Synthesis and characterization of -2 C,N-N -silyliminoacyl tungsten complexes Cp*(CO)2W{-2 C,N -C(R) - NsiR-3} [R = Me, Et, i -Pr, t -Bu; R'3 = (p -Tol) 2Me, (p -Tol)3, Et3; Cp* = - 5-C5Me5]: Thermally induced carbon-carbon bond cleavage of their iminoacyl ligands

Article abstract of DOI:10.1021/om901123w

DMAP-stabilized (p-tolyl)(silylene) complexes Cp*(CO) ₂W(p-Tol){-Si(p-Tol)R′-DMAP} [1a, R′ = Me; 1b, R′ = p-Tol; DMAP = 4-(dimethylamino)pyridine] reacted with excess nitrile RCN (R = Me, Et, i-Pr, t-Bu) in toluene to give k²C,N-N-silyliminoacyl tungsten complexes Cp*(CO)₂W{k²C,N-C(R)-NSi(p-Tol) ₂R′} (2a, R = Me, R′ = Me; 2b, R = Et, R′ = Me; 2c, R = i-Pr, R′ = Me; 2d, R = t-Bu, R′ = Me; 3a, R = Me, R′ = p-Tol; 3b, R = Et, R′ = p-Tol; 3c, R = i-Pr, R′ = p-Tol; 3d, R = t-Bu, R′ = p-Tol). This reaction proceeds through 1,2-migration of a p-tolyl group from a tungsten center to a silylene ligand. Complexes 3a and 3b and similar complexes Cp*(CO)₂W{-²C,N-C(R)- NSiEt₃} (4a, R = Me; 4b, R = Et) were also synthesized by reactions of methyl(nitrile) complexes Cp*(CO)₂W(NCR)Me (A, R = Me; B, R = Et) with hydrosilanes HSiR′₃ (R′ = p-Tol, Et). A kinetic study on the dynamic process of 2c involving inversion of the chiral tungsten center reveals that the inversion can occur via dissociation of the iminoacyl nitrogen atom coordinating to the tungsten center. Thermal reaction of a toluene solution of N-silyliminoacyl complexes 3a and 3b at 120 °C in a sealed tube gave a cis/trans mixture of alkyl(silylisocyanide) complexes cis/trans-Cp*(CO)₂W(R){CNSi(p-Tol)₃} (5a, R = Me; 5b, R = Et) through cleavage of the C-C bond between the iminoacyl carbon and the alkyl substituent R in 3a or 3b. The molecular structures of 3b and cis-5b were determined by X-ray crystallography.

Full text of DOI:10.1021/om901123w

Organometallics 2010, 29, 1839–1848 1839
DOI: 10.1021/om901123w
Synthesis and Characterization of K2C,N-N-Silyliminoacyl Tungsten
Complexes Cp*(CO)2W{K2C,N-C(R)dNSiR03} [R = Me, Et, i-Pr, t-Bu;
R03 = (p-Tol)2Me, (p-Tol)3, Et3; Cp* = η5-C5Me5]: Thermally Induced
Carbon-Carbon Bond Cleavage of Their Iminoacyl Ligands
Eiji Suzuki,† Takashi Komuro,† Yuto Kanno,† Masaaki Okazaki,‡ and Hiromi Tobita*,†
†Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578,
Japan, and ‡Department of Frontier Materials Chemistry, Graduate School of Science and Technology,
Hirosaki University, Hirosaki, Aomori 036-8560, Japan
Received December 26, 2009
DMAP-stabilized (p-tolyl)(silylene) complexes Cp*(CO)2W(p-Tol){dSi(p-Tol)R0 DMAP} [1a, R0 =
3
Me; 1b, R0 = p-Tol; DMAP = 4-(dimethylamino)pyridine] reacted with excess nitrile RCN (R = Me, Et,
i-Pr, t-Bu) in toluene to give κ2C,N-N-silyliminoacyl tungsten complexes Cp*(CO)2W{κ2C,N-C(R)dNSi-
(p-Tol)2R0} (2a, R = Me, R0 = Me; 2b, R=Et, R0 = Me; 2c, R=i-Pr, R0 = Me; 2d, R=t-Bu, R0=Me;
3a, R=Me, R0=p-Tol; 3b,R=Et, R0 =p-Tol; 3c, R=i-Pr, R0 =p-Tol; 3d,R=t-Bu, R0=p-Tol). This
reaction proceeds through 1,2-migration of a p-tolyl group from a tungsten center to a silylene ligand.
Complexes 3a and 3b and similar complexes Cp*(CO)2W{κ2C,N-C(R)dNSiEt3} (4a, R = Me; 4b, R=
Et) were also synthesized by reactions of methyl(nitrile) complexes Cp*(CO)2W(NCR)Me (A, R = Me;
B, R = Et) with hydrosilanes HSiR03 (R0 = p-Tol, Et). A kinetic study on the dynamic process of 2c
involving inversion of the chiral tungsten center reveals that the inversion can occur via dissociation of the
iminoacyl nitrogen atom coordinating to the tungsten center. Thermal reaction of a toluene solution of
N-silyliminoacyl complexes 3a and 3b at 120 °C in a sealed tube gave a cis/trans mixture of alkyl-
(silylisocyanide) complexes cis/trans-Cp*(CO)2W(R){CNSi(p-Tol)3} (5a, R = Me; 5b, R = Et) through
cleavage of the C-C bond between the iminoacyl carbon and the alkyl substituent R in 3a or 3b. The
molecular structures of 3b and cis-5b were determined by X-ray crystallography.
Introduction
activation of acetonitrile by a silyl iron complex Cp(CO)2FeSi-
Me3 under photoirradiation.3 Our group investigated related
C-C bond cleavage reactions of nitriles induced by silylene com-
plexes, i.e., the reaction of a silyl(silylene)iron complex Cp*(CO)-
Fe(dSiMes2)SiMe3 with RCN (R = Me, Ph)4a and the reaction
of a hydrido(hydrosilylene)ruthenium complex Cp*(CO)(H)-
RudSi(H){C(SiMe3)3} withRCN(R=Me,Ph).4b In the former
reaction, a possible mechanism involves the reaction sequence as
follows: 1,2-migration of a silyl ligand from a metal center to a
silylene silicon atom to generate 16-electron silyl complexes,
coordination of nitrile, and insertion of the nitrile ligand into a
M-Si bond to form N-silyliminoacyl complexes.4a A few cata-
lytic reactions involving C-C bond cleavage of nitriles via N-sily-
liminoacyl intermediates were also developed recently. Nakazawa
and co-workers discovered the C-C bond cleavage reactions
of nitriles RCN with Et3SiH catalyzed by iron complexes to
afford RH and Et3SiCN.5 Chatani and co-workers reported
rhodium-catalyzed silylation of nitriles using disilanes via
κ2C,N-N-Silyliminoacyl complexes are attracting consid-
erable attention recently as crucial intermediates in the C-C
bond cleavage of nitriles by transition-metal silyl complexes.1
This type of cleavage reaction can be applied to organic synthesis,
where nitrile is used as a starting material. The C-C bond
cleavage of an iminoacyl ligand in N-silyliminoacyl complexes
easily occurs to give silylisocyanide complexes having an alkyl or
an aryl ligand. A pioneering study on the C-C bond cleavage of
nitriles mediated by N-silyliminoacyl complexes was reported by
Bergman, Brookhart, and co-workers: the reaction of a cationic
silyl rhodium complex [Cp*(PMe3)Rh(SiPh3)(CH2Cl2)]BAr04
[Ar0 = 3,5-(CF3)2C6H3] with nitriles RCN [R = Ph, 4-(CF3)-
C6H4, 4-(MeO)C6H4, Me, i-Pr, t-Bu] produced silylisocyanide
complexes [Cp*(PMe3)Rh(CNSiPh3)(R)]BAr04 through κ2C,N-
N-silyliminoacyl complexes [Cp*(PMe3)Rh{κ2C,N-C(R)dNSi-
Ph3}]BAr04, which have only been observed and isolated at low
temperature.2 Nakazawa and co-workers independently pro-
posed that an N-silyliminoacyl iron complex Cp(CO)Fe{κ2C,
N-C(Me)dNSiMe3} works as an intermediate in the C-C bond
(3) Nakazawa, H.; Kawasaki, T.; Miyoshi, K.; Suresh, C. H.; Koga,
N. Organometallics 2004, 23, 117.
(4) (a) Hashimoto, H.; Matsuda, A.; Tobita, H. Organometallics
2006, 25, 472. (b) Ochiai, M.; Hashimoto, H.; Tobita, H. Angew. Chem.,
Int. Ed. 2007, 46, 8192.
(5) (a) Nakazawa, H.; Kamata, K.; Itazaki, M. Chem. Commun. 2005,
4004. (b) Itazaki, M.; Nakazawa, H. Chem. Lett. 2005, 34, 1054.
(c) Nakazawa, H.; Itazaki, M.; Kamata, K.; Ueda, K. Chem. Asian J.
2007, 2, 882.
*To whom correspondence should be addressed. Tel: þ81-22-795-
6539. Fax: þ81-22-795-6543. E-mail: tobita@m.tains.tohoku.ac.jp.
(1) Tobisu, M.; Chatani, N. Chem. Soc. Rev. 2008, 37, 300.
(2) (a) Taw, F. L.; White, P. S.; Bergman, R. G.; Brookhart, M.
J. Am. Chem. Soc. 2002, 124, 4192. (b) Taw, F. L.; Mueller, A. H.; Bergman,
R. G.; Brookhart, M. J. Am. Chem. Soc. 2003, 125, 9808.
r
2010 American Chemical Society
Published on Web 03/17/2010
pubs.acs.org/Organometallics

1840 Organometallics, Vol. 29, No. 7, 2010
Suzuki et al.
C-CN bond cleavage to form a C-Si bond.6 However, there
are limited examples of the isolation and full-characteriza-
tion of N-silyliminoacyl complexes because they are usually
thermally unstable.
high temperature. A part of this work has been published as a
preliminary report.11
Results and Discussion
Known κ2C,N-N-silyliminoacyl complexes are mostly de-
rived from a nitrile(silyl) complex through insertion of nitrile
into a metal-silicon bond. For example, Bergman, Brookhart,
and co-workers succeeded in the synthesis and the character-
ization of a κ2C,N-N-silyliminoacyl complex [Cp*(PMe3)-
Rh{κ2C,N-C(4-(OMe)C6H4)dNSiPh3}]BAr04 by the thermal
rearrangement of a nitrile(silyl) complex [Cp*(PMe3)Rh(Si-
Ph3){NC(4-(OMe)C6H4)}]BAr04 below room temperature.2b
We also recently reported the synthesis of an N-silyliminoacyl
complex Cp*(CO)(H)W{κ3C,N,Si-C(t-Bu)dN(xantsil)} by
the reaction of a tungsten complex containing a hemilabile
κ3Si,Si,O-bis(silyl) ligand (xantsil), namely, Cp*(CO)(H)W-
(κ3Si,Si,O-xantsil), with t-BuCN.7 This reaction is presumed
to proceed through formation of a nitrile(silyl) complex by
dissociation of the labile oxygen in the κ3Si,Si,O-xantsil ligand
and coordination of nitrile. In this work, we applied the
insertion reaction in nitrile(silyl) complexes to the synthesis of
a new series of N-silyliminoacyl complexes.
Synthesis of K2C,N-N-Silyliminoacyl Complexes. Method
1: Reactions of Silylene Complexes Cp*(CO)2W(p-Tol)-
{dSi(p-Tol)R0 DMAP} (1a, R0 = Me; 1b, R0 = p-Tol) with
Nitriles. DMAP-stabilized (p-tolyl)(silylene)tungsten com-
3
plexes Cp*(CO)2W(p-Tol){dSi(p-Tol)R0 DMAP} (1a, R0 =
3
Me; 1b, R0=p-Tol)8 reacted with excess nitrile RCN (R=Me,
Et, i-Pr, t-Bu) in toluene to give κ2C,N-N-silyliminoacyl com-
plexes Cp*(CO)2W{κ2C,N-C(R)dNSi(p-Tol)2R0} (2a, R =
Me, R0 =Me; 2b, R=Et, R0 =Me; 2c, R=i-Pr, R0 =Me; 2d,
R=t-Bu, R0 =Me; 3a, R=Me, R0 =p-Tol; 3b, R=Et, R0 =
p-Tol; 3c, R = i-Pr, R0 = p-Tol; 3d, R = t-Bu, R0 =p-Tol)
(eq 1). To isolate complexes 2a-d and 3a-d from the reaction
mixture, the Lewis acid BPh3 was added to the mixture to form
the adduct DMAP BPh3 with the byproduct DMAP. After
3
filtration of DMAP BPh3, which was sparingly soluble
3
in hexane, 2a-d and 3a-d were isolated from the filtrate in
58-91% yields. A possible formation mechanism of 2a-d and
3a-d is depicted in Scheme 1. The mechanism involves (i) 1,2-
migration of a p-tolyl group in 1a and 1b from a tungsten center
to a silylene silicon atom to generate a 16-electron silyl complex
Cp*(CO)2W{Si(p-Tol)2R0} (C),8,10 (ii) coordination of nitrile
to tungsten in complex C to form a nitrile(silyl) complex D, and
(iii) insertion of nitrile into a W-Si bond in complex D
(Scheme 1).
We report here the synthesis of tungsten complexes com-
posed of a Cp*(CO)2W moiety and a κ2C,N-N-silyliminoacyl
ligand by the reaction involving insertion of nitrile into a
W-Si bond in a nitrile(silyl) complex. The N-silyliminoacyl
complexes have sufficient stability to be isolated and char-
acterized. To synthesize the N-silyliminoacyl complexes via a
nitrile(silyl) complex, we employed two methods: (1) the reac-
tion of base-stabilized aryl(silylene) complexes Cp*(CO)2W-
(p-Tol){dSi(p-Tol)R0 DMAP} [1a, R0 = Me;1b, R0 = p-Tol;
3
DMAP = 4-(dimethylamino)pyridine]8 with nitriles RCN
(R = Me, Et, i-Pr, t-Bu) and (2) the reaction of methyl(nitrile)
complexes Cp*(CO)2W(NCR)Me (A, R = Me;9 B, R = Et)
with tertiary silanes HSiEt3 and HSi(p-Tol)3. In method 1, we
employed 1,2-migration of an aryl group from tungsten to
silicon in complexes 1a and 1b to generate 16-electron silyl
complexes Cp*(CO)2W{Si(p-Tol)2R0} (C),8,10 whichcan react
with nitrile to form nitrile(silyl) complexes. In method 2, we
used complex A or B as a precursor of nitrile(silyl) complexes,
because the RCN ligand is known to be labile, which facil-
itates the Si-H oxidative addition of hydrosilanes.9 After this
oxidative addition, reductive elimination of methane and
coordination of nitrile are supposed to occur to generate
nitrile(silyl) complexes. We also report here a thermal C-C
bond cleavage reaction of some of the N-silyliminoacyl com-
plexes to give the corresponding silylisocyanide complexes at
Method 2: Reactions of Cp*(CO)2W(NCR)Me (A, R =
Me; B, R = Et) with HSiR03 (R0 = p-Tol, Et). A methyl-
(propiononitrile)tungsten complex Cp*(CO)2W(NCEt)Me
(B), a precursor of N-silyliminoacyl complexes in this re-
search, was synthesized according to the method analogous
to that for the synthesis of the acetonitrile(methyl) complex
Cp*(CO)2W(NCMe)Me (A).9 Thus, irradiation of Cp*-
(CO)3WMe in propiononitrile with a 450 W medium-pres-
sure Hg lamp (λ>300 nm) led to the dissociation of a CO
ligand followed by coordination of EtCN to give complex B
(eq 2). Complex B is thermally unstable in C6D6 at room
temperature but has enough stability to be characterized by
NMR and IR spectroscopy. The 13C{1H} NMR spectrum of
B shows a signal assignable to the nitrile carbon at 138.7 ppm
and a signal assignable to the methyl ligand at -11.7 ppm
with 183W satellites [JWC = 45 Hz]. In the IR spectrum of B, a
(6) (a) Tobisu, M.; Kita, Y.; Chatani, N. J. Am. Chem. Soc. 2006, 128,
8152. (b) Tobisu, M.; Kita, Y.; Ano, Y.; Chatani, N. J. Am. Chem. Soc. 2008,
130, 15982.
(7) Begum, R.; Komuro, T.; Tobita, H. Chem. Commun. 2006, 432.
(8) (a) Suzuki, E.; Okazaki, M.; Tobita, H. Chem. Lett. 2005, 34,
1026. (b) Suzuki, E.; Komuro, T.; Okazaki, M.; Tobita, H. Organometallics
2009, 28, 1791.
(9) (a) Sakaba, H.; Ishida, K.; Horino, H. Chem. Lett. 1995, 1145.
(b) Sakaba, H.; Ishida, K.; Horino, H. Chem. Lett. 1998, 149. (c) Sakaba, H.;
Tsukamoto, M.; Hirata, T.; Kabuto, C.; Horino, H. J. Am. Chem. Soc. 2000,
122, 11511. (d) Sakaba, H.; Watanabe, S.; Kabuto, C.; Kabuto, K. J. Am.
Chem. Soc. 2003, 125, 2842. (e) Sakaba, H.; Yoshida, M.; Kabuto, C.;
Kabuto, K. J. Am. Chem. Soc. 2005, 127, 7276. (f) Okazaki, M.; Suzuki, E.;
Miyajima, N.; Tobita, H.; Ogino, H. Organometallics 2003, 22, 4633.
(10) For a recent review on 1,2-migration in transition-metal silylene
complexes, see: Okazaki, M.; Tobita, H.; Ogino, H. Dalton Trans. 2003,
493.
(11) Suzuki, E.; Komuro, T.; Okazaki, M.; Tobita, H. Organometal-
lics 2007, 26, 4379.

Article
Organometallics, Vol. 29, No. 7, 2010 1841
Scheme 1. Possible Formation Mechanism of N-Silyliminoacyl
Complexes 2a-d and 3a-d
(JWC = 104 Hz) for X = Cl, 237.7 ppm (JWC =92Hz) forX=
GeCl3].12 Moreover, these resonances are even more downfield-
shifted than those of κ2C,N-N-alkyliminoacyl tungsten com-
plexes Cp*(CO)2W{κ2C,N-C(Me)dN(R)} [195.5 (R = t-Bu),
195.9 (R = i-Pr) ppm].13 These comparisons imply that the κ2C,
N-iminoacyl carbons of 2-4 have a strong carbene character
due to the contribution of the amido(carbene) canonical struc-
ture F, as illustrated in Scheme 2, which is also supported by the
crystal structure analysis of complexes 3a and 3b (vide infra).
The 29Si{1H} NMR spectra of 2-4 exhibit one resonance of the
silicon in the range from -7.2 to -8.3 ppm for 2a-d, from
-17.9 to -19.9 ppm for 3a-d, and from 15.1 to 15.2 ppm
for 4a,b. The 29Si NMR chemical shifts for 3a-d, where the
Si(p-Tol)3 group is bound to the iminoacyl nitrogen, are similar
to that for the N-silyliminoacyl rhodium complex [Cp*(PMe3)-
Rh{κ2C,N-C(4-(OMe)C6H4)dNSiPh3}]BAr04 (-21.76 ppm).2b
In the IR spectra of 2-4, a band for a CdN stretching of the
iminoacyl ligand is observed in the range 1591-1637 cm-1
.
band for the CN stretching is observed at 2262 cm-1. Two
CO ligands in B were located at mutually cis positions on the
tungsten center on the basis of the observation of two
inequivalent signals (244.1 and 257.3 ppm) assignable to
the CO ligands in the 13C{1H} NMR spectrum. This mu-
tually cis arrangement is also supported by the observation in
the IR spectrum that shows two bands for a symmetric (1911
cm-1) and an asymmetric (1820 cm-1) CO vibration, where
the intensity of the former band is stronger than that of the
latter one.
These values are comparable with that for the N-silyliminoacyl
tungsten complex Cp*(CO)(H)W{κ3C,N,Si-C(t-Bu)dN(xant-
sil)} (1606 cm-1)7 and shifted to lower wavenumbers com-
pared to those of κ2C,N-N-alkyliminoacyl tungsten complexes
Cp*(CO)2W{κ2C,N-C(Me)dN(R)} [1688 (R = t-Bu), 1678
(R = i-Pr) cm-1].13 This reflects the large contribution of
amido(carbene) resonance structure F in 2-4.
Dynamic Behavior of K2C,N-N-Silyliminoacyl Complexes
1
2a-d in Solution. Comparison of the H NMR spectra of
2a-d in C6D6 at room temperature reveals that the signal of
methyl substituents in the two p-tolyl groups changes the
shape dramatically depending on the substituent R on the
iminoacyl carbon: The methyl signal was observed as one
sharp singlet for 2a (2.08 ppm), one broad singlet for 2b (2.07
ppm), and two slightly broadened singlets for 2c (2.06 and
2.09 ppm) and 2d (2.04 and 2.08 ppm). These observations
suggest the existence of a dynamic process involving the
inversion of the chiral tungsten center in 2a-d on the NMR
time scale. This dynamic behavior becomes slower as the
substituent R becomes bulkier and more electron-donating,
because larger steric demand and electron-donating ability
of the substituent R on the iminoacyl carbon disturb dis-
sociation of the iminoacyl nitrogen atom coordinating to the
tungsten center (Scheme 3, vide infra).
The methyl(nitrile) complexes Cp*(CO)2W(NCR)Me (A,
R = Me; B, R = Et) reacted with HSiR03 (R0 = p-Tol, Et) at
room temperature to give the corresponding κ2C,N-N-silyl-
iminoacyl complexes 3a, 3b, and Cp*(CO)2W{κ2C,N-C-
(R)dNSiEt3} (4a, R = Me; 4b, R = Et) (eq 3). In contrast
to method 1 (eq 1), this method (method 2) for synthesizing
κ2C,N-N-silyliminoacyl complexes is applicable to a wider
variety of hydrosilanes such as trialkylsilanes, which usually
do not lead to stable silylene complexes.
In order to clarify how the inversion of the chiral tungsten
center occurs, variable-temperature 1H NMR spectra of 2c in
C6D12 were measured (Figure 1, left). The rate constants k of
the dynamic process were determined by simulation of the
spectra (Figure 1, right).14 The activation parameters of
the inversion were estimated by the Eyring plot (Figure 2):
ΔHq = 98.6(7) kJ mol-1, ΔSq = 92(2) J K-1 mol-1, and
ΔGq298=71(1) kJ mol-1. The large positive value of the acti-
vation entropy implies that the inversion proceeds by a
dissociative mechanism as depicted in Scheme 3. The mecha-
nism consists of dissociation and recoordination of the
iminoacyl nitrogen atom in a κ2C,N-N-silyliminoacyl com-
plex through a κ1-iminoacyl complex in the transition state.
X-ray Crystal Structure of Cp*(CO)2W{K2C,N-C(Et)d
NSi(p-Tol)3} (3b). The X-ray crystal structure of 3a has
Characterization of K2C,N-N-Silyliminoacyl Complexes
2-4. N-Silyliminoacyl complexes 2a-d, 3a-d, and 4a,b were
characterized on the basis of spectroscopy and elemental ana-
lysis. Their 1H, 13C, and 29Si NMR and IR spectra are summa-
rized in Table 1. The 13C{1H} NMR spectra of complexes 2-4
show a signal assignable to the iminoacyl carbon with 183W
satellites [JWC=53-56 Hz] in the range 228.7-249.6 ppm. The
chemical shifts of these resonances are comparable with those of
carbene complexes Cp*(CO)2W{dC(H)NEt2}(X) [243.8 ppm
€
(12) Filippou, A. C.; Portius, P.; Winter, J. G.; Koiciok-Kohn, G.
J. Organomet. Chem. 2001, 628, 11.
(13) Daff, P. J.; Monge, A.; Palma, P.; Poveda, M. L.; Ruiz, C.;
Valerga, P.; Carmona, E. Organometallics 1997, 16, 2263.
(14) Variable-temperature 1H NMR spectra of 2c in C6D12 were
simulated using the gNMR program package: Peter, H. M. gNMR
V4.1.0; Cherwell Scientific: Oxford, U.K., 1999.

1842 Organometallics, Vol. 29, No. 7, 2010
Table 1. 1H, 13C, and 29Si NMR and IR Data for N-Silyliminoacyl Complexes 2a-d, 3a-d, and 4a,b
Suzuki et al.
1H NMR
(300 MHz, C6D6)
13C{1H} NMR
(75.5 MHz, C6D6)
δ/ppm
29Si{1H} NMR
(59.6 MHz, C6D6)
δ/ppm
compound
δ/ppm
IRa ν/cm-1
Cp*(CO)2W[κ2C,N-C(Me)d 0.64 (s, 3H, SiMe),
-2.1 (SiMe), 11.2 (C5Me5),
-8.3
1894 (s, νCOsym),
1793 (s, νCOasym),
1630 (m, νCN)
N{SiMe(p-Tol)2}] (2a)
1.78 (s, 15H, Cp*),
21.4 (C6H4Me), 23.4 (NCMe),
104.5 (C5Me5), 129.2, 130.7 (br),
131.5 (br), 135.2, 140.4 (ArC),
233.9 [JWC(satellite) = 54 Hz,
W-CdN], 242.9, 245.2 (br, CO)
2.08 (s, 6H, C6H4Me),
2.39 (s, 3H, NCMe),
6.96-7.09 (m, 4H, ArH),
7.39-7.57 (m, 4H, ArH)
Cp*(CO)2W[κ2C,N-C(Et)d
N{SiMe(p-Tol)2}] (2b)
0.66 (s, 3H, SiMe),
1.28 (t, J = 7.6 Hz, 3H, CH2Me),
1.79 (s, 15H, Cp*),
2.07 (br s, 6H, C6H4Me),
2.32-2.59 (m, 2H, CH2Me),
6.99-7.06 (m, 4H, ArH),
7.47 (d, J = 7.4 Hz, 2H, ArH),
7.54 (d, J = 7.3 Hz, 2H, ArH)
-2.1 (SiMe), 11.3 (C5Me5),
11.6 (CH2Me), 21.5 (C6H4Me),
30.3 (CH2Me), 104.5 (C5Me5),
129.2, 130.7, 131.6, 135.2,
140.4 (ArC),
240.7 [JWC(satellite) = 55 Hz,
W-CdN],
243.6, 245.1 (CO)
-8.0
1882 (s, νCOsym),
1786 (s, νCOasym),
1630 (m, νCN
)
Cp*(CO)2W[κ2C,N-C(i-Pr)d 0.69 (s, 3H, SiMe),
N{SiMe(p-Tol)2}] (2c)
-1.6 (SiMe), 11.4 (C5Me5),
-7.7
1896 (s, νCOsym),
1793 (s, νCOasym),
1591 (m, νCN)
1.03 (d, J = 6.7 Hz, 3H, CHMeaMeb), 20.1, 20.4 (CHMe2),
1.04 (d, J = 6.7 Hz, 3H, CHMeaMeb), 21.5 (C6H4Me),
1.80 (s, 15H, Cp*),
2.06 (s, 3H, C6H4Me),
2.09 (s, 3H, C6H4Me),
36.5 (CHMe2), 104.7 (C5Me5),
129.17, 129.22, 130.9,
131.8, 135.2, 135.3,
2.93 (sept, J = 6.7 Hz, 1H, CHMe2),
7.00 (d, J = 7.8 Hz, 2H, ArH),
7.05 (d, J = 7.8 Hz, 2H, ArH),
7.49 (d, J = 7.8 Hz, 2H, ArH),
7.55 (d, J = 7.8 Hz, 2H, ArH)
140.3, 140.4 (ArC),
243.7 [JWC(satellite) = 55 Hz,
W-CdN],
244.5, 244.6 (CO)
Cp*(CO)2W[κ2C,N-C(t-Bu)d 0.80 (s, 3H, SiMe), 1.10 (s, 9H, t-Bu), 0.5 (SiMe), 11.4 (C5Me5),
-7.2
1896 (s, νCOsym),
1793 (s, νCOasym),
1601 (m, νCN)
N{SiMe(p-Tol)2}] (2d)
1.81 (s, 15H, Cp*),
2.04 (s, 3H, C6H4Me),
2.08 (s, 3H, C6H4Me),
6.99 (d, J = 7.8 Hz, 2H, ArH),
7.04 (d, J = 7.8 Hz, 2H, ArH),
7.56 (d, J = 7.8 Hz, 2H, ArH),
7.61 (d, J = 7.8 Hz, 2H, ArH)
21.4 (C6H4Me), 28.6 (CMe3),
41.3 (CMe3), 104.5 (C5Me5),
129.0, 129.1, 131.7, 132.1,
135.6, 135.7, 140.2, 140.3 (ArC),
243.9, 244.4 (CO),
247.9 [JWC(satellite) = 54 Hz,
W-CdN]
Cp*(CO)2W[κ2C,N-C(Me)d 1.79 (s, 15H, Cp*), 2.06
11.2 (C5Me5), 21.5 (C6H4Me),
23.9 (NCMe), 104.3 (C5Me5),
129.3, 129.8, 136.3, 140.5 (ArC),
235.2 [JWC(satellite) = 53 Hz,
W-CdN], 242.4, 244.8 (br, CO)
-17.9
-18.9
1896 (s, νCOsym),
1792 (s, νCOasym),
1620 (m, νCN)
N{Si(p-Tol)3}] (3a)
(s, 9H, C6H4Me),
2.49 (s, 3H, NCMe),
7.04 (d, J = 7.7 Hz, 6H, ArH),
7.63 (d, J = 7.7 Hz, 6H, ArH)
Cp*(CO)2W[κ2C,N-C(Et)d
N{Si(p-Tol)3}] (3b)
1.35 (t, J = 7.6 Hz, 3H, CH2Me),
1.81 (s, 15H, Cp*),
2.06 (s, 9H, C6H4Me),
11.3 (C5Me5), 11.8 (CH2Me),
21.5 (C6H4Me), 30.6 (CH2Me),
104.4 (C5Me5), 129.3, 129.8,
136.3, 140.5 (ArC),
242.2 [JWC(satellite) = 55 Hz,
W-CdN], 243.2, 244.7 (br, CO)
1894 (s, νCOsym),
1788 (s, νCOasym),
1599 (m, νCN)
2.48-2.60 (m, 2H, CH2Me),
7.04 (d, J = 7.8 Hz, 6H, ArH),
7.65 (d, J = 7.8 Hz, 6H, ArH)
Cp*(CO)2W[κ2C,N-C(i-Pr)d 1.01 (d, J = 6.6 Hz, 3H, CHMeaMeb), 11.4 (C5Me5), 20.1, 20.8 (CHMe2),
N{Si(p-Tol)3}] (3c) 1.17 (d, J = 6.6 Hz, 3H, CHMeaMeb), 21.5 (C6H4Me),
-19.9
-19.0
15.2
1894 (s, νCOsym),
1793 (s, νCOasym),
1606 (m, νCN)
1.83 (s, 15H, Cp*),
2.06 (s, 9H, C6H4Me),
3.04 (sept, J = 6.6 Hz, 1H, CHMe2),
7.04 (d, J = 7.8 Hz, 6H, ArH),
7.69 (d, J = 7.8 Hz, 6H, ArH)
37.0 (CHMe2), 104.7 (C5Me5),
129.2, 130.0, 136.4, 140.5 (ArC),
244.3 [JWC(satellite) = 182 Hz, CO],
245.3 [JWC(satellite) = 56 Hz,
W-CdN]
Cp*(CO)2W[κ2C,N-C(t-Bu)d 1.15 (s, 9H, t-Bu), 1.79 (s, 15H, Cp*), 11.3 (C5Me5), 21.4 (C6H4Me),
1890 (s, νCOsym),
1784 (s, νCOasym),
1597 (m, νCN)
N{Si(p-Tol)3}] (3d)
2.05 (s, 9H, C6H4Me),
7.04 (d, J = 7.7 Hz, 6H, ArH),
7.75 (d, J = 7.7 Hz, 6H, ArH)
29.0 (CMe3), 42.2 (CMe3),
104.5 (C5Me5), 129.1, 130.7,
136.9, 140.3 (ArC),
243.7, 244.3 (CO),
249.6 [JWC(satellite) = 54 Hz,
W-CdN]
Cp*(CO)2W{κ2C,N-C(Me)d 0.47-0.68 (m, 6H, SiCH2Me),
4.8, 6.9 (SiEt), 11.3 (C5Me5),
22.4 (NdCMe), 104.1 (C5Me5),
228.7 [JWC(satellite) = 53 Hz,
W-CdN], 242.1, 246.0 (CO)
1901 (s, νCOsym),
1801 (s, νCOasym),
NSiEt3} (4a)
0.84 (t, J = 7.8 Hz, 9H, SiCH2Me),
1.83 (s, 15H, Cp*),
2.42 (s, 3H, NdCMe)
1637 (w, νCN
)

Article
Organometallics, Vol. 29, No. 7, 2010 1843
Table 1. Continued
4.9, 7.0 (SiEt), 11.4 (C5Me5),
11.9 (NdCCH2Me),
Cp*(CO)2W{κ2C,N-C(Et)d
NSiEt3} (4b)
0.44-0.72 (m, 6H, SiCH2Me),
0.86 (t, J = 7.8 Hz, 3H,
SiCH2Me),
15.1
1901 (s, νCOsym),
1801 (s, νCOasym),
1620 (w, νCN)
29.3 (NdCCH2Me),
104.1 (C5Me5),
235.8 [JWC(satellite) = 55 Hz,
W-CdN],
1.39 (t, J = 7.7 Hz, 3H,
NdCCH2Me), 1.85 (s, 15H, Cp*),
2.36-2.61 (m, 2H, NdCCH2Me)
242.7 [JWC(satellite) = 187 Hz, CO],
245.6 [JWC(satellite) = 178 Hz, CO]
a KBr pellet (for 2a-d and 3a-d) or C6D6 solution (for 4a,b). Abbreviations: w, weak; m, medium; s, strong.
Scheme 2. Resonance Hybrid of N-Silyliminoacyl Complexes
2-4
Scheme 3. Dynamic Process by Inversion of Chirality on a
Tungsten Center in Complexes 2-4
Figure 1. Observed (left, in cyclohexane-d12) and calculated
1
(right) line shape of H NMR signals for the methyl protons
in the isopropyl group of 2c at various temperatures. The rate
constants k used for the spectral simulation are shown on the
right side.
already been reported in a preliminary report.11 This time,
single-crystal X-ray analysis was performed for 3b (Figure 3,
Table 2). Complex 3b adopts a four-legged piano-stool geo-
metry: the tungsten center possesses a pentamethylcyclopenta-
dienyl, a κ2C,N-N-silyliminoacyl, and two carbonyl ligands, in
which the two carbonyl ligands are located at mutually cis
positions. The bond distances and angles in the W-C-N three-
membered ring are comparable with those in 3a and those in the
N-silyliminoacyl tungsten complex Cp*(CO)(H)W{κ3C,N,Si-
C(t-Bu)dN(xantsil)}.7 The short W-C(iminoacyl) bond dis-
˚
tance in 3a and 3b [2.086(9) (3a), 2.088(6) (3b) A] is similar
to that of the carbene complex Cp*(CO)2W{dC(H)NEt2}-
12
(Cl) [2.141(3) A], indicating the significant contribution
˚
of the amido(carbene) canonical structure F in the bonding
modes of complexes 3a and 3b (Scheme 2). The W-N bond of
3b [2.225(5) A] is slightly longer than that of the N-alkylimi-
˚
noacyl complex (η5-C9H7)(CO)2W{κ2C,N-C(Me)dN(t-Bu)}
Figure 2. Eyring plot [ln(k/T) vs 1000/T] for the inversion
of the chiral tungsten center of 2c in C6D12 [ln(k/T) = 34.91 -
11.86(1000/T) (R = 0.9986)].
[2.144(5) A].15 This elongation of the W-N bond is probably
˚
due to the larger steric repulsion between the bulky silyl group
on the N atom and the Cp*(CO)2W{C(Et)dN} moiety in 3b:
the distances between aryl carbons C6 and C7 on a p-Tol group
˚
on a p-Tol group [C2 C20, 3.603(10) A; C2 C25,
3 3 3
3 3 3
˚
˚
3.641(10) A] are comparable with the sum (3.7 A) of the van
˚
and a methyl carbon C32 on Cp* [C6 C32, 3.902(9) A;
3 3 3
˚
C7 C32, 3.904(10) A] and between the methylene carbon C2
bonded to the iminoacyl carbon and aryl carbons C20 and C25
˚
der Waals radii of the methyl group (2.0 A) and the half-
˚
thickness of the plane of aromatic rings (1.7 A).
3 3 3
16
(15) Amador, U.; Daff, P. J.; Poveda, M. L.; Ruiz, C.; Carmona, E.
J. Chem. Soc., Dalton Trans. 1997, 3145.
(16) Pauling L. The Nature of the Chemical Bonds, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; pp 257-264.

1844 Organometallics, Vol. 29, No. 7, 2010
Suzuki et al.
compared to those of the rhodium and iron N-silyliminoacyl
complexes involving a Cp0(L)M moiety (M = Rh, Cp0 =
Cp*, L = PMe3; M = Fe, Cp0 = Cp or Cp*, L = CO).2,3,4a,5
This difference is attributable to the more sterically crowded
tungsten center (four-legged piano-stool geometry) in the
former complexes compared to the iron and rhodium centers
(three-legged piano-stool geometry) in the latter complexes.
According to the mechanism of the C-C bond cleavage of
nitrile proposed by Nakazawa et al. on the basis of calcula-
tion,3 the R group on the nitrile carbon has to migrate to the
metal center to form a silylisocyanide complex. This step must
be retarded by the steric crowding around the metal center.
Figure 3. ORTEP drawing of 3b. Thermal ellipsoids are drawn
at the 50% probability level, and all hydrogen atoms are omitted
for clarity.
˚
Table 2. Selected Bond Distances (A) and Angles (deg) in
Cp*(CO)2W[K2C,N-C(Et)dN{Si(p-Tol)3}] (3b)
W-N
2.225(5)
1.937(6)
1.742(5)
33.9(2)
W-C1
2.088(6)
1.972(6)
1.264(8)
113.3(2)
92.3(3)
75.9(3)
67.1(3)
152.3(5)
128.6(6)
W-C4
W-C5
Si-N
N-C1
Characterization of Silylisocyanide Complexes 5a and 5b.
Silylisocyanide complexes 5a and 5b were characterized on
the basis of NMR spectroscopy and elemental analysis for
the mixtures of their cis/trans isomers. Each of the 1H NMR
spectra of 5a and 5b shows two sets of signals assignable to
their cis and trans isomers, namely, cis-5a and trans-5a for 5a
and cis-5b and trans-5b for 5b. In the 1H NMR spectra of 5b,
two signals assignable to the diastereotopic CH2 protons in
cis-5b are observed at 0.70 and 0.74 ppm, which are slightly
upfield-shifted compared to that of trans-5b (0.79 ppm). The
N-W-C1
N-W-C5
C1-W-C5
W-N-Si
W-C1-N
Si-N-C1
N-W-C4
C1-W-C4
C4-W-C5
W-N-C1
W-C1-C2
N-C1-C2
92.0(2)
113.4(3)
148.0(3)
79.0(4)
143.4(4)
Thermal Rearrangement of Cp*(CO)2W{K2C,N-C(R)d
NSi(p-Tol)3} (3a, R = Me; 3b, R = Et). The previously iso-
lated κ2C,N-N-silyliminoacyl complexes [Cp*(PMe3)Rh-
2b
{κ2C,N-C(4-(OMe)C6H4)dNSiPh3}]BAr04 and Cp*(CO)-
1
(H)W{κ3C,N,Si-C(t-Bu)dN(xantsil)}7 are thermally unstable
even at room temperature. In contrast, complexes 2-4 did
not show any sign of decomposition in C6D6 overnight at
room temperature, according to their 1H NMR spectra. To
the best of our knowledge, there is only one example of a κ2C,
N-N-silyliminoacyl complex that is stable at room tem-
perature, namely, [(η5-C5H5)2(CNSiMe3)Ti{κ2C,N-C(Me)d
NSiMe3}]BPh4.17 In order to determine the thermal stability
of κ2C,N-N-silyliminoacyl complexes 3a and 3b, thermolysis
of these complexes was examined at high temperatures.
Thus, heating a toluene-d8 solution of complexes 3a,b in a
sealed NMR tube by raising the temperature in stages from
90 to 120 °C (for 3a) or from 100 to 120 °C (for 3b), which
intensity of the H signals for cis-5b is larger than that for
trans-5b, and the molar ratio of cis-5b to trans-5b is 1.7 on the
basis of the intensity ratio of their Cp* signals. Similarly, in
the 1H NMR spectra of 5a, the upfield-shifted signal of the
methyl ligand (-0.04 ppm) can be assigned to that of the cis
isomer. The cis isomer is also the major component in 5a (cis-
5a:trans-5a = 1.6:1, based on the intensity ratio of their Cp*
signals). The same type of upfield shift for the cis isomer has
also been observed in an alkylisocyanide complex: the signal
of the methyl ligand in the cis isomer of (η5-C9H7)(CO)2W-
(Me){CN(t-Bu)} (-0.09 ppm) is upfield-shifted compared to
that of the trans isomer (0.33 ppm).15
In the 13C{1H} NMR spectra of 5a and 5b, two sets of
signals assignable to their cis/trans isomers are also observed.
Since the cis isomer is the major component, we tentatively
assigned a set of signals having larger intensity to the cis
isomer (cis-5a and cis-5b). The signals of the carbon coordi-
nated to the tungsten center in the methyl or ethyl ligand of
the two isomers are observed at -22.5 ppm (JWC = 36 Hz,
cis-5a) and -24.6 (JWC = 31 Hz, trans-5a) for 5a and -5.2
ppm (JWC = 35 Hz, cis-5b) and -7.1 (JWC = 32 Hz, trans-
5b) for 5b. The chemical shifts for 5a are comparable with
those for the (alkylisocyanide)(methyl) complex (η5-C9H7)-
(CO)2W(Me){CN(t-Bu)} [cis isomer, -20.4 ppm (W-Me);
1
was monitored by H NMR spectroscopy, led mainly to
the formation of silylisocyanide complexes Cp*(CO)2W(R)-
{CNSi(p-Tol)3} (5a, R = Me; 5b, R = Et) as a mixture of
cis/trans isomers. A large-scale experiment of the thermolysis
was carried out for 3a in toluene at 120 °C for 54 h or for 3b in
toluene-d8 at 120 °C for 24 h to give 5a or 5b as a cis/trans
mixture in 77% (5a) or 49% (5b) yield (eq 4). Thus, the C-C
bond cleavage in 3a,b requires a much higher temperature
(17) Bochmann, M.; Wilson, L. M.; Hursthouse, M. B.; Motevalli,
M. Organometallics 1988, 7, 1148.

Article
Organometallics, Vol. 29, No. 7, 2010 1845
˚
Table 3. Selected Bond Distances (A) and Angles (deg) in
cis-Cp*(CO)2W(Et){CNSi(p-Tol)3} (cis-5b)
W-C1
2.013(4)
1.941(5)
1.743(3)
74.60(16)
114.17(19)
74.2(2)
W-C2
2.297(4)
1.959(5)
1.183(5)
80.22(17)
129.37(18)
77.4(2)
W-C4
W-C5
Si-N
N-C1
C1-W-C2
C1-W-C5
C2-W-C5
W-C1-N
C1-W-C4
C2-W-C4
C4-W-C5
Si-N-C1
175.1(3)
166.0(3)
similar to those of previously reported silylisocyanide com-
2a,3,4a,18
˚
˚
plexes [C-N = 1.13-1.23 A, N-Si = 1.70-1.79 A].
Further Thermal Reaction of 5b. Prolonged heating of κ2C,
N-iminoacyl complex 3b at 120 °C for 2 weeks in toluene-d8
afforded not only 5b (24% NMR yield, cis/trans mixture) but
also the η3-N-silyl-1-azaallyl complex Cp*(CO)2W{η3-
HMeCCHNSi(p-Tol)3} (6, 46% NMR yield) (eq 5).
Figure 4. ORTEP drawing of cis-5b. Thermal ellipsoids are
drawn at the 50% probability level, and all hydrogen atoms
are omitted for clarity.
trans isomer, -24.1 ppm (W-Me)].15 For 5a, the signals of
the isocyanide CN carbons are observed at 204.6 ppm for cis-
5a and 211.1 ppm for trans-5a, and those of CO are observed
at 230.8 and 242.7 ppm for cis-5a and 226.1 ppm for trans-5a.
For 5b, the signals of isocyanide CN carbons are observed at
207.4 ppm for cis-5b and 211.5 ppm for trans-5b, and those of
CO are observed at 233.1 and 241.8 ppm for cis-5b and 228.9
ppm for trans-5b. These observations support the structures
of 5a,b having an alkyl ligand and a silylisocyanide ligand.
The 29Si{1H} NMR spectra of 5a,b at room temperature did
not show any signal. On the other hand, in the 29Si{1H} NMR
spectrum of 5a at 233 K, two signals assignable to the cis/trans
isomers were observed at -25.3 and -25.4 ppm. These chemi-
cal shifts are similar to that for the silylisocyanide rhodium com-
plex [Cp*(PMe3)Rh(CNSiPh3)(Me)]BAr04 (-17.95 ppm).2a
The broadening of the 29Si signals of 5a,b at room temperature
may be attributed to the rapid isomerization between cis-5a,b
and trans-5a,b on the NMR time scale.
1
In the H NMR spectrum of the mixture of 5b and 6, the
signals of the hydrogen atoms bound to the azaallyl carbons in 6
are observed at 2.30 ppm (dq, 3JHH = 6.0, 6.9 Hz, HMeCCHN)
and5.20 ppm (d, 3JHH = 6.9 Hz, HMeCCHN). The large coup-
ling constant between the signals (3JHH = 6.9 Hz) indicates that
these hydrogen atoms are located at mutually anti positions. In
addition, the doublet signal of the methyl group bound to the
azaallyl carbon is observed at 1.76 ppm (d, 3JHH = 6.0 Hz). The
chemical shifts of these signals are comparable with those of the
η3-N-alkyl-1-azaallyl complex Cp*(CO)2W(η3-HMeCCHNEt)
[1.54 ppm (dq, 3JHH = 6.1, 6.3 Hz, HMeCCHNEt), 1.82 ppm
(d, 3JHH = 6.1 Hz, HMeCCHNEt), and 4.53 ppm (d, 3JHH
=
6.3 Hz, HMeCCHNEt)].19 The 13C{1H} NMR spectrum of the
mixture of 5b and 6 shows the signals of the azaallyl ligand in
complex 6 at 59.7 ppm (HMeCCHN) and 113.5 ppm
(HMeCCHN). The chemical shifts of these signals are also
comparable with those of the η3-N-alkyl-1-azaallyl complex
Cp*(CO)2W(η3-HMeCCHNEt) [47.0 ppm (HMeCCHNEt)
and 118.1 ppm (HMeCCHNEt)].19 These observations support
the structure of complex 6, but the geometry (exo/endo and syn/
anti configurations) of the η3-1-azaallyl ligand in 6 is not clear.
X-ray Crystal Structure of cis-Cp*(CO)2W(Et){CNSi(p-
Tol)3} (cis-5b). Recrystallization of a cis/trans mixture of 5b
from toluene afforded a single crystal of cis isomer cis-5b
suitable for X-ray crystallography. The molecular structure
of cis-5b is illustrated in Figure 4, and selected bond distances
and angles are listed in Table 3. Complex cis-5b adopts a
four-legged piano-stool geometry where the tungsten center
possesses an η5-pentamethylcyclopentadienyl ligand, two
carbonyl ligands, an ethyl ligand, and a silylisocyanide
ligand. The ethyl ligand and the silylisocyanide ligand are
located mutually at cis positions on the tungsten center. The
W-C(isocyanide) and W-C(alkyl) bond distances of cis-5b
Conclusion
In this work, we synthesized κ2C,N-N-silyliminoacyl tung-
sten complexes 2a-d, 3a-d, and 4a,b. Two methods were uti-
lized for the synthesis: (1) the reaction of DMAP-stabilized
(18) (a) da Silva, M. F. C. G.; Lemos, M. A. N. D. A.; da Silva, J. J. R.
F.; Pombeiro, A. J. L.; Pellinghelli, M. A.; Tiripicchio, A. J. Chem. Soc.,
Dalton Trans. 2000, 373. (b) Nakazawa, H.; Itazaki, M.; Owaribe, M. Acta
Crystallogr., Sect. E 2005, 61, m1073. (c) Nakazawa, H.; Itazaki, M.;
Owaribe, M. Acta Crystallogr., Sect. E 2005, 61, m1172.
˚
˚
[W-C1, 2.013(4) A; W-C2, 2.297(4) A, respectively] are
comparable with those of the alkylisocyanide complex (η5-
C9H7)(CO)2W(Me){CN(t-Bu)} [W-C(isocyanide), 2.04(2)
15
˚
˚
A; W-C(alkyl), 2.26(2) A]. The CtN and N-Si bond
€
(19) Filippou, A. C.; Grunleitner, W.; Kiprof, P. J. Organomet.
˚
˚
distances of cis-5b [C1-N, 1.183(5) A; N-Si, 1.743(3) A] are
Chem. 1991, 410, 175.

1846 Organometallics, Vol. 29, No. 7, 2010
Suzuki et al.
(aryl)(silylene) complexes 1a,b with excess nitrile, and (2) the
reaction between methyl(nitrile) complexes A and B with
hydrosilane. Complexes 2-4 are stable at room temperature.
Upon raising the temperature, thermal rearrangements of
complexes 3a,b via C-C bond cleavage occurred at 120 °C
to give silylisocyanide complexes 5a,b.
NMR spectra of 2a-d showed that their chiral tungsten
center undergoes inversion around room temperature. The
kinetic study on the inversion process of 2c implies that this
inversion proceeds through cleavage of the bond between
tungsten and iminoacyl nitrogen. This means that the imi-
noacyl ligand in complexes 2-4 is hemilabile. The consider-
able thermal stability of complexes 2-4 is suitable for the
investigation on their reactivity through the W-N bond
cleavage. We are now trying to find reactions of complexes
2-4 with small molecules, which can be applied to new types
of transformations of organic molecules. For instance, we
already found that the reaction of complexes 3a and 4a in the
presence of excess acetonitrile caused C-N coupling to give
W-C-N-C-N five-membered-ring complexes.11
yield (44 mg, 0.099 mmol). 1H NMR (300 MHz, C6D6): δ 0.26 (s,
3H, WMe), 0.33 (t, J = 7.6 Hz, 3H, CH2Me), 1.45 (q, J = 7.6
Hz, 2H, CH2Me), 1.79 (s, 15H, Cp*). 13C{1H} NMR (75.5 MHz,
C6D6): δ -11.7 [JWC(satellite) = 45 Hz, WMe], 10.6 (C5Me5),
10.8, 12.4 (Et), 101.4 (C5Me5), 138.7 (NCEt), 244.1, 257.3 (CO).
IR (C6D6, cm-1): 2262 (w, νCN), 1911 (s, νCOsym), 1820 (m,
ν
depicted in Figure S1 in the Supporting Information.
COasym). The 1H NMR spectrum of crude product B in C6D6 is
Synthesis of Cp*(CO)2W[K2C,N-C(Me)dN{SiMe(p-Tol)2}]
(2a). A toluene (2 mL) solution of 1a 0.5toluene (54 mg, 0.070
3
mmol) and MeCN (207 mg, 5.04 mmol) in a round-bottomed
flask was allowed to stand at room temperature for 1 day. The
resulting deep red mixture was evaporated to dryness. BPh3 (16
mg, 0.066 mmol) and hexane (2 mL) were added to the residue,
and the mixture was stirred for 1 h. DMAP BPh3 was precipi-
3
tated as a white powder. The mixture was filtered, and the
residue was washed with hexane (1 mL). After the filtrate and
the washing were combined, the mixture was evaporated
under vacuum. Recrystallization of the residual oil from hexane
at -35 °C afforded a red powder of 2a in 67% yield (30 mg,
0.047 mmol). Anal. Calcd for C29H35NO2SiW: C, 54.29; H, 5.50;
N, 2.18. Found: C, 54.01; H, 5.40; N, 2.32.
Synthesis of Cp*(CO)2W[K2C,N-C(Et)dN{SiMe(p-Tol)2}]
(2b). The title compound was synthesized by a procedure similar
to that for 2a using a toluene solution (2 mL) of 1a 0.5toluene
Experimental Section
3
General Procedures. All manipulations were carried out under
dry nitrogen in a glovebox or using a standard high-vacuum line.
Benzene-d6, toluene, toluene-d8, hexane, cyclohexane-d12, di-
chloromethane-d2, and nitriles RCN (R = Me, Et, i-Pr, t-Bu)
were dried over calcium hydride and distilled before use. BPh3
(Sigma Aldrich) was used as received. Cp*(CO)3WMe20 and
(73 mg, 0.095 mmol) and EtCN (239 mg, 4.34 mmol). After
addition of BPh3 (20 mg, 0.083 mmol) and hexane (2 mL) to the
evaporated reaction mixture and stirring for 1 h, workup similar
to that for 2a afforded a red powder of 2b in 58% yield (36 mg,
0.055 mmol). Anal. Calcd for C30H37NO2SiW: C, 54.96; H, 5.69;
N, 2.14. Found: C, 55.33; H, 5.73; N, 2.17.
Cp*(CO)2W(p-Tol){dSi(p-Tol)R0 DMAP} (1a, R0 = Me; 1b,
3
Synthesis of Cp*(CO)2W[K2C,N-C(i-Pr)dN{SiMe(p-Tol)2}]
(2c). The title compound was synthesized by a procedure similar
to that for 2a using a toluene solution (2 mL) of 1a 0.5toluene
R0 = p-Tol)8b were prepared according to the literature meth-
ods.
3
Physical Measurements. 1H, 13C{1H}, and 29Si{1H} NMR
spectra were recorded on a Bruker ARX-300 or AVANCE-300
spectrometer. 29Si{1H} NMR experiments except for 3a were
performed using the DEPT pulse sequence. The residual proton
(C6D5H, 7.15 ppm; C6D5CD2H, 2.09 ppm; C6D11H, 1.38 ppm;
CDHCl2, 5.28 ppm) and the carbon resonances (C6D6, 128.0
ppm; C6D5CD3, 20.4 ppm; CD2Cl2, 53.7 ppm) of deuterated
(75 mg, 0.098 mmol) and i-PrCN (324 mg, 4.69 mmol) (reaction
period: 3 days). After addition of BPh3 (22 mg, 0.091 mmol) and
hexane (3 mL) to the evaporated reaction mixture and stirring
for 1 h, workup similar to that for 2a afforded a red powder
of 2c in 61% yield (40 mg, 0.060 mmol). Anal. Calcd for C31H39-
NO2SiW: C, 55.61; H, 5.87; N, 2.09. Found: C, 56.11; H, 5.86;
N, 2.15.
1
solvents were used as internal references for H and 13C reso-
Synthesis of Cp*(CO)2W[K2C,N-C(t-Bu)dN{SiMe(p-Tol)2}]
(2d). The title compound was synthesized by a procedure similar
to that for 2a using a toluene solution (2 mL) of 1a 0.5toluene
nances, respectively. Aromatic proton or carbon is abbreviated
as ArH or ArC. 29Si{1H} NMR chemical shifts were referenced
to SiMe4 as an external standard. The NMR data were collected
at room temperature unless indicated otherwise. Infrared spec-
tra were recorded with a C6D6 solution placed between KBr
plates in a liquid cell or with a KBr pellet using a Horiba FT-730
spectrometer. Mass and high-resolution mass spectra were
recorded on a Hitachi M-2500S spectrometer operating in the
electron impact (EI) mode. Mass spectrometric analysis and
elemental analysis were performed at the Research and Analy-
tical Center for Giant Molecules, Tohoku University. NMR and
IR data for N-silyliminoacyl complexes 2a-d, 3a-d, and 4a,b
are listed in Table 1.
Synthesis of Cp*(CO)2W(NCEt)Me (B). The title compound
was prepared by modifying a literature method for the synthesis
of Cp*(CO)2W(NCMe)Me (A).9 A propiononitrile (2.5 mL)
solution of Cp*(CO)3WMe (57 mg, 0.14 mmol) in a Pyrex
sample tube with a Teflon vacuum valve was degassed by three
freeze-pump-thaw cycles on a vacuum line. The mixture was
irradiated for 40 min with a 450 W medium-pressure Hg lamp
immersed in a water bath (ca. 5 °C). During the photoreaction,
the reaction mixture was degassed at 10 min of irradiation by a
freeze-pump-thaw cycle on a vacuum line. After irradiation
was completed, the reaction mixture was evaporated to dryness.
A brown powder of B was obtained as a crude product in 71%
3
(77 mg, 0.10 mmol) and t-BuCN (285 mg, 3.43 mmol) (reaction
period: 3 days). After addition of BPh3 (21 mg, 0.087 mmol) and
hexane (3 mL) to the evaporated reaction mixture and stirring
for 1 h, workup similar to that for 2a afforded a red powder of 2d
in 91% yield (62 mg, 0.091 mmol). Anal. Calcd for C32H41NO2-
SiW: C, 56.22; H, 6.05; N, 2.05. Found: C, 56.68; H, 6.18;
N, 2.04.
Synthesis of Cp*(CO)2W[K2C,N-C(Me)dN{Si(p-Tol)3}](3a).
Method 1: Reaction of 1b with Acetonitrile. The title com-
pound was synthesized by a procedure similar to that for 2a
using a toluene solution (2.5 mL) of 1b 0.5toluene (83 mg,
3
0.098 mmol) and MeCN (208 mg, 5.07 mmol) (reaction period:
1 day). After addition of BPh3 (22 mg, 0.091 mmol) and hexane
(6 mL) to the evaporated reaction mixture and stirring for 1 h,
workup similar to that for 2a afforded a red powder of 3a in 61%
yield (43 mg, 0.060 mmol).
Method 2: Reaction of Cp*(CO)2W(NCMe)Me (A) with HSi-
(p-Tol)3. An acetonitrile (6 mL) solution of Cp*(CO)3WMe
(152 mg, 0.364 mmol) in a Pyrex sample tube with a Teflon
vacuum valve was degassed by three freeze-pump-thaw cycles
on a vacuum line. The mixture was irradiated for 70 min with a
450 W medium-pressure Hg lamp immersed in a water bath
(ca. 5 °C). After 15 and 40 min of irradiation, the reaction mix-
ture was degassed by a freeze-pump-thaw cycle on a vacuum
line. After irradiation was completed, the reaction mixture in-
volving Cp*(CO)2W(NCMe)Me (A) was evaporated to dryness.
(20) Mahmoud, K. A.; Rest, A. J.; Alt, H. G.; Eichner, M. E.; Jansen,
B. M. J. Chem. Soc., Dalton Trans. 1984, 175.

Article
Organometallics, Vol. 29, No. 7, 2010 1847
Table 4. Crystallographic Data for 3b and cis-5b
The residue was dissolved in toluene (1.5 mL), and the solution
was added onto a solid of HSi(p-Tol)3 (110 mg, 0.364 mmol) in a
round-bottomed flask. The mixture was allowed to stand at
room temperature for 15 min. After the resulting red solution
was evaporated under vacuum, the residue was extracted with
hexane (3 mL). The red extract was concentrated and cooled at
-35 °C to give analytically pure 3a as a red powder in 59% yield
(153 mg, 0.213 mmol). Anal. Calcd for C35H39NO2SiW: C,
58.58; H, 5.48; N, 1.95. Found: C, 58.18; H, 5.65; N, 1.97.
Synthesis of Cp*(CO)2W[K2C,N-C(Et)dN{Si(p-Tol)3}] (3b).
Method 1: Reaction of 1b with Propiononitrile. The title com-
pound was synthesized by a procedure similar to that for 2a
3b
cis-5b
formula
fw
C36H41NO2SiW
731.64
C36H41NO2SiW
731.64
cryst size/mm
cryst color
cryst syst
space group
0.40 ꢀ 0.35 ꢀ 0.30
0.28 ꢀ 0.07 ꢀ 0.02
red
yellow
monoclinic
P21/c (No. 14)
9.0675(3)
14.7448(4)
24.3446(8)
91.9946(10)
3252.86(18)
4
monoclinic
P21/c (No. 14)
13.590(4)
14.312(4)
17.018(5)
97.2518(11)
3283.4(16)
4
˚
a/A
˚
b/A
˚
c/A
β/deg
3
˚
V/A
using a toluene solution (2 mL) of 1b 0.5toluene (70 mg,
3
0.083 mmol) and EtCN (246 mg, 4.47 mmol) (reaction period:
1 day). After addition of BPh3 (17 mg, 0.070 mmol) and hexane
(6 mL) to the evaporated reaction mixture and stirring for 1 h,
workup similar to that for 2a afforded a red powder of 3b in 76%
yield (46 mg, 0.063 mmol).
Z
Dcalcd/g cm-3
F(000)
1.494
1472
1.480
1472
μ(Mo KR)/mm-1
reflns collected
unique reflns (Rint
refined params
R1, wR2 (all data)
3.62
26 148
7063 (0.128)
379
0.059, 0.158
0.051, 0.140
1.13
3.59
23 363
7506 (0.061)
379
0.055, 0.070
0.034, 0.062
0.99
)
Method 2: Reaction of Cp*(CO)2W(NCEt)Me (B) with HSi(p-
Tol)3. Cp*(CO)2W(NCEt)Me (B) was prepared by a procedure
analogous to the synthesis of B (vide supra) using a propiononi-
trile (11 mL) solution of Cp*(CO)3WMe (275 mg, 0.658 mmol)
(period of irradiation: 2 h, degassed at 30 and 70 min of
irradiation). After irradiation, the reaction mixture involving
B was evaporated to dryness. The residue was dissolved in
toluene (7 mL), and the solution was added onto a solid of
HSi(p-Tol)3 (216 mg, 0.714 mmol) in a round-bottomed flask.
The mixture was allowed to stand at room temperature for
25 min. After the resulting red solution was evaporated under
vacuum, the residue was extracted with hexane (4 mL). The red
extract was cooled at -35 °C to give analytically pure 3b as a red
powder (359 mg, 0.491 mmol) in 75% yield. Anal. Calcd for
C36H41NO2SiW: C, 59.10; H, 5.65; N, 1.91. Found: C, 59.08; H,
5.65; N, 1.90.
R1, wR2 [I > 2σ(I)]
GOF
largest residual peak,
1.84, -3.16
1.06, -0.52
-3
˚
hole/e A
analysis. The 1H NMR spectrum of isolated 4a in C6D6 is
depicted in Figure S2 in the Supporting Information.
Synthesis of Cp*(CO)2W{K2C,N-C(Et)dNSiEt3} (4b). Cp*-
(CO)2W(NCEt)Me (B) was prepared by a procedure analogous
to the synthesis of B (vide supra) using a propiononitrile (10 mL)
solution of Cp*(CO)3WMe (257 mg, 0.615 mmol) (period of
irradiation: 2 h, degassed after 30 and 70 min of irradiation).
After irradiation, the reaction mixture involving B was evapo-
rated to dryness. The residue was dissolved in toluene (6 mL),
and the solution was added to a liquid of HSiEt3 (82 mg, 0.71
mmol) by a syringe. The mixture was allowed to stand at room
temperature for 30 min. After the resulting red solution was
evaporated under vacuum, the residue was extracted with
hexane (4 mL). The red extract was concentrated (ca. 1/3) and
cooled at -35 °C to give 4b as a red powder in 61% yield
(205 mg, 0.376 mmol). EI-MS (70 eV): m/z 545 (Mþ, 25), 517
(Mþ - CO, 13), 487 (100). Exact mass (EI) for C21H35NO2SiW:
calcd, m/z 545.1941; found, m/z 545.1938. Contamination with a
trace of impurities has prevented correct elemental analysis. The
1H NMR spectrum of isolated 4b in C6D6 is depicted in Figure
S3 in the Supporting Information.
Synthesis of Cp*(CO)2W[K2C,N-C(i-Pr)dN{Si(p-Tol)3}] (3c).
The title compound was synthesized by a procedure similar
to that for 2a using a toluene solution (3 mL) of 1b 0.5toluene
(90 mg, 0.11 mmol) and i-PrCN (341 mg, 4.93 mmol) (reaction
period: 2 days). After addition of BPh3 (22 mg, 0.091 mmol) and
hexane (4 mL) to the evaporated reaction mixture and stirring for
1 h, workup similar to that for 2a afforded a red powder of 3c in
75% yield (61 mg, 0.082 mmol). Anal. Calcd for C37H43NO2SiW:
C, 59.60; H, 5.81; N, 1.88. Found: C, 59.69; H, 5.95; N, 2.10.
Synthesis of Cp*(CO)2W[K2C,N-C(t-Bu)dN{Si(p-Tol)3}] (3d).
The title compound was synthesized by a procedure similar
3
to that for 2a using a toluene solution (1.5 mL) of 1b 0.5toluene
3
Measurement of Variable-Temperature 1H NMR Spectrosco-
py of Cp*(CO)2W[K2C,N-C(i-Pr)dN{SiMe(p-Tol)2}] (2c). A
Pyrex NMR tube was charged with a solution of complex 2c
(4 mg, 6 μmol) in cyclohexane-d12 (0.5 mL). This NMR tube was
attached to a vacuum line and flame-sealed under high vacuum.
The 1H NMR spectra of 2c were measured at various tempera-
tures (283-343 K). 1H NMR (300 MHz, C6D12, 283 K): δ 0.58
(s, 3H, SiMe), 0.91 (d, J = 6.7 Hz, 3H, CHMeaMeb), 1.10 (d,
J = 6.7 Hz, 3H, CHMeaMeb), 1.84 (s, 15H, Cp*), 2.30 (s, 3H,
C6H4Me), 2.31 (s, 3H, C6H4Me), 2.87 (sept, J = 6.7 Hz, 1H,
CHMe2), 7.09 (d, J = 7.7 Hz, 2H, ArH), 7.11 (d, J = 7.7 Hz, 2H,
ArH), 7.34 (d, J = 7.7 Hz, 2H, ArH), 7.39 (d, J = 7.7 Hz, 2H,
ArH).
(51 mg, 0.060 mmol) and t-BuCN (224 mg, 2.69 mmol) (reaction
period: 2 days). After addition of BPh3 (13 mg, 0.054 mmol) and
hexane (6 mL) to the evaporated reaction mixture and stirring for
1 h, workup similar to that for 2a afforded a red powder of 3d in
83% yield (38 mg, 0.050 mmol). Anal. Calcd for C38H45NO2-
SiW: C, 60.08; H, 5.97; N, 1.84. Found: C, 59.63; H, 6.36; N, 1.91.
Synthesis of Cp*(CO)2W{K2C,N-C(Me)dNSiEt3} (4a). Cp*-
(CO)2W(NCMe)Me (A) was prepared by a procedure analo-
gous to the synthesis of 3a (method 2) using an acetonitrile
(8 mL) solution of Cp*(CO)3WMe (201 mg, 0.481 mmol)
(period of irradiation: 90 min, degassed at 20, 50, and 90 min
of irradiation). After the reaction mixture involving A was
transferred into a round-bottomed flask, HSiEt3 (67 mg, 0.58
mmol) was added to the flask by a syringe. After keeping the
mixture at room temperature for 1 day, the resulting red
solution was evaporated under vacuum. The residual oil was dis-
solved in hexane (1 mL). Concentration and cooling at -35 °C
of the solution afforded a red oil. The supernatant liquid was
separated from the red oil (unidentified products) by a syringe
and was cooled at -35 °C to yield a red powder of 4a in 74%
yield (188 mg, 0.354 mmol). EI-MS (70 eV): m/z 531 (Mþ, 17),
503 (Mþ - CO, 15), 473 (100). Exact mass (EI) for C20H33NO2-
SiW: calcd, m/z 531.1784; found, m/z 531.1779. Contamina-
tion with a trace of impurities has prevented correct elemental
Synthesis of cis/trans-Cp*(CO)2W(Me){CNSi(p-Tol)3} (5a).
A toluene (4 mL) solution of 3a (102 mg, 0.142 mmol) in a Pyrex
sample tube (12 mm o.d.) with a Teflon vacuum valve was
attached to a vacuum line. This tube was flame-sealed under
high vacuum. The toluene solution was heated at 120 °C for 54 h.
The solution color changed from red to yellow. The reaction
mixture was transferred into a round-bottomed flask and
evaporated to dryness. After the residual brown oil was allowed
to stand for 1 h, a solid was deposited. Washing the mixture to
remove an oil with hexane afforded a pale yellow solid of 5a as a
cis/trans mixture (cis-5a:trans-5a = 1.6:1 molar ratio in CD2Cl2,

1848 Organometallics, Vol. 29, No. 7, 2010
Suzuki et al.
based on the intensity ratio of the Cp* signals in their 1H NMR
spectra) in 77% yield (82 mg, 0.11 mmol). Data for the mixture
of cis-5a and trans-5a: 1H NMR data for cis-5a (300 MHz,
CD2Cl2): δ -0.04 [s, 3H, JWH(satellite) = 3.7 Hz, WMe], 1.87 (s,
15H, Cp*), 2.36 (s, 9H, C6H4Me), 7.23 (br d, J = 8.0 Hz, 6H,
ArH), 7.50 (d, J = 8.0 Hz, 6H, ArH). 1H NMR data for trans-5a
(300 MHz, CD2Cl2): δ 0.01 [s, 3H, JWH(satellite)=3.6 Hz,
WMe], 1.82 (s, 15H, Cp*), 2.36 (s, 9H, C6H4Me), 7.24
(br d, J = 7.9 Hz, 6H, ArH), 7.55 (d, J = 7.9 Hz, 6H, ArH).
13C{1H} NMR data for cis-5a (75.5 MHz, CD2Cl2): δ -22.5
[JWC(satellite) = 36 Hz, WMe], 10.6 (C5Me5), 21.7 (C6H4Me),
102.3 (C5Me5), 128.8, 129.4, 135.4, 141.5 (ArC), 204.6 (CN),
230.8, 242.7 (CO). 13C{1H} NMR data for trans-5a (75.5 MHz,
CD2Cl2): δ -24.6 [JWC(satellite) = 31 Hz, WMe], 10.4 (C5Me5),
21.7 (C6H4Me), 101.6 (C5Me5), 129.0, 129.4, 135.5, 141.5 (ArC),
211.1 (CN), 226.1 (CO). 29Si{1H} NMR (59.6 MHz, CD2Cl2,
233 K): δ -25.3, -25.4. Anal. Calcd for C35H39NO2SiW: C,
58.58; H, 5.48; N, 1.95. Found: C, 58.98; H, 5.39; N, 1.98.
Synthesis of cis/trans-Cp*(CO)2W(Et){CNSi(p-Tol)3} (5b). A
toluene-d8 solution (0.5 mL) of 3b (51 mg, 0.070 mmol) in a
Pyrex NMR sample tube with a Teflon vacuum valve was
attached to a vacuum line. This NMR tube was flame-sealed
under high vacuum. The toluene solution was heated at 120 °C
for 24 h. The solution color changed from red to brown. The
reaction mixture was transferred into a round-bottomed flask
and evaporated to dryness. After the residual red oil was allowed
to stand for 1 day, a solid was deposited. Washing the mixture to
remove an oil with hexane afforded a pale yellow solid of 5b as a
cis/trans mixture (cis-5b:trans-5b = 1.7:1 molar ratio in CD2Cl2,
based on the intensity ratio of the Cp* signals in their 1H NMR
spectra) in 49% yield (25 mg, 0.034 mmol). Data for the mixture
of cis-5b and trans-5b: 1H NMR data for cis-5b (300 MHz,
CD2Cl2): δ 0.70 (q, J = 7.6 Hz, 1H, WCHaHbMe), 0.74 (q, J =
7.6 Hz, 1H, WCHaHbMe), 1.41 (t, J = 7.6 Hz, 3H, WCH2Me),
1.84 (s, 15H, Cp*), 2.36 (s, 9H, C6H4Me), 7.23 (br d, J = 7.9 Hz,
to a vacuum line and flame-sealed under high vacuum. This
sealed tube was heated at 120 °C, and the reaction was mon-
itored by 1H NMR spectroscopy. After 2 weeks, not only
complex 5b (24% NMR yield, cis/trans mixture) but also
complex 6 (46% NMR yield) were observed in the 1H and
13C{1H} NMR spectra. The NMR yields were determined by
1
comparing the intensity of the Cp* signal of 5b or 6 in the H
NMR spectrum of the reaction mixture to that of the internal
standard. The molar ratio of the cis/trans isomers of 5b is major:
minor = 1.3:1 based on the intensity ratio of their Cp* signals,
but we could not determine which isomer is the major compo-
nent. NMR signals assignable to 6 in the reaction mixture: 1H
NMR (300 MHz, toluene-d8): δ 1.54 (s, 15H, Cp*), 1.76 [d, J =
6.0 Hz, 3H, HMeCC(H)N], 2.14 (s, 9H, C6H4Me), 2.30 [dq, J =
6.0, 6.9 Hz, 1H, HMeCC(H)N], 5.20 [d, J = 6.9 Hz, 1H, HMe-
CC(H)N], 7.07 (d, J = 7.8 Hz, 6H, ArH), 7.81 (d, J=7.8 Hz, 6H,
ArH). 13C{1H} NMR (75.5 MHz, toluene-d8): δ 10.5 (C5Me5),
16.8 [HMeCC(H)N], 21.4 (C6H4Me), 59.7 [HMeCC(H)N],
103.9 (C5Me5), 113.5 [HMeCC(H)N], 237.8, 240.1 (CO); aro-
matic carbons could not be assigned.
X-ray Crystal Structure Determination. Selected crystallo-
graphic data for 3b and cis-5b are summarized in Table 4.
X-ray quality single crystals of 3b were obtained from hexane
at -35 °C as red blocks. Recrystallization of a cis/trans mixture
of 5b from toluene at room temperature gave an X-ray quality
single crystal of cis-5b as a yellow plate. Intensity data for the
analysis were collected on a Rigaku RAXIS-RAPID imaging
plate or a Rigaku Saturn CCD diffractometer with graphite-
˚
monochromated Mo KR radiation (λ = 0.71069 A) under a cold
nitrogen stream [T = 150 K (for 3b) and 173 K (for cis-5b)].
Numerical absorption corrections were applied to the data. The
structures were solved by the Patterson method using the
DIRDIF-99 program21 and refined by full matrix least-squares
techniques on all F2 data with SHELXL-97.22 Anisotropic
refinement was applied to all non-hydrogen atoms, and all the
hydrogen atoms were put at calculated positions. CCDC refer-
ence numbers: 765983 (3b) and 765984 (cis-5b). Crystallo-
graphic data are available as a CIF file.
1
6H, ArH), 7.51 (d, J = 7.9 Hz, 6H, ArH). H NMR data for
trans-5b (300 MHz, CD2Cl2): δ 0.79 (q, J = 7.6 Hz, 2H, WCH2-
Me), 1.56 (t, J = 7.6 Hz, 3H, WCH2Me), 1.80 (s, 15H, Cp*), 2.36
(s, 9H, C6H4Me), 7.24 (br d, J = 7.9 Hz, 6H, ArH), 7.54 (d, J =
7.9 Hz, 6H, ArH). 13C{1H} NMR data for cis-5b (75.5
MHz, CD2Cl2): δ -5.2 [JWC(satellite) = 35 Hz, WCH2Me],
10.4 (C5Me5), 20.6 (WCH2Me), 21.6 (C6H4Me), 102.1 (C5Me5),
128.9, 129.1, 135.3, 141.4 (ArC), 207.4 (CN), 233.1, 241.8 (CO).
13C{1H} NMR data for trans-5b (75.5 MHz, CD2Cl2): δ -7.1
[JWC(satellite) = 32 Hz, WCH2Me], 10.2 (C5Me5), 20.7 (WCH2-
Me), 21.6 (C6H4Me), 101.5 (C5Me5), 129.0, 129.1, 135.4, 141.3
(ArC), 211.5 (CN), 228.9 (CO). Anal. Calcd for C36H41NO2-
SiW: C, 59.10; H, 5.65; N, 1.91. Found: C, 59.24; H, 5.60; N,
1.95.
Acknowledgment. This work was supported by
Grants-in-Aid for Scientific Research (Nos. 18350027,
18064003, and 20750040) from the Ministry of Educa-
tion, Culture, Sports, Science and Technology of Japan.
Supporting Information Available: 1H NMR spectra of com-
plexes B, 4a, and 4b as a PDF file; X-ray crystallographic data as
a CIF file. These materials are available free of charge via the
Internet at http://pubs.acs.org.
Formation of η3-1-Azaallyl Complex Cp*(CO)2W{η3-
HMeCC(H)NSi(p-Tol)3} (6) on the Thermal Reaction of 3b. A
Pyrex NMR tube was charged with a solution of complex 3b (42
mg, 0.057 mmol) and Si(SiMe3)4 (less than 1 mg, internal
standard) in toluene-d8 (0.5 mL). This NMR tube was attached
(21) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Garcia-Granda,
S.; Gould, R. O.; Israel, R.; Smits, J. M. M. The DIRDIF-99 Program
System; Crystallography Laboratory, University of Nijmegen: The
Netherlands, 1999.
(22) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112.