Dinuclear Palladium and platinum complexes with bridging silylene ligands. Preparation using (Aminosilyl)boronic ester as the ligand precursor and their reactions with alkynes

Article abstract of DOI:10.1021/om200156g

Equimolar reactions of (aminosilyl)boronic ester Et₂NSiPh ₂BOCMe₂CMe₂O with zerovalent complexes of Pt and Pd, M(PMe₃)₄ (M = Pt, Pd), afforded the dinuclear complexes with bridging silylene ligands {M(PMe₃)₂} ₂(μ-SiPh₂)₂ (1: M = Pt, 2: M = Pd). X-ray crystallographic studies of 1 and 2 revealed a Sii interaction in the M ₂Si₂ four-membered ring. Diplatinum complex 1 reacted with arylacetylenes HC≡CAr (Ar = C₆H₅, C ₆H₄Me-4), yielding 3,5-disila-4-platinacyclopentene Pt(SiPh₂CAr=CHSiPh₂)(PMe₃)₂ (3a: Ar = C₆H₅, 3b: Ar = C₆H₄Me-4), although the reaction mixture also contained complexes with the alkyne or the alkynyl ligands. The reaction of PhC≡CPh with dipalladium complex 2 gave Pd(SiPh₂CPh=CPhSiPh₂)(PMe₃)₂ as well as alkyne complex Pd(η²-PhC≡CPh)(PMe₃) ₂. The reactions of HC≡CAr (Ar = C₆H₅, C₆H₄Me-4) with Pt(SiHPh₂)₂(PMe ₃)₂ also formed 3a and 3b accompanied by 6-sila-3-platina-1,4-cyclohexadienes Pt(CAr=CHSiPh₂CH=CAr)(PMe ₃)₂ as the byproduct. A similar reaction of HC≡CCOOMe with Pt(SiPh₂H)₂(PMe₃) ₂ yielded the five-membered disilaplatinacycle Pt(SiPh ₂C(COOMe)=CHSiPh₂)(PMe₃)₂ as the sole product. Both the dinuclear complexes of Pd and Pt with bridging silylene ligands and mononuclear Pt complexes with two silyl ligands were converted to the disilaplatinacyclopentene via independent pathways. Details of the mechanism are discussed.

Full text of DOI:10.1021/om200156g

ARTICLE
pubs.acs.org/Organometallics
Dinuclear Palladium and Platinum Complexes with Bridging Silylene
Ligands. Preparation Using (Aminosilyl)boronic Ester as the Ligand
Precursor and Their Reactions with Alkynes
Makoto Tanabe,† Jian Jiang,† Hideto Yamazawa,† Kohtaro Osakada,*,† Toshimichi Ohmura,‡ and
Michinori Suginome‡
†Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1-3 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
‡Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura,
Nishikyo-ku, Kyoto 615-8510, Japan
S Supporting Information
b
ABSTRACT: Equimolar reactions of (aminosilyl)boronic ester
Et2NSiPh2BOCMe2CMe2 O with zerovalent complexes of Pt
and Pd, M(PMe3)4 (M = Pt, Pd), afforded the dinuclear com-
plexes with bridging silylene ligands {M(PMe3)2}2(μ-SiPh2)2
(1: M = Pt, 2: M = Pd). X-ray crystallographic studies of 1 and 2
revealed a Si Si interaction in the M2Si2 four-membered ring. Diplatinum complex 1 reacted with arylacetylenes HCtCAr (Ar =
3 3 3
C6H5, C6H4Me-4), yielding 3,5-disila-4-platinacyclopentene Pt(SiPh2CArdCHSiPh2)(PMe3)2 (3a: Ar = C6H5, 3b: Ar =
C6H4Me-4), although the reaction mixture also contained complexes with the alkyne or the alkynyl ligands. The reaction of
PhCtCPh with dipalladium complex 2 gave Pd(SiPh2CPhdCPhSiPh2)(PMe3)2 as well as alkyne complex Pd(η2-PhCtCPh)-
(PMe3)2. The reactions of HCtCAr (Ar = C6H5, C6H4Me-4) with Pt(SiHPh2)2(PMe3)2 also formed 3a and 3b accompanied
by 6-sila-3-platina-1,4-cyclohexadienes Pt(CArdCHSiPh2CHdCAr)(PMe3)2 as the byproduct. A similar reaction of
HCtCCOOMe with Pt(SiPh2H)2(PMe3)2 yielded the five-membered disilaplatinacycle Pt(SiPh2C(COOMe)dCHSiPh2)-
(PMe3)2 as the sole product. Both the dinuclear complexes of Pd and Pt with bridging silylene ligands and mononuclear Pt
complexes with two silyl ligands were converted to the disilaplatinacyclopentene via independent pathways. Details of the
mechanism are discussed.
’ INTRODUCTION
subsequent intramolecular hydrosilylation of the latter ligand
leads to the formation of the metallacycle product. The authors
did not prefer a pathway involving an intermediate having silylene
(SiR2) ligands bonded to Pt, although they mentioned that the
bis(silyl)platinum complexes were known to generate Pt-silylene
species upon heating.4
Dinuclear Fe and Ru complexes with two bridging silylene
ligands, {Fe(CO)4}2(μ-SiPh2)2 and (Cp*Ru)2(μ-H)2(μ-SiPh2)2,
were reported to react with internal alkynes or acetylene to form
disilametallacyclopentenes (Scheme 2(i) and (ii)).5 The Pd or Pt
version of this reaction would provide the disilapallada- or
disilaplatinacyclopentenes, but this reaction pathway has not been
discussed in the reports of the reactions of alkynes with silyl
complexes of these metals so far. We studied the reaction of
dimethyl acetylenedicarboxylate with Pt(SiHPh2)2(PMe3)2 and
Reactions of alkynes with Pd and Pt complexes having Si ligands
have been extensively studied because they are related to the
mechanism of hydrosilylation and bissilylation of alkynes catalyzed
by complexes of the group 10 transition metals.1 Insertion of
alkynes into MꢀSi bonds (M = Pd, Pt) and coupling of the silyl and
alkenyl ligands from the alkenyl(silyl)metal complexes are believed
to be the fundamental reactions that provide new CꢀSi bonds in
the above catalysis. The Pt complexes with tertiary silyl ligands
actually undergo insertion of alkynes into the PtꢀSi bond.2 Eaborn
et al. reported that terminal alkynes, such as acetylene and
phenylacetylene, reacted with cis-Pt(SiHPh2)2(PMe2Ph)2 to afford
five-membered 3,5-disila-4-platinacyclopentenes (Scheme 1).3
They proposed the multiple-step pathway shown in Scheme 1
to account for the reaction product. It involves initial formation of
alkynylsilane formed via dehydrosilylation of the alkyne. Oxida-
tive addition of the alkynylsilane to the Pt complex, forming an
intermediate with diphenylsilyl and alkynylsilyl ligands, and
Received: February 18, 2011
Published: July 06, 2011
r
2011 American Chemical Society
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Scheme 1
’ RESULTS AND DISCUSSION
Dinuclear complexes of Pt,7 Pd,8 and Ni9 with bridging
silylene (SiR2) ligands have been commonly prepared from the
reactions of primary and secondary silanes with low-valent
complexes of these metals. Oxidative addition of the silanes to
these metals and dehydrogenative dimerization of the resulting
mononuclear silyl complexes produces silylene-bridged dinuc-
lear complexes. The preparation reactions, however, are often
accompanied by formation of the byproduct, because once
obtained, dinuclear complexes with bridging silylene ligands
can be converted to mono- and dinuclear complexes with silyl
(SiHR2) ligands in the reaction mixture. Organosilanes release
the SiꢀH hydrogen easily to the bridging silylene ligand via
SiꢀH bond activation reactions with Pd and Pt centers. Recently,
we reported that H2SiPh2 enhanced the equilibrium between
Pd(SiHPh2)2(dmpe) and {Pd(dmpe)}2(μ-SiPh2)2 (dmpe = 1,
2-bis(dimethylphosphino)ethane).8e On the other hand,
Scheme 2
(aminosilyl)boronic ester Et2NSiPh2BOCMe2CMe2O10 has re-
cently been found to act as a silylene precursor in palladium-
catalyzed reactions with unsaturated hydrocarbons.11,12 Thus, we
used the (aminosilyl)boronic ester as a precursor of the silylene
ligands of the dinuclear Pd and Pt complexes in this study.
M(PMe3)4 (M = Pt, Pd), which were generated in situ by
ligand substitution of M(PCy3)2 with PMe3 (1:4 ratio), reacted
with an equimolar amount of Et2NSiPh2BOCMe2CMe2O at
60 °C to produce the diplatinum or dipalladium complexes with
bridging silylene ligands {M(PMe3)2}2(μ-SiPh2)2 (1: M = Pt;
80%, 2: M = Pd; 48%), as shown in eq 1. Accompanying
Scheme 3
1
formation of Et2NBOCMe2CMe2O was observed in the H
NMR spectra of the reaction mixture. The experiments using a
smaller amount of PMe3 ([M]:[PMe3] = 1:2) gave the same
products in lower yields (less than 30% in NMR yields).
4-sila-3-platinacyclobutene (B) after insertion of the unsaturated
molecules into the PtꢀSi bond followed by γ-hydrogen elimina-
tion (Scheme 3).6 The produced 4-sila-3-platinacyclobutene (B)
reacts with H2SiPh2 to cause the reverse reaction, forming the
3-sila-1-propenylplatinum complex (A), whereas it reacts with
further alkynes, giving 6-sila-3-platina-1,4-cyclohexadiene with π-
coordinated alkyne (C).
In this study, we conducted the reaction of alkynes with
dinuclear Pd and Pt complexes having bridging silylene
ligands expecting to form metallacyclic products. These
reactions are compared with those of the alkyne with mono-
nuclear bis(silyl)platinum complexes (Schemes 1 and 3).
Structures and properties of the produced complexes are also
described.
Figure 1 shows the molecular structures of 1 and 2 with a
square-planar geometry, determined by X-ray crystallography.
Table 1 compares their bond parameters and those of the
analogues with a dmpe ligand. The Pd2Si2 rhombus of 2 forms a
plane, whereas the Pt2Si2 ring of 1 has a slightly bent structure with
the dihedral angle between two PtSi2 planes being 169.4°. The
angle, however, is larger than the Pt2Si2 ring of {Pt(PEt3)2}2-
(μ-SiHCy)2 (dihedral angle = 132.3°).7b The Si Si distances
3 3 3
in the M2Si2 ring of 1, 2, and the dmpe complexes decrease in
the order, {Pt(dmpe)}2(μ-SiPh2)2 (2.718(2) Å)7l > 1 (2.645(1)
Å) > {Pd(dmpe)}2(μ-SiPh2)2 (2.5227(7) Å)8e > 2 (2.428(1) Å).
The PdꢀSi bond distances of 2 (2.4086(7), 2.4098(9) Å) are
similar to the PtꢀSi bonds of 1 (2.3902(7)ꢀ2.4065(7) Å).
Accordingly, the SiꢀMꢀSi angles decrease in the same order,
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{Pt(dmpe)}2(μ-SiPh2)2 (69.48(4)°)7l > 1 (67.12(2)°, 66.92(2)°)
> {Pd(dmpe)}2(μ-SiPh2)2 (63.92(2)°)8e > 2 (60.51(2)°). The
above results can be ascribed to more significant π-back-donation
of the Pt center to the Si ligands than the Pd center. Sakaki
Formal transfer of SiPh2 groups from the (aminosilyl)boronic
ester to the zerovalent complexes of Pd and Pt yielded dinuclear
complexes, similarly to the proposed mechanism of the Pd-
catalyzed silylation of various unsaturated molecules using the
(aminosilyl)boronic ester.11 Mononuclear silylene platinum
complexes were isolated by introducing bulky mesityl groups
to the Si ligand.14 Kira and Iwamoto reported the preparation of a
dipalladium complex having one bridging dialkylsilylene ligand,
reported that Si Si interaction in the four-membered Pd2Si2
3 3 3
and Pt2Si2 rings was influenced by the degree of π-back-donation
between the metal center and the coordinating Si atom based on
their results of theoretical calculation.13 More significant π-back-
{Pd(PCy3)}2(μ-SiRH2) (RH = 1,1,4,4-tetrakis(trimethylsilyl)-
2
donation of the Pt complexes weakens the Si Si interaction,
3 3 3
butane-1,4-diyl), and proposed the formation pathway involving
the reaction of the mononuclear silylene palladium intermediate
while lower energy levels of Pd weaken the π-back-donation and
retain the Si Si bonding interaction. Since the chelating dipho-
3 3 3
(Cy3P)PddSiRH with a Pd(0)-phosphine complex.15 The
sphines enhance π-back-donation to the Si ligand,13a the Si Si
2
3 3 3
reaction in eq 1 may involve mono- or dinuclear complexes as
the intermediate, although the reaction details are not clear at
present.
Diplatinum complex 1 reacted with a 3-fold molar amount
of HCtCAr (Ar = C6H5, C6H4Me-4) at room temperature
to produce a mixture of 3,5-disila-4-platinacyclopentene
distances of the dmpe complex are longer than the PMe3 complex
in both Pt and Pd systems. The 29Si NMR resonances of the
bridging SiPh2 ligands are observed in the order, {Pt(dmpe)}2-
(μ-SiPh2)2 (δ ꢀ95.5),7l 1 (δ ꢀ75.8), {Pd(dmpe)}2(μ-SiPh2)2
(δ ꢀ51.0),8e and 2 (δ ꢀ35.3).
Pt(SiPh2CArdCHSiPh2)(PMe3)2 (3a: Ar = C6H5; 62%, 3b:
Ar = C6H4Me-4; 60%) and alkyne-coordinated complex Pt-
(PMe3)2(η2-HCtCAr) (4a: Ar = C6H5, 4b: Ar = C6H4Me-4)
after 10 h (eq 2). The reaction of 4-ethynyltoluene yielded the
dialkynyl platinum complex trans-Pt(CtCAr)2(PMe3)2 (5b) as
the product. Roundhill proposed the conversion of the Pt
complexes with π-coordinated alkyne ligands to the dialkynylpla-
tinum complexes in the presence of excess alkynes.16
Five-membered disilaplatinacycles 3a and 3b were isolated
and characterized by X-ray crystallography and NMR spectros-
copy. Figure 2a shows the molecular structure of 3b, and
selected bond distances and angles are listed in Table 2. The
CdC bond distance of 3b (1.340(5) Å) is comparable with that
of the unstrained disilylolefin (Z)-(PhSCH2)Me2SiC(Ph)d
C(H)SiMe2(CH2SPh) (1.341(10) Å).17 The PtꢀSi bond
Figure 1. Thermal ellipsoids (50% probability) of (a) 1 and (b) 2.
Carbon-bound hydrogen atoms are omitted for simplicity. The molecule
of 2 has a crystallographic symmetry at the midpoint of the two
Pd atoms.
Table 1. Selected Bond Distances (Å) and Angles (deg) of 1, 2, and {M(dmpe)}2(μ-SiPh2)2 (M = Pt, Pd)
a
b
1 (M = Pt)
{Pt(dmpe)}2(μ-SiPh2)2
2 (M = Pd)
{Pd(dmpe)}2(μ-SiPh2)2
M
M
3.9775(1)
3.9193(2)
4.162(2)
4.0438(2)
3 3 3
MꢀSi
2.3930(6), 2.3916(7)
2.3902(7), 2.4065(7)
2.3248(6), 2.3327(7)
2.3340(6), 2.3312(7)
2.645(1)
2.385(1), 2.3847(9)
2.4086(7), 2.4098(9)
2.3792(7), 2.389(1)
2.3822(4), 2.3840(6)
MꢀP
2.3053(8), 2.299(1)
2.3346(7), 2.3423(3)
Si Si
2.718(2)
69.48(4)
110.52(4)
85.48(3)
2.428(1)
60.51(2)
119.49(3)
101.26(3)
2.5227(7)
63.92(2)
116.08(2)
85.75(2)
3 3 3
SiꢀMꢀSi
67.12(2), 66.92(2)
112.51(3), 111.98(3)
96.63(2), 95.64(2)
MꢀSiꢀM
PꢀMꢀP
a Ref 7l. b Ref 8e.
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2
distances (2.3705(9) and 2.357(1) Å) and SiꢀPtꢀSi angle
(80.56(4)°) are similar to those reported for 2,5-disila-1-plati-
doublets at δ ꢀ19.7 and ꢀ19.3 with JPꢀP = 29 Hz due to the
unsymmetrical molecular structure. The 31P{1H} NMR spectra of
the reaction mixture showed the signals due to the complex with a π-
coordinated alkyne ligand, 4a and 4b. The coupling constants of 4a
(JPtꢀP = 3227, 3350 Hz, JPꢀP = 36 Hz) and 4b (JPtꢀP = 3180, 3345
Hz, JPꢀP = 36 Hz) are comparable with those of Pt(η2-HCtCPh)-
(PPh3)2 (JPtꢀP = 3464, 3547 Hz, JPꢀP = 33 Hz).22
nacyclopentane Pt(SiPh2CH2C(dCHC6H4F)SiPh2)(PMe3)2
(PtꢀSi: 2.365(2) and 2.374(2) Å, SiꢀPtꢀSi: 79.74(7)°).18
Complexes 3a and 3b show 1H NMR peaks due to vinyl
hydrogens in the five-membered rings at δ 7.42 and 7.44 flanked
with 195Pt satellite signals (3JPtꢀH = 67 Hz). They are at lower
magnetic field than the vinyl hydrogen signals of (Z)-Me3SiCPhd
A similar reaction of dipalladium complex 2 with PhCtCPh in
1:2 ratio smoothly proceeded at room temperature to give the 3,5-
CHSiMe3 (δ6.36)19 and (o-C6H4)(SitBuMe)CPhdCH(SitBuMe)
(δ 6.86)20 and are close to that of the disilanickelacyclopentene
disila-4-palladacyclopentene Pd(SiPh2CPhdCPhSiPh2)(PMe3)2
(6) after 10 h, along with Pd(η2-PhCtCPh)(PMe3)2 (7) in 50%
and 30% yields, respectively (eq 3). The reactions of terminal
alkynes formed a complicated mixture of products, which were not
identified.
Ni(SiF2CtBudCHSiF2)(CO)2 (δ 7.27).21 The 29Si NMR signals of
3b are observed as two doublets at δ 23.9 and 34.6 flanked with the
satellite signals of 195Pt nuclei (JPtꢀSi = 1176 and 1264 Hz,
respectively). The 31P{1H} NMR spectrum of 3b exhibits a pair of
Complex 6 was characterized by X-ray crystallography
(Figure 2b). The five-membered chelating ring has a symmetrical
structure with similar SiꢀCꢀC bond angles within the ring
(SiꢀC1ꢀC2: 114.9(2)°; SiꢀC2ꢀC1: 114.5(3)°). The 29Si and
31P NMR signals of 6 are observed at δSi 34.5 and δP ꢀ33.5,
respectively, with JSiꢀP = 64 Hz.
Scheme 4 displays a plausible pathway for the formation of
disilametallacyclopentene starting from dinuclear complexes and
alkynes. Insertion of alkynes into a MꢀSi bond generates a six-
membered cyclic intermediate (D), and subsequent reductive
elimination of the unsaturated complex M(PMe3)2 affords the
five-membered metallacycle (E). Coordination of RCtCR0 in
the mixture to M(PMe3)2 produces an alkyne complex (F). In
Scheme 4
Figure 2. Thermal ellipsoid plots of (a) 3b (50% probability), (b) 6
(50% probability), and (c) 9 (30% probability). Carbon-bound hydro-
gen atoms are omitted for simplicity.
Table 2. Selected Bond Distances (Å) and Angles (deg) of 3b, 6, and 9
3b (M = Pt)
6 (M = Pd)
9 (M = Pt)
MꢀSi
2.3705(9), 2.357(1)
2.3420(8), 2.353(1)
1.340(5)
2.3637(9), 2.3523(9)
2.3811(9), 2.3993(9)
1.353(5)
2.370(4), 2.359(3)
2.344(5), 2.350(5)
1.30(2)
MꢀP
CdC
Si1ꢀMꢀSi2
P1ꢀMꢀP2
Si1ꢀC1ꢀC2
Si2ꢀC2ꢀC1
80.56(4)
77.60(3)
81.1(1)
95.49(4)
95.36(3)
97.0(2)
114.4(3)
114.9(2)
116(1)
119.6(3)
114.5(3)
120.5(9)
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the case of terminal alkynes, the alkyne complex is converted slowly
into the dialkynyl complex via CꢀH bond activation. Loss of H2 is
presumably involved in the reaction to produce the dialkynyl
complexes. The reaction pathway is similar to those proposed for
the reaction of alkynes with dinuclear Fe and Ru complexes.5
Disilametallacycles containing group 10 metal complexes have
been investigated as possible intermediates in the bissilylation of
unsaturated compounds catalyzed by these metal complexes23,24
and have been prepared via SiꢀH or SiꢀSi bond activation of
o-disilylbenzenes,25 o-disilylcarboranes,26 and disilacyclobutenes,27
and bis(disilane)s28 promoted by low-valent transition metals.
The reactions of alkynes with mononuclear bis(silyl)plati-
num complexes were reported to yield several different pro-
ducts. They involve insertion of the alkyne into the PtꢀSi bond
of the mononuclear complexes in most cases. Reactions of
bis(silyl)platinum complex Pt(SiHPh2)2(PMe3)2 with a 3-fold
molar amount of arylacetylenes HCtCAr (Ar = C6H5,
C6H4Me-4) gave a mixture of the 3,5-disila-4-platinacyclopen-
tene 3a or 3b and 6-sila-3-platina-1,4-cyclohexadienes
C6H4Me-4) (eq 4). The 31P{1H} NMR spectra of the reaction
mixture indicated formation of these complexes with approxi-
mately 1:2 ratio. Use of a large excess of arylacetylenes caused
exclusive formation of 8a and 8b. A similar six-membered cyclic
complex with PEt3 ligands, Pt(CPhdCHSiMe2CHdCPh)-
(PEt3)2, was obtained from the reaction of Pt(SiHMe2)2(PEt3)2
with excess HCtCPh.29
Figure 3 displays the molecular structures of 8a and 8b, which
have a square-planar geometry around Pt. The six-membered
silaplatinacyclohexadiene rings are equipped with two aryl
groups at the R-carbons and have a boat conformation. The
bond distances and angles are similar to the PEt3 analogue
Pt(CArdCHSiPh2CHdCAr)(PMe3)2 (8a: Ar = C6H5, 8b: Ar =
Pt(CPhdCHSiMe2CHdCPh)(PEt3)229 (Table 3). Two phenyl
groups attached to the Si atom are not equivalent in the crystal
1
structure, and the H and 13C{1H} NMR signals of 8a and 8b
suggest the presence of magnetically nonequivalent SiPh groups
probably due to much slower inversion of the six-membered ring
than the NMR time scale.
Pt(SiHPh2)2(PMe3)2 reacted with HCtCCOOMe at 50 °Cfor20h
to give disilaplatinacyclopentene Pt{SiPh2C(COOMe)dCHSiPh2}-
(PMe3)2 (9, 67%) as the sole product (eq 5).
The molecular structure of 9 determined by X-ray crystallogra-
phy is shown in Figure 2c. The CdC bond of 9 (1.30(2) Å) is
slightly shorter than those of disilaplatinacycle 3b (1.340(5) Å) and
disilapalladacycle 6 (1.353(5) Å). The 1H NMR peak of the vinyl
hydrogen (δ 8.60) is observed at lower magnetic field compared to
the peaks of 3a (δ 7.42) and 3b (δ 7.44) probably due to electron-
withdrawing COOMe groups. The observation of two 31P NMR
signals (δP ꢀ19.7 and ꢀ19.1) and two 29Si NMR signals (δSi 24.4
Figure 3. Thermal ellipsoids of 8a (30% probability) and 8b (50%
probability). Carbon-bound hydrogen atoms are omitted for simplicity.
There are two crystallographically independent molecules of 8b in the
unit cell.
Table 3. Selected Bond Distances (Å) and Angles (deg) of 8a, 8b, and the PEt3 Analogue
a
8a
8b
Pt(CPhdCHSiMe2CHd CPh)(PEt3)2
PtꢀC
PtꢀP
CdC
2.067(5)
2.060(6)
2.320(2)
2.313(2)
1.365(9)
1.343(9)
86.1(2)
2.077(6), 2.082(6)
2.077(6), 2.075(6)
2.323(2), 2.311(2)
2.327(2), 2.329(2)
1.353(9), 1.344(9)
1.349(9), 1.366(9)
86.1(3), 88.1(3)
2.08(1)
2.05(1)
2.355(4)
2.354(4)
1.35(2)
1.34(2)
85.2(5)
97.2(1)
CꢀPtꢀC
PꢀPtꢀP
96.42(7)
96.76(6), 94.70(6)
a Ref 29.
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Scheme 5
intermediate (H), accompanied by elimination of H2SiPh2.
Subsequent oxidative addition of H2SiPh2 to H followed by
dehydrogenative cyclization of the γ-SiꢀH bond produces a
five-membered disilaplatinacycle along with loss of H2. The four-
membered cyclic intermediate was not observed in the reaction in
Scheme 5, although the corresponding complex was isolated and
fully characterized from the reaction mixture using dimethyl
acetylenedicarboxylate (Scheme 3). Two COOMe groups prob-
ably stabilize the ring-strained silaplatinacyclobutene. The reac-
tion of arylacetylene with Pt(SiHPh2)2(PMe3)2 yields both
disilaplatinacyclopentene and silaplatinacyclohexadiene, as shown
in eq 4. The former product is formed via the reaction of H2SiPh2
with intermediate H, while the latter is obtained from the further
reaction of alkyne with H. Formation of the two products can be
explained by the pathway involving the common mononuclear
intermediates (Schemes 5 and 6).
Scheme 6
’ CONCLUSION
The amino-substituted silylboronic ester can be employed as
the silylene precursor in the synthesis of the organotransition
metal complexes as shown in this study, similarly to the catalytic
reactions involving formal silylene transfer to the organic
substrates.11 This method may also provide an effective access
to the preparation of multinuclear complexes having Si ligands.30
The diplatinum and dipalladium complexes with bridging sily-
lene ligands react with alkynes smoothly to produce the dis-
ilametallacyclopentenes. This reaction as well as already reported
reactions of diiron and diruthenium complexes probably involves
insertion of alkynes into a MꢀSi bond in the M2Si2 framework. A
mononuclear bis(silyl)platinum complex also reacts with alkynes
to produce the same product via the mononuclear intermediate.
The insertion of an alkyne into the MꢀSi bond and coupling of
the alkenyl and silyl ligands occur not only in the reaction of
mononuclear complexes but also in that of the dinuclear com-
plexes. We found the occurrence of these independent pathways,
although mono- and dinuclear Pt complexes can be converted to
each other. Details of the two pathways were revealed by previous
and current studies. The dinuclear reaction mechanism is to be
considered in discussions of the reaction of organosilanes and
alkynes catalyzed by Pd and Pt complexes.
and 32.8) suggests an unsymmetrical ring structure similar to
complex 3. The experiment performed at room temperature for a
short period of time (3 h) gave a 3-sila-1-propenylplatinum complex
Pt(SiPh2H){C(COOMe)dCHSiPh2H}(PMe3)2 (10) (or its re-
gioisomer (100)) in 50% yield, as shown in Scheme 5. The NMR
data for 10 are comparable to those for the previously reported
3-sila-1-propenylplatinum complex A, which involves intramolecu-
lar interaction between the SiH group of the silapropenyl ligand
and Pt via the SiꢀHꢀPt bond.6 The 31P NMR signals at δ ꢀ29.3
(JPtꢀP = 1994 Hz) and ꢀ19.6 (JPtꢀP = 1457 Hz) are assigned to
the P atom trans to the silapropenyl ligand and trans to the SiHPh2
’ EXPERIMENTAL SECTION
General Procedures. All manipulations of the complexes were
carried out in a nitrogen-filled glovebox (Miwa MFG) or using standard
Schlenk techniques under an argon or nitrogen atmosphere. Hexane and
toluene were purified by using a solvent purification system (Glass
1
ligand, respectively. The H NMR spectrum shows two SiꢀH
1
Contour). H, 13C{1H}, 29Si{1H}, and 31P{1H} NMR spectra were
signals at δ 5.48 (JPtꢀH = 40 Hz) and 5.70 (JPtꢀH
=
recorded on Bruker Biospin Avance III 400 or Varian Mercury 300
spectrometers. Chemical shifts in 1H and 13C{1H} NMR spectra were
referenced to theresidual peaks of thesolvents used. The aromatic signals
17 Hz). The former signal with larger JPtꢀH value is attributed
to the SiPh2H group bonded with the Pt atom directly, and the
latter is matched to SiPh2H groups of the silapropenyl ligand. The
extended reaction time of 24 h at room temperature afforded a
mixture of 9 and 10 in 14% and 50% NMR yields, and further
heating of the mixture at 50 °C for 20 h produced 9 as the sole
product. Thus, formation of the disilaplatinacyclopentene 9
involves the sila(propenyl)platinum complex as the intermediate.
Scheme 6 summarizes the pathways for the formation of
disilaplatinacyclopentene from the bis(silyl)platinum complex and
terminal alkynes. Insertion of a CtC bond into the PtꢀSi bond
gives a silyl(silapropenyl)platinum complex (G). Intramolecular γ-
SiꢀH bond activation of G produces a silaplatinacyclobutene
1
of 3a, 3b, 6, 8a, and 8b in the H and 13C{1H} NMR spectra were
assigned by 2D HMQC NMR experiments. The peak positions of the
29Si{1H} or 31P{1H} NMR spectra were referenced to external SiMe4 (δ
0) or H3PO4 (δ 0) in C6D6. Elemental analysis was carried out using a
LECO CHNS-932 or Yanaco MT-5 CHN autorecorder at the Center for
Advanced Materials Analysis, Technical Department, Tokyo Institute of
Technology. IR absorption spectra were recorded on a Shimadzu FT/IR-
8100 spectrometer. Et2NSiPh2BOCMe2CMe2O,10 Pd(PCy3)2,31 Pt-
(PCy3)2,32 and Pt(SiHPh2)2(PMe3)233 were prepared according to the
reported procedure. HCtCPh, PhCtCPh, HCtCC6H4Me-4, and
3986
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ARTICLE
2
3
HCtCCOOMe were purchased from Tokyo Chemical Industry and
distilled prior to use. Commercially available PMe3 (Sigma-Aldrich) was
used without any purification.
Preparation of {Pt(PMe3)2}2(μ-SiPh2)2 (1). To a toluene solu-
tion (5 mL) of Pt(PMe3)4,34 prepared in situ from the ligand exchange of
Pt(PCy3)2 (500 mg, 0.66 mmol) with PMe3 (273 μL, 2.6 mmol) in 1:4
5.9 Hz, JPtꢀC = 127 Hz), 169.2 (apparent triplet, dCC6H4, JPꢀC
=
2
5.7 Hz, JPtꢀC = 128 Hz). The para and meta carbon signals of the
SiC6H5 group and meta and ortho carbon signals of the CC6H4 group
were overlapped with the solvent signals. 31P{1H} NMR (162 MHz,
C6D6, rt): δ ꢀ19.8 (JPtꢀP = 1542 Hz, 2JPꢀP = 29 Hz), ꢀ19.3 (JPtꢀP
=
1571 Hz, 2JPꢀP = 29 Hz).
Preparation of Pt{SiPh2C(C6H4Me-4)dCHSiPh2}(PMe3)2
(3b). Complex 3b, a white solid (94 mg, 60%), was obtained by a
similar procedure to the preparation of 3a from 1 (200 mg, 0.19 mmol)
and HCtCC6H4Me-4 (72 μL, 0.57 mmol) in toluene (5 mL). The
31P{1H} NMR spectrum of the reaction mixture after 10 h exhibited two
ratio, was added Et2NSiPh2BOCMe2CMe2O (252 mg, 0.66 mmol) at
room temperature. The mixture was stirred at 60 °C for 40 h. The initially
pale yellow solution gradually turned dark red. The 1H NMR spectra of the
crude products displayed formation of 1 and Et2NBOCMe2CMe2O. The
solvent and volatile materials were removed under reduced pressure. The
residual material was washed three times with 3 mL of hexane and dried in
vacuo to give complex 1 as a yellow solid (280 mg, 80%). Anal. Calcd for
doublets at δ ꢀ30.5 (JPtꢀP = 3180 Hz, JPꢀP = 36 Hz) and ꢀ28.2 (JPtꢀP
=
3345 Hz, JPꢀP = 36 Hz), which were assigned as inequivalent phosphines
of Pt(η2-HCtCC6H4Me-4)(PMe3)2 (4b). Cooling the filtrate for 5
days in a refrigerator resulted in the formation of trans-Pt(CtCC6H4-
Me-4)2(PMe3)2 (5b) (22 mg, 20%) as a white solid. Complex 5b was
characterized on the basis of the NMR spectroscopic data in the litera-
1
C36H56P4Pt2Si2: C, 40.83; H, 5.33. Found: C, 40.58; H, 4.95. H NMR
(400 MHz, C6D6, rt): δ 0.86 (d, 36H, PCH3, 2JPꢀH = 6.4 Hz, 3JPtꢀH
=
18 Hz), 7.18 (t, 4H, C6H5 para, 3JHꢀH = 7.5 Hz), 7.33 (t, 8H, C6H5 meta,
ture.36 Data for 3b: Anal. Calcd for C39H46P2PtSi2 1/2hexane: C, 57.91;
3
3JHꢀH = 7.5 Hz), 8.23 (d, 8H, C6H5 ortho, JHꢀH = 7.5 Hz). 13C{1H}
3
1
NMR (101 MHz, C6D6, rt): δ 20.2 (m, PCH3), 126.1 (C6H5 para, 5JPtꢀC
=
H, 6.13. Found: C, 57.59; H, 5.99. H NMR (400 MHz, C6D6, rt):
δ 0.78 (br d, 9H, PCH3, 2JPꢀH = 8.0 Hz), 0.85 (br d, 9H, PCH3, 2JPꢀH
=
7.4 Hz), 126.6 (C6H5 meta), 137.1 (C6H5 ortho, 3JPtꢀC = 23 Hz), 152.1
(C6H5 ipso, 3JPꢀC = 5.8 Hz). 29Si{1H} NMR (79 MHz, C6D6, rt): δ ꢀ75.8
(apparent quintet, JPtꢀSi = 715 Hz, 2JPꢀSi = 52 Hz). 31P{1H} NMR (162
8.0 Hz), 2.00 (s, 3H, C6H4CH3), 6.74 (d, 2H, CC6H4 ortho, 3JHꢀH = 8.0
Hz), 6.88 (d, 2H, CC6H4 meta, 3JHꢀH = 8.0 Hz), 7.25 (m, 6H, SiC6H5
3
3
MHz, C6D6, rt): δ ꢀ14.4 (JPtꢀP = 1665 Hz, 3JPtꢀP = 266 Hz, 2JSiꢀP
=
para and meta, JHꢀH = 7.3 Hz), 7.34 (t, 4H, SiC6H5 meta, JHꢀH
7.3 Hz), 7.44 (m, 1H, dCH, 4JPꢀH = 2.5 Hz, 3JPtꢀH = 67 Hz), 8.10 (d,
4H, SiC6H5 ortho, 3JHꢀH = 8.0 Hz), 8.15 (d, 4H, SiC6H5 ortho, 3JHꢀH
8.0 Hz). One of the para hydrogen signals was overlapped with solvent
signals. 13C{1H} NMR (101 MHz, C6D6, rt): δ 18.7 (br, PCH3, JPꢀC
=
52 Hz, 4JPꢀP =18 Hz).
=
Preparation of {Pd(PMe3)2}2(μ-SiPh2)2 (2). Complex 2 (158 mg,
48%) as a yellow solid was obtained by the reaction of Et2NSi-
=
13 Hz), 21.1 (C6H4CH3), 134.4 (CC6H4 para), 136.9 (SiC6H5 ortho,
3JPtꢀC = 24 Hz), 144.5 (CC6H4 ipso, 3JPtꢀC = 22 Hz), 146.6 (m, SiC6H5
ipso), 155.9 (apparent triplet, dCH, 3JPꢀC = 5.7 Hz, 2JPtꢀC = 127 Hz),
169.0 (apparent triplet, dCC6H5, 3JPꢀC = 5.9 Hz, 2JPtꢀC = 129 Hz). The
para and meta carbon signals of the SiC6H5 group and meta and ortho
carbon signals of the C6H4Me group were overlapped with the solvent
Ph2BOCMe2CMe2O (286 mg, 0.75 mmol) with Pd(PMe3)4,35 which
was generated from phosphine exchange of Pd(PCy3)2 (500 mg, 0.75 mmol)
and PMe3 (310 μL, 3.0 mmol) in 1:4 ratio. The procedure was similar to
the preparation of 1. Anal. Calcd for C36H56P4Pd2Si2: C, 49.04; H, 6.40.
Found: C, 48.60; H, 6.30. 1H NMR(400 MHz, C6D6, rt): δ 0.76 (d, 36H,
PCH3, 2JPꢀH = 2.8 Hz), 7.12 (t, 4H, C6H5 para, 3JHꢀH = 7.5 Hz), 7.24
signals. 29Si{1H} NMR (79 MHz, THF-d8, rt): δ 23.9 (d, JPtꢀSi
=
(t, 8H, C6H5 meta, 3JHꢀH = 7.5 Hz), 8.14 (d, 8H, C6H5 ortho, 3JHꢀH
=
=
1176 Hz, 2JPꢀSi = 137 Hz), 34.6 (d, JPtꢀSi = 1264 Hz, 2JPꢀSi = 144 Hz).
7.5 Hz). 13C{1H} NMR (101 MHz, C6D6, rt): δ 19.2 (d, PCH3, JPꢀC
9.2 Hz), 125.9 (C6H5 para), 126.9 (C6H5 meta), 136.1 (C6H5 ortho),
149.4 (C6H5 ipso). 29Si{1H} NMR (79 MHz, C6D6, rt): δ ꢀ35.3 (br).
31P{1H} NMR (162 MHz, C6D6, rt): δ ꢀ33.7 (br).
31P{1H} NMR (162 MHz, C6D6, rt): δ ꢀ19.7 (JPtꢀP = 1539 Hz, 2JPꢀP
=
29 Hz), ꢀ19.3 (JPtꢀP = 1572 Hz, 2JPꢀP = 29 Hz). Data for 5b: 1H NMR
(400 MHz, CDCl3, rt): δ 1.73 (br, 18H, PCH3), 2.29 (s, 6H, C6H4CH3),
3
7.02 (d, 4H, C6H4 meta, JHꢀH = 8.0 Hz), 7.24 (d, 4H, C6H4
ortho, JHꢀH = 8.0 Hz). 31P{1H} NMR (162 MHz, CDCl3, rt): δ
3
Preparation of Pt(SiPh2CPhdCHSiPh2)(PMe3)2 (3a). A mix-
ture of 1 (200 mg, 0.19 mmol) and HCtCPh (58 mg, 0.57 mmol) in
toluene (5 mL) was stirred at room temperature for 10 h. The initially
yellow solution gradually turned red, and precipitation of a white solid
was observed. The solid was washed three times with 2 mL of hexane
and dried in vacuo to give 3a (95 mg, 62%) as a white solid. The 31P{1H}
NMR spectrum of the reaction mixture after 10 h exhibited two doublets
at δ ꢀ30.5 (JPtꢀP = 3227 Hz, JPꢀP = 36 Hz) and ꢀ28.3 (JPtꢀP = 3350 Hz,
JPꢀP = 36 Hz), which were assigned as inequivalent phosphine ligands of
Pt(η2-HCtCPh)(PMe3)2 (4a). The coupling constants are compar-
able to those of Pt(PPh3)2(η2-HCtCPh) (δ 27.1, JPtꢀP = 3547 and
JPꢀP = 33.4 Hz; δ 31.0, JPtꢀP = 3464 and JPꢀP = 33.4 Hz).22 Data for 3a:
ꢀ20.3 (JPtꢀP = 2480 Hz).
Preparation of Pd(SiPh2CPhdCPhSiPh2)(PMe3)2 (6). To a
toluene solution (3 mL) of 2 (200 mg, 0.23 mmol) was added a 2-fold
molar amount of PhCtCPh (81 mg, 0.45 mmol), and then the resulting
mixture was stirred at room temperature for 10 h. The initially dark red
solution gradually turned gray. The solvent and volatile materials were
removed under reduced pressure to produce an oily residue, which was
washed three times with 2 mL of hexane and dried in vacuo to give
complex 6 as a white solid (90 mg, 50%). The filtrate was stored in a
refrigerator overnight to afford Pd(η2-PhCtCPh)(PMe3)2 (7) as a
white solid (30 mg, 30%). The NMR data of 7 are comparable to those of
an analogue, Pd(η2-PhCtCPh)(PMe2Ph)2.2d Data for 6: Anal. Calcd
Anal. Calcd for C38H44P2PtSi2 1/2toluene: C, 57.96; H, 5.63. Found:
3
1
1
C, 58.23; H, 6.04. H NMR (400 MHz, C6D6, rt): δ 0.77 (br d, 9H,
for C44H48P2PdSi2: C, 65.94; H, 6.04. Found: C, 65.66; H, 5.89. H
PCH3, 2JPꢀH = 7.0 Hz), 0.85 (br d, 9H, PCH3, 2JPꢀH = 7.0 Hz), 6.92 (s,
5H, dCC6H5), 7.24 (m, 6H, SiC6H5 para and meta, 3JHꢀH = 7.3 Hz),
NMR (400 MHz, C6D6, rt): δ 0.63 (m, 18H, PCH3, 2JPꢀH = 6.0 Hz),
6.57 (d, 4H, =CC6H5 ortho, 3JHꢀH = 6.7 Hz), 6.71 (t, 2H, =CC6H5 para,
3JHꢀH = 7.0 Hz), 6.77 (t, 4H, dCC6H5 meta, 3JHꢀH = 7.2 Hz), 7.21 (t,
7.34 (t, 4H, SiC6H5 meta, 3JHꢀH = 7.3 Hz), 7.42 (m, 1H, dCH, 4JPꢀH
=
2.5 Hz, 3JPtꢀH = 67 Hz), 8.07 (d, 4H, SiC6H5 ortho, 3JHꢀH = 8.0 Hz), 8.15
(d, 4H, SiC6H5 ortho, 3JHꢀH = 8.0 Hz). One of the para hydrogen signals
was overlapped with the solvent signals. 13C{1H} NMR (101 MHz,
C6D6, rt): δ 18.7 (br, PCH3, JPꢀC = 13 Hz), 125.4 (dCC6H5 para),
4H, SiC6H5 para, 3JHꢀH = 7.2 Hz), 7.29 (t, 8H, SiC6H5 meta, 3JHꢀH
=
7.2 Hz), 8.06 (d, 8H, SiC6H5 ortho, 3JHꢀH = 7.8 Hz). 13C{1H} NMR
(101 MHz, C6D6, rt): δ 17.5 (dd, PCH3, JPꢀC = 8.7, 11 Hz), 124.5
(dCC6H5 para), 127.0 (dCC6H5 meta), 127.5 (SiC6H5 meta), 129.1
(dCC6H5 ortho), 137.1 (SiC6H5 ortho), 144.9 (dCC6H5 ipso), 145.1
(apparent triplet, SiC6H5 ipso, 3JPꢀC = 13 Hz). 166.5 (apparent triplet,
3
136.9 (SiC6H5 ortho, JPtꢀC = 24 Hz), 146.7 (m, SiC6H5 ipso), 147.5
(dCC6H5 ipso, 3JPtꢀC = 21 Hz), 156.4 (apparent triplet, dCH, 3JPꢀC
=
3987
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ARTICLE
Table 4. Crystallographic Data and Details of Refinement of 1, 2, 3b, 6, 8a, 8b, and 9
1
2
3b 1/2toluene
6 1/2toluene
3
3
formula
C
36H56P4Pt2Si2
C36H56P4Pd2Si2
881.70
C39H46P2PtSi2 (1/2 C7H8)
C44H48P2PdSi2 (1/2 C7H8)
3
3
fw
1059.08
874.07
847.45
cryst size/mm
cryst syst
0.50 ꢁ 0.60 ꢁ 0.70
monoclinic
yellow
0.15 ꢁ 0.20 ꢁ 0.30
triclinic
0.25 ꢁ 0.30 ꢁ 0.30
monoclinic
colorless
0.12 ꢁ 0.15 ꢁ 0.15
monoclinic
colorless
cryst color
space group
a/Å
yellow
P21/n (No. 14)
11.574(2)
P1 (No. 2)
9.609(4)
10.751(5)
11.421(5)
98.784(1)
111.692(4)
106.126(7)
1009.2(8)
1
P21/c (No. 14)
12.678(3)
P21/n (No. 14)
10.113(2)
b/Å
18.941(2)
18.481(4)
20.167(3)
c/Å
19.224(2)
18.113(4)
21.381(3)
R/deg
β/deg
107.014(2)
108.257(3)
96.812(2)
γ/deg
V/Å3
4029.8(9)
4
4030(2)
4
4330(1)
4
Z
Dcalcd/g cmꢀ3
1.746
1.451
1.440
1.300
F(000)
2064
452
1764
1764
μ/mmꢀ1
7.1496
32 570
9181
1.1331
3.6343
32 417
9213
0.5895
33 888
9841
no. of reflns measd
no. of unique reflns
Rint
8254
4427
0.030
0.030
0.0539
7504
0.0737
7738
no. of obsd reflns (I > 2σ(I))
no. of variables
R, Rw (I > 2σ(I))
R, Rw (all data)
GOF on F2
8098
3408
410
200
442
479
0.0199, 0.0422
0.0241, 0.0438
1.024
0.0316, 0.0828
0.0404, 0.0861
0.989
0.0299, 0.0699
0.0371, 0.0700
0.994
0.0470, 0.1080
0.0666, 0.1175
1.093
8a
8b
9
formula
C34H40P2PtSi
733.81
C36H44P2PtSi
761.87
C34H42O2P2PtSi2
795.91
fw
cryst size/mm
cryst syst
0.26 ꢁ 0.32 ꢁ 0.64
monoclinic
colorless
0.10 ꢁ 0.10 ꢁ 0.15
monoclinic
colorless
0.22 ꢁ 0.28 ꢁ 0.55
monoclinic
colorless
cryst color
space group
a/Å
P21/c (No. 14)
17.963(5)
P21/c (No. 14)
20.1864(6)
15.5085(3)
21.8311(6)
P21/n (No. 14)
13.006(7)
b/Å
10.544(4)
17.015(7)
c/Å
18.541(3)
16.417(6)
R/deg
β/deg
111.40(2)
92.608(2)
101.849(7)
γ/deg
V/Å3
3270(2)
4
6827.4(3)
8
3556(3)
4
Z
Dcalcd/g cmꢀ3
1.491
1.482
1.487
F(000)
1464
3056
1592
μ/mmꢀ1
4.4292
7732
4.2454
55 076
15 605
12 578
737
4.1154
8511
no. of reflns measd
no. of unique reflns
no. of obsd reflns (I > 2σ(I))
no. of variables
R, Rw (I > 2σ(I))
R, Rw (all data)
GOF on F2
7499
8160
6373
5415
349
377
0.0462, 0.1279
0.0553, 0.1348
1.027
0.0439, 0.1137
0.0597, 0.1536
1.099
0.0754, 0.2026
0.1195, 0.2286
1.048
2
CdC, 3JPꢀC = 7.3 Hz). The para carbon signal of the SiC6H5 group was
overlapped with the solvent signals. 29Si{1H} NMR (79 MHz, C6D6, rt):
δ 34.5 (apparent triplet, JPꢀSi = 64 Hz). 31P{1H} NMR (162 MHz,
C6D6, rt): δ ꢀ33.5 (2JSiꢀP = 64 Hz). Data for 7: 1H NMR (400 MHz,
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ARTICLE
C6D6, rt): δ 1.05 (br, 18H, PCH3), 7.03 (t, 2H, C6H5 para, 3JHꢀH = 7.2
Hz), 7.19 (t, 4H, C6H5 meta, 3JHꢀH = 7.2 Hz), 7.64 (d, 4H, C6H5 ortho,
3JHꢀH = 7.2 Hz). 13C{1H} NMR (101 MHz, C6D6, rt): δ 20.0 (br,
PCH3), 119.2 (br d, CtC, 2JPꢀC = 64 Hz), 125.1 (br, C6H5 para), 128.7
(br, C6H5 ortho), 137.5 (br, C6H5 ipso). The meta carbon signal of the
C6H5 group was overlapped with the solvent signals. 31P{1H} NMR
(162 MHz, C6D6, rt): δ ꢀ25.6.
evaporated under reduced pressure to produce a residue, which was washed
three times with 5 mL of hexane and dried in vacuo to give complex 9 as a
pale yellow solid (139 mg, 67%). Anal. Calcd for C34H42O2P2PtSi2: C,
51.31; H, 5.32. Found: C, 51.09; H, 5.30. 1H NMR (400 MHz, C6D6, rt): δ
0.74 (d, 9H, PCH3, 2JPꢀH = 8.0 Hz, 3JPtꢀH = 20 Hz), 0.83 (d, 9H, PCH3,
2JPꢀH = 8.0 Hz, 3JPtꢀH = 19 Hz), 3.17 (s, 3H, OCH3), 7.17ꢀ7.22 (m, 4H,
C6H5 para), 7.27 (t, 4H, C6H5 meta, 3JHꢀH = 8.0 Hz), 7.32 (t, 4H, C6H5
meta, 3JHꢀH = 8.0 Hz), 8.03 (d, 4H, C6H5 ortho, 3JHꢀH = 8.0 Hz), 8.43 (d,
4H, C6H5 ortho, 3JHꢀH = 8.0 Hz), 8.60 (d, 1H, dCH, 4JPꢀH = 6.0 Hz,
3JPtꢀH = 66 Hz). 13C{1H} NMR (101 MHz, CD2Cl2, rt): δ 18.6 (m,
PCH3, JPꢀC = 3.9 and 25 Hz), 19.1 (m, PCH3, J = 3.9 and 25 Hz), 50.9
(OCH3), 127.4 (C6H5 meta), 127.9 (C6H5 meta and para), 128.1 (C6H5
Reaction of Pt(SiHPh2)2(PMe3)2 with HCtCPh. To a toluene
solution (10 mL) of Pt(SiHPh2)2(PMe3)2 (321 mg, 0.45 mmol) was
added a 3-fold molar amount of HCtCPh (140 μL, 1.27 mmol), and
then the resulting mixture was stirred at 60 °C for 7 h. The yellow
solution gradually turned orange. The solvent and volatile materials
were removed under reduced pressure. The obtained residue was
washed three times with 5 mL of hexane to give a mixture of 3a and
para), 136.7 (C6H5 ortho, 3JPtꢀC = 23 Hz), 137.0 (C6H5 ortho, 3JPtꢀC
=
3
2
23 Hz), 144.8 (d, C6H5 ipso, JPꢀC = 3.9 Hz, JPtꢀC = 35 Hz), 145.5
(d, C6H5 ipso, 3JPꢀC = 9.7 Hz, 2JPtꢀC = 38 Hz), 157.6 (apparent triplet,
dCH, 3JPꢀC = 9.7 Hz, 2JPtꢀC = 142 Hz), 168.3 (apparent triplet, =CCOO,
Pt(CPhdCHSiPh2CHdCPh)(PMe3)2 (8a) in 1:1.9 ratio estimated
by NMR spectroscopy. Repeated recrystallization with toluene/
hexane at room temperature gave 8a (84 mg, 25%) as a white solid.
Anal. Calcd for C34H40P2PtSi: C, 55.65; H, 5.49. Found: C, 55.38; H,
2
3
3JPꢀC = 3.9 Hz, JPtꢀC = 137 Hz), 169.4 (CdO, JPtꢀC = 35 Hz).
29Si{1H} NMR (79 MHz, CD2Cl2, rt): δ 24.4 (dd, JPtꢀSi = 1251 Hz,
2JPtransꢀSi = 145 Hz, 2JPcisꢀSi = 5.5 Hz), 32.8 (dd, JPtꢀSi = 1270 Hz, 2JPtransꢀSi
= 147 Hz, 2JPcisꢀSi =3.7Hz). 31P{1H} NMR (162 MHz, C6D6, rt):δꢀ19.7
5.39. 1H NMR (400 MHz, C6D6, rt): δ 0.64 (d, 18H, PCH3, 2JPꢀH
=
2
8.0 Hz, 3JPtꢀH = 18 Hz), 7.06 (t, 2H, dCC6H5 para, 3JHꢀH = 7.6 Hz),
7.18ꢀ7.22 (m, 6H, SiC6H5 meta and para), 7.26 (t, 4H, dCC6H5
(d, JPtꢀP = 1501 Hz, JPꢀP = 31 Hz), ꢀ19.1 (d, JPtꢀP = 1595 Hz,
2JPꢀP = 31 Hz). IR (KBr): 1695 (νCdO) cmꢀ1
.
meta, 3JHꢀH = 7.6 Hz), 7.66 (d, 2H, dCH, 4JPꢀH = 15 Hz, 3JPtꢀH
=
Preparation of Pt(SiPh2H){C(COOMe)dCHSiPh2H}(PMe3)2
(10). To a toluene solution (6 mL) of Pt(SiHPh2)2(PMe3)2 (172 mg,
0.24 mmol) was added HCtCCOOMe (20 μL, 0.24 mmol), and then the
resulting mixture was stirred at room temperature for 3 h. The initial yellow
solution gradually turned pale yellow. The solvent and volatile materials
were evaporated under reduced pressure to produce a residue, which was
washed three times with 3 mL of hexane and driedin vacuo to givecomplex
10 or its regioisomer (100) as a white solid (96 mg, 50%). 1H NMR (300
MHz, C6D6, rt): δ 0.84 (d, 9H, PCH3, 2JPꢀH = 8.1 Hz, 3JPtꢀH = 17 Hz),
1.05 (d, 9H, PCH3, 2JPꢀH = 8.4 Hz, 3JPtꢀH = 23 Hz), 3.35 (s, 3H, OCH3),
5.48 (dd, 1H, PtSiH, 3JPcisꢀH = 10 Hz, 3JPtransꢀH = 14 Hz, 2JPtꢀH = 40 Hz),
5.70 (d, 1H, CSiH, J = 5.6 Hz, JPtꢀH = 17 Hz), 7.08ꢀ7.30 (m, 12H, C6H5
meta and para), 7.49 (m, 2H, C6H5 ortho), 7.61 (m, 2H, C6H5 ortho), 7.90
126 Hz), 7.77 (m, 2H, SiC6H5 ortho), 7.88 (m, 2H, SiC6H5 ortho),
8.05 (d, 4H, dCC6H5 ortho, JHꢀH = 8.0 Hz). 13C{1H} NMR
(100 MHz, C6D6, rt): δ 16.7 (m, PCH3, JPꢀC = 30 Hz), 126.1
(dCC6H5 para), 127.5 (dCH, JPtꢀC was not observed), 127.8
(dCC6H5 meta), 128.6 (dCC6H5 ortho), 135.6 (SiC6H5 ortho),
136.3 (SiC6H5 ortho), 140.4 (SiC6H5 ipso), 143.8 (SiC6H5 ipso),
3
2
152.6 (apparent triplet, dCC6H5 ipso, JPꢀC = 5.5 Hz, JPtꢀC
=
44 Hz), 192.8 (dd, dCC6H4, 2JPcisꢀC = 13 Hz, 2JPtransꢀC = 109 Hz,
JPtꢀC = 811 Hz). The para and meta carbon signals of the SiC6H5
group were overlapped with the solvent signals. 31P{1H} NMR
(162 MHz, C6D6, rt): δ ꢀ29.5 (JPtꢀP = 1765 Hz).
Reaction of Pt(SiHPh2)2(PMe3)2 with HCtCC6H4Me-4. A
mixture of Pt(SiHPh2)2(PMe3)2 (300 mg, 0.42 mmol) and a 3-fold
molar amount of HCtCC6H4Me-4 (244 mg, 2.1 mmol) in toluene
(5 mL) was stirred at 60 °C for 10 h. The ratio of 3b and
(d, 2H, C6H5 ortho, JHꢀH = 8.1 Hz), 8.03 (d, 2H, C6H5 ortho, JHꢀH
=
6.6 Hz), 8.16 (apparent double triplet, 1H, dCH, J = 5.6, 18 Hz). 31P{1H}
NMR (122 MHz, C6D6, rt): δ ꢀ29.3 (d, JPtꢀP = 1994 Hz, 2JPꢀP = 21 Hz),
ꢀ19.6 (d, JPtꢀP = 1457 Hz, 2JPꢀP = 21 Hz). IR (KBr): 2130 (νSiꢀH), 2039
(νSiꢀH), 1690 (νCdO) cmꢀ1. The extended reaction of Pt(SiHPh2)2-
(PMe3)2 and HCtCCOOMe for 24 h at room temperature gave9 and 10
as mixtures in 14% and 50% NMR yields, followed by heating of the
mixture at 50 °C for 20 h to afford 9 as the sole product.
Pt(CArdCHSiPh2CHdCAr)(PMe3)2 (8b: Ar = C6H4Me-4) was esti-
mated as 1:2 by 31P NMR spectroscopy. Repeated recrystallization from
toluene/hexane at room temperature gave 8b (65 mg, 20%) as a white
solid. Anal. Calcd for C36H44P2PtSi: C, 56.75; H, 5.82. Found: C, 56.88
X-ray Crystallography. Crystals of 1, 2, 3b, 6, 8a, 8b, and 9 suitable
for X-ray crystallography were obtained by slow diffusion from toluene/
hexane at room temperature and were mounted on MicroMounts
(MiTeGen). The crystallographic data for 1, 2, 3b, 6, and 8b were
collected on a Rigaku Saturn CCD area detector equipped with mono-
chromated Mo KR radiation (λ = 0.71073 Å) at ꢀ160 °C, and the data for
8a and 9 were collected on a Rigaku AFC-5R automated four-cycle
diffractometer at room temperature. Calculations were carried out using
the program package Crystal Structure, version 4.0, for Windows. The
positional and thermal parameters of non-hydrogen atoms were refined
anisotropically on F2 by the full-matrix least-squares method using
SHELXL-97.37 Hydrogen atoms were placed at calculated positions and
refined with a riding mode on their corresponding carbon atoms. Crystal-
lographic data and details of refinement of 1, 2, 3b, 6, 8a, 8b, and 9 are
summarized in Table 4.
H, 5.33. 1H NMR (400 MHz, C6D6, rt): δ 0.67 (d, 18H, PCH3, 2JPꢀH
=
8.0 Hz, 3JPtꢀH = 17 Hz), 2.18 (s, 6H, C6H4CH3), 7.09 (d, 4H, dCC6H4
meta, 3JHꢀH = 8.0 Hz), 7.18ꢀ7.21 (m, 6H, SiC6H5 meta and para), 7.64
(d, 2H, dCH, 4JPꢀH = 15 Hz, 3JPtꢀH = 127 Hz), 7.78 (m, 2H, SiC6H5
ortho), 7.91 (m, 2H, SiC6H5 ortho), 7.99 (d, 4H, =CC6H4 ortho, 3JHꢀH
=
=
8.0 Hz). 13C{1H} NMR (101 MHz, C6D6, rt): δ 16.8 (m, PCH3, JPꢀC
2
30 Hz), 21.2 (C6H4CH3), 126.3 (dCH, JPtꢀC = 27 Hz), 128.5
(dCC6H4 meta or ortho), 128.6 (dCC6H4 meta or ortho), 135.3
(dCC6H4 para), 135.7 (SiC6H5 ortho), 136.3 (SiC6H5 ortho), 140.7
(SiC6H5 ipso), 144.1 (SiC6H5 ipso), 149.9 (apparent triplet, dCC6H4
ipso, 3JPꢀC =5.5Hz, 2JPtꢀC = 41 Hz), 192.9 (dd, dCC6H4, 2JPcisꢀC =13Hz,
2JPtransꢀC = 108 Hz, JPtꢀC = 806 Hz). The para and meta carbon signals of
the SiC6H5 group were overlapped with the solvent signals. 31P{1H}
NMR (162 MHz, C6D6, rt): δ ꢀ29.4 (JPtꢀP = 1761 Hz).
Preparation of Pt(SiPh2C(COOMe)dCHSiPh2)(PMe3)2 (9).
To a toluene solution (7 mL) of Pt(SiHPh2)2(PMe3)2 (186 mg, 0.26 mmol)
was added an equimolar amount of HCtCCOOMe (22 μL, 0.26 mmol),
and then the resulting mixture was stirred at 50 °C for 20 h. The yellow
solution gradually turned orange. The solvent and volatile materials were
’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic data for 1, 2,
b
3b, 6, 8a, 8b, and 9 as a CIF file. This material is available free of
charge via the Internet at http://pubs.acs.org.
3989
dx.doi.org/10.1021/om200156g |Organometallics 2011, 30, 3981–3991

Organometallics
ARTICLE
’ AUTHOR INFORMATION
P. J. Organomet. Chem. 2002, 649, 141–146. (e) Tanabe, M.; Mawatari,
A.; Osakada, K. Organometallics 2007, 26, 2937–2940.
(9) (a) Lappert, M. F.; Speier, G. J. Organomet. Chem. 1974,
80, 329–339. (b) Shimada, S.; Rao, M. L. N.; Hayashi, T.; Tanaka, M.
Angew. Chem., Int. Ed. 2001, 40, 213–216.
Corresponding Author
*E-mail: kosakada@res.titech.ac.jp.
(10) Ohmura, T.; Masuda, K.; Furukawa, H.; Suginome, M. Orga-
nometallics 2007, 26, 1291–1294.
’ ACKNOWLEDGMENT
(11) (a) Ohmura, T.; Masuda, K.; Suginome, M. J. Am. Chem. Soc.
2008, 130, 1526–1527. (b) Ohmura, T.; Masuda, K.; Takase, I.;
Suginome, M. J. Am. Chem. Soc. 2009, 131, 16624–16625. (c) Masuda,
K.; Ohmura, T.; Suginome, M. Organometallics 2011, 30, 1322–1325.
(12) Our recent studies on catalytic reactions of silylboronic esters:
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T.; Oshima, K.; Taniguchi, H.; Suginome, M. J. Am. Chem. Soc. 2010,
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Chem. Commun. 2007, 4717–4725. (g) Ohmura, T.; Suginome, M. Bull.
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This work was financially supported by Grants-in-Aid for
Scientific Research for Scientific Research on Priority Areas
(No. 19027018), from the Ministry of Education, Culture, Sport,
Science, and Technology, Japan.
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dx.doi.org/10.1021/om200156g |Organometallics 2011, 30, 3981–3991