3·C6H6, 9·C6H6 and
11·C6H6
Colourless crystals of the complexes 3·C6H6, 9·C6H6 and
11·C6H6 precipitated from concentrated benzene solutions at
298 K. Crystallographic data are listed in Table 4. The crystal of
complex 9 contains two independent molecules in the asym-
Treatment of [Pt(SiH3)2(dcpe)] (2) with iodomethane-d3
A Young NMR tube with [Pt(SiH3)2(dcpe)] (2) (53 mg, 78 µmol) metric unit. In both molecules all silicon-bound methyl groups
in a benzene-d6 solution (0.5 mL) was treated with deuterated show substitutional disorder with respect to the chloride substi-
iodomethane (10 µL, 0.16 mmol) at room temperature. After tuents. Along with distance restraints, the application of SUMP
3 days the NMR spectroscopic data revealed the quantitative restraints (SHELX-2013)64,65 ties the densities of the chlorine
formation of [Pt(I)2(dcpe)] (11) and SiH3CD3. Complex 11 55,56 atoms bound at each silicon atom into three occupancies. This
and methylsilane52 were identified by comparison with litera- led to occupancies of 0.74 (Cl2), 0.26 (Cl3), 0.20 (Cl4), 0.80 (Cl6),
ture NMR data.
0.94 (Cl7), 0.94 (Cl8), 0.12 (Cl9), 0.93 (Cl10), 0.80 (Cl11) and 0.27
Table 4 Crystallographic data
Compound
[Pt(SiH2Me)2(dcpe)] (3)·C6H6
[Pt(SiMeCl2)2(dcpe)] (9)·C6H6
[Pt(I)2(dcpe)] (11)·C6H6
Empirical formula
C28H58P2PtSi2, C6H6
786.06
0.16 × 0.06 × 0.04
0.71073
C28H54Cl4P2PtSi2, C6H6
923.83
0.23 × 0.08 × 0.04
0.71073
C26H48I2P2Pt, C6H6
949.58
0.26 × 0.25 × 0.17
0.71073
Formula weight
Crystal size (mm3)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
Orthorhombic
P212121
11.2140(4)
14.0280(5)
23.0967(7)
Triclinic
P1
Monoclinic
P21/c
12.1585(17)
18.428(3)
ˉ
11.5338(8)
18.0570(13)
20.1236(14)
85.305(2)
73.897(2)
83.984(2)
3998.3(5)
4
1.535
3.940
2.248–25.174
171 341
14 241
0.0485
1.047
99.9%
0.0620, 0.1297
0.0514, 0.1229
12 129
4.647/−3.000
1439202
15.976(3)
101.390(12)
γ (°)
V (Å3)
Z
3633.3(2)
4
1.437
4.037
2.284–26.754
20 086
7646
0.0336
0.998
99.8%
0.0257, 0.0463
0.0229, 0.0456
7258
1.483/−0.608
1439201
3509.1(9)
4
1.797
5.868
3.22–28.00
88 723
8448
0.0531
0.906
99.8%
0.0359, 0.0747
0.0265, 0.0731
6821
1.440/−2.227
1439203
Calculated density (Mg m−3
)
µ (Mo-Kα) (mm−1
θ range (°)
)
Reflections collected
Independent reflections
Rint
Goodness-of-fit on F2
Completeness to max. θ
R1, ωR2 on all data
R1, ωR2 [I0 > 2σ(I0)]
Reflect. with [I0 > 2σ(I0)]
Largest diff. peak, hole (e A−3
)
CCDC
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(Cl12). Only for the first independent molecule the occu- 18 C. Mitzenheim and T. Braun, Angew. Chem., 2013, 125,
pancies of Cl1 and Cl5 were given full occupancy. All atoms
involved in disorder have been isotropically refined.
8787–8790, (Angew. Chem. Int. Ed., 2013, 52, 8625–8628).
19 C. A. Jaska, A. J. Lough and I. Manners, Dalton Trans.,
2005, 326–331.
The diffraction data were obtained with a Bruker D8
Venture or a Stoe IPDS 2 T diffractometer. Multi-scan absorp- 20 D. J. Schwartz and R. A. Andersen, J. Am. Chem. Soc., 1995,
tion corrections66 for 3·C6H6 and 9·C6H6 and numerical correc-
117, 4014–4025.
tions67 for 11·C6H6 were applied to the data. The structures 21 D. Carmichael, P. B. Hitchcock, J. F. Nixon and A. Pidcock,
were solved by direct methods (SHELXS-97)68 or by intrinsic
J. Chem. Soc., Chem. Commun., 1988, 1554–1556.
phasing method (SHELXT-2014)64 and refined by full-matrix 22 M. Brand, A. Frings, P. Jenkner, R. Lehnert,
least-square procedures based on F2 with all measured reflec-
H. J. Metternich, J. Monkiewicz and J. Schram, Z. Natur-
forsch., B: Chem. Sci., 1999, 54, 155–164.
tions (SHELX-97 and SHELXL-2013)65,69 with anisotropic temp-
erature factors for all non-hydrogen atoms. All hydrogen atoms 23 D. Chan, S. B. Duckett, S. L. Heath, I. G. Khazal,
were added geometrically, except the silicon-bound hydrogen
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