η3-silaallyl/alkenylsilyl molybdenum complex: Synthesis, structure, and reactivity toward primary amines to form Mo-N-Si three-membered cyclic complexes

Article abstract of DOI:10.1021/om500996r

The new η³-silaallyl/alkenylsilyl molybdenum complex CpMo(CO)₂(η³-Ph₂SiCHCMe₂) (3) was synthesized by the reaction of CpMo(CO)₂(py)Me with Ph₂HSiCH-CMe₂. Reactions of 3 with primary amines RNH₂ (R = ^tBu, ⁱPr, Et) gave Mo-N-Si three-membered cyclic complexes CpMo(CO)₂(η²-N,Si-RHNSiPh₂) (5a, R = ^tBu; 5b, R = ⁱPr; 5c, R = Et) with elimination of isobutene. In NMR tube reactions using ⁱPrNH₂ and EtNH₂, the Mo-N-Si-C four-membered cyclic complexes CpMo(CO)₂(η²-N,C-RHNSiPh₂CHⁱPr) (4b, R = ⁱPr; 4c, R = Et) were observed as intermediates leading to 5b and 5c, respectively. Complex 4c was successfully isolated in a preparative reaction. The molecular structures of 3, 4c, and 5b were determined by X-ray crystal analyses. Interestingly, the contribution of silylene character was suggested for the SiPh₂ moiety of 5b from the X-ray structure. The reaction of 5b with MeOH gave the dinuclear complex Cp(CO)₂Mo(η-OMe)(η -H)Mo(CO)₂Cp as a major product.

Full text of DOI:10.1021/om500996r

Article
pubs.acs.org/Organometallics
η3‑Silaallyl/Alkenylsilyl Molybdenum Complex: Synthesis, Structure,
and Reactivity toward Primary Amines To Form Mo−N−Si Three-
Membered Cyclic Complexes
,†
†
†
‡
Hiroyuki Sakaba,* Hiroki Tonosaki, Kazuyoshi Isozaki, 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
3
3
ABSTRACT: The new η -silaallyl/alkenylsilyl molybdenum complex Cp*Mo(CO) (η -Ph SiCHCMe ) (3) was synthesized by
2
2
2
t
i
the reaction of Cp*Mo(CO) (py)Me with Ph HSiCHCMe . Reactions of 3 with primary amines RNH (R = Bu, Pr, Et)
2
2
2
2
2
t
i
gave Mo−N−Si three-membered cyclic complexes Cp*Mo(CO) (κ -N,Si-RHNSiPh ) (5a, R = Bu; 5b, R = Pr; 5c, R = Et) with
2
2
i
elimination of isobutene. In NMR tube reactions using PrNH and EtNH , the Mo−N−Si−C four-membered cyclic complexes
2
2
2
i
i
Cp*Mo(CO) (κ -N,C-RHNSiPh CH Pr) (4b, R = Pr; 4c, R = Et) were observed as intermediates leading to 5b and 5c,
2
2
respectively. Complex 4c was successfully isolated in a preparative reaction. The molecular structures of 3, 4c, and 5b were
determined by X-ray crystal analyses. Interestingly, the contribution of silylene character was suggested for the SiPh moiety of
2
5
b from the X-ray structure. The reaction of 5b with MeOH gave the dinuclear complex Cp*(CO) Mo(μ-OMe)(μ-
2
H)Mo(CO) Cp* as a major product.
2
INTRODUCTION
■
3
The structures and reactivity of η -allyl transition-metal
complexes have been extensively studied to reveal their
important roles in stoichiometric and catalytic transformations
1
3
of a variety of organic substrates. For a silicon analogue, a η -
2
silaallyl complex, we previously reported the synthesis of
3
Cp*W(CO) (η -Me SiCHCMe ) (1) via Si−H bond activa-
2
2
2
tion of the alkenylsilane Me HSiCHCMe and revealed the
2
2
3
X-ray crystal structure of the η -silaallyl type complex for the
2
b
first time. After the structure determination of 1, a theoretical
study of the model complex CpW(CO) (η -H SiCHCH ) was
3
2
2
2
performed by Sakaki and co-workers, and its bonding nature
was clarified; the π conjugation in the Si−C moiety of the
ligand is weak in comparison to that in the C−C moiety, and
3
the electronic structure of the η -H SiCHCH group is
2
2
3
3,4
general, however, information about the structure and reactivity
intermediate between η -silaallyl and vinylsilyl groups.
3
of η -silaallyl type complexes is still very limited.
According to the theoretical study, complex 1 is better
described as a η -silaallyl/alkenylsilyl complex.
A reactivity study of 1 was also performed to show its high
3
3
We also synthesized the related η -silapropargyl/alkynylsilyl
3
t
complexes Cp*Mo(CO) (η -Ph SiCCR) (2a, R = Bu; 2b, R =
2
2
i
5
Pr), the bonding nature of which is described as intermediate
reactivity toward methanol to give the four-membered cyclic
3
2
i
between η -silapropargyl and alkynylsilyl coordination modes
by a theoretical study. These complexes showed intriguing
reactivity toward methanol to give the four-membered cyclic
complex Cp*W(CO) (κ -C,O- PrHCSiMe OMe) via Si−W
2
2
4
bond cleavage by nucleophilic attack of methanol to the silicon
center of 1 to form alkene hydride intermediates, which were
2
t
2b
complex Cp*Mo(CO) {κ -C,O-C(CH Bu)SiPh OMe} from
spectroscopically assigned at −60 °C (eq 1). Very recently,
2
2
3
3
3
2a or the silyl-substituted η -allyl complex Cp*Mo(CO) {η -
Tilley and co-workers have synthesized several η -sila- and
2
germaallyl type complexes of rhodium via interesting net alkyne
insertion into a Si/Ge−H bond of (dtbpm)Rh(EHMes )
Received: October 1, 2014
Published: March 9, 2015
2
2c
(
dtbpm = di(tert-butylphosphino)methane; E = Si, Ge). In
©
2015 American Chemical Society
1029
DOI: 10.1021/om500996r
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Organometallics
MeOPh Si)HCCHCMe } from 2b, depending on the
Article
(
2
2
5
substituent R (eq 2). Furthermore, a unique interconversion
Figure 1. Molecular structure of 3. Thermal ellipsoids are drawn at the
5
0% probability level, and all hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Mo1−Si1 2.5574(9),
Mo1−C1 2.306(2), Mo1−C2 2.489(3), Si1−C1 1.817(3), C1−C2
1.414(3); Si1−Mo1−C1 43.50(7), C1−Mo1−C2 34.02(8), Si1−C1−
C2 122.7(2), C1−Si1−C5 112.64(12), C1−Si1−C11 123.22(11),
C5−Si1−C11 108.60(11), C1−C2−C3 118.0(2), C1−C2−C4
3
between the η -silapropargyl/alkynylsilyl complex Cp*Mo-
3
(
CO) (η -Ph SiCCSiHPh ) and its structural isomer, the
acetylide−silylene complex Cp*Mo(CO) (SiPh )(CCSiHPh ),
was revealed by a variable low-temperature NMR study. As an
extension of these studies, we have synthesized the new η -
silaallyl/alkenylsilyl molybdenum complex Cp*Mo(CO) (η -
Ph SiCHCMe ) (3) to compare its structure and reactivity with
2
2
2
2
2
2
6
1
21.9(2), C3−C2−C4 111.9(2).
3
3
3
2
alkynylsilyl molybdenum complex Cp*Mo(CO) (η -
2
t
5
2
2
Ph SiCC Bu) (2a) are summarized in Table 1. The Mo−Si
2
those of the silaallyl/alkenylsilyl tungsten and silapropargyl/
alkynylsilyl molybdenum complexes. We report here the
synthesis and molecular structure of 3 and its reactions with
methanol and primary amines. The latter reactions resulted in
the interesting transformation of 3 to metallacycles having
Mo−N−Si−C four-membered and Mo−N−Si three-mem-
bered frameworks. In addition, the reaction of the Mo−N−Si
three-membered cyclic complex with methanol is described.
Table 1. Comparison of Selected Bond Lengths (Å) and
Angles (deg) of 1, 2a, and 3
RESULTS AND DISCUSSION
Synthesis and Structure of η -Silaallyl/Alkenylsilyl
Molybdenum Complex 3. The reaction of Cp*Mo-
■
3
(
CO) (py)Me with the alkenylsilane Ph HSiCHCMe in
2
2
2
toluene proceeded with generation of pyridine and methane at
room temperature to give the expected complex Cp*Mo-
3
(
CO) (η -Ph SiCHCMe ) (3), which was isolated as an air-
2
2
2
sensitive brownish yellow powder in 71% yield (eq 3). The
bond length (2.5574(9) Å) of 3 is in the range for typical Mo−
7
Si single-bond lengths (2.513−2.670 Å) of silyl molybdenum
complexes. The Si−C1 bond length (1.817(3) Å) is
8
intermediate between usual Si−C single (1.86−1.91 Å) and
8,9
double bond (1.70−1.76 Å) lengths, similar to those of 1 and
2
a (1.800(4) and 1.806(3) Å, respectively). The C1−C2 bond
(
1.414(3) Å) is intermediate between C−C single and double
2b
formation of 3 can be explained by the following steps: (i)
oxidative addition of the Si−H bond of the silane to the 16e
bonds, similar to that (1.411(5) Å) of 1 and longer than that
5
(1.251(4) Å) of 2a, which is intermediate between C−C
complex Cp*Mo(CO) Me generated from the labile pyridine
double and triple bonds. The sum of three bond angles about
the Si atom (∑Si: C1−Si1−C5, C1−Si1−C11, and C5−Si1−
C11) is 344.5°, and that about the C2 atom (∑C2: C1−C2−
C3, C1−C2−C4, and C3−C2−C4) is 351.8° for 3. Both angles
2
complex, (ii) reductive elimination of methane in the resulting
intermediate Cp*Mo(CO) (Me)(H)(SiPh CHCMe ) to
2
2
2
1
form Cp*Mo(CO) (η -SiPh CHCMe ), and (iii) coordina-
2
2
2
2
3
tion of the C−C double bond to the coordinatively unsaturated
metal center to give 3.
are intermediate between the expected values for sp and sp
hybridization, and the smaller value about the Si atom is
The molecular structure of 3 was determined by X-ray
analysis of crystals obtained by recrystallization from a toluene/
pentane solution (Figure 1). Selected bond lengths and angles
ascribable to the weaker pπ−pπ interaction in the Si−C1 bond
3
,4
in the theoretical study. A similar tendency is found in the
corresponding angles (∑Si = 346.3° and ∑C2 = 350.9°) in 1.
The difference in the Si−C1−C2 angles between 3 (122.7(2)°)
and 2a (138.4(3)°) reflects the different hybridization of their
3
of 3 and the related η -silaallyl/alkenylsilyl tungsten complex
3
2b
3
Cp*W(CO) (η -Me SiCHCMe ) (1) and η -silapropargyl/
2
2
2
1
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Article
1
C1 atoms. For the silaallyl ligand of 3, the H NMR signals of
the central proton and two Me groups were observed at δ 2.19
fied minor products after 5.5 h. After 2 days, the reaction was
completed to give 5a (69%) and isobutene (50%). No definite
(
CH), 1.56 (Me), and 1.73 (Me), and the Me signals were
intermediate was observed during the reaction. In comparison
i
observed separately also in THF-d8 (δ 1.41 and 2.30),
indicating no sign of fluxional behavior, although η -allyl
ligands often show such behavior. The signal assignments of
the C1 and C2 atoms were based on HMQC and HMBC
to this reaction, the reaction using PrNH (5 equiv) was much
2
3
faster. After 10 min, 98% of 3 reacted to give the four-
10
2
i
i
membered complex Cp*Mo(CO) (κ -N,C-PrHNSiPh CH Pr)
2
2
2
(4b, 63%), the three-membered complex Cp*Mo(CO) (κ -
N,Si-PrHNSiPh ) (5b, 24%), and isobutene (18%). After 1
2
29
i
correlations with the central CH proton, respectively. The Si
2
and 13C signals resonated at δ 9.6 (Si), 45.9 (C1), and 84.3
day, 3 disappeared and 4b was completely transformed into 5b
29
2b
(
C2). The Si resonance is similar to that (δ 8.8) for 1, and
(91%) and isobutene (69%). Even with use of a small excess
i
these values are close to the lower-field end of those for the
amount of PrNH (1.3 equiv), 84% of 3 was consumed to give
2
11
silene complexes (δ +6 to −21).
4b as a major product after 10 min, and its complete conversion
Reactivity of 3 toward Methanol and Primary Amines.
We first examined the reaction of 3 with MeOH to compare its
reactivity with that of tungsten complex 1, which gave the four-
to 5b was observed after 1 day. The reactivity of EtNH (1.4
2
equiv) was further enhanced to lead to complete consumption
2
of 3 in 10 min, affording Cp*Mo(CO) (κ -N,C-EtHN-
2
2
i
i
2
membered metallacycle Cp*W(CO) (κ -C,O- PrHCSiMe -
OMe) on treatment with MeOH (eq 1). In contrast to the
case for 1, however, the reaction of 3 afforded a complex
mixture including Cp*(CO) MoMo(CO) Cp* and isobu-
tene along with several unidentified products.
SiPh CH Pr) (4c, 72%), Cp*Mo(CO) (κ -N,Si-EtHNSiPh )
2
2
2
2
2
2
b
(5c, 18%), and isobutene (16%). Interestingly, the trans-
formation of the four-membered metallacycle into the three-
membered metallacycle is considerably slower in 4c than in 4b,
as shown by the yield changes of 4b,c and 5b,c in the reactions
with 1.3−1.4 equiv of the amines: 4c (63%) and 5c (25%) vs
4b (0%) and 5b (91%) after 1 day. Utilizing this property of 4c,
it could be isolated in 58% yield from a preparative reaction and
fully characterized, including X-ray crystal analysis. For the
three-membered complexes, X-ray-quality crystals were ob-
tained for 5b. Their molecular structures will be discussed
below.
12
2
2
Next, we investigated the reactivity of 3 toward primary
amines (eq 4 and Table 2). When the reaction of 3 with
t
BuNH (5 equiv) in C D in an evacuated sealed NMR tube
2
6
6
1
was monitored by H NMR spectroscopy, slow reaction was
observed; 47% of 3 reacted to form Cp*Mo(CO) (κ -
N,Si- BuHNSiPh ) (5a; 32%), isobutene (25%), and unidenti-
2
2
t
2
A possible mechanism for the formation of 4, 5, and
isobutene is shown in Scheme 1. Considering the similarity in
the nucleophilic reactivities of methanol and amines, Si−Mo
bond cleavage of 3 to form the alkene hydride complex A is
conceivable as the first step, similar to the reaction of 1 with
methanol (eq 1). The intermediate A undergoes migratory
insertion and coordination of the NHR group to give the four-
membered metallacycle 4. Dissociation of the NHR group and
1
,2-silyl migration to the metal center can form silyl
13
isobutylidene complex B. After ligand isomerization of
14
isobutylidene to isobutene, dissociation of isobutene and
coordination of the NHR group take place to afford the three-
membered cyclic complex 5. Differences in the reaction rate
can be explained by the steric bulkiness of the substituent R of
the amines RNH (R = Bu, Pr, Et) as follows. The most bulky
amine BuNH is the least reactive in the first step to slow the
t
i
2
t
2
t
reaction, and coordination of the BuNH group is expected to
be favored in the three-membered metallacycle in comparison
to the four-membered metallacycle because of the larger N−
Mo−CO angle in the former (e.g., N1−Mo−C2 = 90.79(11)°
in 5b; Figure 3) than in the latter (e.g., N1−Mo−C6 =
8
4.58(17)° in 4c; Figure 2). The larger angle would reduce
Table 2. Yield Changes in the Reactions of 3 with RNH (R
2
= tBu, iPr, Et)
steric repulsion toward the metal fragment especially for the
bulky group, accelerating conversion to three-membered
metallacycle 5a; no four-membered metallacyclic intermediate
was detected in the reaction. In the case of the least bulky
NMR yield (%)
amt
conversn of 3
amine EtNH , the first step proceeds very rapidly, and relatively
R
(equiv)
time
(%)
4b,c 5a−c Me CCH
2
2
2
strong coordination of the EtNH group in the four-membered
metallacycle 4c increases its stability enough to be isolable and
slows the further conversion.
tBu
tBu
iPr
iPr
iPr
iPr
Et
5
5.5 h
47
100
98
32
69
24
91
20
91
18
25
25
50
18
69
13
68
16
23
5
2 days
10 min
1 day
5
63
0
Molecular Structures of Four-Membered and Three-
Membered Cyclic Complexes 4c and 5b. The molecular
structures of cyclic complexes 4c and 5b are shown in Figures 2
and 3, respectively. Complex 4c has a four-legged piano-stool
structure. The N1−Mo1−C1 (71.05(13)°) and C5−Mo1−C6
5
100
84
1.3
1.3
1.4
1.4
10 min
1 day
53
0
100
100
100
10 min
1 day
72
63
Et
(
73.37(19)°) angles are smaller than the N1−Mo1−C6
1
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Organometallics
Article
Scheme 1. Possible Mechanism for the Reactions of 3 with Primary Amines
Figure 3. Molecular structure of 5b. Thermal ellipsoids are drawn at
the 50% probability level, and all hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Mo1−Si1
Figure 2. Molecular structure of 4c. Thermal ellipsoids are drawn at
the 50% probability level, and all hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Mo1−N1
2
.4351(12), Mo1−N1 2.286(3), Si1−N1 1.778(3), N1−C3 1.496(4);
2
.309(4), Mo1−C1 2.329(4), Si1−N1 1.785(4), Si1−C1 1.833(4);
Si1−Mo1−N1 44.10(6), Si1−Mo1−C1 70.06(9), N1−Mo1−C2
0.79(11), C1−Mo1−C2 83.83(12), Mo1−N1−Si1 72.41(9), Mo1−
Si1−N1 63.49(9), Mo1−Si1−C6 120.69(10), Mo1−Si1−C12
26.62(9), C6−Si1−C12 110.62(13).
N1−Mo1−C1 71.05(13), Mo1−N1−Si1 93.22(15), N1−Si1−C1
9
96.30(17), Mo1−C1−Si1 91.34(15).
1
(
84.58(17)°) and C1−Mo1−C5 (80.43(17)°) angles. The
Si1−C1 bond (1.833(4) Å) is somewhat shorter than a normal
Si−C bond (1.86−1.91 Å), and similar Si−C bond shortening
in four-membered metallasilacycles has been observed in
Cp*W(CO) (κ -C,O- PrHCSiMe OMe) (Si−C = 1.833(5)
Å)
with the Mo−Si bond distances (2.444−2.501 Å) of donor-
stabilized silylene molybdenum complexes with a
(
)
7,18
Cp * (CO) Mo fragment.
The sum of three bond angles
2
2
i
about the Si atom (Mo1−Si1−C6, Mo1−Si1−C12, and C6−
Si1−C12) is 357.9°. These features of the bond length and
angles suggest silylene character of the Si atom. On the other
hand, the Si−N bond length (1.778(3) Å) is shorter than those
2
2
2
b
2
and [rac-(C H )(indenyl) Zr{κ -C,Cl-(Me Si)-
2 4 2 3
15
+
HCSiMe Cl}] (Si−C = 1.820(5) Å). The Si1−N1 bond
2
(
1.785(4) Å) is at the upper end of normal Si−N single-bond
16
1
7
lengths (1.70−1.78 Å). In the upfield region of the H NMR
spectrum of 4c, two characteristic doublets assigned to MoNH
and MoCH were observed at δ −0.15 (br, J = ca. 6 Hz) and
(1.908−2.007 Å) in N-donor-stabilized silylene molybdenum
complexes and is within the range of normal Si−N single-bond
1
6
lengths (1.70−1.78) Å).
0
.24 (J = 9.2 Hz), respectively. The NH signal of a silylamine
In relation to the structure of 5b, the W−Si−N three-
2
RHNSiR generally appears in a relatively upfield region (δ ca.
0
to a metal center for the silyl-substituted amine moiety in 4c.
The MoNH and MoCH signals showed H− Si HMBC
correlation with the Si signal at δ 9.2, supporting the linkage
membered-ring complex Cp′W(CO) {κ -N,Si-N(CHMe)-
3
2
1
7
5
.5−1), and a further upfield shift is caused by coordination
SiHC(SiMe ) } (Cp′ = η -C Me Et, 6) has been reported by
3
3
5
4
1
6
Tobita and co-workers. The Si−N bond length (1.760(5) Å)
of 6 is similar to that of 5b, but the W−Si bond length
(2.549(2) Å) of 6 is within the W−Si single-bond range (2.47−
1
29
2
9
i
i
16
of the PrHN-SiPh −CH Pr moiety.
2.63 Å) (Table 3). In contrast to the M−Si bond shortening
2
Complex 5b adopts a distorted four-legged piano-stool
structure with a Mo−Si−N three-membered-ring framework
in 5b (Mo−Si = 2.4351(12) Å) relative to 6 (W−Si = 2.549(2)
Å), the Mo−N bond (2.286(3) Å) in 5b is longer than the W−
N bond (2.184(5) Å) in 6. Considering the difference in the
(
Figure 3). Interestingly, the Mo−Si bond length (2.4351(12)
19
Å) is shorter than typical Mo−Si single-bond lengths (2.513−
2
covalent radii of Mo (1.54 Å) and W (1.62 Å) atoms, the
7
.670 Å) of silyl molybdenum complexes and is comparable
much longer Mo−N bond in comparison to the W−N bond is
1
032
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Organometallics
Article
Table 3. Comparison of Selected Bond Lengths (Å) and
Angles (deg) of 5b and 6
the enhanced contribution of form I in 5b in comparison to
that in 6. Similar considerable contribution of silylene character
has been observed in the Fe−Si−P three-membered cyclic
2
20
complex Cp*Fe(CO)(κ -Si,P-Me SiPCy ); the Fe−Si bond
2
2
(
2.2569(5) Å) is in the range (2.20−2.29 Å) for base-stabilized
silylene iron complexes and the SiMe fragment has an almost
2
planar geometry (the sum of three bond angles about Si is
3
55.1°). Another characteristic difference between 5b and 6 is
found in the M−N−Si bond angles. The Mo−N−Si angle
(
(
72.41(9)°) in 5b is smaller by 7° than the W−N−Si angle
79.75(18)°) in 6, suggesting that the hybridization of the
nitrogen atoms would be important for the bonding in the M−
3
2
Si−N framework: sp -based hybridization for 5b and sp -based
for 6. Supposing the interaction between the lone-pair electrons
on the nitrogen atom and the p orbital of the silylene type
(
)
ligand in R N−[M]SiR ([M] = Cp* ′ (CO) M) in the
2
2
2
unusual. The overall bonding interaction between the metal
and R NSiR fragments may be balanced by these structural
composition of the M−Si−N three-membered ring, a smaller
M−N−LP (LP = a lone pair orbital) angle is expected in 5b
2
2
modulations. For this type of complex with a M−Si−N three-
i
3
(
R N = PrHN(sp )) in comparison to that in 6 (R N =
2
2
membered ring, the resonance contribution of forms I and I′ is
2
MeHCN(sp )), in accordance with the observed difference
in the M−N−Si bond angles. The difference in the M−N−LP
angles seems to make some important contribution to the M−
Si bond shortening through the interaction of the LP with the p
orbital at least, although the effects of the substituents at the
silicon atom and the metal center must be also strictly
16
conceivable, as described by Tobita (eq 5).
1
considered. The upfield-shifted H NMR signal of the NH
proton was observed at δ 0.04, which showed the correlation
with the 29Si signal at δ 10.5 in the H− Si HMBC spectrum.
In the IR spectrum, NH and CO vibrations were observed at
3282 (w, νNH), 1867 (m, νCO), and 1786 cm− (s, νCO).
1
29
The increased double-bond character of the Mo−Si bond in
b in comparison to the W−Si bond in 6 and the sum of three
5
1
bond angles about Si in 5b, which is very close to 360°, suggest
Scheme 2. Possible Mechanism for the Reaction of 5b with MeOH
1
033
DOI: 10.1021/om500996r
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Article
As described above, the reaction of 3 with MeOH gave a
complex mixture including Cp*(CO) MoMo(CO) Cp* and
isobutene together with several unidentified products. Consid-
ering the reactions of 3 with primary amines, the formation of
that with MeOH in C D suggests an important role of MeOH:
6
6
for instance, a stabilization effect for F such as the formation of
Cp*Mo(CO) (MeOH)H and/or Cp*Mo(CO) (OMe)H .
2
2
2
2
2
These complexes may actually act as key intermediates,
although coupling of F and G is formally shown as a possible
formation mechanism for 7 in Scheme 2. In relation to this
reaction, the formation of the similar dinuclear complex
Cp(CO) W(μ-OMe)(μ-H)W(CO) Cp along with CO, ethyl-
the Mo−Si−O three-membered metallacycle Cp*Mo-
2
(
CO) (κ -O,Si-MeOSiPh ) and isobutene is suggested in the
2
2
reaction with MeOH, and it is speculated that coordination of
the oxygen to the metal center in the metallacycle is weak,
causing its decomposition and/or secondary reaction with
MeOH to give a complex mixture.
2
2
ene, and ethane has been reported in the photoreaction of
CpW(CO) Et with MeOH, and the intermediacy of hydride
3
Reaction of Three-Membered Cyclic Complex 5b with
Methanol. When complex 5b was treated with neat MeOH for
complexes such as CpW(CO) H, CpW(CO) (C H )H, and
3
2
2
4
2
4
CpW(CO) (MeOH)H has been pointed out.
2
3
0 min, the dinuclear complex trans-Cp*(CO) Mo(μ-OMe)(μ-
2
H)Mo(CO) Cp* (7) was obtained in 71% isolated yield
SUMMARY
2
■
1
(
Scheme 2). In the H NMR spectrum, the signals of the
bridging OMe and H ligands were observed at δ 3.89 and
7.80, respectively, in addition to the Cp* signal at δ 1.71. In
the IR spectrum, two CO stretching vibrations were observed at
3
The new η -silaallyl/alkenylsilyl molybdenum complex 3 was
synthesized, and its X-ray crystal structure and reactivity toward
primary alkyl amines RNH (R = Bu, Pr, Et) were studied.
−
t
i
2
The X-ray structure of 3 showed the coordination mode of the
−1
1
921 and 1837 cm . The X-ray crystal structure of 7 is shown
silaallyl/alkenylsilyl moiety similar to that in tungsten complex
in the Supporting Information, though the quality of the data is
low mainly because of severe disorder of CO ligands. Although
1
reported previously. The reactivity study of 3 with amines
revealed unique transformation to Mo−N−Si three-membered
5
no X-ray crystallographic data for complexes of the type (η -
metallacycles 5 via Mo−N−Si−C four-membered metallacycles
5
C R )(CO) Mo(μ-OMe)(μ-H)Mo(CO) (η -C R ) (R = H,
5
5
2
2
5 5
4
, demonstrating reactivity differences due to the substituent R.
alkyl, etc.) have been reported so far, the structure of the closely
Interestingly, the molecular structure of the three-membered
related complex cis-Cp(CO) Mo(μ-SMe)(μ-H)Mo(CO) Cp
i
2
2
cyclic complex 5b (R = Pr) suggested the contribution of
2
1
has been determined by X-ray analysis. In solution,
silylene character in the Si atom of the cyclic Mo−N−Si
framework. Complex 5b reacted with MeOH to give dinuclear
complex 7 with bridging methoxide and hydride ligands via
nucleophilic attack of MeOH at the Si atom.
Cp(CO) Mo(μ-SMe)(μ-H)Mo(CO) Cp exists as a mixture
2
2
of cis and trans isomers, which have been characterized by
variable-temperature NMR spectroscopy. The low-temperature
1
H NMR experiment (room temperature to −70 °C) of 7 did
not show such dynamic behaviors; only a single set of Cp*, μ-
OMe, and μ-H signals was observed. This could be rationalized
by the steric bulkiness of the Cp* ligand, which disfavors the
formation of the cis isomer of 7, whereas a less bulky Cp ligand
allows the formation of the cis and trans isomers in
Cp(CO) Mo(μ-SMe)(μ-H)Mo(CO) Cp.
EXPERIMENTAL SECTION
■
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 JASCO FT/IR-4100
spectrometer. High-resolution mass spectra were recorded on a Bruker
Daltonics solariX 9.4T FT-ICR mass spectrometer. Mass spectro-
metric analysis and X-ray crystal analysis were performed at the
Research and Analytical Center for Giant Molecules, Tohoku
University. Hexane, pentane, toluene, Et O, THF, benzene-d , and
2
2
1
H NMR monitoring of the reaction of 5b with MeOH (8
equiv) in C D showed 91% consumption of 5b and its
6
6
i
i
conversion to 7 (34%), PrHNSiPh (OMe) (11%), PrNH
2
2
(
48%), Ph Si(OMe) (36%), H , and several unidentified
2 2 2
products including hydride species after 4 h. After 1 day, 5b and
i
i
PrHNSiPh (OMe) disappeared, and the yields of PrNH and
2
2
2
6
Ph Si(OMe) were increased to 97% and 74%, respectively. A
2
2
toluene-d were distilled from sodium benzophenone ketyl. Acetoni-
8
possible reaction mechanism is shown in Scheme 2.
Considering a contribution of the metal−silylene type structure
I, addition of MeOH to the MSi bond would be a reasonable
process because a number of precedents of alcohol addition to
such bonds in base-free and stabilized silylene complexes have
trile, pyridine, and pyridine-d were dried over molecular sieves 3A.
5
Ph SiHCl, Me CCHMgBr (0.5 M in THF), and isobutene were
purchased from Sigma-Aldrich. BuNH , PrNH , and EtNH were
2 2 2
2
2
t
i
purchased from TCI Chemicals. Ph Si(OMe)Cl was prepared
2
2
5
according to the literature method.
Cp*Mo(CO) (py)Me. A solution of Cp*Mo(CO) Me (300 mg,
2
2
2
3
been reported. Addition of MeOH to 5b forms intermediate
i
0.91 mmol) in acetonitrile (15 mL) was irradiated with a 100 W
medium-pressure Hg lamp with cooling in an ice−water bath for 25
min. Liberated CO was removed by two freeze−pump−thaw cycles,
and the solution was photolyzed for an additional 25 min. After
removal of the volatiles under vacuum, the resulting crude Cp*Mo-
D, from which PrHNSiPh (OMe) is eliminated to give the 16e
2
i
hydride complex F, presumably via E. PrHNSiPh (OMe)
reacts with MeOH to give PrNH and Ph Si(OMe) , and this
process was actually confirmed by the reaction of PrHNSi-
Ph (OMe) with MeOH. A higher yield of PrNH in
2
i
2
2
2
i
i
(CO) (MeCN)Me was dissolved in pyridine (3 mL) and the solution
2
2
2
comparison to that of Ph Si(OMe) might be attributable to
was stirred for 30 min at room temperature. The volatiles were
2
2
i
removed, and the residual solid was washed with hexane (2 × 3 mL) to
the existence of competitive reductive elimination of PrNH
2
i
2
give Cp*Mo(CO) (py)Me as a highly air sensitive dark orange solid
from D and/or the formation of Cp*Mo(CO) (NH Pr)-
2
2
(
241 mg, ca. 91% purity, ca. 63% yield). NMR spectra were recorded
{
SiPh (OMe)} via Si−N bond cleavage of 5b by MeOH
2
23
for Cp*Mo(CO) (py-d )Me formed by dissolving Cp*Mo(CO) (py)-
Me in pyridine-d . H NMR (400 MHz, C D N): δ 0.28 (s, 3H,
MoMe), 1.72 (s, 15H, Cp*). C{ H} NMR (100 MHz, C D N): δ
6
2
5
2
i
followed by dissociation of PrNH . Another possible route
1
2
i
5
5
5
leading to PrHNSiPh (OMe) based on the contribution of
13
1
2
5 5
form I′ is also conceivable; methanolysis of 5b affords E, from
.5 (MoMe), 10.8 (C Me ), 103.8 (C Me ), 124.9 (py-d , J = 25.7
5 5 5 5 5 CD
i
which PrHNSiPh (OMe) and F are formed. The much higher
Hz), 136.9 (py-d , J = 26.3 Hz), 155.3 (py-d , J = 27.5 Hz), 253.8
2
5 CD 5 CD
−
1
yield of 7 in the reaction in neat MeOH in comparison with
(CO), 269.2 (CO). IR (C H N, cm ): 1904 (s, νCO), 1807 (m, νCO).
5 5
1
034
DOI: 10.1021/om500996r
Organometallics 2015, 34, 1029−1037

Organometallics
Article
Ph HSiCHCMe . A THF solution (5.0 mL) of Ph SiHCl (7.00 g,
pentane (3 × 1 mL) to give a 75:25 mixture of 4b and 5b as an air-
sensitive orange powder (16 mg). 4b was characterized by comparison
of the NMR data of the mixture of 4b and 5b with those of 5b. H
2
2
2
3
1.9 mmol) was added dropwise to a THF solution of Me C
2
1
CHMgBr (0.5 M, 70 mL, 35 mmol). The mixture was stirred
overnight at room temperature and then refluxed for 5 h. After
hydrolysis with 3% HCl solution, the organic layer was washed with a
NMR (600 MHz, C D , −30 °C): δ −0.38 (d, 1H, J = 11.0 Hz,
7
8
MoNH), 0.21 (d, 1H, J = 9.0 Hz, MoCH), 0.62 (d, 3H, J = 5.4 Hz,
NCHMeMe), 0.76 (d, 3H, J = 5.4 Hz, NCHMeMe), 1.09 (d, 3H, J =
5.4 Hz, CCHMeMe), 1.15 (d, 3H, J = 5.4 Hz, CCHMeMe), 1.60 (s,
15H, Cp*), 2.56 (br m, 1H, NCHMe ), 2.70 (br m, 1H, CCHMe ),
saturated NaCl solution and dried over MgSO . The solvent was
4
removed under vacuum, and the residue was subjected to flash
chromatography on silica gel (hexane) to give a colorless oil (6.93 g,
2
2
1
9
1%). The H NMR spectrum is the same as that obtained from a
7.16−7.34 (m, 6H, Ph), 7.60−7.65 (m, 2H, Ph), 8.37−8.43 (m, 2H,
2
6
13 1
different sample preparation method.
Ph). C{ H} NMR (150 MHz, C D , −30 °C): δ 11.9 (C Me ), 14.1
7
8
5
5
3
Cp*Mo(CO) (η -Ph SiCHCMe ) (3). On a vacuum line, a toluene
(MoCH), 26.8 (NCHMeMe), 28.1 (NCHMeMe), 29.4 (CCHMeMe),
31.5 (CCHMeMe), 33.6 (CCHMe ), 53.1 (NCHMe ), 104.4
2
2
2
solution (4 mL) of Ph HSiCHCMe (114 mg, 0.478 mmol) was
2
2
2
2
cooled to −70 °C and placed in a reaction flask containing
(C Me ), 129.1, 131.6, 132.2, 135.0, 138.0, 143.2 (Ph), 256.9 (CO),
5 5
Cp*Mo(CO) (py)Me (150 mg, 0.393 mmol). The mixture was
267.7 (CO). Several aromatic carbon signals were not assigned due to
their overlap with solvent signals. 29Si{ H} NMR (119 MHz, C D ,
2
1
warmed to room temperature with stirring. After 1.5 h at room
temperature, the volatiles were removed under vacuum. The residual
solid was washed with pentane (2 × 2 mL) to give 3 as an air-sensitive
7
8
−30 °C): δ 11.5.
2
i
Cp*Mo(CO) (κ -N,Si- PrHNSiPh ) (5b). On a vacuum line, a
2
2
1
i
brownish yellow powder (146 mg, 71%). Mp: 126−127 °C dec. H
toluene solution (1 mL) of PrNH (0.48 mmol) was placed in a
2
NMR (400 MHz, C D ): δ 1.49 (s, 15H, Cp*), 1.56 (s, 3H, 
reaction flask containing 3 (50 mg, 0.095 mmol) cooled to −70 °C.
The mixture was warmed to room temperature with stirring. After 1
day at room temperature, the volatiles were removed under vacuum.
The residual solid was washed with pentane (2 × 1 mL) to give 5b as
an air-sensitive yellow powder (26 mg, 52%). Mp: 188−189 °C dec.
6
6
CMeMe), 1.73 (s, 3H, CMeMe), 2.19 (s, 1H, SiCH), 6.98−7.02 (m,
13
1
3
H, Ph), 7.12−7.14 (m, 3H, Ph), 7.77−7.82 (m, 4H, Ph). C{ H}
NMR (100 MHz, C D ): δ 10.4 (C Me ), 29.7 (CMeMe), 31.5 (
6
6
5
5
CMeMe), 45.9 (SiCH), 84.3 (CMe ), 103.5 (C Me ), 127.9, 128.1,
2
5
5
1
1
29.8, 129.9, 133.3, 134.7, 134.9, 138.0 (Ph), 230.8 (CO), 237.8
H NMR (600 MHz, C D ): δ 0.04 (d, 1H, J = 12.0 Hz, NHCHMe ),
6
6
2
1
−1
(
(
5
CO). 29Si{ H} NMR (79 MHz, C D ): δ 9.6. IR (C D , cm ): 1900
0.71 (d, 3H, J = 6.0 Hz, CHMeMe), 0.93 (d, 3H, J = 6.0 Hz,
CHMeMe), 1.63 (s, 15H, Cp*), 2.29 (dqq, 1H, JHCNH = 12.0 Hz,
6
6
6
6
+
s, νCO), 1798 (m, νCO). HRMS: m/z calcd for C H MoO Si
28
32
2
26.1220, found 526.1224.
NMR Tube Reaction of 3 with BuNH . On a vacuum line,
JHCCH = 6.0 Hz, NHCHMe ), 7.08−7.19 (m, 6H, Ph), 7.53−7.58 (m,
2
t
13
1
2
2H, Ph), 7.95−7.98 (m, 2H, Ph). C{ H} NMR (150 MHz, C D ): δ
6
6
t
benzene-d (0.5 mL) and BuNH (76 μmol) were vacuum-transferred
11.2 (C Me ), 24.9 (CHMeMe), 27.9 (CHMeMe), 56.1 (CHMe ),
6
2
5
5
2
into an NMR tube containing 3 (8.0 mg, 15 μmol) with cooling in a
liquid nitrogen bath, and the tube was flame-sealed under vacuum. The
reaction was periodically monitored by H NMR spectroscopy. After 2
102.6 (C Me ), 128.6, 128.8, 129.7, 131.0, 133.1, 134.4, 135.5, 138.5
5 5
29
1
(Ph), 235.7 (CO), 241.4 (CO). Si{ H} NMR (119 MHz, C D ): δ
6
6
1
−1
10.5 (s). IR (KBr, cm ): 3282 (w, ν ), 1867 (m, νCO), 1786 (s,
νCO). HRMS: m/z calcd for C H MoNO SiNa 552.1227, found
NH
+
days at room temperature, 3 reacted completely to give 5a (69%) and
isobutene (50%) along with unidentified minor products. Isobutene
was identified by spectral comparison with an authentic sample.
27
33
2
+
552.1230 [M + Na] .
NMR Tube Reaction of 3 with EtNH . On a vacuum line,
2
2
t
Cp*Mo(CO) (κ -N,Si- BuHNSiPh ) (5a). On a vacuum line, a
benzene-d (0.5 mL) and EtNH (27 μmol) was vacuum-transferred
2
2
6
2
t
toluene solution (2 mL) of BuNH (0.953 mmol) was placed in a
into an NMR tube containing 3 (11 mg, 21 μmol) with cooling in a
liquid nitrogen bath, and the tube was flame-sealed under vacuum. The
2
reaction flask containing 3 (100 mg, 0.191 mmol) cooled to −70 °C.
The mixture was warmed to room temperature with stirring. After 2
days at room temperature, the volatiles were removed under vacuum.
The residual solid was washed with pentane (3 × 1.5 mL) to give 5a as
1
reaction was periodically monitored by H NMR spectroscopy. After 1
day at room temperature, 4c, 5c, and isobutene were observed in 63%,
25%, and 23% yields, respectively. When the mixture was heated to 50
°C, complete conversion of 4c to 5c was observed after 1 day.
1
an air-sensitive yellow powder (55 mg, 53%). H NMR (400 MHz,
t
2
i
C D ): δ 0.90 (s, 9H, Bu), 1.00 (s, 1H, NH), 1.62 (s, 15H, Cp*),
Cp*Mo(CO) (κ -N,C-EtHNSiPh CH Pr) (4c). On a vacuum line,
6
6
2
2
7
.05−7.20 (m, 6H, Ph), 7.53−7.59 (m, 2H, Ph), 8.02−8.08 (m, 2H,
Ph). C{ H} NMR (100 MHz, C D ): δ 10.8 (C Me ), 31.9 (CMe ),
toluene (3 mL) and EtNH (0.21 mmol) were vacuum-transferred
2
13
1
6
6
5
5
3
into a reaction flask containing 3 (75 mg, 0.14 mmol) with cooling in a
liquid nitrogen bath. The mixture was thawed at −70 °C and then
warmed to room temperature with stirring. After 15 min, the volatiles
were removed under vacuum, and the residual solid was washed with
pentane (2 × 1.5 mL) to give 4c as an air-sensitive orange powder (47
5
7.0 (CMe ), 102.1 (C Me ), 127.9, 128.4, 129.2, 130.7, 133.4, 133.5,
3 5 5
29
1
1
37.0, 139.4 (Ph), 235.4 (CO), 242.2 (CO). Si{ H} NMR (79 MHz,
C D ): δ 7.5 (s). IR (KBr, cm ): 1865 (m, νCO), 1784 (s, νCO). The
−1
6
6
NH stretching absorption was not observed definitely. HRMS: m/z
+
+
1
calcd for C H MoNO SiNa 566.1383, found 566.1387 [M + Na] .
mg, 58%). Mp: 151−152 °C dec. H NMR (400 MHz, C D ): δ
28
35
2
7
8
i
NMR Tube Reaction of 3 with PrNH . On a vacuum line,
benzene-d (0.5 mL) and PrNH (76 μmol) were vacuum-transferred
−0.15 (br d, J = ca. 6 Hz, 1H, MoNH), 0.24 (d, 1H, J = 9.2 Hz,
MoCH), 0.64 (t, 3H, J = 7.0 Hz, NCH Me), 1.07 (d, 3H, J = 6.4 Hz,
2
i
6
2
2
into an NMR tube containing 3 (8.0 mg, 15 μmol) with cooling in a
liquid nitrogen bath, and the tube was flame-sealed under vacuum. The
reaction was periodically monitored by H NMR spectroscopy. After 1
CHMeMe), 1.12 (d, 3H, J = 6.4 Hz, CHMeMe), 1.63 (s, 15H, Cp*),
2.36 (m, 1H, NCHHMe), 2.57 (m, 1H, NCHHMe), 2.76 (dqq, J =
1
9.2, 6.4, 6.4 Hz, 1H, CHMe ), 7.15−7.35 (m, 6H, Ph), 7.52−7.58 (m,
2
13
1
day at room temperature, 3 disappeared to form 5b (91%) and
2H, Ph), 8.13−8.20 (m, 2H, Ph). C{ H} NMR (150 MHz, C D ,
7
8
isobutene (69%). In the reaction using 3 (8.0 mg, 15 μmol) and
−30 °C): δ 11.5 (C Me ), 16.0 (MoCH), 20.6 (NCH Me), 29.0
5
5
2
i
PrNH (20 μmol), 5b (91%) and isobutene (68%) were observed
(CCHMeMe), 31.9 (CCHMeMe), 33.5 (CCHMe ), 47.9 (NCH Me),
2
2 2
after 1 day.
104.5 (C Me ), 129.1, 131.6, 131.7, 134.8, 138.4, 144.0 (Ph), 258.0
5 5
2
i
i
Cp*Mo(CO) (κ -N,C- PrHNSiPh CH Pr) (4b). On a vacuum line, a
(CO), 265.9(CO). Several aromatic carbon signals were not assigned
2
2
29
1
toluene solution (2 mL) of Ph HSiCHCMe (38 mg, 0.16 mmol)
due to their overlap with solvent signals. Si{ H} NMR (119 MHz,
2
2
−
1
was placed in a reaction flask containing Cp*Mo(CO) (py)Me (50
C D , −30 °C): δ 9.2. IR (KBr, cm ): 1898 (s, νCO), 1799 (s, νCO).
2
7
8
mg, 0.13 mmol) cooled to −70 °C. The mixture was warmed to room
temperature with stirring. After 90 min at room temperature, the
volatiles were removed under vacuum. The residual solid was washed
The NH stretching absorption was not observed definitely. HRMS: m/
z calcd for C H MoNO SiNa 594.1696, found 594.1700 [M +
+
30
39
2
+
Na] .
2
with pentane (2 × 1 mL) to leave crude 3, to which toluene (1.5 mL)
Cp*Mo(CO) (κ -N,Si-EtHNSiPh ) (5c). On a vacuum line,
2
2
i
and PrNH (0.46 mmol) were vacuum-transferred with cooling in a
toluene-d8 (0.5 mL) was vacuum-transferred into an NMR tube
containing 4c (30 mg, 0.053 mmol) with cooling in a liquid nitrogen
bath. The tube was flame-sealed under vacuum and then heated to 50
°C for 20 h. In a glovebox, the volatiles were removed under vacuum
2
liquid nitrogen bath. The mixture was thawed at −70 °C and warmed
to room temperature. After the mixture was stirred for 8 min, the
volatiles were removed under vacuum. The residue was washed with
1
035
DOI: 10.1021/om500996r
Organometallics 2015, 34, 1029−1037

Organometallics
Article
and the residue was washed with pentane (2 × 1 mL) to give 5c as an
air-sensitive yellow powder (18 mg, 66%). 1H NMR (400 MHz,
C D ): δ 0.13 (t, 1H, J = 7.2 Hz, NH), 0.73 (t, 3H, J = 7.1 Hz,
in Table S1 in the Supporting Information. The structure
determination of 7 is also described in the Supporting Information.
7
8
NCH Me), 1.65 (s, 15H, Cp*), 2.32 (dq, 1H, J = 7.2, 7.1 Hz,
ASSOCIATED CONTENT
Supporting Information
Text, figures, tables, and CIF files giving H and C{ H} NMR
spectra of new compounds, selected X-ray crystallographic data
of 3, 4c, and 5b, and the structure determination of 7. This
material is available free of charge via the Internet at http://
pubs.acs.org.
2
■
NCHHMe), 2.59 (dq, 1H, J = 7.2, 7.1 Hz, NCHHMe), 7.12−7.23 (m,
*
S
1
3
1
6
H, Ph), 7.52−7.57 (m, 2H, Ph), 7.89−7.94 (m, 2H, Ph). C{ H}
1
13
1
NMR (100 MHz, C D ): δ 10.8 (C Me ), 19.2 (NCH Me), 50.8
7
8
5
5
2
(
1
NCH Me), 102.4 (C Me ), 128.3, 128.4, 129.5, 130.7, 132.7, 134.2,
2 5 5
29
1
35.5, 138.2 (Ph), 235.2 (CO), 240.2 (CO). Si{ H} NMR (79 MHz,
−1
C D ): δ 10.8. IR (KBr, cm ) 3302 (w, ν ), 1876 (m, νCO), 1798 (s,
νCO). HRMS: m/z calcd for C H MoNO SiNa 538.1070, found
5
7
8
NH
+
26
31
2
+
38.1071 [M + Na] .
NMR Tube Reaction of 5b with MeOH. On a vacuum line,
AUTHOR INFORMATION
Corresponding Author
E-mail for H.S.: sakaba@m.tohoku.ac.jp.
■
*
benzene-d (0.5 mL) and MeOH (112 μmol) were vacuum-transferred
6
into an NMR tube containing 5b (7 mg, 14 μmol) with cooling in a
liquid nitrogen bath, and the tube was flame-sealed under vacuum. The
1
reaction was periodically monitored by H NMR spectroscopy. After 4
Notes
h at room temperature, 91% of 5b was consumed and 7 (34%),
The authors declare no competing financial interest.
i
i
PrHNSiPh (OMe) (11%), PrNH (48%), Ph Si(OMe) (36%), and
2
2
2
2
H were detected along with unidentified products. After 1 day 5b and
REFERENCES
2
■
i
i
PrHNSiPh (OMe) disappeared, and the yields of PrNH2 and
2
(
1) For example, see: (a) Hegedus, L. S.; Soderberg, B. C. G.
i
Ph Si(OMe) were increased to 97% and 74%, respectively. PrHNSi-
Ph (OMe), PrNH , Ph Si(OMe) , and H were identified by spectral
2
2
Transition Metals in the Synthesis of Complex Organic Molecules, 3rd ed.;
University Science Books: Saualito, CA, 2010; Chapter 9. (b) Bates, R.
Organic Synthesis Using Transition Metals, 2nd ed.; Wiley: New York,
2012; Chapter 9. (b) Hartwig, J. F. Organotransition Metal Chemistry:
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010; Chapters 3, 11, and 12.
2) (a) Dysard, J. M.; Tilley, T. D.; Woo, T. K. Organometallics 2001,
0, 1195. (b) Sakaba, H.; Watanabe, S.; Kabuto, C.; Kabuto, K. J. Am.
Chem. Soc. 2003, 125, 2842. (c) Fasulo, M. E.; Calimano, E.;
Buchanan, J. M.; Tilley, T. D. Organometallics 2013, 32, 1016.
(3) Ray, M.; Nakao, Y.; Sato, H.; Sakaki, S. Organometallics 2007, 26,
4413.
(4) Ray, M.; Nakao, Y.; Sato, H.; Sakaba, H.; Sakaki, S.
Organometallics 2009, 28, 65.
(5) Yabe-Yoshida, M.; Kabuto, C.; Kabuto, K.; Kwon, E.; Sakaba, H.
J. Am. Chem. Soc. 2009, 131, 9138.
(6) Sakaba, H.; Oike, H.; Kawai, M.; Takami, M.; Kabuto, C.; Ray,
M.; Nakao, Y.; Sato, H.; Sakaki, S. Organometallics 2011, 30, 4515.
7) Hirotsu, M.; Nunokawa, T.; Ueno, K. Organometallics 2006, 25,
1554.
(8) Sheldrick, W. S. The Chemistry of Organic Silicon Compounds;
Wiley: New York, 1989; Chapter 3.
(9) (a) Brook, A. G.; Brook, M. A. Adv. Organomet. Chem. 1996, 39,
71. (b) Brook, M. A. Silicon in Organic, Organometallic, and Polymer
Chemistry; Wiley: New York, 2000, Chapter 2.
(10) Ariafard, A.; Bi, S.; Lin, Z. Organometallics 2005, 24, 2241 and
references therein.
(11) (a) Campion, B. K.; Heyn, R. H.; Tilley, T. D. J. Am. Chem. Soc.
1988, 110, 7558. (b) Koloski, T. S.; Carroll, P. J.; Berry, D. H. J. Am.
Chem. Soc. 1990, 112, 6405. (c) Campion, B. K.; Heyn, R. H.; Tilley,
T. D. J. Am. Chem. Soc. 1990, 112, 4079. (d) Campion, B. K.; Heyn, R.
H.; Tilley, T. D.; Rheingold, A. L. J. Am. Chem. Soc. 1993, 115, 5527.
i
2
2
2
2
2
comparison with authentic samples.
Cp*(CO) Mo(μ-OMe)(μ-H)Mo(CO) Cp*(7). On a vacuum line,
2
2
MeOH (4 mL) was placed in a reaction flask containing 5b (100 mg,
.195 mmol), and the mixture was stirred for 30 min at room
0
2
(
2
temperature. After removal of volatiles under vacuum, the residue was
washed with hexane (3 × 2 mL) to give 7 as an air-sensitive brownish
1
yellow powder (42 mg, 71%). Mp: 230−232 °C dec. H NMR (400
MHz, C D ): δ −7.80 (s, 1H, MoH), 1.71 (s, 30H, Cp*), 3.89 (s, 3H,
6
6
1
3
1
OMe). C{ H} NMR (150 MHz, C D ): δ 11.1 (C Me ), 70.2
6
6
5
5
−1
(
1
OMe), 107.0 (C Me ), 257.4 (CO), 259.4 (CO). IR (toluene, cm ):
5 5
+
921 (s, νCO), 1837 (s, ν ). HRMS: [M − CH O] m/z calcd for
CO
4
+
C H Mo O 578.0247, found 578.0260.
2
4
30
2
4
i
i
PrHNSiPh (OMe). To a solution of PrNH (0.520 g, 8.80 mmol)
2
2
in Et O (10 mL) was added dropwise a solution of Ph Si(OMe)Cl
2
2
(
1.03 g, 4.14 mmol) in Et O (2 mL) at room temperature. After the
2
mixture was stirred for 1 h, the resulting salt was removed by filtration.
i
Distillation of the mixture under reduced pressure gave PrHNSi-
(
Ph (OMe) as a pale yellow oil (bp 140−145 °C at 0.2 Torr, 0.412 g,
2
1
3
7%). H NMR (400 MHz, C D ): δ 0.98 (d, 6H, J = 6.4 Hz,
6 6
CHMe ), 1.22 (br d, 1H, J = 10.0 Hz, NH), 3.12 (d of sept, 1H, J =
2
1
7
0.0, 6.4 Hz, CHMe ), 3.54 (s, 3H, OMe), 7.17−7.25 (m, 6H, Ph),
2
13 1
.77−7.83 (m, 4H, Ph). C{ H} NMR (100 MHz, C D ): δ 27.6
6
6
(
(
3
CHMe ), 43.1 (CHMe ), 50.1 (OMe), 128.1, 130.0, 135.3, 135.6
2
2
Ph). 29Si{ H} NMR (79 MHz, C D ): δ −25.6. IR (neat, cm ):
1
−1
6
6
+
395 (w, ν ), 1124 (s, ν ). HRMS: [M + H] calcd for
NH
SiO
+
C H NOSi 272.1465, found 272.1465.
16
22
i
NMR Tube Reaction of PrHNSiPh (OMe) with MeOH. On a
2
vacuum line, benzene-d6 (0.5 mL) and MeOH (85 μmol) were
i
vacuum-transferred into an NMR tube containing PrHNSiPh (OMe)
2
(
17 μmol) with cooling in a liquid nitrogen bath, and the tube was
flame-sealed under vacuum. The reaction was periodically monitored
(
3
e) Klei, S. R.; Tilley, T. D.; Bergman, R. G. Organometallics 2001, 20,
220.
(12) King, R. B.; Iqbal, M. Z.; King, A. D., Jr. J. Organomet. Chem.
1
by H NMR spectroscopy. After 2 h at room temperature, 85% of
i
i
PrHNSiPh (OMe) was consumed, and PrNH and Ph Si(OMe)2
2
2
2
were observed in 98% and 95% yield, respectively, on the basis of the
conversion of the starting material. The products were identified by
spectral comparison with authentic samples.
1979, 171, 53.
(13) Unique reversible α-silyl migration between a metal and a
carbene ligand has been found in ruthenium amidinato-carbene
complexes: Hayashida, T.; Nagashima, H. Organometallics 2001, 20,
4996.
(14) For alkylidene-to-alkene ligand isomerization in group 6
transition-metal complexes, see: (a) Fischer, E. O.; Held, W. J.
Organomet. Chem. 1976, 112, C59. (b) Casey, C. P.; Albin, L. D.;
Burkhardt, T. J. J. Am. Chem. Soc. 1977, 99, 2533. (c) Winter, M. J.;
Woodward, S. Chem. Commun. 1989, 457.
X-ray Crystal Structure Determination. Single crystals of 3, 4c,
and 5b were obtained by recrystallization from toluene/pentane,
toluene/hexane, and toluene/pentane, respectively. The diffraction
data were collected on a Rigaku Saturn70 with graphite-monochro-
mated Mo Kα radiation at 150 K for 3 and 173 K for 4c and 5b. The
27
structures were solved by direct methods, SHELXS-97 for 3 and 4c
28
and SIR2004 for 5b, and refined by full-matrix least-squares
27
procedures (SHELXL-97). The non-hydrogen atoms were refined
anisotropically, and hydrogen atoms were refined using the riding
model. Selected crystallographic data of 3, 4c, and 5b are summarized
(15) Horton, A. D.; Orpen, A. G. Organometallics 1992, 11, 1193.
(16) Watanabe, T.; Hashimoto, H.; Tobita, H. J. Am. Chem. Soc.
2006, 128, 2176.
1
036
DOI: 10.1021/om500996r
Organometallics 2015, 34, 1029−1037

Organometallics
Article
(
17) For example,
δ 0.68 for the NH proton of
CH (CH ) NHSiPh Me: Takaki, K.; Kamata, T.; Miura, Y.;
3
2
4
2
Shishido, T.; Takehira, K. J. Org. Chem. 1999, 64, 3891.
18) Ueno, K.; Masuko, A.; Ogino, H. Organometallics 1999, 18,
694.
19) Cordero, B.; Gomez, V.; Platero-Prats, A. E.; Reves, M.;
Echeverria, J.; Cremades, E.; Barragan, F.; Alvarez, S. Dalton Trans.
008, 2832.
20) Okazaki, M.; Yoshitomi, T.; Naito, J.; Sato, A.; Komuro, T.;
Tobita, H. J. Am. Chem. Soc. 2008, 130, 17674.
21) Schollhammer, P.; Petillon, F. Y.; Pichon, R.; Poder-Guillou, S.;
Talarmin, J.; Muir, K. W.; Girdwood, S. E. J. Organomet. Chem. 1995,
86, 183.
22) For recent reviews on silylene complexes, see: (a) Eisen, M. S.
(
2
(
2
(
(
́
4
(
In The Chemistry of Organic Silicon Compounds; Rappoport, Z.,
Apeloig, Y., Eds.; Wiley: New York, 1998; Vol. 2, Chapter 35.
(
b) Ogino, H. Chem. Rec. 2002, 2, 291. (c) Okazaki, M.; Tobita, H.;
Ogino, H. Dalton Trans. 2003, 493. (d) Waterman, R.; Hayes, P. G.;
Tilley, T. D. Acc. Chem. Res. 2007, 40, 712.
(
23) Si−P bond cleavage in reactions of the Fe−Si−P three-
2
membered ring complex Cp*(CO)Fe(κ -P,Si-Ph PSiMe ) with
2
2
alcohols has been reported: Okazaki, M.; Jung, K. A.; Tobita, H.
Organometallics 2005, 24, 659.
(
24) Alt, H. G.; Eichner, M. E. Angew. Chem., Int. Ed. Engl. 1982, 21,
05.
25) Ohshita, J.; Taketsugu, R.; Nakahara, Y.; Kunai, A. J. Organomet.
Chem. 2004, 689, 3258.
2
(
(
(
26) Lee, M.; Ko, S.; Chang, S. J. Am. Chem. Soc. 2000, 122, 12011.
27) (a) Sheldrick, G. M. SHELX-97, Programs for Crystal Structure
Analysis; University of Go
b) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112.
28) SIR2004: Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini,
̈ ̈
ttingen, Gottingen, Germany, 1997.
(
(
B.; Cascarano, G. L.; De Caro, L.; Giacovazzo, C.; Polidori, G.;
Spagna, R. J. Appl. Crystallogr. 2005, 38, 381.
1
037
DOI: 10.1021/om500996r
Organometallics 2015, 34, 1029−1037