Chemical properties of tetragermaplatinacyclopentane. Insertion of an alkyne into a Pt-Ge bond and silylation caused by H2SiPh2

Article abstract of DOI:10.1021/om200275w

A platinum complex having dibutylgermyl ligands, [Pt(GeHBu ₂)₂(dmpe)] (dmpe = 1,2-bis(dimethylphosphino)ethane), reacted with excess H₂GeBu₂ at 90 °C to yield a five-membered tetragermaplatinacycle, [Pt(GeBu₂GeBu ₂GeBu₂GeBu₂)(dmpe)] (6). The direct reaction of H₂GeBu₂ with [Pt(dmpe)₂] in 5:1 ratio also gave 6 in 67% yield. The reaction of dimethyl acetylenedicarboxylate with 6 caused insertion of a C≡C bond into a Pt-Ge bond to form a seven-membered germaplatinacycloheptene, which was characterized by X-ray crystallography. Complex 6 reacted with H₂GePh₂ and H₂SiPh ₂ in 1:2 ratio to produce a mixture of tetragermane dihydride H(GeBu₂)₄H and bis(silyl)- or bis(germyl)platinum complexes [Pt(EHPh₂)₂(dmpe)] (E = Si, Ge).

Full text of DOI:10.1021/om200275w

ARTICLE
pubs.acs.org/Organometallics
Chemical Properties of Tetragermaplatinacyclopentane. Insertion of
an Alkyne into a PtꢀGe Bond and Silylation Caused by H2SiPh2
Makoto Tanabe, Takashi Deguchi, and Kohtaro Osakada*
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1-3 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
S Supporting Information
b
ABSTRACT:
A platinum complex having dibutyl-
germyl ligands, [Pt(GeHBu2)2(dmpe)] (dmpe = 1,2-bis(di-
methylphosphino)ethane), reacted with excess H2GeBu2 at
90 °C to yield a five-membered tetragermaplatinacycle,
[Pt(GeBu2GeBu2GeBu2GeBu2)(dmpe)] (6). The direct
reaction of H2GeBu2 with [Pt(dmpe)2] in 5:1 ratio also
gave 6 in 67% yield. The reaction of dimethyl acetylenedicarboxylate with 6 caused insertion of a CtC bond into a PtꢀGe
bond to form a seven-membered germaplatinacycloheptene, which was characterized by X-ray crystallography. Complex 6
reacted with H2GePh2 and H2SiPh2 in 1:2 ratio to produce a mixture of tetragermane dihydride H(GeBu2)4H and bis(silyl)-
or bis(germyl)platinum complexes [Pt(EHPh2)2(dmpe)] (E = Si, Ge).
’ INTRODUCTION
from the reaction of HGePh2(SiMe2)nPh2GeH with [Pt(η2-
C2H4)(PPh3)2].7 Braddock-Wilking reported preparation
Persilylated and pergermylated metallacycles (Chart 1) are
much less common than their carbon analogues, metallacyclo-
alkanes, because of limitation in the preparation reactions.1 Sila-2
and germametallacycles3 containing early transition metal com-
plexes were reported to be obtained from metathesis reactions of
dianionic oligosilanes or oligogermanes with dihalo complexes of
these metals. The above metallacycles of late transition metals
can be obtained by oxidative addition of two EꢀH (E = Si, Ge)
bonds of oligosilanes or oligogermanes or EꢀE bond activa-
tion of the cyclic oligosilanes and oligogermanes to low-valent
metal complexes. West reported that Pd-catalyzed reactions of
cyclotetrasilane (SiEt2)4 with alkynes produced cyclotetra-
of five-membered platinacycles [Pt(ER2ER2ER2ER2)-
(dppe)] (ER2 = SiC12H8 or GeC12H8) from the reaction of
[PtMe2(dppe)] with excess sila- and germafluorenes.8
We found conversion of bis(germyl)palladium and -plati-
num complexes [M(GeHPh2)2(dmpe)] (M = Pd, Pt (1))
to
a
four-membered platinum trigermane complex,
[Pt(GePh2GePh2GePh2)(dmpe)] (2), and further to tetra-
germametallacyclopentanes [M(GePh2GePh2GePh2GePh2)-
(dmpe)] (M = Pd,9 Pt (3)10) upon their reactions with
H2GePh2, as shown in Scheme 1. In this paper, we report the
preparation of a new germaplatinacycle composed of dibutyl-
germylene groups as well as their new chemical properties.
silahexenes SiEt2SiEt2SiEt2SiEt2CRdCR. They proposed the
reaction mechanism that involved a persilylated palladacyclo-
pentane intermediate, [Pd(SiEt2SiEt2SiEt2SiEt2)(PPh3)n],
and its conversion into a seven-membered palladacycle,
’ RESULTS AND DISCUSSION
A
platinum complex with dibutylgermyl ligands,
[Pd(SiEt2SiEt2SiEt2SiEt2CRdCR)(PPh3)n], via insertion of
alkynes into the PdꢀSi bond.4 Mochida reported ring en-
largement of cyclotetragermane (GeiPr2)4 with alkynes cata-
lyzed by the Pd complexes and suggested via insertion of
alkynes into the PdꢀGe bond of five-membered tetragerma-
palladacycle intermediates.5 In these reactions, the postulated
insertion of alkynes into the MꢀGe bond was not demon-
strated. Chemistry of persilylated and pergermylated metalla-
cycles has become significant in recent years. Schram reported
[Pt(GeHBu2)2(dmpe)] (4), was obtained in 71% yield from
the reaction of [Pt(dmpe)2] with H2GeBu2 in 1:2 ratio at
room temperature. Further reaction of 4 with excess
H2GeBu2 at 90 °C for 230 h produced a tetragermaplat-
inacyclopentane, [Pt(GeBu2GeBu2GeBu2GeBu2)(dmpe)]
(6), in 37% yield (Scheme 2). The 31P{1H} NMR spectra
during the reaction indicated formation of a four-membered triger-
maplatinum intermediate, [Pt(GeBu2GeBu2GeBu2)(dmpe)] (5)
(vide infra). Direct reaction of [Pt(dmpe)2] with H2GeBu2 in
1:5 ratio on heating at 90 °C for 45 h produced 6 in 67% yield.
[Pt(SiPh2SiPh2SiPh2SiPh2)(PPh3)2] as the first example of
a transition metal cyclo-oligosilane complex.6 Four- and
five-membered platinacycles containing Si and Ge atoms
Received: March 28, 2011
Published: May 27, 2011
[Pt{GePh2(SiMe2)nGePh2}(PPh3)2] (n = 1, 2) were prepared
r
2011 American Chemical Society
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Chart 1
Scheme 1
Figure 1. Thermal ellipsoids (50% probability) of 4. Carbon-bound
hydrogen atoms except for GeꢀH hydrogens are omitted for simplicity.
Table 1. Selected Bond Distances (Å) and Angles (deg) of 4
and 1
4
1a
PtꢀGe
2.4454(5), 2.4380(5)
2.267(1), 2.276(1)
1.70(6), 1.61(4)
86.04(2)
2.4527(4), 2.4411(6)
2.293(1), 2.295(2)
1.57(4), 1.87(3)
90.63(2)
PtꢀP
GeꢀH
GeꢀPtꢀGe
PꢀPtꢀP
86.29(4)
85.06(4)
a Data from ref 10.
Scheme 2
with 195Pt nuclei (JPtꢀC = 55 and 23 Hz, respectively). The
n-butyl carbon signals of 6 are observed as eight peaks, indicating
the presence of two sets of GeBu2 groups. The R-carbon signal at
δ 19.6 with a large coupling constant (38 Hz) is assigned to the
GeBu2 groups bonded to the Pt atom, while the signal at δ 14.5
3
with a small JPtꢀC value (16 Hz) is due to the R-carbon of
internal GeBu2 groups.
Figure 2 shows the 31P{1H} NMR spectra during the 1:2
reaction of 4 and H2GeBu2 at 90 °C in toluene-d8. After 14 h, the
signal of 4 (δ 36.9, JPtꢀP = 1762 Hz) was decreased upon heating
the reaction mixture, and a small signal of tetragermaplatinacy-
clopentane 6 at δ 33.7 (JPtꢀP = 1726 Hz) was observed
(Figure 2a). A major signal at δ 36.3 (JPtꢀP = 1652 Hz) was
assigned to trigermaplatinacyclobutane 5 because further heating of
the solution caused a decrease of the peak of 4 and an increase of the
signal due to 6 after 42 h of heating (Figure 2b). We reported the
reaction of H2GePh2 with [Pt(GeHPh2)2(dmpe)] to produce
1
The H NMR spectrum of the product mixture showed accom-
panying formation of oligogermane dihydrides, H(GeBu2)nH (n =
2, 3; GeꢀH signals at δ 4.09 and 4.13). Complexes 4 and 6 were air
and thermally stable, and complex 6 was separated by silica gel
column chromatography.
[Pt(GePh2GePh2GePh2)(dmpe)] (2, M = Pt), which was con-
verted into [Pt(GePh2GePh2GePh2GePh2)(dmpe)] (3, M =
Pt), as well as the structures and spectroscopic data of the
isolated complexes.10 Complex 5 is not isolable from the reaction
mixture, but it shows a smaller JPtꢀP value (1652 Hz) than 4
(1762 Hz) and 6 (1726 Hz), similarly to 2 (1819 Hz, 1 = 1895
Hz, 3 = 1851 Hz). Two small doublets with an AB pattern at δ
34.1 (JPtꢀP = 1810 Hz) and δ 34.7 (JPtꢀP = 1674 Hz) may be
attributed to unsymmetrical Pt intermediates having two differ-
ent Ge ligands (ꢀGeHBu2 and ꢀ(GeBu2)2ꢀGeHBu2, for
example), formed during the reaction.
Figure 1 shows the molecular structure of 4 having Pt with a
square-planar geometry. Table 1 compares their bond param-
eters with those of the GePh2 analogue 1. The PtꢀGe bonds
of 4 (2.4454(5), 2.4380(5) Å) are within the range of the PtꢀGe
bonds of cis-bis(germyl)platinum complexes with phosphine
ligands (2.427(2)ꢀ2.499(1) Å).7,8,10,11 The PtꢀP bonds of 4
(2.267(1), 2.276(1) Å) are slightly shorter than those of 1 (M =
Pt, 2.293(1), 2.295(2) Å).10 The 1H NMR spectrum of 4 exhibits
a GeꢀH hydrogen signal at δ 4.16 flanked with 195Pt satellites
(2JPtꢀH = 69 Hz). The peak is shifted downfield compared to
H2GeBu2 (δ 3.86), similarly to the GeꢀH signal of 1 (M = Pt: δ
5.82, H2GePh2: δ 5.15). The 13C{1H} NMR spectrum of 4
displays four signals of n-butyl carbons at δ 33.1, 27.5, 18.2, and
14.4. The R- and β-carbon signals (δ 18.2, 33.1) show coupling
Germaplatinacycle 6 reacted with dimethyl acetylenedi-
carboxylate (DMAD) in 1:3 ratio at 90 °C for 46 h
to afford
a
4,5,6,7-tetragerma-3-platinacycloheptene,
[Pt{C(COOMe)dC(COOMe)GeBu2GeBu2GeBu2GeBu2}-
(dmpe)] (7), in 82% yield (eq 1). The reaction involves
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are longer than those of cyclo-(GeMe2)6 (2.409(2)ꢀ2.430(2) Å),12
but shorter than that of tBu3GeGetBu3 (2.705(1), 2.714(1) Å,
the longest GeꢀGe bond).13 The PtꢀGe1ꢀGe2 and
Ge1ꢀGe2ꢀGe3 angles (119.80(5)°, 113.81(5)°) are larger
than Ge2ꢀGe3ꢀGe4 and Ge3ꢀGe4ꢀC2 angles (103.90(5)°,
105.6(3)°) to cause more severe deviation of Ge3 and
Ge4 from the coordination plane than Ge1 and Ge2. The
31P{1H} NMR spectrum of 7 displays two signals at δ 31.9
and 16.6 coupled with the 195Pt nuclei (JPtꢀP = 1696 and
2003 Hz, respectively). The former signal shows a similar
coupling constant to that of 6 (JPtꢀP = 1726 Hz) and is
assigned to the phosphorus trans to the coordinating Ge
atom based on the larger trans influence of Ge than C. Two
13C NMR signals of the vinyl carbons appear as a doublet of
doublets at δ 181.0 (JPꢀC = 106 and 12 Hz) and 138.0 (JPꢀC = 9
and 3 Hz) and are flanked with 195Pt satellite signals (JPtꢀC
=
Figure 2. 31P{1H} NMR spectra during conversion of 4 into 6 in the
presence of 2-fold H2GeBu2 at 90 °C in toluene-d8 (a) after 14 h and (b)
769 and 28 Hz, respectively). The aliphatic region of
the 13C{1H} NMR spectrum contains 32 signals due to
the carbons of eight n-butyl groups. This suggests a fixed
conformation of the seven-membered chelate ring even in
the solution.
after 42 h. Two doublets at δ 34.1 (JPtꢀP = 1810 Hz) and 34.7 (JPtꢀP
=
1674 Hz) labeled with an asterisk may be assigned as platinum
intermediates with two different Ge ligands.
Thus, the tetragermaplatinacyclopentane 6 undergoes in-
sertion of DMAD into a PtꢀGe bond, forming the seven-
membered metallacycle. This is in contrast to the GePh2
analogue 3, which does not react with DMAD even under
heating at 80 °C. Mochida proposed the formation of a
tetragermapalladacyclopentane, insertion of an alkyne into
a PdꢀGe bond, and reductive elimination of a six-membered-
ring compound in the discussion of the mechanism of a Pd-
catalyzed reaction.5 Related CꢀSi bond forming reactions of
the mononuclear silyl(alkyl)platinum complexes were re-
ported to be enhanced by coordination of π-acidic com-
pounds or phosphine ligands.14 Reactions of the seven-
membered platinacycle 7 with a 3-fold molar amount of
DMAD, DMPE, H2GeBu2, and H2GePh2 at room tempera-
ture and even at 80 °C, however, did not afford any products
via the reductive elimination.
Figure 3. Thermal ellipsoids (50% probability) of 7. All β-, γ-, and δ-
carbons of n-Bu groups and carbon-bound hydrogen atoms are omitted
for simplicity. Selected bond distances [Å] and angles [deg]: PtꢀGe1
2.497(1), PtꢀP1 2.321(3), PtꢀP2 2.310(4), PtꢀC1 2.05(1),
Ge1ꢀGe2 2.481(2), Ge2ꢀGe3 2.455(2), Ge3ꢀGe4 2.435(2),
Ge4ꢀC2 2.01(1), C1ꢀC2 1.36(2), Ge1ꢀPtꢀP2 96.35(8),
Ge1ꢀPtꢀC1 88.1(3), P1ꢀPtꢀP2 84.6(1), P1ꢀPtꢀC1 91.2(3),
PtꢀGe1ꢀGe2, 119.80(5), Ge1ꢀGe2ꢀGe3 113.81(5), Ge2ꢀGe3ꢀ
Ge4 103.90(5), Ge3ꢀGe4ꢀC2 105.6(3), PtꢀC1ꢀC2 131.1(9),
Ge4ꢀC2ꢀC1 124.3(9).
Recently, preparation of discrete linear and branched
oligogermanes was accomplished by stepwise GeꢀGe cou-
pling reactions of R3GeꢀH with R03GeꢀCH2CN in the
absence of transition metal complexes.15 We reported that
oligogermaplatinacycles 2 and 3 underwent the exchange
of tri- and tetragermanediyl groups with H3GePh, providing
the oligogermane dihydrides H(GePh2)nH (n = 3, 4) and
unidentified germaniumꢀplatinum complexes.10 The ex-
change reactions of H2GePh2 and H2SiPh2 with 6 were
conducted with expectation of elimination of the oligoger-
mane ligand. Addition of H2GePh2 to the solution of 6 in 2:1
ratio at room temperature produced a mixture of bis-
(germyl)platinum complex 1 and tetragermane H(GeBu2)4H
in 80% and 90% yields, respectively (eq 2). The ana-
logous exchange reaction using H2SiPh2 also afforded bis-
(silyl)platinum complex [Pt(SiHPh2)2(dmpe)] (8)16 and
H(GeBu2)4H as a mixture (97% and 67%, respectively).
The isolated H(GeBu2)4H was characterized on the basis of
insertion of DMAD into a PtꢀGe bond.
Figure 3 shows the molecular structure of 7, which has a
seven-membered ring with a boat conformation. Three n-butyl
chains are disordered and the corresponding carbons are
refined isotropically. The PtꢀGe bond of 7 (2.497(1) Å)
is slightly longer than those of bis(germyl)platinum com-
plex 4 (2.4454(5), 2.4380(5) Å) and germaplatinacycles 2
(2.451(1), 2.4542(9) Å) and 3 (2.4643(4), 2.4769(4) Å).10
Three GeꢀGe bonds of 7 (2.481(2), 2.455(2), 2.435(2) Å)
1
1
the H and 13C{1H} NMR spectroscopic data. In the H
NMR spectra, the GeꢀH hydrogen signal displays a quintet at
δ 4.10, which is shifted downfield from the position of
H2GeBu2 (δ 3.86). These reactions proceed smoothly with-
out byproduct at room temperature. The equimolar reaction
of H2SiPh2 with 6 gives a mixture of the product 8 and
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Scheme 3
recorded on Varian Mercury 300 MHz and Bruker BioSpin Avance III
1
400 MHz NMR spectrometers. Chemical shifts in H and 13C{1H}
NMR spectra were referenced to the residual peaks of the solvents used.
The peak position of the 31P{1H} NMR spectrum was referenced to
external 85% H3PO4 (δ 0) in C6D6. IR absorption spectra were recorded
on a Shimadzu FT/IR-8100 spectrometer. Elemental analysis was
performed using a LECO CHNS-932 or Yanaco MT-5 CHN auto-
recorder at the Center for Advanced Materials Analysis, Technical
Department, Tokyo Institute of Technology. Mass spectroscopic data
were obtained on a Bruker Daltonics micrOTOF II (APCI) spectrom-
eter. H2GeBu2 and H2GePh2 were synthesized from reduction of
Cl2GeBu2 (Wako Pure Chemical Industries) and Cl2GePh2 (Sigma-
Aldrich) by LiAlH4. [Pt(dmpe)2] was prepared according to the
literature procedure.17 Dimethyl acetylenedicarboxylate (Tokyo Chemi-
cal Industry) was distilled by trap-to-trap under vacuum prior to use.
H2SiPh2 (Wako Pure Chemical Industries) was used without further
purification.
unreacted 6 in equimolar ratio, and no other compounds were
obtained in the reaction mixture.
Preparation of [Pt(GeHBu2)2(dmpe)] (4). In the glovebox, to a
hexane solution (3 mL) of [Pt(dmpe)2] (201 mg, 0.41 mmol) was added
2-fold H2GeBu2 (153 mg, 0.81 mmol). The reaction mixture was stirred at
room temperature for 18 h, and the solid in the mixture was removed by
filtration. The solution was stored in a freezer overnight to produce 4 as
colorless crystals suitable for X-ray crystallography (209 mg, 71%). Anal.
Calcd for C22H54Ge2P2Pt: C, 36.65; H, 7.55. Found: C, 36.83; H, 7.35.
1H NMR (400 MHz, C6D6, rt): δ 4.16 (m, 2H, GeH, 3JHꢀH = 3.6 Hz,
2JPtꢀH = 69 Hz), 1.80 (m, 8H, GeCH2CH2), 1.59 (m, 12H, GeCH2,
These results were compared with a similar exchange using the
bis(germyl)platinum complex 4. The reaction of H2GePh2 with
4 in 3:1 ratio at room temperature for 46 h caused quantitative
exchange of GeBu2H with GePh2H groups to form complex 1,
together with elimination of H2GeBu2, which were confirmed by
1H and 31P{1H} NMR spectroscopy (Scheme 3). In contrast,
treatment of a 3-fold molar amount of H2SiPh2 with 4 at room
temperature for 46 h gave a mixture of bis(silyl)platinum
complex 8 (44%) and a silyl(germyl)platinum intermediate,
[Pt(SiHPh2)(GeHBu2)(dmpe)] (9, 51%), as well as a small
amount of unreacted compound 4 (5%). The 31P NMR signals of
9 in the reaction mixture are observed as two doublets at δ 35.3
(JPtꢀP = 1766 Hz) and 39.2 (JPtꢀP = 1440 Hz) with equal JPꢀP
constant values (10 Hz). The JPtꢀP values are compar-
able to those of bis(germyl)platinum 4 (JPtꢀP = 1762 Hz)
and of bis(silyl)platinum complex 8 (JPtꢀP = 1457 Hz).16
These results suggest that exchange of PtꢀGeBu2H with
PtꢀSiPh2H occurs more slowly than the reaction in eq 2,
probably because the GeꢀH bond activation of H2GePh2 is
kinetically dominant over the SiꢀH bond activation of
H2SiPh2.
In summary, we prepared a new tetragermaplatinacyclopen-
tane composed of GeBu2 groups. The insertion of DMAD into a
PtꢀGe bond takes place similarly to the mechanism proposed for
the Pd-catalyzed cycloaddition of tetrasilanes4 or -germanes5 to
alkynes. The seven-membered germaplatinacycle is successfully
isolated and fully characterized. Smooth and facile exchange
reactions of the five-membered germaplatinacycle 6 occur due to
strained energy of the metallacycle or formation of H(GeBu2)4H
having stable GeꢀH bonds.
GeCH2CH2CH2), 1.36 (m, 4H, GeCH2), 1.17 (d, 12H, PCH3, 2JPꢀH
8.0 Hz, 3JPtꢀH = 24 Hz), 1.03 (t, 12H, GeCH2CH2CH2CH3, 3JHꢀH
=
=
8.0 Hz), 0.83 (m, 4H, PCH2, J = 16.0 Hz). 13C{1H} NMR (101 MHz,
C6D6, rt): δ 33.1 (GeCH2CH2, 3JPtꢀC = 23 Hz), 30.0 (m, PCH2), 27.5
3
(GeCH2CH2CH2), 18.2 (vt, GeCH2, |3JPꢀC þ JPꢀC| = 4.7 Hz, 2JPtꢀC
=
55 Hz), 14.4 (GeCH2CH2CH2CH3), 13.2 (m, PCH3). 31P{1H} NMR
(162 MHz, C6D6, rt): δ 36.7 (JPtꢀP = 1762 Hz). IR (KBr): 1865 (br,
νGeꢀH) cmꢀ1
.
Preparation of [Pt(GeBu2GeBu2GeBu2GeBu2)(dmpe)] (6).
To a toluene solution (1 mL) of 4 (106 mg, 0.15 mmol) was added
excess H2GeBu2 (140 mg, 0.74 mmol). The reaction mixture was
stirred at 90 °C for 230 h, and the solution was removed under reduced
pressure to get a yellow, oily residue. The crude product was purified by
silica gel chromatography with ether/hexane (1:5) as eluent (Rf = 0.45)
1
to obtain 6 as a white solid (60 mg, 37%). The H NMR spectrum
of the crude product displayed two quintets at δ 4.09 and 4.13
assigned to oligogermanes H(GeBu2)nH (n = 2, 3). All signals of 6
in the 1H and 13C{1H} NMR spectra were characterized by 2D
NMR experiments. Anal. Calcd for C38H88Ge4P2Pt: C, 41.77; H, 8.12.
Found: C, 41.92; H, 7.84. 1H NMR (400 MHz, C6D6, rt): δ 1.80 (m,
8H, GeCH2CH2), 1.74 (m, 8H, GeCH2CH2), 1.65ꢀ1.39 (m, 32H,
GeCH2, GeCH2CH2CH2), 1.23 (d, 12H, PCH3), 1.09 (t, 12H,
3
GeCH2CH2CH2CH3, JHꢀH = 7.4 Hz), 1.05 (t, 12H, GeCH2CH2-
3
2
CH2CH3, JHꢀH = 7.4 Hz), 0.76 (m, 4H, PCH2, JPꢀH = 18 Hz).
13C{1H} NMR (101 MHz, C6D6, rt): δ 32.8 (GeCH2CH2, JPtꢀC
27 Hz), 31.8 (GeCH2CH2), 31.2 (m, PCH2), 27.8 (GeCH2CH2CH2),
27.4 (GeCH2CH2CH2), 19.6 (vt, GeCH2, |3JPꢀC 3JPꢀC| =
6 Hz, JPtꢀC = 38 Hz), 15.3 (d, PCH3, JPꢀC = 24 Hz, JPtꢀC = 37
Hz), 14.5 (GeCH2, 3JPtꢀC = 16 Hz), 14.1 (GeCH2CH2CH2CH3), 13.9
(GeCH2CH2CH2CH3). 31P{1H} NMR (162 MHz, C6D6, rt): δ 33.6
(JPtꢀP = 1726 Hz). HRMS (APCI): calcd for C38H89Ge4P2Pt [M þ
H]þ 1098.2934, found m/z 1098.3054.
=
3
þ
2
2
3
’ EXPERIMENTAL SECTION
Direct Preparation of 6 from [Pt(dmpe)2]. A mixture of
[Pt(dmpe)2] (307 mg, 0.62 mmol) and H2GeBu2 (593 mg, 3.14 mmol)
in 1:5 ratio in toluene (3 mL) was heated at 90 °C for 45 h. The
purification was conducted similarly to give 6 (456 mg, 67%).
NMR Experiments during the Reaction Converting 4 and
H2GeBu2 into 6. Atoluene-d8 solution(0.5mL) of4(20 mg, 0.028 mmol)
General Procedures. All manipulations of the complexes were
carried out using standard Schlenk techniques under an argon or
nitrogen atmosphere or in a nitrogen-filled glovebox (Miwa MFG).
Hexane and toluene were purified by using a solvent purification system
1
(Glass Contour). The H, 13C{1H}, and 31P{1H} NMR spectra were
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and H2GeBu2 (11 mg, 0.058 mmol) was heated at 90 °C in an NMR sample
tube. The 31P{1H} NMR spectrum of the reaction solution displayed a
mixture of 4 (δ 36.9, JPtꢀP = 1762 Hz), 5 (δ 36.3, JPtꢀP = 1652 Hz), and 6
Table 2. Crystallographic Data and Details of Refinement of
4 and 7
4
7
(δ33.7, JPtꢀP = 1726 Hz), together with two small doublets at δ34.1 (JPtꢀP
=
1810 Hz) and 34.7 (JPtꢀP = 1674 Hz) with the same JPꢀP values (8.1 Hz).
The ratio of 4:5:6 (20:45:35) after 14 h changed to 5:37:58 after 42 h based
on the intensity of 31P NMR signals.
formula
C22H54Ge2P2Pt
720.89
C44H94Ge4O4P2Pt
1234.62
fw
cryst size/mm
cryst syst
cryst color
space group
a/Å
0.20 ꢁ 0.25 ꢁ 0.30
monoclinic
colorless
0.16 ꢁ 0.22 ꢁ 0.24
tetragonal
Preparation of [Pt{C(COOMe)dC(COOMe)GeBu2GeBu2-
colorless
GeBu2GeBu2}(dmpe)] (7). To a toluene solution (4 mL) of 6
(213 mg, 0.19 mmol) was added DMAD (83.5 mg, 0.59 mmol). The
reaction mixture was heated at 90 °C for 46 h. The solvent was
pumped off to get a crude product. Separation by column chroma-
tography with ether/hexane (2:1) as eluent (Rf = 0.29) gave complex
7 as a white solid (193 mg, 82%). Recrystallization from hexane
at ꢀ20 °C afforded crystals of 7 suitable for X-ray crystallography.
All signals of 7 in the 1H and 13C{1H} NMR spectra were assigned by
2D NMR experiments. Anal. Calcd for C44H94Ge4O4P2Pt: C, 42.80;
H, 7.67. Found: C, 42.90; H, 7.67. 1H NMR (400 MHz, C6D6, rt): δ
3.61 (s, 3H, COOCH3), 3.57 (s, 3H, COOCH3), 1.8ꢀ1.4 (48H,
GeCH2, GeCH2CH2, GeCH2CH2CH2), 1.4ꢀ0.9 (40H, PCH3,
PCH2, GeCH2CH2CH2CH3). 13C{1H} NMR (101 MHz, C6D6, rt):
P21/c (No. 14)
9.025(1)
I41/a (No. 88)
20.392(2)
b/Å
17.619(3)
c/Å
19.008(3)
54.171(6)
R/deg
β/deg
93.872(2)
γ/deg
V/Å3
3015.5(8)
4
22526(4)
16
Z
Dcalcd/g cmꢀ3
1.588
1432
1.456
F(000)
10016
4.6652
104 074
12 886
0.0996
9495
2
δ 181.0 (dd, PtC=, JPꢀC = 12, 106 Hz, JPtꢀC = 769 Hz), 177.0 (m,
μ/mmꢀ1
no. of reflns meads
no. of unique reflns
Rint
6.7012
24 236
6741
PtCdCCdO, 3JPtꢀC = 17 Hz), 171.0 (dd, PtCCdO, 3JPꢀC = 2.8, 14 Hz,
3
2
2JPtꢀC = 111 Hz), 138.0 (dd, PtCdC, JPꢀC = 3.0, 9.1 Hz, JPtꢀC
=
28 Hz), 50.7, 50.5 (COOCH3), 32.7 (GeCH2CH2, 3JPtꢀC = 25 Hz), 31.9
(GeCH2CH2, 3JPtꢀC = 14 Hz), 31.4, 31.3, 31.0, 30.9 (GeCH2CH2), 30.2
0.032
5739
2
no. of obsd reflns
(I > 2σ(I))
no. of variables
R, Rw (I > 2σ(I))
R, Rw (all data)
GOF on F2
(dd, PCH2, JPtꢀC = 19, 34 Hz), 29.5, 29.3 (GeCH2CH2), 28.6 (dd,
2
PCH2, JPꢀC = 13, 30 Hz), 28.3, 28.2, 27.9, 27.8, 27.8, 27.7, 27.6, 27.1
(GeCH2CH2CH2), 19.7 (vt, GeCH2, |3JPꢀC þ JPꢀC| = 8.7 Hz, 2JPtꢀC
=
3
260
497
21 Hz), 19.5 (d, GeCH2, 3JPꢀC = 4.4 Hz, 2JPtꢀC = 40 Hz), 16.9 (GeCH2,
JPtꢀC = 24 Hz), 16.2 (2C), 15.8, 15.5, 14.8 (GeCH2), 14.5, 14.5, 14.3, 14.3,
0.0293, 0.0755
0.0339, 0.0783
0.999
0.0829, 0.2229
0.1039, 0.2468
1.046
14.2, 14.1 (2C), 14.1 (GeCH2CH2CH2CH3). 12.7 (d, PCH3, JPꢀC
26 Hz, 2JPtꢀC = 30 Hz), 10.6 (dd, PCH3, JPꢀC = 3.0, 26 Hz, 2JPtꢀC
34 Hz). 31P{1H} NMR (162 MHz, C6D6, rt): δ 31.9 (Ptrans to Ge, JPtꢀP
=
=
=
equimolar H2SiPh2 (12 mg, 0.065 mmol). The 1H and 31P{1H} NMR
spectra of the reaction mixture after 22 h at room temperature displayed
a mixture of 6 and 8 in 1:1 ratio.
1696 Hz), 16.6 (Ptrans to C, JPtꢀP = 2003 Hz). IR (KBr): 1688 (νCdO), 1198
(νCꢀO) cmꢀ1
.
Reaction of H2GePh2 with 6. To a toluene solution (2 mL) of 6
(102 mg, 0.093 mmol) was added 2-fold H2GePh2 (43 mg, 0.19 mmol),
and then the resulting mixture was stirred at room temperature for 23 h.
The solvent and volatile materials were evaporated under reduced
pressure. The oily residue was separated with hexane (3 mL), washed
with hexane (3 mL) three times, and dried in vacuo to give bis-
(germyl)platinum complex 1 (60 mg, 80%). The crude product in
hexane solution was purified by column chromatography with hexane
eluent (Rf = 0.95) to yield H(GeBu2)4H as a colorless oil (63 mg, 90%).
Data for H(GeBu2)4H: Anal. Calcd for C32H74Ge4: C, 51.28; H, 9.95.
Found: C, 50.47; H, 10.19. 1H NMR (400 MHz, C6D6, rt): δ 4.10 (quin,
2H, GeH, JHꢀH = 3.4 Hz), 1.37ꢀ1.68 (m, 16H, GeCH2CH2),
1.39ꢀ1.50 (m, 16H, GeCH2CH2CH2), 1.29ꢀ1.33 (m, 16H, GeCH2),
Reaction of 4 with H2GePh2. To a C6D6 solution (0.5 mL) of 4
(20 mg, 0.028 mmol) and dibenzyl as an internal standard (8.3 mg, 0.046
mmol) in an NMR sample tube was added 3-fold H2GePh2 (20 mg,
0.087 mmol). The 1H and 31P{1H} NMR spectra of the reaction mixture
after 46 h at room temperature exhibited complete conversion to afford
complex 1 and H2GeBu2.
Reaction of 4 with H2SiPh2. To a C6D6 solution (0.5 mL) of 4
(22 mg, 0.031 mmol) and dibenzyl as an internal standard (8.5 mg,
0.047 mmol) in an NMR sample tube was added 3-fold H2SiPh2
(17 mg, 0.092 mmol) at room temperature. The 31P{1H} NMR
spectrum of the reaction mixture after 46 h exhibited two doublets at
δ 35.3 (JPtꢀP = 1766 Hz) and 39.2 (JPtꢀP = 1440 Hz) with the same JPꢀP
values (10 Hz), which were assigned to the Pt intermediate
[Pt(GeHBu2)(SiHPh2)(dmpe)] (9). Resonances were also observed
for the bis(silyl)platinum complex 8 (δ 37.0, JPtꢀP = 1457 Hz) and the
starting material 4 (δ 36.7, JPtꢀP = 1762 Hz). The ratio of 4:8:9 was
estimated as 5:44:51 on the basis of the intensity of 31P NMR signals. In
the 1H NMR spectrum, the GeꢀH hydrogen signal of free Bu2GeH2 was
observed also at δ 3.86.
3
0.98 (t, 12H, GeCH2CH2CH2CH3, JHꢀH = 7.2 Hz), 0.96 (t, 12H,
3
GeCH2CH2CH2CH3, JHꢀH = 7.2 Hz). 13C{1H} NMR (101 MHz,
C6D6, rt): δ 31.0, 30.9 (GeCH2CH2), 27.2, 26.7, (GeCH2CH2CH2),
15.2 (GeCH2), 14.4, 14.0 (GeCH2CH2CH2CH3), 13.6 (GeCH2). IR
(neat): 1983 (νGeꢀH) cmꢀ1. HRMS (APCI): calcd for C32H73Ge4
[M ꢀ H]þ 753.2559, found m/z 753.2542.
Reaction of H2SiPh2 with 6. The procedure was similar to the
reaction with H2GePh2. To a toluene solution (4 mL) of 6 (103 mg,
0.094 mmol) was added 2-fold H2SiPh2 (35 mg, 0.19 mmol), and then
the reaction mixture was stirred at room temperature for 37 h. After
purification of the crude product, [Pt(SiHPh2)2(dmpe)]16 (8) (65 mg,
97%) and H(GeBu2)4H (47 mg, 67%) were isolated.
X-ray Crystallography. Crystals of 4 and 7 suitable for an X-ray
diffraction study were mounted on MicroMounts (MiTeGen). The
crystallographic data of 4 and 7 were collected on a Rigaku Saturn CCD
area detector equipped with monochromated Mo KR radiation (λ =
0.71073 Å) at 150 K. 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
Equimolar Reaction of H2SiPh2 with 6. To a C6D6 solution
(0.6 mL) of 6 (70 mg, 0.064 mmol) in an NMR sample tube was added
3390
dx.doi.org/10.1021/om200275w |Organometallics 2011, 30, 3386–3391

Organometallics
ARTICLE
on F2 by the full-matrix least-squares method using SHELXL-97.18
Hydrogen atoms, except for the GeꢀH hydrogens of 4, were placed at
calculated positions and refined with a riding mode on their corres-
ponding carbon atoms. Disordered carbon atoms of the n-Bu group on
Ge3 and at the terminal position on Ge1 and Ge4 were calculated
isotropically. Crystallographic data and details of refinement of 4 and 7
are summarized in Table 2.
(15) (a) Subashi, E.; Rheingold, A. L.; Weinert, C. S. Organometallics
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Gardinier, J. R.; Weinert, C. S. Organometallics 2008, 27, 3753–3760.
(d) Weinert, C. S. Dalton Trans. 2009, 1691–1699.
(16) Tanabe, M.; Osakada, K. Chem. Eur. J. 2004, 10, 416–424.
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’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic data for 4 and
b
7 as a CIF file. Spectroscopic data of H(GeBu2)4H. These materials
are available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: kosakada@res.titech.ac.jp.
’ ACKNOWLEDGMENT
This work was financially supported by Grants-in-Aid for
Scientific Research for Young Chemists (No. 21750057), for
Scientific Research (No. 1925008), and for Scientific Research
on Priority Areas (No. 19027018), from the Ministry of Education,
Culture, Sport, Science, and Technology Japan.
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