Reactions of a silyl(silylene)iron complex with nitriles: Carbon-carbon bond cleavage of nitriles by the transiently generated disilanyliron(II) intermediate

Article abstract of DOI:10.1021/om0507530

A silyl(silylene) iron complex, Cp*Fe(CO)(=SiMes₂) SiMe₃ (1), which was prepared by the photoreaction of Cp*Fe(CO)₂Me (2) with hydrodisilane Mes ₂MeSiSiMe₂H (3), reacted with nitriles RCN (R = Ph, Me)

Full text of DOI:10.1021/om0507530

472
Organometallics 2006, 25, 472-476
Reactions of a Silyl(silylene)iron Complex with Nitriles:
Carbon-Carbon Bond Cleavage of Nitriles by the Transiently
Generated Disilanyliron(II) Intermediate
Hisako Hashimoto,* Akihisa Matsuda, and Hiromi Tobita*
Department of Chemistry, Graduate School of Science, Tohoku UniVersity, Aoba-ku,
Sendai 980-8578, Japan
ReceiVed September 1, 2005
A silyl(silylene) iron complex, Cp*Fe(CO)(dSiMes2)SiMe3 (1), which was prepared by the photoreaction
of Cp*Fe(CO)2Me (2) with hydrodisilane Mes2MeSiSiMe2H (3), reacted with nitriles RCN (R ) Ph,
Me) at 80 °C to afford a mixture of a disilanyl isocyanide complex Cp*Fe(CO)(R)(CNSiMe2SiMes2Me)
(5a, R ) Ph; 5b, R ) Me) and a pair of diastereomers of Cp*Fe(CO)(R)(CNSiMesMeSiMesMe2) (6a,
R ) Ph; 6b, R ) Me). The molecular structure of 5a was determined by X-ray crystallography. On the
other hand, when the photoreaction of 2 with 3 was performed in the presence of benzonitrile, acetonitrile,
or acetonitrile-d3, at ca. 5 °C, only the disilanyl isocyanide complex 5a, 5b, or 5b-d3 was obtained as a
single product. The formation of these disilanyl isocyanide complexes is understood by the action of
coordinatively unsaturated disilanyliron(II) intermediates Cp*Fe(CO)SiMe2SiMes2Me, etc., which are
transiently generated by thermal isomerization of 1 or photoreaction of 2 with 3, to incoming nitriles.
The C-C bond of the nitrile ligand is activated through migration of the disilanyl group to the nitrogen
atom of nitriles.
atom of the silylene ligand.3 Against our expectations, reactions
of 1 with nitriles did not produce the simple nitrile analogues
of 4 or the base-stabilized forms of 1, but gave disilanyl
isocyanide complexes Cp*Fe(CO)(R)(CNSiMe2SiMes2Me) and
Cp*Fe(CO)(R)(CNSiMeMesSiMesMe2) (R ) Ph, Me). The
formation of these disilanylisocyanide complexes implies that
the C-C bond cleavage of nitriles took place after 1,2- and
1,3-group migration reactions in the organosilicon moieties.
The C-C bond activation of unstrained nitriles using transi-
tion metal complexes is usually difficult, but some interesting
C-C bond cleavages of unstrained nitriles have been demon-
strated in reactions involving complexes of Ni,4a-d,5,6 Pd,4a Pt,4a
Mo,4e Rh,7 Ir,8 and Fe.9 Especially, very recently some silyl
complexes have been demonstrated to cleave the C-C bonds
of nitriles. Bergman, Brookhart, et al. reported that the reaction
of [Cp*(PMe3)Rh(SiPh3)(ClCH2Cl)]+ with RCN produced
[Cp*(PMe3)RhR(CNSiPh3)]+ (R ) alkyl and aryl groups).7
Introduction
Silyl(silylene) complexes are regarded as key intermediates
in various reactions involving organosilicon compounds, and
1,2- and 1,3-group migrations on these complexes have been
postulated to cause the metal-catalyzed oligomerization/deoli-
gomerization, isomerization, and redistribution of organosilicon
compounds.1 Recently, we succeeded in giving direct experi-
mental evidence for the 1,3-alkyl migration between two silicon
atoms and 1,2-silyl migration from Fe to Si on a donor-free
silyl(silylene)iron complex, Cp*Fe(CO)(dSiMes2)SiMe3 (1,
Mes ) mesityl), which was synthesized by the photoreaction
of Cp*Fe(CO)2Me (2) with hydrodisilane Mes2MeSiSiMe2H
(3).2 Thus, the reaction of 1 with tBuNC afforded the disilanyl
complex Cp*Fe(CO)(CNtBu)(SiMesMeSiMesMe2) (4) via 1,2-
and 1,3-group migrations. With our continuing interest in the
reactivity of the silyl(silylene) complex, we have investigated
the reactivity of 1 toward nitriles, which were expected to act
as a two-electron donor to the metal center or to the silicon
(3) Straus, D. A.; Grumbine, S. D.; Tilley, T. D. J. Am. Chem. Soc. 1987,
109, 5872.
(4) (a) Parshall, G. W. J. Am. Chem. Soc. 1974, 96, 2360. (b) Favero,
G.; Gaddi, M.; Morvillo, A.; Turco, A. J. Organomet. Chem. 1978, 149,
395. (c) Abla, M.; Yamamoto, T. J. Organomet. Chem. 1997, 532, 267.
(d) Miller, J. A. Tetrahedron Lett. 2001, 42, 6991. (e) Churchill, D.; Shin,
J. H.; Hascall, T.; Hahn, J. M.; Bridgewater, B. M.; Parkin, G. Organo-
metallics 1999, 18, 2403.
(5) (a) Garcia, J. J.; Jones, W. D. Organometallics 2000, 19, 5544. (b)
Garcia, J. J.; Brunkaan, N. M.; Jones, W. D. J. Am. Chem. Soc. 2002, 124,
9547. (c) Garcia, J. J.; Arevalo, A.; Brunkaan, N. M.; Jones, W. D.
Organometallics 2004, 23, 3997.
(6) Nakao, Y.; Oda, S.; Hiyama, T. J. Am. Chem. Soc. 2004, 126, 13904.
(7) (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.
(8) Klei, S. R.; Tilley, T. D.; Bergman, R. G. Organometallics 2002,
21, 4648.
(9) (a) Nakazawa, H.; Kawasaki, T.; Miyoshi, K.; Suresh, C. H.; Koga,
N. Organometallics 2004, 23, 117. (b) Nakazawa, H.; Kamata, K.; Itazaki,
M. Chem. Commun. 2005, 4004. (c) Itazaki, M.; Nakazawa, H. Chem. Lett.
2005, 1054. (d) Nakazawa, H.; Itazaki, M.; Owaribe, M. Acta Crystallogr.
2005, E61, m1073.
* To whom correspondence should be addressed. Fax: +81-22-
795-6543. E-mail:
mail.tains.tohoku.ac.jp.
hhashimoto@mail.tains.tohoku.ac.jp; tobita@
(1) (a) Tobita, H.; Ueno, K.; Ogino, H. Chem. Lett. 1986, 1777. (b)
Pannell, K. H.; Cervantes, J.; Hernandez, C.; Cassias, J.; Vincenti, S. P.
Organometallics 1986, 5, 1056. (c) Pannell, K. H.; Wang, L.-J.; Rozell, J.
M. Organometallics 1989, 8, 550. (d) Hernandez, C.; Sharma, H. K.;
Pannell, K. H. J. Organomet. Chem. 1993, 462, 259. (e) Pannell, K. H.;
Brun, M.-C.; Sharma, H.; Jones, K.; Sharma, S. Organometallics 1994,
13, 1075. (f) Zhang, Z.; Sanchez, R.; Pannell, K. H. Organometallics 1995,
14, 2605. (g) Sharma, H. K.; Pannell, K. H. Chem. ReV. 1995, 95, 1351.
(h) Ueno, K.; Nakano, K.; Ogino, H. Chem. Lett. 1996, 459. (i) Ueno, K.;
Asami, S.; Watanabe, N.; Ogino, H. Organometallics 2002, 21, 1326. (j)
Ogino, H. Chem. Rec. 2002, 2, 291. (k) Okazaki, M.; Tobita, H.; Ogino,
H. Dalton Trans. 2003, 493, and references therein. (l) Pannell, K. H.;
Kobayashi, T.; Cervantes-Lee, Francisco, J. Organomet. Chem. 2003, 685,
189.
(2) (a) Tobita, H.; Matsuda, A.; Hashimoto, H.; Ueno, K.; Ogino, H.
Angew. Chem., Int. Ed. 2004, 43, 221. (b) Hashimoto, H.; Matsuda, A.;
Tobita, H. Chem. Lett. 2005, 1374.
10.1021/om0507530 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 12/16/2005

Reactions of a Silyl(silylene)iron Complex
Organometallics, Vol. 25, No. 2, 2006 473
Tilley et al. found that a similar activation of nitrile occurred
using a cationic Ir(III) silyl complex.8 Nakazawa et al. also
reported the related C-C bond cleavage of nitrile using an Fe(II)
silyl complex9a and its application to catalytic aryl-CN bond
cleavage reaction9b as well as catalytic silylcyanation of
aldehydes and ketones.9c In these examples, it is suggested that
nitrile-coordinated silyl complexes are key intermediates, and
the following silyl migration to the nitrile nitrogen and
subsequent C-C bond cleavage afford silyl isocyanide com-
plexes.
We report here the details of the formation of disilanyl
isocyanide complexes by the reaction of silyl(silylene)iron
complex 1 with nitriles RCN (R ) Ph, Me) and also by the
photoreaction of 2 and 3 in the presence of nitriles. The X-ray
crystal structure of one of the disilanyl isocyanide complexes,
Cp*Fe(CO)(Ph)(CNSiMe2SiMes2Me) (5a), and possible reaction
mechanisms are also discussed.
Results and Discussion
Thermal Reaction of Cp*Fe(CO)(dSiMes2)SiMe3 (1) with
Nitriles. Silyl(silylene)iron complex 1 was heated in toluene at
80 °C for 5 h with an excess of benzonitrile to afford a 3:2
mixture of Cp*Fe(CO)(Ph)(CNSiMe2SiMes2Me) (5a) and a pair
of diastereomers of Cp*Fe(CO)(Ph)(CNSiMesMeSiMesMe2)
(6a) in 40% combined yield (eq 1). Similar heating of 1 in
acetonitrile as a solvent at 80 °C for 6 h afforded an approxi-
mately 5:6 mixture of disilanyl isocyanide complexes, Cp*Fe-
(CO)(Me)(CNSiMe2SiMes2Me) (5b) and a pair of diastereomers
of Cp*Fe(CO)(Me)(CNSiMesMeSiMesMe2) (6b) in 31% com-
Figure 1. ORTEP drawing of 5a, showing 50% thermal ellipsoids.
Hydrogen atoms are omitted for clarity. Selected bond distances
(Å) and angles (deg): Fe(1)-C(12) 1.79(1), C(12)-N(1) 1.18(2),
N(1)-Si(1) 1.76(1), Si(1)-Si(2) 2.364(5), Fe(1)-C(34) 2.01(1),
Fe(1)-C(11) 1.78(1), C(11)-O(1) 1.13(2); Fe(1)-C(12)-N(1)
177(1), C(12)-N(1)-Si(1) 166(1), N(1)-Si(1)-Si(2) 99.0(4).
Photochemical Reaction of 2 and 3 in the Presence of
Nitriles. Interestingly, the photoreaction of 2 and 3 in the
presence of nitriles also produced the same type of disilanyl
isocyanide complexes but only as a single product. Thus,
irradiation of a toluene solution of 2 and 3 containing a slight
excess of benzonitrile in a Pyrex glass tube at ca. 5 °C afforded
Cp*Fe(CO)(Ph)(CNSiMe2SiMes2Me) (5a) as yellow crystals in
77% isolated yield (eq 2). In a similar manner, 5b was isolated
as a yellow solid in 22% yield by employing acetonitrile as a
solvent. This low yield of 5b is mainly due to its high instability.
In an NMR experiment using acetonitrile-d3 as a solvent, 5b-
d3 formed as a single product in 82% NMR yield. Complex 6a
or 6b was not observed in every case of these photochemical
reactions.
1
bined yield (eq 1). Monitoring of the reactions by H NMR
spectroscopy shows that each reaction proceeds almost quan-
titatively. Their low isolated yields are mainly attributable to
their instabilities; the products slowly decompose in solution
to give Cp*2Fe2(CO)4, which disturbs purification of the
products by recrystallization. Although the characterization of
these products was difficult only from their spectroscopic data,
the structure of 5a was successfully confirmed by the X-ray
crystal structure determination. Other complexes (5b, 6a, and
6b) were characterized on the basis of the similarity of their
spectroscopic data with those of 5a (see Experimental Section).
A Possible Mechanism for the Formation of 5 and 6. The
fact that 5 and 6 have a disilanyl isocyanide ligand and an R
group (from nitrile RCN) on the iron center indicates that the
C-C bond of nitriles is activated by the insertion of the iron
fragment into the C-C bond and simultaneous migration of
the disilanyl group to the nitrogen of nitriles. In addition, as
mentioned in the Introduction, 1 reacted with isocyanide tBuNC
at 60 °C to produce mainly the disilanyl complex Cp*Fe(CO)-
(CNtBu)(SiMesMeSiMesMe2) (4). This result suggests that an
unsaturated disilanyl intermediate is generated from 1 at the
initial stage under heating conditions and can be trapped by a
X-ray Crystal Structure Determination of 5a. The ORTEP
drawing of 5a is depicted in Figure 1 with the selected bond
lengths (Å) and bond angles (deg). The X-ray crystal structure
analysis of 5a clearly reveals that 5a is a disilanyl isocyanide
complex having an unprecedented Fe-C-N-Si-Si linkage.
The iron atom adopts a typical three-legged piano-stool structure,
which consists of Cp*, carbonyl, phenyl, and disilanyl isocya-
nide ligands. Therefore, the iron atom becomes a chiral center
and the crystal consists of the enantiomers. The Fe(1)-C(12)
(1.79(1) Å), C(12)-N(1) (1.18(2) Å), and N(1)-Si(1) (1.76(1)
Å) bond lengths are comparable with the Fe-C (1.790(5) Å),
C-N (1.181(7) Å), and N-Si (1.701(6) Å) bond lengths of
Cp*Fe(PPh3)(CNSiPh3)Me,9a typical of iron isocyanide com-
plexes.10
t
two-electron donor such as BuNC. Taking these results into
consideration, a possible mechanism for the formation of
disilanyl isocyanide complexes in the reaction of 1 with nitriles
(10) Based on a search of the Cambridge Structural Database, CSD
version 5.25 (November 2003).

474 Organometallics, Vol. 25, No. 2, 2006
Hashimoto et al.
Scheme 1. A Possible Mechanism for the Formation of
5 and 6
stabilized by coordination of bases including nitriles. The
stability of the adduct must depend on the steric interaction
between the nitrile and silylene ligand, and the largest steric
interaction is expected to the adduct between benzonitrile and
B having a mesityl(methyl)silylene ligand, which is apparently
the least stable. Therefore, the ratio of A to B is predicted to be
higher in the adducts of bulkier benzonitrile than in those of
acetonitrile. The above-mentioned ratios of 5 to 6, which are
considered to reflect the ratios of A to B, are consistent with
this hypothesis. We recently demonstrated through the thermal
reaction of 1 with CO that disilanyl complex D forms preferably
to C due to the steric repulsion among two mesityl groups and
other parts of the molecule, which is less in B than A.2b This is
retained in the acetonitrile adducts of A and B, while reversed
in the corresponding benzonitrile adducts.
Conclusions
We found that not only 1,2-silyl migration but also C-C bond
activation of nitriles occur in the reaction of the silyl(silylene)
iron complex Cp*Fe(CO)(dSiMes2)SiMe3 (1) with nitriles at
80 °C to produce disilanylisocyanide complexes Cp*Fe(CO)-
(R)(CNSiMe2SiMes2Me) (5) and Cp*Fe(CO)(R)(CNSiMesMe-
SiMesMe2) (6). Complex 5 was also produced as a single
product by the photoreaction of Cp*Fe(CO)2Me (2) with Mes2-
MeSiSiMe2H (3) in the presence of nitriles at low temperature.
We proposed a reaction mechanism involving the transient
formation of unsaturated disilanyliron complexes Cp*Fe(CO)-
(SiMe2SiMes2Me) (C) and Cp*Fe(CO)(SiMesMeSiMesMe2)
(D). Coordination of nitriles to C or D followed by migration
of the disilanyl group from Fe to N and addition of C-C bond
of nitriles gives 5 (and 6).
is illustrated in Scheme 1. The mechanism consists of (1) 1,3-
migration of a methyl group followed by a mesityl group on 1
to produce other isomeric silyl(silylene) complexes A and B,
(2) 1,2-silyl migration from A and B to generate 16e disilanyl
complexes C and D, respectively, (3) coordination of nitriles
to C and D to produce E and F, respectively, and (4) disilanyl
group migration from Fe to N and subsequent oxidative addition
of a C-C bond of the resulting η2-iminoacyl ligand to the iron
center to produce 5 and 6. The final path is thought to be
irreversible, while the other paths are reversible. Although we
could not observe any intermediates, Jones observed the
formation of an η2-nitrile complex and subsequent oxidative
addition to produce (dippe)Ni(Ph)(CN) (dippe ) diisopropyl-
phosphinoethane) in the reaction of [(dippe)NiH]2 with PhCN.5
Bergman and Brookhart also observed an η1-nitrile intermediate
as well as an η2-iminoacyl intermediate, [Cp*(PMe3)Rh(η2-C(4-
(OMe)C6H4)dN(SiPh3))]+, which was isolated and structurally
confirmed, in the reaction of [Cp*(PMe3)Rh(SiPh3)(ClCH2Cl)]+
with MeOC6H4CN.7b Nakazawa et al. also suggested a mech-
anism involving η2-nitrile- and η2-iminoacyl-coordinated species
for their C-C bond activation of acetonitrile using an Fe(II)
silyl complex based on DFT calculation.9a Probably, the step
of C-C bond cleavage of nitriles in our system would also
proceed via a similar mechanism involving η2-nitrile (E and F)
and/or η2-iminoacyl intermediates.
Experimental Section
General Procedures. All manipulations were carried out under
argon using standard Schlenk or vacuum line techniques. Benzene-
d6, toluene, hexane, pentane, acetonitrile, and acetonitrile-d3 were
dried over calcium hydride and distilled before use. Benzonitrile
was dried over 4 Å molecular sieves before use. Cp*Fe(CO)-
(dSiMes2)SiMe3 (1),2 Cp*Fe(CO)2Me (2) (Cp* ) η5-C5Me5),11 and
Mes2MeSiSiMe2H (3)12 were synthesized according to the previ-
1
1
ously reported procedures. H, 13C{1H}, 29Si{1H}, and H-29Si-
{1H} COLOC NMR spectra were recorded on a Bruker ARX-300,
a Bruker AVANCE-300, or a JEOL ECA-600 spectrometer. H
NMR chemical shifts ware referenced to the residual H NMR
1
1
signal of the deuterated solvents. 13C{1H} and 29Si{1H} NMR
chemical shifts were referenced to an external standard of TMS.
Infrared spectra were obtained using a HORIBA FT-730 spectro-
photometer. Mass spectra were recorded on a Shimadzu GCMS-
QP5000 mass spectrometer operating in electron impact (EI) mode.
Exact mass spectra were recorded on a Bruker Daltonics APEX-
(III) mass spectrometer operating in electrospray ionization (ESI)
mode. Elemental analyses were performed at the Instrumental
Analysis Center for Chemistry, Tohoku University.
Exclusive formation of 5 in the photoreaction of 2 and 3 in
the presence of nitriles is explained as follows. In this case, the
initial product is the 16e disilanyl complex C. At low temper-
ature, 1,2-silyl migration from C to A is suppressed, while
coordination of nitriles to C and the following C-C bond
activation process of nitriles (C f E f 5) still occurs smoothly
to give only 5.
Thermal Reaction of Cp*Fe(CO)(dSiMes2)SiMe3 (1) with
PhCN. A toluene (5 mL) solution of 1 (109 mg, 0.195 mmol) and
benzonitrile (94 mg, 0.91 mmol) was heated at 80 °C for 5 h. After
removal of volatiles, the residue was recrystallized from pentane
(3 mL) to afford yellow crystals of an isomeric mixture of Cp*Fe-
(CO)(Ph)(CNSiMe2SiMes2Me) (5a) and Cp*Fe(CO)(Ph)(CNSiMes-
MeSiMesMe2) (6a) (5a:6a ) 3:2) in 40% combined yield (52 mg,
0.079 mmol). 5a and 6a were not separated even by repeated
It should be pointed out again here that the product ratio of
5 to 6 in the thermal reaction was different depending on the
nitriles employed: When benzonitrile was used, the ratio of 5a
to 6a was 3:2, while when acetonitorile was used, that of 5b to
6b was 5:6. However, as demonstrated in the previous para-
graph, if the C-C bond activation process of nitriles (C f
E f 5 and also D f F f 6) is faster than the processes before
that, the ratio of the products 5 and 6 must be independent of
the nitriles. A plausible explanation is the existence of the
interaction between a nitrile molecule and silyl(silylene) com-
plexes A and B. It is well known that silylene complexes are
(11) Catheline, D.; Astruc, D. J. Organomet. Chem. 1982, 226, C52.
(12) Ueno, K.; Asami, S.; Watanabe, N.; Ogino, H. Organometallics
2002, 21, 1326.

Reactions of a Silyl(silylene)iron Complex
Organometallics, Vol. 25, No. 2, 2006 475
Chart 1
207.5 (FeCNSi), 221.3 (CO). 29Si{1H} NMR (59.6 MHz, C6D6): δ
-27.6 (SiMes2Me), -8.6 (SiMe2). IR (C6D6): 1924 (νCO), 2017
(νCN) cm-1. MS (EI, 70 eV): 661 (M+, 13), 633 (M+ - CO, 21),
618 (M+ - CO - Me, 4), 421 (M+ - Cp* - CO - Ph, 100).
Anal. Calcd for C39H51FeNOSi2: C, 70.77; H, 7.77; N, 2.12.
Found: C, 70.50; H, 7.77; N, 2.06.
Photoreaction of 2 and 3 in the Presence of Acetonitrile:
Isolation of Cp*Fe(CO)(Me)(CNSiMe2SiMes2Me) (5b). Cp*Fe-
(CO)(Me)(CNSiMe2SiMes2Me) (5b) was prepared as a relatively
unstable yellow solid in 22% yield (60 mg, 0.10 mmol) by a
procedure similar to that for 5a employing an acetonitrile solution
(5 mL) of 2 (144 mg, 0.549 mmol) and 3 (156 mg, 0.458 mmol).
Data of 5b: 1H NMR (300 MHz, C6D6): δ 0.19 (s, 3H, FeMe),
0.287 (s, 3H, R-SiMe2), 0.293 (s, 3H, R-SiMe2), 0.88 (s, 3H,
SiMes2Me), 1.62 (s, 15H, C5Me5), 2.07 (s, 6H, p-Me), 2.315 (s,
6H, o-Me), 2.324 (s, 6H, o-Me), 6.68 (s, 4H, m-H). 13C{1H} NMR
(75.5 MHz, C6D6): δ -12.0 (FeMe), 1.4 (R-SiMe), 1.6 (R-SiMe),
2.8 (â-SiMe), 9.7 (C5Me5), 21.1 (p-Me), 24.8 (o-Me), 92.7 (C5-
Me5), 130.0 (C6H2Me3), 133.0 (C6H2Me3), 138.9 (C6H2Me3), 143.4
(C6H2Me3), 210.0 (FeCNSi), 222.1 (CO). 29Si{1H} NMR (59.6
MHz, C6D6): δ -27.7 (SiMes2Me), -10.2 (SiMe2). IR (C6D6):
recrystallization from the mixture, but pure 5a was isolated from
the reaction of Cp*Fe(CO)2Me (2) and Mes2MeSiSiMe2H (3) in
the presence of benzonitrile (vide infra). Complex 6a was found
1
to be a mixture of two diasteromers and was characterized by H,
29Si{1H}, and 1H-29Si{1H} COLOC NMR (see Supporting Infor-
mation). Data of 6a (a mixture of two diastereomers): 1H NMR
(300 MHz, C6D6): δ 0.47, 0.53, 0.54, 0.60 (s, SiMesMe2), 0.75,
0.78 (s, SiMesMe), 1.53, 1.55 (s, C5Me5), 1.986, 1.992, 2.03, 2.04
(s, p-Me), 2.16, 2.22, 2.23, 2.28 (s, o-Me), 6.56-6.60 (m-H), 7.06-
7.22 (m, p-H or m-H of FePh), 7.73-7.80 (m, o-H of FePh). 13C-
{1H} NMR (75.5 MHz, C6D6): δ 2.4, 2.5, 4.75, 4.81 (SiMe), 9.78,
9.81 (C5Me5), 21.0 (p-Me), 24.52, 24.55, 25.2, 25.3 (o-Me), 94.2
(C5Me5), 112.9, 119.0, 127.1, 128.8, 128.9, 129.6, 131.9, 139.6,
143.9, 144.1, 144.6, 165.0, 165.5 (C6H2Me3 or FeC6H5), 207.2
(FeCNSi), 221.4 (CO). Some of these carbon signals seem to be
overlapped. 29Si{1H} NMR (59.6 MHz, C6D6): δ -22.0 (â-Si),
-21.9 (â-Si), -16.7 (R-Si), -16.5 (R-Si, see Chart 1). Exact mass
(ESI) for the isomeric mixture of 5a and 6a: calcd for C39H51-
FeNOSi2+Na 684.2751, found 684.2753.
1909 (νCO), 2003 (νCN) cm-1. MS (EI): 599 (M+, 9), 571 (M+
-
CO, 21), 556 (M+ - CO - Me, 27), 421 (M+ - Cp* - CO -
Me, 100). Anal. Calc for C34H49FeONSi2: C, 68.09; H, 8.23; N,
2.34. Found: C, 67.95; H, 8.27; N, 2.28.
Photoreaction of 2 and 3 in the Presence of Acetonitrile-d3.
In a procedure similar to that of 5b, Cp*Fe(CO)(CD3)(CNSiMe2-
SiMes2Me) (5b-d3) was obtained in 82% NMR yield by irradiation
of an acetonitrile-d3 solution (0.5 mL) containing 2 (10 mg, 0.037
mmol), 3 (10 mg, 0.030 mmol), and an internal standard, Si(SiMe3)4
(1 mg, 0.003 mmol). The spectral data of 5b-d3 were essentially
identical to those of 5b except the signals for the CD3 group. Data
of 5b-d3: 1H NMR (300 MHz, CD3CN): δ 0.327 (s, 3H, R-SiMe2),
0.337 (s, 3H, R-SiMe2), 0.81 (s, 3H, SiMes2Me), 1.64 (s, 15H, C5-
Me5), 2.22 (s, 6H, p-Me), 2.24 (s, 12H, o-Me), 6.80 (s, 4H, m-H).
29Si{1H} NMR (59.6 MHz, CD3CN): δ -28.0 (SiMes2Me), -9.4
(SiMe2).
X-ray Crystal Structure Determination of 5a. The yellow
crystals of 5a suitable for X-ray crystal structure determination were
grown by keeping a mixture of hexane and toluene containing 5a
at -30 °C. One of the crystals was mounted on a glass fiber. The
intensity data for 5a were collected on a Rigaku RAXIS-RAPID
imaging plate diffractometer with graphite-monochromated Mo KR
radiation to a maximum 2θ value of 55.0 at 150 K. A total of 44
images, corresponding to 220.0° oscillation angles, were collected
with two different goniometer settings. Exposure time was 5.0 min
per degree. Readout was performed in the 0.100 mm pixel mode.
Numerical absorption collections were applied on the crystal shape.
The structure of 5a was solved by the heavy-atom method
(DIRDIF94 PATTY)13 and refined by the block-diagonal least-
squares method with individual anisotropic thermal parameters for
non-hydrogen atoms. The positions of all hydrogen atoms were
calculated and fixed. The final residue R1 for reflections (3316)
with I > 4σ(I) was R1 ) 0.099. All calculations were performed
using the teXsan crystal structure analysis package.14 Crystal-
lographic information has been deposited with the Cambridge
Crystallographic Data Centre (CCDC No. 215874 (5a)).
Thermal Reaction of Cp*Fe(CO)(dSiMes2)SiMe3 (1) with
MeCN. An isomeric mixture of Cp*Fe(CO)(Me)(CNSiMe2SiMes2-
Me) (5b) and Cp*Fe(CO)(Me)(CNSiMesMeSiMesMe2) (6b) (5b:
6b ) 5:6) was obtained in 31% combined yield (52 mg, 0.079
mmol) in a procedure similar to that for 5a and 6a by heating (80
°C for 6 h) an acetonitrile (5 mL) solution of 1 (213 mg, 0.381
mmol). Pure 5b was prepared by the photoreaction of 2 and 3 in
acetonitrile (vide infra). Data of 6b (a mixture of two diastereo-
mers): 1H NMR (300 MHz, C6D6): δ 0.22, 0.23 (s, FeMe), 0.30,
0.59, 0.61, 0.66, 0.67, 0.74 (s, SiMe), 1.630, 1.635 (s, C5Me5), 2.00,
2.04 (s, p-Me), 2.26, 2.29, 2.34, 2.35 (s, o-Me), 6.60, 6.64 (s, m-H).
13C{1H} NMR (75.5 MHz, C6D6): δ -12.4, -12.0 (FeMe), 1.4,
2.5, 4.7, 4.9 (SiMe), 9.6, 9.7 (C5Me5), 21.0 (p-CH3), 24.75, 24.77,
25.2, 25.3 (o-CH3), 92.74, 92.83 (C5Me5), 128.76, 128.79, 129.3,
129.6, 130.4, 138.6, 139.5, 144.0, 144.6 (C6H2Me3), 209.7 (FeCN-
Si), 222.1, 222.3 (CO). Some of these carbon signals seem to be
overlapped. 29Si{1H} NMR (59.6 MHz, C6D6): δ -22.7 (â-Si),
-21.9 (â-Si), -17.8 (R-Si), -17.6 (R-Si). Exact mass (ESI) for
the isomeric mixture of 5b and 6b: calcd for C34H49FeNOSi2
599.2697, found 599.2699.
Photoreaction of 2 and 3 in the Presence of Benzonitrile:
Isolation of Cp*Fe(CO)(Ph)(CNSiMe2SiMes2Me) (5a). A toluene
solution (5 mL) of Cp*Fe(CO)2Me (2) (90.6 mg, 0.346 mmol),
Mes2MeSiSiMe2H (3) (119 mg, 0.349 mmol), and PhCN (46 mg,
0.45 mmol) in a Pyrex sample tube with a Teflon vacuum valve
was irradiated for 2 h with a 450 W medium-pressure Hg lamp
immersed in a water bath (ca. 5 °C). The reaction mixture was
degassed every 20 min of irradiation by a conventional freeze-
pump-thaw cycle on a vacuum line. After removal of volatiles,
the residue was recrystallized from acetonitrile to afford yellow
crystals of 5a in 77% yield (176 mg, 0.266 mmol). Data of 5a: 1H
NMR (300 MHz, C6D6): δ 0.32 (s, 3H, SiMe2), 0.33 (s, 3H, SiMe2),
0.79 (s, 3H, SiMes2Me), 1.52 (s, 15H, C5Me5), 2.05 (s, 3H, p-Me),
2.06 (s, 3H, p-Me), 2.226 (s, 6H, o-Me), 2.232 (s, 6H, o-Me), 6.64
(s, 2H, m-H), 6.65 (s, 2H, m-H), 7.10 (d, JHH ) 7.2 Hz, 1H, p-H
Acknowledgment. This work was supported by the Ministry
of Education, Culture, Sports, Science and Technology of Japan
[Grants-in-Aid for Scientific Research Nos. 14204065, 14078202,
14044010, and 16750044].
(13) Beurskens, P. T.; Admireal, G.; Beurskens, G.; Bosman, W. P.; de
Gelder, R.; Isreal, R.; Smits, J. M. M. The DIRDIF-94 program system;
Technical Report of the Crystallography Laboratory; University of
Nijimegen: The Netherlands, 1994.
(14) teXsan, Crystal Structure Analysis Package; Molecular Structure
Corporation, 1985 and 1999.
of FePh), 7.19 (t, JHH ) 7.2 Hz, 2H, m-H of FePh), 7.75 (d, JHH
)
7.2 Hz, 2H, o-H of FePh). 13C{1H} NMR (75.5 MHz, C6D6): δ
1.4 (R-SiMe), 1.5 (R-SiMe), 2.8 (â-SiMe), 9.7 (C5Me5), 21.0 (p-
Me), 24.7 (o-Me), 94.1 (C5Me5), 122.1, 127.2, 129.5, 129.6, 132.5,
133.0, 138.6, 143.2, 143.3, 143.7, 165.3 (C6H2Me3 or FeC6H5),

476 Organometallics, Vol. 25, No. 2, 2006
Hashimoto et al.
Supporting Information Available: Crystallographic data for
5a and the CIF file, including tables of atomic coordinates,
anisotropic thermal parameters, bond distances and angles, and
1H-29Si{1H} COLOC NMR spectrum of a mixture of 5a and 6a.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM0507530