Synthesis, structure, and reactivity of tungsten acetylide-germylene complexes

Article abstract of DOI:10.1021/om4000264

The novel acetylide-germylene complexes Cp*(CO) ₂W(GePh₂)(CCR) (7a, R = SiMe₃; 7b, R = CMe ₃) were synthesized by the reactions of Cp*(CO) ₂W(NCMe)Me with Ph₂HGeCi - CR (R = SiMe₃, CMe₃). X-ray crystal analysis of 7a revealed significantly increased germylene-tungsten and decreased germylene-acetylide interactions in comparison to the corresponding interactions in the previously reported acetylide-silylene complex Cp*(CO)₂W(SiPh₂)(CCSiMe₃) (1). Complexes 7a,b reacted with acetone to give the six-membered cyclic vinylidene complexes Cp*(CO)₂W=C=C(R)CMe₂OGePh₂ (8a, R = SiMe₃; 8b, R = CMe₃) by acetone insertion reaction, similar to the case of 1 affording Cp*(CO)₂W=C=C(SiMe ₃)CMe₂OSiPh₂ (2). In the presence of 4-(dimethylamino)pyridine (DMAP), complexes 8a,b gave trans- and cis-DMAP-stabilized germylene acetylide complexes Cp*(CO) ₂W(GePh₂·DMAP)(CCR) (trans- and cis-9a, R = SiMe₃; trans- and cis-9b, R = CMe₃) and acetone, showing a reactivity different from that of the silicon analogue 2. Complexes cis-9a,b were isolated as crystals from the reaction of 7a,b with DMAP and formed mixtures with trans-9a,b in solutions, respectively. A mixture of cis- and trans-9a reacted with acetone to form an equilibrium mixture with 8a and DMAP. The reactivity of 7a,b toward Me₃COH was also investigated to reveal the formation of the vinylidene complexes Cp*(CO)₂W{GePh ₂(OCMe₃)}=C=CHR (10a, R = SiMe₃; 10b, R = CMe₃); 10a is equilibrated with 7a and Me₃COH, whereas 10b is further converted to the carbyne complex Cp*(CO)₂Wi - CCH(CMe₃){GePh₂(OCMe₃)} (11).

Full text of DOI:10.1021/om4000264

Article
pubs.acs.org/Organometallics
Synthesis, Structure, and Reactivity of Tungsten Acetylide−
Germylene Complexes
,†
†
†
‡
Hiroyuki Sakaba,* Yasuhiro Arai, Kensei Suganuma, and Eunsang Kwon
†
‡
Department of Chemistry and Research and Analytical Center for Giant Molecules, Graduate School of Science,
Tohoku University, Aoba-ku, Sendai 980-8578, Japan
*
S Supporting Information
ABSTRACT: The novel acetylide−germylene complexes Cp*-
CO) W(GePh )(CCR) (7a, R = SiMe ; 7b, R = CMe ) were
(
2
2
3
3
synthesized by the reactions of Cp*(CO) W(NCMe)Me with
2
Ph HGeCCR (R = SiMe , CMe ). X-ray crystal analysis of 7a
2
3
3
revealed significantly increased germylene−tungsten and de-
creased germylene−acetylide interactions in comparison to the
corresponding interactions in the previously reported acetylide−
silylene complex Cp*(CO) W(SiPh )(CCSiMe ) (1). Complexes
2
2
3
7a,b reacted with acetone to give the six-membered cyclic vinylidene
complexes Cp*(CO) WCC(R)CMe OGePh (8a, R =
2
2
2
SiMe ; 8b, R = CMe ) by acetone insertion reaction, similar to
3
3
the case of 1 affording Cp*(CO) WCC(SiMe )CMe OSiPh
2
3
2
2
(
2). In the presence of 4-(dimethylamino)pyridine (DMAP),
complexes 8a,b gave trans- and cis-DMAP-stabilized germylene acetylide complexes Cp*(CO) W(GePh ·DMAP)(CCR) (trans-
2
2
and cis-9a, R = SiMe ; trans- and cis-9b, R = CMe ) and acetone, showing a reactivity different from that of the silicon analogue
3
3
2
. Complexes cis-9a,b were isolated as crystals from the reaction of 7a,b with DMAP and formed mixtures with trans-9a,b in
solutions, respectively. A mixture of cis- and trans-9a reacted with acetone to form an equilibrium mixture with 8a and DMAP.
The reactivity of 7a,b toward Me COH was also investigated to reveal the formation of the vinylidene complexes
3
Cp*(CO) W{GePh (OCMe )}CCHR (10a, R = SiMe ; 10b, R = CMe ); 10a is equilibrated with 7a and Me COH,
2
2
3
3
3
3
whereas 10b is further converted to the carbyne complex Cp*(CO) WCCH(CMe ){GePh (OCMe )} (11).
2
3
2
3
INTRODUCTION
DMAP-coordinated silylene acetylide complexes trans- and cis-
Cp*(CO) W(SiPh ·DMAP)(CCSiMe ) (trans- and cis-4) and
■
2
2
3
Among the heavy group 14 element analogues of transition-
the silylvinylidene/silenylcarbyne complex Cp*(CO) WCC-
2
metal carbene complexes L MER (E = Si, Ge, Sn, Pb),
n
2
5
1
(SiPh ·DMAP)(SiMe ) (5). In this paper, to compare the
2 3
silylene complexes L MSiR have been extensively studied,
n
2
structure and reactivity of germanium analogues with those of 1,
we have synthesized the acetylide−germylene complexes
Cp*(CO) W(GePh )(CCR) (7a, R = SiMe ; 7b, R = CMe )
and it has been revealed that they play important roles in various
stoichiometric and catalytic transformations of organosilicon
compounds. In contrast, studies of the germanium analogues, the
2
2
3
3
2
and studied their reactions with acetone, DMAP, and alcohol.
germylene complexes L MGeR , are still relatively limited,
n
2
especially their reactivity toward organic substrates. We recently
RESULTS AND DISCUSSION
synthesized the novel acetylide−silylene complexes Cp*-
■
3
(
CO) W(SiPh )(CCR), whose unique bonding nature, dual
2
2
Synthesis and Structure of Acetylide−Germylene
Complexes 7a,b. Reactions of the labile acetonitrile complex
charge transfer interactions between the silylene and acetylide
ligands, has been revealed by a theoretical study. Their
interesting reactivity has also been demonstrated; for instance,
the reaction of Cp*(CO) W(SiPh )(CCSiMe ) (1) with
4
Cp*(CO) W(NCMe)Me (6) with the alkynylgermanes
2
Ph HGeCCR (R = SiMe , CMe ) in toluene took place at
2
3
3
2
2
3
room temperature with generation of methane to afford the
expected complexes Cp*(CO) W(GePh )(CCR) (7a, R =
acetone resulted in acetone insertion reaction to give the cyclic
2
2
SiMe ; 7b, R = CMe ) as air-sensitive yellow solids in 58% and
vinylidene complex Cp*(CO) WCC(SiMe )CMe OSiPh
3
3
2
3
2
2
6
5% yields, respectively (eq 1). Their formation is explained by
(
2), which reacted with 4-(dimethylamino)pyridine (DMAP) to
the following steps: (i) oxidative addition of the Ge−H bond of
give the alkenylcarbyne complex Cp*(CO) WCC(CMe )-
2
2
the germane to the 16e complex Cp*(CO) WMe generated
(
SiMe ) (3) and cyclic diphenylsiloxanes (n = 3, 4) via DMAP-
2
3
3b
induced diphenylsilanone elimination (Scheme 1).
On the other hand, the direct treatment of 1 with DMAP
led to the formation of a novel equilibrium mixture of
Received: January 13, 2013
Published: August 29, 2013
©
2013 American Chemical Society
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Scheme 1. Reactions of Acetylide−Silylene Complex 1 with Acetone and DMAP
from the acetonitrile complex, (ii) reductive elimination of
methane in the resulting intermediate Cp*(CO) W(Me)(H)-
2
(
GePh CCR) to form the coordinatively unsaturated species
2
Cp*(CO) W(GePh CCR), and (iii) Ge−C bond activation
2
2
(
alkynyl migration) followed by coordination of the C−C triple
bond to the germylene center to give 7a,b.
X-ray-quality crystals of 7a were obtained by recrystallization
from pentane, and the X-ray molecular structure is shown in
Figure 1. Although the W−Ge bond (2.5446(7) Å) of 7a is
slightly longer than the WGe bond (2.5279(6) Å) of the
typical donor-stabilized germyl germylene complex Cp*-
2m
Figure 1. ORTEP drawing of 7a. Thermal ellipsoids are drawn at the
(
CO) W(GeMe ·pyridine)(GeMe ), it is within the range
2
2
3
5
0% probability level, and all hydrogen atoms are omitted for clarity.
(
2.429−2.593 Å) for WGe type bonds of known germylene
2s
Selected bond lengths (Å) and angles (deg): W1−Ge1, 2.5446(7);
W1−C1, 2.099(3); Ge1−C1, 2.085(3); Ge1−C2, 2.442(3); Si1−C2,
tungsten complexes. Thus, the W−Ge bond of 7a has a
considerable double-bond character in contrast to the single-
1
5
.847(3); C1−C2, 1.241(3); Ge1−W1−C1, 52.30(6); W1−Ge1−C1,
2.80(6); W1−C1−C2, 165.63(19); C1−Ge1−C2, 30.55(8); C1−
3
b,6
bond-like character of the W−Si bond (2.5474(16) Å) in 1.
The sum of three bond angles (W−Ge−C6, W−Ge−C12, and
C6−Ge−C12) about the Ge atom is 359.3°, indicating a nearly
C2−Si1, 161.4(2); W1−Ge1−C6, 125.67(7); W1−Ge1−C12,
124.17(7); C6−Ge1−C12, 109.47(10).
2
sp -type hybridization. The increased germylene−metal inter-
action is caused by the decrease in the germylene−acetylide
interaction, as shown by the following comparison of the bond
angles and lengths between 7a and 1: Ge−W−C1 (52.30(6)°)
and W−C1−C2 (165.63(19)°) angles in 7a larger than the
the silylene. Elevation of the empty p orbital causes a decrease in
π electron donation from the acetylide to the germylene
accompanied by an increase in back-donation from the metal,
and that of the lone-pair orbital also increases the germylene−
metal interaction.
Reactions of Acetylide−Germylene Complexes 7a,b
with Acetone. Complexes 7a,b exhibited the same reactivity
toward acetone as the silicon analogue 1 to afford acetone
insertion products, the six-membered cyclic vinylidene com-
3b
corresponding angles of 48.12(15) and 156.2(4)° in 1 and
C1−C2 length (1.241(3) Å) in 7a shorter than that (1.278(9) Å)
in 1. In addition, the Ge−C1 (2.085(3) Å) and Ge−C2
(
2.442(3) Å) distances in 7a are significantly longer than the
3b
corresponding Si−C distances of 1.930(5) and 2.059(6) Å in 1
7
and the usual Ge−C single-bond distances (1.90−2.05 Å).
These structural differences between 7a and 1 can be qualita-
plexes Cp*(CO) WCC(R)CMe OGePh (8a, R = SiMe ;
2
2
2
3
2
tively explained by the higher energy levels of the sp lone pair
8b, R = CMe ), which were formed in quantitative yields in NMR
3
and empty p orbitals of the germylene in comparison to those of
tube reactions using a large excess of acetone (20 equiv) (eq 2).
5
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8
a,b and the silicon analogue 2 resemble each other well: W−C1 =
1
.963(3)/1.972(8) Å, C1−C2 = 1.315(5)/1.322(11) Å, and W−
C1−C2 = 174.7(3)/174.2(6)° in 8a/8b and W−C1 = 1.957(3) Å,
3b
C1−C2 = 1.309(4) Å, and W−C1−C2 = 174.9(3)° in 2. The
W−Ge bond lengths (2.6760(7) Å in 8a and 2.6636(9) Å in 8b)
are longer than a typical W−Ge single bond (2.6304(6) Å) in
2m
Cp*(CO) W(GeMe ·pyridine)(GeMe ) but are not longer
2
2
3
than the W−Si bond length (2.6778(10) Å) in 2, in contrast to a
general tendency that the covalent radius (1.20 Å) of Ge is larger
8
than that (1.11 Å) of Si. On the other hand, the Ge−O bond
lengths (1.817(3) Å in 8a and 1.798(5) Å in 8b) are much longer
than a typical Ge−O single-bond length (1.76 Å) and the Si−O
From preparative-scale reactions, 8a,b were isolated as pale red-
9
13
1
violet solids in 55% and 59% yields, respectively. In their C{ H}
NMR spectra, two characteristic signals assigned to the vinylidene
C and C atoms were observed at δ 320.9 and 143.9 for 8a and δ
3b
bond length (1.666(2) Å) in 2. These features suggest that the
ring strain of the six-membered metallacycle involving the linear
vinylidene moiety is mainly relieved by elongation of the W−Si
bond in 2, whereas it is reduced by that of the Ge−O bond in
8a,b. This is ascribable to a weaker Ge−O bond in comparison to
α
β
3
32.3 and 161.6 for 8b, respectively.
The molecular structures of 8a,b determined by X-ray crystal
analysis are shown in Figure 2. The WC1C2 backbones of
−1
10a
an Si−O bond (for example, 447 kJ mol for Me Ge−OEt
3
and 484 kJ mol− for Me Si−OEt ). Reflecting the weaker Ge−
1
10b
3
O interaction in 8a,b in comparison to the Si−O interaction in 2,
the sums of three bond angles about the Ge atom (334.6° for W−
Ge−C9, W−Ge−C15, and C9−Ge−C15 in 8a and 335.0° for
W−Ge−C10, W−Ge−C16, and C10−Ge−C16 in 8b) are larger
3
b
by 6° than the corresponding value (328.8°) about the Si atom in 2.
Reactions of Six-Membered Cyclic Vinylidene Com-
plexes 8a,b with DMAP. We first examined the reaction of 8a
with DMAP in benzene-d at 50 °C to compare its reactivity to
6
that of 2, which afforded carbyne complex 3 via DMAP-induced
diphenylsilanone elimination under the same conditions
(
Scheme 1). When a mixture of 8a and DMAP (1.4 equiv) in
benzene-d was heated at 50 °C for 2 h in an evacuated sealed
6
NMR tube, 55% of 8a was converted into the DMAP-stabilized
germylene acetylide complex Cp*(CO) W(GePh ·DMAP)-
2
2
(
CCSiMe ) (9a) together with acetone (44%) via Ge−O
3
bond cleavage without detection of the carbyne complex 3,
showing a reactivity different from that of 2 (eq 3). In the
Figure 2. ORTEP drawings of 8a (top) and 8b (bottom). Thermal
ellipsoids are drawn at the 50% probability level, and all hydrogen atoms
are omitted for clarity. Selected bond lengths (Å) and angles (deg) are as
follows. For 8a: W1−Ge1, 2.6760(7); W1−C1, 1.963(3); Ge1−O1,
presence of 3 equiv of DMAP, 95% of 8a was transformed into
1
.817(3); Si1−C2, 1.895(3); C1−C2, 1.315(5); Ge1−W1−C1,
9.85(8); W1−C1−C2, 174.7(3); C1−C2−Si1, 116.7(2); W1−Ge1−
9
a. This reactivity of 8a is ascribed to the weak Ge−O interaction
5
found in its molecular structure (Figure 2). Indeed, when a
C9, 114.56(11); W1−Ge1−C15, 113.62(9); C9−Ge1−C15,
benzene-d solution of 8a was heated in the absence of DMAP at
1
06.37(11). For 8b: W1−Ge1, 2.6636(9); W1−C1, 1.972(8); Ge1−
6
5
0 °C for 2 h, small amounts of 7a (12%) and acetone (10%)
O1, 1.798(5); C1−C2, 1.322(11); Ge1−W1−C1, 59.83(18); W1−
C1−C2, 174.2(6); C1−C2−C4, 119.4(6); W1−Ge1−C10, 113.6(2);
W1−Ge1−C16, 114.1(2); C10−Ge1−C16, 107.3(2).
were formed via Ge−O bond cleavage along with unreacted 8a.
Similarly, the reaction of 8b with DMAP (3 equiv) cleanly
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afforded the corresponding the DMAP-stabilized germylene
acetylide complex Cp*(CO) W(GePh ·DMAP)(CCCMe )
length (2.5642(10) Å) is within the range (2.429−2.593 Å) for
2s
WGe type bonds of germylene tungsten complexes and
longer by 0.02 Å than that of 7a. The sum of three bond angles
about the Ge atom (346.9° for W−Ge−C7, W−Ge−C13, and
C7−Ge−C13) is smaller by 12° than that (359.3°) in 7a,
indicating lesser germylene character of cis-9b in comparison to
7a due to a stronger interaction with the nitrogen Lewis base in
cis-9b. However, similar to an interesting observation in the
2
2
3
1
(
9b). In the room-temperature H NMR spectra of 9a,b,
coalescent signals of their trans and cis isomers were observed,
and variable-temperature NMR experiments were carried out
using their authentic samples isolated from the reactions of 7a,b
with DMAP, as shown below.
Synthesis and Structure of DMAP-Stabilized Germy-
lene Acetylide Complexes 9a,b. The authentic samples of
corresponding silicon analogue cis-Cp*(CO) W(SiPh ·DMAP)-
2 2
9
a,b were isolated as air-sensitive pale yellow solids from the
reactions of 7a,b with DMAP in 72% and 75% yields, respectively
eq 4). X-ray crystal analyses of 9a,b confirmed that both
(CCCMe
3
) that the Si−W−C(acetylide) angle (62.59(7)°) is
the smallest among the four basal interligand angles (74.40(7)−
5
(
83.50(11)° for the other three angles), the Ge−W−C1 angle
(
(
66.7(3)°) is smaller than the other three interligand angles
Ge−W−C26 = 76.9(3)°, C1−W−C27 = 81.2(4)°, and C26−
W−C27 = 75.5(4)°), despite the fact that the germylene and
acetylide ligands have bulky substituents. Also in this case, a week
interaction between the germylene and acetylide ligands may still
operate, though the interaction seems to be reduced in
comparison to that in the silicon analogue, taking into account
that the Ge−W−C1 angle (66.7(3)°) and the Ge−C1 and Ge−
C2 interatomic distances (2.614(9) and 3.313(9) Å) are larger
than the corresponding angle (62.59(7)°) and interatomic
distances (2.436(3) and 3.141(3) Å) in cis-Cp*(CO) W(SiPh ·
2
2
5
DMAP)(CCCMe ).
3
A toluene-d solution of isolated cis-9a showed temperature-
8
1
dependent H NMR spectral changes. A single set of Cp*, NMe ,
2
and SiMe signals were observed at δ 2.05, 1.93, and 0.10,
3
respectively, at 10 °C (Figure 4). Upon cooling the sample, signal
complexes have cis-DMAP-stabilized germylene acetylide struc-
tures cis-9a and cis-9b in the solid state. Although the bonding
parameters for cis-9a can not be discussed because of its poor
1
1
quality, the structural data of cis-9b can be compared with those
of the corresponding silicon analogue cis-Cp*(CO) W(SiPh ·
2
2
5
DMAP)(CCCMe ) obtained previously. cis-9b has two
3
crystallographically independent molecules in the crystal, and
the ORTEP drawing of one of them is shown in Figure 3 along
with selected average bond lengths and angles. The W−Ge bond
1
Figure 4. Variable-temperature H NMR spectra of 9a in toluene-d : (*)
8
C D H; (×) impurity.
7
7
broadening became noticeable at −50 °C, and they clearly
decoalesced into two sets of signals assigned to trans and cis
isomers in a ratio of 58:42 at −80 °C. The trans and cis isomers
1
3
were characterized on the basis of similarity of the C chemical
shifts of the acetylide C atoms of trans-9a (δ 134.3 at −90 °C)
β
and cis-9a (δ 141.7) and the related silylene complexes trans- and
cis-Cp*(CO) W(SiPh ·DMAP)(CCCMe ) (δ 136.5 for the
2
2
3
5
trans isomer and δ 146.2 for the cis isomer at −70 °C). These
1
13
signal assignments were based on H− C HMBC correlations
between SiMe and C for 9a and between CMe and C for the
3
β
3
β
silylene complex. Similar spectral changes were observed for 9b
Figure 3. ORTEP drawing of one of the two crystallographically
independent molecules of cis-9b. Thermal ellipsoids are drawn at the
(
1
Figure 5). One set of Cp*, NMe , and CMe signals (δ 2.09,
2 3
.98, and 1.09, respectively) at 20 °C decoalesced into two sets of
50% probability level, and all hydrogen atoms are omitted for clarity.
signals due to trans and cis isomers in a ratio of 27:73 at −70 °C,
which was obtained by the relative intensities of the CMe signals
Selected average bond lengths (Å) and angles (deg): W1−Ge1,
3
2
1
.5642(10); Ge1−N1, 2.062(8); W1−C1, 2.154(9); C1−C2,
.196(13); Ge1−W1−C1, 66.7(3); Ge1−W1−C26, 76.9(3); C1−
at δ 1.24 and 1.12. The isomers were characterized by the
chemical shifts of the acetylide C signals of trans-9b (δ 135.9 at
W1−C27, 81.2(4); C26−W1−C27, 75.5(4); W1−C1−C2, 179.0(9);
W1−Ge1−C7, 121.0(3); W1−Ge1−C13, 120.5(3); C7−Ge1−C13,
β
−70 °C) and cis-9b (δ 143.3) similar to the above. The increased
relative ratio of the cis isomer to the trans isomer in 9b in
105.4(4).
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Reactions of Acetylide−Germylene Complexes 7a,b
with Alcohol. Reactivity of 7a,b toward alcohol was also
examined. Treatment of 7b with MeOH (1.5 equiv) in benzene-
d6 at room temperature gave a complex mixture, whereas the
reaction using Me COH (9 equiv) led to the rapid formation of a
3
1
:3.5 equilibrium mixture of 7b and the germyl vinylidene
intermediate Cp*(CO) W{GePh (OCMe )}CCH-
2
2
3
(
CMe ) (10b), which was characterized by low-temperature
3
NMR spectroscopy as described below (eq 7). After 30 min at
1
Figure 5. Variable-temperature H NMR spectra of 9b in toluene-d :
8
(
*) C D H; (×) impurity.
7 7
comparison to 9a may suggest a more enhanced interaction
between the germylene and acetylide ligands in cis-9b than in
cis-9a, although it is unable to clarify details by their structural
comparison owing to the poor X-ray data of cis-9a.
Reaction of DMAP-Stabilized Germylene Acetylide
Complex 9a with Acetone. Interestingly, when a benzene-d6
solution of 9a and acetone (3 equiv) was periodically monitored
by H NMR spectroscopy at room temperature, the reaction
slowly proceeded to give cyclic vinylidene complex 8a and free
DMAP and reached to an equilibrium state of 9a:8a = 14:86 after
room temperature, new signals assigned to the carbyne complex
1
Cp*(CO) WCCH(CMe ){GePh (OCMe )} (11) appeared,
2
3
2
3
and conversion of 7b and 10b to 11 was observed with
retainment of the ratio of 7b and 10b. After 2 h, 87% of 7b was
converted to 10b (45%), 11 (25%), and unidentified minor
products. Complexes 7b and 10b disappeared after 1 day, and 11
was formed in 70% yield.
1
day (eq 5). In the NMR spectra, the signals of DMAP were
To characterize intermediate 10b, a large excess amount (15
equiv) of Me COH was added to a toluene-d solution of 7b to
3
8
favor the formation of 10b, and NMR spectra were measured at
1
−
40 °C to suppress the conversion to 11. In the H NMR
spectrum, 10b was observed as a major component (ca. 85%),
which showed a singlet of the methine proton at δ 5.16 in
t
addition to a Cp* signal at δ 1.80 and two Bu signals at δ 1.42
and 1.15. The 13C{ H} NMR spectrum features two signals of
1
the vinylidene C and C atoms at δ 344.6 and 136.3, which are
α
β
similar to the chemical shifts of the corresponding atoms of 8a,b.
1
13
The H− C HMBC and HMQC correlations were observed
between the methine proton signal and the C and C signals,
α
β
respectively. These spectroscopic data support the germyl
vinylidene structure of 10b. At room temperature, 10b was
converted to 11 after 1 day. Complex 11 was isolated in 60% yield
from a preparative-scale reaction and fully characterized by
1
3
1
spectroscopic data and X-ray crystal analysis. The C{ H} NMR
spectrum of 11 showed a carbyne carbon (C ) signal at δ 315.2
α
(
JWC = 215 Hz) and a C signal at δ 71.7 (J = 37 Hz). These
β WC
signals exhibited HMBC and HMQC correlations with the C H
β
proton signal at δ 3.04. The X-ray structure of 11 is depicted in
Figure 6. It adopts a three-legged piano-stool structure, and the
W−C1−C2 bond angle is 176.6(4)°. The W−C1 and C1−C2
bond lengths are 1.836(4) and 1.468(6) Å, respectively, and the
former bond length is comparable to the W−C triple-bond
lengths (1.81−1.82 Å) in the structurally related tungsten
1
2
carbyne complexes Cp(CO) WCR (R = p-Tol, SiPh ).
2
3
Thus, addition of Me COH to 7b led to its successive conversion
3
to vinylidene complex 10b and carbyne complex 11.
The reaction of 7a with Me COH (32 equiv) in benzene-d
3
6
observed as broad coalesced signals of free and coordinated
DMAP, suggesting the intermediacy of acetylide−germylene
complex 7a; it is formed by dissociation of DMAP from cis-9a
and reacts with acetone to give 8a. Supportive evidence was
obtained by the rapid reaction of 9a with BPh in benzene-d at
formed a 55:45 equilibrium mixture of 7a and the germyl
vinylidene complex Cp*(CO) W{(GePh (OCMe )}C
2
2
3
CH(SiMe ) (10a) at 25 °C. In contrast to 10b, conversion of
3
10a to the carbyne complex Cp*(CO) WCCH(SiMe )-
2
3
{GePh (OCMe )} was not observed after 3 days at room
3
6
2
3
room temperature, which cleanly afforded 7a and DMAP·BPh3
(eq 6).
temperature. Complex 10a could not be isolated and was
characterized by NMR spectroscopic data. In the C{ H} NMR
13
1
5
042
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Organometallics
Article
Figure 6. Molecular structure of 11. Thermal ellipsoids are drawn at the
50% probability level, and hydrogen atoms except for the methine
proton at C2 are omitted for clarity. Selected bond lengths (Å) and
angles (deg): W1−C1, 1.836(4); C1−C2, 1.468(6); Ge1−C2,
2
1
.007(4); Ge1−O1, 1.788(3); W1−C1−C2, 176.6(4); C1−C2−C3,
14.3(4); C1−C2−Ge1, 105.0(3); C1−W1−C23, 93.6(2); C1−W1−
vinylidene complexes 8a,b and DMAP-stabilized germylene
acetylide complexes 9a,b, respectively. Interestingly, complexes
C24, 91.1(2); C23−W1−C24, 87.5(2).
8a,b reacted with DMAP to give 9a,b and free acetone, showing
reactivity different from that of the silicon analogue 2, which led
to DMAP-induced diphenylsilanone elimination. In addition, the
reaction of 9a with acetone resulted in DMAP dissociation to
form an equilibrium mixture involving 8a and DMAP. These
reactivity differences from the silicon analogue are ascribable to
Ge−O and Ge−N bonds being weaker than Si−O and Si−N
spectrum, the vinylidene C and C signals were observed at δ
α
β
3
39.0 and 113.2, respectively, similar to those of 10b. The
methine proton signal appeared at δ 5.06, showing HMBC and
HMQC correlations with the C and C signals, respectively.
α
β
Considering steric repulsion of the substituents on the C atom
β
10
bonds, respectively. Addition of Me COH to complexes 7a,b
in the carbyne complexes 11 and Cp*(CO) WCCH(SiMe )-
3
2
3
gave germyl vinylidene complexes 10a,b, whose behaviors
{
GePh (OCMe )}, the formation of the latter complex with a
2 3
depend upon the SiMe and CMe substituents; for SiMe , 10a
SiMe group is expected to be more favorable than that of
3
3
3
3
stays as an equilibrium mixture with 7a, while for CMe , 10b is
complex 11 with a more sterically hindered CMe group. The
3
3
converted to carbyne complex 11, demonstrating the contrasting
observed behaviors of 10a,b are not consistent with this, which
may be attributable to the stabilizing effect on the vinylidene
substituent effects of SiMe and CMe groups.
3
3
3
b,13
structure by substitution of a silyl group at a C position
β
EXPERIMENTAL SECTION
relative to the carbyne complex.
■
General Procedures. All experiments were carried out under a
nitrogen atmosphere on a vacuum line using Schlenk techniques or in a
glovebox, unless otherwise stated. Reactions with low-boiling liquids
were performed by vacuum transfer of a calculated pressure of gas from a
calibrated gas bulb into a reaction flask or an NMR tube. NMR spectra
were recorded on a Bruker AV-400 or a Bruker AV-600 spectrometer,
and IR spectra were obtained on a Shimadzu FTIR-8100M spectro-
meter. High-resolution mass spectra were recorded on a Bruker
Daltonics solariX 9.4T FT-ICR mass spectrometer. Mass spectrometric
analysis and X-ray crystal analysis were performed at the Research and
Analytical Center for Giant Molecules, Tohoku University.
Reaction of Six-Membered Cyclic Vinylidene Complex
b with tert-Butyl Alcohol. Considering the reactivity of cyclic
8
vinylidene complexes 8a,b toward DMAP giving the same
products as those obtained in the reactions of acetylide−
germylene complexes 7a,b with DMAP, the reaction of 8b with
Me COH was expected to afford carbyne complex 11 (eq 8).
3
When a benzene-d solution of 8b and Me COH (2 equiv) was
6
3
heated in an evacuated sealed NMR tube at 50 °C, a complex
mixture of 7b, 8b, 10b, and 11 (ca. 1:0.7:0.6:1.1) was observed
together with unidentified minor products after 2 days, indicating
that elimination of acetone from 8b occurred to give 7b, which
was equilibrated with 10b (vide supra). In the presence of 9 equiv
Hexane, pentane, THF, toluene, benzene-d , and toluene-d were
6
8
distilled from sodium benzophenone ketyl. Acetone was distilled from
calcium hydride. (Trimethylsilyl)acetylene and EtMgBr (3.0 M solution
of Me COH under the same conditions, the reaction was
3
in Et O) were purchased from Tokyo Kasei Kogyo and Sigma-Aldrich,
2
accelerated and relatively cleanly afforded 11 (75%) together
with acetone (59%) after 1 day. Only a trace amount of
vinylidene complex 10b was detected at the early stage of the
reaction.
14
15
respectively. Complex 6 and chlorodiphenylgermane were prepared
according to the literature methods.
Synthesis of Ph HGeCCSiMe . An ethereal solution of EtMgBr
2
3
(3.0 M, 1.5 mL, 4.5 mmol) was added dropwise to a solution of
(trimethylsilyl)acetylene (0.53 g, 5.3 mmol) in THF (10 mL) with
SUMMARY
cooling in an ice−water bath. The mixture was warmed to room
■
temperature and stirred for 30 min. After the mixture was heated at
New acetylide−germylene complexes 7a,b were synthesized, and
the X-ray crystallographic analysis of 7a revealed the significantly
increased germylene−tungsten and decreased germylene−
acetylide interactions in comparison to the corresponding
interactions in acetylide−silylene complex 1. Complexes 7a,b
reacted with acetone and DMAP to give six-membered cyclic
5
0 °C for 5 h, a solution of chlorodiphenylgermane (0.93 g, 3.5 mmol) in
THF (3 mL) was added dropwise at room temperature. The reaction
mixture was stirred at room temperature overnight and then hydrolyzed
with a saturated aqueous NH Cl solution. The organic layer was
4
separated from the aqueous layer, washed with a saturated aqueous
NaCl solution, and dried over MgSO . After removal of the solvent, the
4
5
043
dx.doi.org/10.1021/om4000264 | Organometallics 2013, 32, 5038−5046

Organometallics
Article
residue was subjected to flash chromatography on Florisil (toluene) to
(100 MHz, benzene-d ): δ 1.6 (SiMe ), 10.9 (C Me ), 31.3 (CMeMe),
6
3
5
5
1
give an oil (0.81 g, 71%). H NMR (400 MHz, benzene-d ): δ 0.16 (s,
35.2 (CMeMe), 78.1 (CMe ), 106.5 (C Me ), 128.1, 128.2, 129.2, 129.4,
6
2 5 5
9
4
1
H, SiMe ), 5.66 (s, 1H, GeH), 7.03−7.17 (m, 6H, Ph), 7.58−7.66 (m,
134.6, 134.9 (Ph), 143.9 (WCC), 145.4, 146.3 (Ph), 226.0 (CO), 227.2
3
13
1
29
1
H, Ph). C{ H} NMR (100 MHz, benzene-d ): δ −0.10 (SiMe ),
(CO), 320.9 (WCC). Si{ H} NMR (79 MHz, benzene-d ): δ −8.1. IR
6
3
6
29
1
−1
06.6 (CC), 117.2 (CC), 128.8, 129.8, 134.2, 134.8 (Ph). Si{ H}
(toluene, cm ): 1944 (s, ν ), 1868 (s, ν ). HRMS (ESI): m/z calcd
for [C H GeO SiW + Na] 781.13560, found 781.13567 [M + Na] .
32 40 3
CO
CO
−1
+
+
NMR (79 MHz, benzene-d ): δ −18.3. IR (toluene, cm ): 2075 (m,
6
ν
GeH
). HRMS: m/z calcd for C H GeSi 326.05460, found 326.05387.
17 20
Synthesis of Cp*(CO) WCC(CMe )CMe OGePh (8b). On
2
3
2
2
Synthesis of Ph HGeCCCMe . An ethereal solution of EtMgBr
2
3
a vacuum line, a toluene solution (5.0 mL) of Ph HGeCCCMe
2
3
(
3.0 M, 3.3 mL, 9.9 mmol) was added dropwise to a solution of 3,3-
(
(
93 mg, 0.30 mmol) was added into a reaction flask containing 6
dimethyl-1-butyne (0.822 g, 10.0 mmol) in THF (20 mL) with cooling
in an ice-water bath. The mixture was warmed to room temperature and
stirred for 30 min. After the mixture was heated at 60 °C for 5 h, a
solution of chlorodiphenylgermane (2.37 g, 9.0 mmol) in THF (5 mL)
was added dropwise at room temperature. The reaction mixture was
stirred at room temperature overnight and then hydrolyzed with a
saturated aqueous NH Cl solution. The organic layer was separated
from the aqueous layer, washed with a saturated aqueous NaCl solution,
and dried over MgSO . After removal of the solvent, the residue was
subjected to flash chromatography on Florisil (toluene) to give a
100 mg, 0.23 mmol) at −40 °C, and the mixture was warmed to room
temperature with stirring. After 15 min at room temperature, volatiles
were removed under vacuum to leave crude 7b, to which acetone (0.66
mmol) was vacuum-transferred and the mixture was stirred for 30 min at
room temperature. After removal of the solvent, the residual solid was
extracted with pentane (2 × 2.0 mL). The extract was concentrated to
4
1
give 8b as a pale red-violet solid (101 mg, 59% based on 6). H NMR
(
400 MHz, benzene-d ): δ 1.11 (s, 3H, CMeMe), 1.25 (s, 9H, CMe ),
6
3
4
1
7
.61 (s, 3H, CMeMe), 1.71 (s, 15H, Cp*), 7.05−7.30 (m, 6H, Ph),
13 1
.75−7.85 (m, 2H, Ph), 8.15−8.25 (m, 2H, Ph). C{ H} NMR (100
1
colorless oil (2.17 g, 78%). H NMR (400 MHz, benzene-d ): δ 1.19 (s,
6
MHz, benzene-d ): δ 10.9 (C Me ), 30.6 (CMeMe), 32.7 (CMe ), 33.7
6
5
5
3
9
4
H, CMe ), 5.68 (s, 1H, GeH), 7.03-7.23 (m, 6H, Ph), 7.62-7.70 (m,
3
(
1
2
CMe ), 35.6 (CMeMe), 76.3 (CMe ), 107.1 (C Me ), 128.1, 129.2,
H, Ph). 1 C{ H} NMR (150 MHz, benzene-d ): δ 28.6 (CMe ), 31.0
3
1
3 2 5 5
6
3
2
29.4, 134.7, 134.8, 144.8, 146.8 (Ph), 161.6 (WCC, J = 18 Hz),
WC
(
CMe ), 75.3 (CC), 118.9 (CC), 128.7, 129.6, 134.7, 135.1 (Ph).
1
3
26.7 (CO), 226.9 (CO), 332.3 (WCC, J = 115 Hz). IR (toluene,
−1
WC
IR (neat, cm ): 2057 (m, ν ). HRMS: m/z calcd for C H Ge
−1
GeH
18 20
cm ): 1941 (s, ν ), 1862 (s, ν ). HRMS (ESI): m/z calcd for
CO
CO
310.07713, found 310.07697.
+
+
[
C H GeO W + Na] 765.1610, found 765.1603 [M + Na]
33 40 3
Synthesis of Cp*(CO) W(GePh )(CCSiMe ) (7a). On a vacuum
2
2
3
Synthesis of Cp*(CO) W(GePh ·DMAP)(CCSiMe ) (9a). On a
2
2
3
line, a toluene solution (3.5 mL) of Ph HGeCCSiMe (96 mg,
2
3
vacuum line, toluene (2.5 mL) was vacuum-transferred into a reaction
flask containing 7a (90 mg, 0.13 mmol) and DMAP (15 mg, 0.13 mmol)
cooled with a liquid nitrogen bath. The mixture was warmed to room
temperature with stirring. After 30 min at room temperature, the solvent
was removed under vacuum, and the residual solid was washed with
0
0
.30 mmol) was added into a reaction flask containing 6 (100 mg,
.22 mmol) at −40 °C, and the mixture was warmed to room temperature
with stirring. After 20 min at room temperature, the volatiles were
removed under vacuum. The residual solid was extracted with pentane
(
1.5 mL), and the extract was cooled at −30 °C to give 7a as an air-
1
hexane to give 9a as a pale yellow solid (77 mg, 72%). H NMR (600
1
sensitive yellow solid (94 mg, 58%). H NMR (400 MHz, benzene-d ):
6
MHz, toluene-d , 10 °C): δ 0.10 (s, 9H, SiMe ), 1.93 (s, 6H, NMe ),
6
3
2
δ −0.12 (s, 9H, SiMe ), 1.80 (s, 15H, Cp*), 7.08−7.20 (m, 6H, Ph),
3
2
.05 (s, 15H, Cp*), 5.52−5.56 (m, 2H, DMAP), 7.21−7.36 (m, 6H,
13
1
7
.65−7.75 (m, 4H, Ph). C{ H} NMR (100 MHz, benzene-d ): δ 0.2
1
6
Ph), 7.84−7.97 (br, 4H, Ph), 8.07−8.13 (m, 2H, DMAP); H NMR
(
(
(
(
(
7
SiMe ), 11.0 (C Me ), 102.1 (C Me ), 128.4, 129.4, 134.9 (Ph), 136.1
WCC, J = 85 Hz), 137.3 (Ph), 159.7 (WCC, J = 20 Hz), 231.2
CO, J = 163 Hz). Si{ H} NMR (79 MHz, benzene-d ): δ −17.3
SiMe ). IR (toluene, cm ): 1936 (s, ν ), 1856 (s, ν ). HRMS
3 5 5 5 5
(
600 MHz, toluene-d , −80 °C): δ 0.15 (s, SiMe , cis-9a), 0.25 (s, SiMe ,
1
2
6
3
3
WC
WC
trans-9a), 1.68 (s, NMe , trans-9a), 1.80 (s, NMe , cis-9a), 2.02 (s, Cp*,
1
29
1
2
2
WC
6
trans-9a), 2.08 (s, Cp*, cis-9a), 5.14 (br, DMAP, cis-9a + trans-9a),
−1
3
CO
CO
7
9
.17−7.44 (m, Ph, cis-9a + trans-9a), 7.59−7.73 (m, Ph, cis-9a + trans-
+
ESI): m/z calcd for [C H GeO SiW + H] 701.11179, found
13 1
29
34
2
a), 8.02−8.28 (m, Ph and DMAP, cis-9a + trans-9a). C{ H} NMR
+
01.11249 [M + H] .
Synthesis of Cp*(CO) W(GePh )(CCCMe ) (7b). On a vacuum
(150 MHz, toluene-d , −90 °C): δ 2.0 (SiMe , cis-9a), 2.7 (SiMe , trans-
8
3
3
2
2
3
9
9
9
1
1
a), 12.4 (C Me , trans-9a), 12.6 (C Me , cis-9a), 39.0 (NMe , trans-
5 5 5 5 2
line, a toluene solution (5.0 mL) of Ph HGeCCCMe (93 mg, 0.30
2
3
a), 39.1 (NMe , cis-9a), 101.3 (C Me , trans-9a), 101.5 (C Me , cis-
2
5
5
5
5
mmol) was added into a reaction flask containing 6 (100 mg, 0.22
mmol) at −40 °C, and the mixture was warmed to room temperature
with stirring. After 15 min at room temperature, the volatiles were
removed under vacuum. The residual solid was extracted with pentane
a), 106.4 (NC H NMe , cis-9a + trans-9a), 134.3 (WCC, trans-9a),
5
4
2
36.0, 136.5, 137.4, 141.7 (WCC, cis-9a), 144.7, 145.2, 146.7, 147.4,
48.5, 154.9, 155.2 (Ar), 239.7 (CO), 250.5 (CO). Several carbonyl,
aromatic, and acetylide carbon signals were not assigned due to their
(
2.0 mL), and the extract was cooled at −30 °C to give 7b as an air-
29
1
poor intensities or overlap with solvent signals. Si{ H} NMR (79
1
sensitive yellow solid (104 mg, 65%). H NMR (400 MHz, benzene-d ):
6
MHz, toluene-d , −90 °C): δ −28.9 (SiMe , trans-9a), −27.8 (SiMe ,
8
3
3
δ 0.92 (s, 9H, CMe ), 1.84 (s, 15H, Cp*), 7.08−7.20 (m, 6H, Ph), 7.66−
−1
3
cis-9a). IR (toluene, cm ): 1942 (w, ν ), 1913 (s, ν ), 1857 (w, ν ),
13
1
CO
CO
CO
7.77 (m, 4H, Ph). C{ H} NMR (100 MHz, benzene-d ): δ 11.3
6
1
825 (s, νCO). Anal. Calcd for C H GeN O SiW: C, 52.65; H, 5.40; N,
1
36 44 2 2
(
(
2
C Me ), 32.2 (CMe ), 33.8 (CMe ), 90.1 (WCC, J = 87 Hz), 102.1
C Me ), 129.6, 128.4, 135.2, 138.8 (Ph), 166.4 (WCC, J = 21 Hz),
32.6 (CO, J = 161 Hz). IR (toluene, cm ): 1919 (s, νCO), 1847 (s,
5
5
3
3
WC
3
.41. Found: C, 53.15; H, 5.48; N, 3.66.
2
5
5
WC
Synthesis of Cp*(CO) W(GePh ·DMAP)(CCCMe ) (9b). On a
1
−1
2
2
3
WC
vacuum line, toluene (2.0 mL) was vacuum-transferred into a reaction
flask containing 7b (39mg, 0.057mmol)andDMAP(8.3mg, 0.068mmol)
cooled with a liquid nitrogen bath. The mixture was warmed to room
temperature with stirring. After 30 min at room temperature, the solvent
was removed under vacuum, and the residual solid was washed with
νCO). Anal. Calcd for C H GeO W: C, 52.75; H, 5.02. Found: C,
30
34
2
52.84; H, 4.94.
Synthesis of Cp*(CO) WCC(SiMe )CMe OGePh (8a). On
2
3
2
2
a vacuum line, a toluene solution (2.0 mL) of Ph HGeCCSiMe
2
3
1
(49 mg, 0.15 mmol) was added into a reaction flask containing 6 (50 mg,
pentane (1.0 mL) to give 9b as a pale yellow solid (34 mg, 75%). H
0
.12 mmol) at −40 °C, and the mixture was warmed to room tem-
NMR (600 MHz, toluene-d , 20 °C): δ 1.09 (s, 9H, CMe ), 1.98 (s, 6H,
8
3
perature with stirring. After 15 min at room temperature, volatiles were
removed under vacuum to leave crude 7a, to which acetone (0.36 mmol)
was vacuum-transferred and the mixture was stirred for 30 min at room
temperature. After removal of the solvent, the residual solid was
extracted with pentane (4 × 1.0 mL). The extract was concentrated to
NMe ), 2.09 (s, 15H, Cp*), 5.60−5.61 (m, 2H, DMAP), 7.21−7.32 (m,
2
1
6H, Ph), 7.92−7.93 (m, 4H, Ph), 8.01−8.02 (m, 2H, DMAP); H NMR
(600 MHz, toluene-d , −70 °C): δ 1.12 (s, CMe , cis-9b), 1.24 (s, CMe ,
8
3
3
trans-9b), 1.69 (s, NMe , trans-9b), 1.83 (s, NMe , cis-9b), 2.09 (s,
2
2
Cp*, trans-9b), 2.14 (s, Cp*, cis-9b), 5.21 (br, DMAP, cis-9b), 5.24 (br,
DMAP, trans-9b), 7.15−7.40 (m, Ph, cis-9b + trans-9b), 7.58−7.72 (m,
Ph, cis-9b + trans-9b), 8.00−8.28 (m, Ph and DMAP, cis-9b + trans-9b).
1
give 8a as a pale red-violet solid (49 mg, 55% based on 6). H NMR
(
400 MHz, benzene-d ): δ 0.28 (s, 9H, SiMe ), 0.98 (s, 3H, CMeMe),
6
3
1
3
1
1.55 (s, 3H, CMeMe), 1.71 (s, 15H, Cp*), 7.05−7.32 (m, 6H, Ph),
7.73−7.78 (m, 2H, Ph), 8.21−8.26 (m, 2H, Ph). C{ H} NMR
C{ H} NMR (150 MHz, toluene-d , −70 °C): δ 11.7 (C Me , trans-
8
5
5
13
1
9b), 11.9 (C Me , cis-9b), 30.1 (CMe , trans-9b), 30.4 (CMe , cis-9b),
5 5 3 3
5
044
dx.doi.org/10.1021/om4000264 | Organometallics 2013, 32, 5038−5046

Organometallics
Article
3
2.0 (CMe , cis-9b), 32.8 (CMe , trans-9b), 38.0 (NMe , trans-9b),
Me COH (0.11 mmol) were vacuum-transferred into a J. Young NMR
3
3
2
3
3
8.1 (NMe , cis-9b), 82.2 (WCC, cis-9b), 86.4 (WCC, trans-9b), 100.2
tube containing 7b (8.0 mg, 0.012 mmol), and the valve of the tube was
closed under vacuum. The reaction was monitored by H NMR
2
1
(C Me , trans-9b), 100.4 (C Me , cis-9b), 105.5 (NC H NMe , cis-9b +
5
5
5
5
5
4
2
trans-9b), 135.1 (Ar), 135.9 (WCC, trans-9b), 136.5, 137.1, 143.3
WCC, cis-9b), 146.0, 147.1, 148.4, 154.1, 154.5 (Ar), 248.8 (br, CO),
51.3 (br, CO). Several aromatic and carbonyl carbon signals were not
assigned due to their poor intensities, signal broadening, or overlap with
spectroscopy at room temperature. A 1:3.5 mixture of 7b and 10b was
observed after 10 min, and ca. 87% of 7b was consumed to form 10b
(45%), 11 (25%), and unidentified minor products after 2 h. After 1 day,
7b and 10b disappeared and 11 was observed in ca. 70% yield. In a
preparative-scale reaction, a mixture of 7b (60 mg, 0.088 mmol) and
(
2
−1
solvent signals. IR (toluene, cm ): 1908 (s, νCO), 1817 (m, νCO). Anal.
Calcd for C H GeN O W: C, 55.19; H, 5.51; N, 3.48. Found: C,
Me COH (0.80 mmol) in toluene (1.0 mL) was stirred at room
37
44
2
2
3
55.51; H, 5.83; N, 3.36.
temperature for 1 day. After removal of the volatiles, the residue was
Reaction of 8a with DMAP. On a vacuum line, benzene-d (0.50
mL) was vacuum-transferred into a J. Young NMR tube containing 8a
8.0 mg, 0.011 mmol) and DMAP (1.8 mg, 0.015 mmol), and the valve
extracted with hexane (4.0 mL), and the extract was cooled at −80 °C to
6
1
give 11 as a yellow powder (40 mg, 60%). H NMR (400 MHz, benzene-
(
d ): δ 1.21 (s, 9H, CMe ), 1.34 (s, 9H, CMe ), 1.82 (s, 15H, Cp*), 3.04
6
3
3
of the tube was closed under vacuum. The tube was heated at 50 °C, and
(s, 1H, WCCH), 7.20−7.43 (m, 6H, Ph), 7.80−7.90 (m, 2H, Ph), 8.20−
1
13 1
the reaction was periodically monitored by H NMR spectroscopy. After
8.28 (m, 2H, Ph). C{ H} NMR (151 MHz, benzene-d ): δ 10.8
6
2
2
h, 55% of 8a was converted into 9a along with the formation of acetone
(C Me ), 31.5 (CMe ), 32.7 (OCMe ), 35.8 (CMe ), 71.7 (WCC, J
=
5
5
3
3
3
WC
(
44%). The conversion ratio was obtained from the integrations of the
37 Hz), 73.8 (OCMe ), 103.4 (C Me ), 129.7, 129.8, 135.90, 135.93,
3 5 5
1
1
SiMe signals of 8a and 9a. The signal of acetone was overlapped with
that of one of the CMe signals of 8a at δ 1.55. The yield of acetone was
138.6, 140.2 (Ph), 226.5 (CO, J = 198 Hz), 227.5 (CO, J
=
WC
3
WC
1
197 Hz), 315.2 (WCC, J = 215 Hz). Several aromatic carbon signals
2
WC
calculated using subtraction of the integration of the other CMe signal
at δ 0.98 from that of the overlapped signal.
were not assigned due to overlap with solvent signals. IR (toluene,
2
−
1
cm ): 1969 (m, νCO), 1891 (s, νCO). Anal. Calcd for
1
Thermolysis of 8a. On a vacuum line, benzene-d (0.60 mL) was
C H GeO W· / (toluene): C, 56.07; H, 6.02. Found: C, 56.08; H, 5.95.
6
35 44
3
2
vacuum-transferred into a J. Young NMR tube containing 8a (8.0 mg,
Reaction of 7b with tert-Butyl Alcohol: Characterization of
10b by Low-Temperature NMR Measurement. On a vacuum line,
0
.011 mmol), and the valve of the tube was closed under vacuum. The
1
tube was heated at 50 °C, and the reaction was monitored by H NMR
spectroscopy. After 2 h, 12% of 8a was converted into 7a along with the
formation of acetone (10%). The conversion ratio was obtained from
toluene-d (0.5 mL) and Me COH (0.15 mmol) were vacuum-
8 3
transferred into an NMR tube containing 7b (7 mg, 0.010 mmol),
1
and the tube was flame-sealed under vacuum. The H NMR spectrum at
the integrations of the SiMe signals of 8a and 7a, and the yield of
−40 °C showed the formation of 10b as a major component (ca. 85%).
3
The 13C{ H} NMR spectrum was recorded using a sample prepared
1
acetone was obtained by a procedure similar to that described above.
Reaction of 8b with DMAP. On a vacuum line, benzene-d6
0.50 mL) was vacuum-transferred into a J. Young NMR tube con-
from 7b (30 mg, 0.044 mmol) and Me COH (0.66 mmol) in toluene-d
3
8
1
(
(0.5 mL). Data for 10b are as follows. H NMR (600 MHz, toluene-d
−40 °C): δ 1.15 (s, 9H, CMe ), 1.42 (s, 9H, CMe ), 1.80 (s, 15H, Cp*),
5.16 (s, 1H, WCCH), 7.10−7.30 (m, 6H, Ph), 8.06−8.13 (m, 4H, Ph).
6
,
taining 8b (8.0 mg, 0.011 mmol) and DMAP (4.0 mg, 0.033 mmol), and
3
3
the valve of the tube was closed under vacuum. The tube was heated at
1
13
1
5
0 °C, and the reaction was periodically monitored by H NMR
C{ H} NMR (151 MHz, toluene-d
6
, −40 °C): δ 11.7 (C
5
Me
), 107.6 (C
5
), 32.3
Me ),
spectroscopy. After 5 h, 8b was almost completely converted into 9b
(CMe ) 33.7 (OCMe ), 35.6 (CMe ), 74.4 (OCMe
3
3
3
3
5
5
along with the formation of acetone (82%).
Reaction of 9a with Acetone. On a vacuum line, benzene-d (0.33 mL)
135.0, 135.5 (Ph), 136.3 (WCC), 136.4 (br), 138.0 (Ph), 217.0 (br,
1
CO), 344.6 (WCC, J = 118 Hz). Several aromatic carbon signals
6
WC
and acetone (0.021 mmol) were vacuum-transferred into a medium-
walled J. Young NMR tube containing 9a (6.0 mg, 0.007 mmol), and
were not assigned due to their poor intensities or overlap with solvent
signals.
the valve of the tube was closed under an N atmosphere. The reaction
Reaction of 8b with tert-Butyl Alcohol. On a vacuum line,
2
was periodically monitored by 1H NMR spectroscopy at room
temperature. The signals of 8a and DMAP appeared gradually, and
the reaction reached to an equilibrium state (9a:8a = 14:86) after 1 day.
The ratio of 9a and 8a was obtained from the integrations of their SiMe3
signals.
benzene-d (0.5 mL) and Me COH (0.10 mmol) were vacuum-
6
3
transferred into an NMR tube containing 8b (8 mg, 0.011 mmol), and
the tube was flame-sealed under vacuum. The reaction was monitored
1
by H NMR spectroscopy. After 2 h at 50 °C, 13% of 8b was converted
to 11, and a trace amount (ca. 5%) of 10b was detected. After 1 day, 8b
disappeared, and 11 and acetone were observed in 75% and 59% yields,
respectively.
Reaction of 9a with Triphenylborane. On a vacuum line,
benzene-d (0.50 mL) was vacuum-transferred into a J. Young NMR
6
tube containing 9a (7.0 mg, 0.009 mmol) and BPh (2.2 mg, 0.009
X-ray Crystal Structure Determination. Single crystals of 7a,
8a,b, cis-9b, and 11 were obtained by recrystallization from pentane,
toluene, toluene, pentane/toluene, and hexane/toluene, respectively.
The diffraction data were collected on a Rigaku Saturn70 or a Rigaku
XtaLAB mini diffractometer with graphite-monochromated Mo Kα
3
mmol), and the valve of the tube was closed under vacuum. The
1
H NMR spectrum showed the quantitative formation of 7a and DMAP·
BPh after 5 min.
3
NMR Tube Reaction of 7a with tert-Butyl Alcohol. On a vacuum
16
line, benzene-d (0.50 mL) and Me COH (0.35 mmol) were vacuum-
radiation. The structures were solved by direct methods, SHELX97 for
6
3
1
7
18
transferred into a J. Young NMR tube containing 7a (8.0 mg, 0.011
7a, 8a, and 11, SIR2004 for 8b, and SIR92 for cis-9b, and refined by
16
mmol), and the valve of the tube was closed under vacuum. The reaction
full-matrix least-squares procedures (SHELXL97). The non-hydrogen
atoms were refined anisotropically, and hydrogen atoms were refined
using the riding model. Selected crystallographic data for 7a, 8a,b, cis-9b,
and 11 are summarized in Tables S1 and S2 in the Supporting
Information.
1
was monitored by H NMR spectroscopy at room temperature. After 10
min, 7a and 10a were observed in an equilibrium ratio of 55:45, which
was obtained by the integrations of their SiMe signals at δ −0.14 (7a)
3
and 0.20 (10a). The 13C{ H} NMR spectrum was obtained using a
1
1
benzene-d solution of 7a (30 mg) and Me COH (1.0 mmol). 10a: H
6
3
t
NMR (400 MHz, benzene-d ) δ 0.20 (s, 9H, SiMe ), 1,35 (s, 9H, Bu),
6
3
ASSOCIATED CONTENT
1
8
.78 (s, 15H, Cp*), 5.06 (s, 1H, WCCH), 7.21−7.23 (m. 6H, Ph) 8.02−
■
.04 (m, 4H, Ph). 13C{ H} NMR (150 MHz, benzene-d ): δ 1.4
1
*
S
Supporting Information
6
(
SiMe ), 11.1 (C Me ), 33.3 (CMe ), 74.0 (CMe ), 106.4 (C Me ),
1
13
1
3
5
5
3
3
5
5
Figures, tables, and CIF files giving H and C{ H} NMR
spectra of Ph HGeCCSiMe , Ph HGeCCCMe , 7a,b, 8a,b,
113.2 (WCC), 129.6, 136.0, 148.4 (Ph), 218.3 (CO), 339.0 (WCC).
2
3
2
3
Several aromatic carbon signals were not assigned due to their poor
1
intensities or overlap with solvent signals. 2 Si{ H} NMR (79 MHz,
9
1
9a,b, 10a,b, and 11, the H NMR spectra of NMR tube reactions,
and X-ray crystallographic data of 7a, 8a,b, cis-9a, cis-9b and 11.
This material is available free of charge via the Internet at http://
pubs.acs.org.
benzene-d ): δ −4.24 (SiMe ).
6
3
Reaction of 7b with tert-Butyl Alcohol: NMR Tube Reaction
and Isolation of 11. On a vacuum line, benzene-d (0.50 mL) and
6
5
045
dx.doi.org/10.1021/om4000264 | Organometallics 2013, 32, 5038−5046

Organometallics
Article
(
8) Beatriz Cordero, B.; Gom
Echeverrıa, J.; Cremades, E.; Barragan
008, 2832.
(9) Power, P. P. Nat. Chem. 2012, 4, 343.
10) (a) Riviere, P.; Riviere-Baudet, M.; Satge,
́
ez, V.; Platero-Prats, A. E.; Reves
́
, M.;
AUTHOR INFORMATION
■
*
́
́
, F.; Alvarez, S. Dalton Trans.
Corresponding Author
E-mail for H.S.: sakaba@m.tohoku.ac.jp.
2
(
̀
̀
́
J. In Comprehensive
Notes
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds.; Pergamon Press: New York, 1982; Vol. 2, Chapter 9, p 502.
The authors declare no competing financial interest.
(
b) Brook, M. A. Silicon in Organic, Organometallic, and Polymer
Chemistry; Wiley: New York, 2000; Chapter 2, p 30.
11) Although the structural assignment of cis-9a is supported by
ACKNOWLEDGMENTS
■
(
This work was supported by Grants-in-Aid for Scientific
Research (No. 22550051) from the Ministry of Education,
Culture, Sports, Science and Technology of Japan.
single-crystal X-ray crystallography, the quality of the data was not
enough to allow a detailed discussion. The molecular structure and
Cartesian coordinates for cis-9a are shown in the Supporting
Information.
(
12) (a) Fischer, E. O.; Lindner, T. L.; Huttner, G.; Friedrich, P.;
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dx.doi.org/10.1021/om4000264 | Organometallics 2013, 32, 5038−5046