Photochemistry of bridged disilyldiiron complexes (SiMe2)[(η5-C5H4)Fe(CO) 2SiMe2SiMe2R]2, R=Me, Ph

Article abstract of DOI:10.1016/S0022-328X(01)01094-4

Photochemical irradiation of the new bimetallic disilyliron complexes (SiMe₂)[(η⁵-C₅H₄)Fe(CO) ₂SiMe₂SiMe₂R]₂, R=Me, Ph, results in silylene elimination chemistry, as observed for the mono-metallic analogs, resulting in the formation of complexes (SiMe₂)[(η⁵-C₅H₄)Fe(CO) ₂SiMe₂R]₂. The intermediate silyl(silylene) complexes can be intercepted with HMPA. Apart from a very reactive minor product that we have been unable to identify at this time, the proximity of the two transition metal centers has little impact upon the observed chemistry.

Full text of DOI:10.1016/S0022-328X(01)01094-4

Journal of Organometallic Chemistry 634 (2001) 102–108
www.elsevier.com/locate/jorganchem
Photochemistry of bridged disilyldiiron complexes
(SiMe2)[(h5-C5H4)Fe(CO)2SiMe2SiMe2R]2, R=Me, Ph
Yongqiang Zhang, Francisco Cervantes-Lee, Keith H. Pannell *
Department of Chemistry, Uni6ersity of Texas at El Paso, El Paso, TX 79968, USA
Received 5 July 2001; accepted 7 July 2001
Abstract
Photochemical irradiation of the new bimetallic disilyliron complexes (SiMe2)[(h5-C5H4)Fe(CO)2SiMe2SiMe2R]2, R=Me, Ph,
results in silylene elimination chemistry, as observed for the mono-metallic analogs, resulting in the formation of complexes
(SiMe2)[(h5-C5H4)Fe(CO)2SiMe2R]2. The intermediate silyl(silylene) complexes can be intercepted with HMPA. Apart from a very
reactive minor product that we have been unable to identify at this time, the proximity of the two transition metal centers has
little impact upon the observed chemistry. © 2001 Published by Elsevier Science B.V.
Keywords: Photochemistry; Iron carbonyl complexes; Silyl(silylene)iron intermediates; Silylene elimination
1. Introduction
FpCH2SiR2SiR2CH2Fp resulted in the unprecedented
stereospecific formation of 1,3-disilacyclobutanes rein-
forces the idea that binuclear systems offer a fertile
region for chemical investigation [23]. We report the
synthesis and photochemical irradiation of the monosi-
Photochemical irradiation of (h5-C5H5)Fe(CO)2-sub-
stituted oligosilanes results, subsequent to CO expul-
sion, in formation of silyl(silylene) intermediates
(h5-C5H5)Fe(CO)(ꢀSiR2)(SiR3) via an a-elimination
process. These intermediates lead to either silylene elim-
inations, Eq. (1), or rearrangements, Eq. (2) [1]. Both
may be effected catalytically under appropriate condi-
tions [2–13].
lyl-bridged
diiron
complexes
(SiMe2)[(h5-
C5H4)Fe(CO)2SiMe2SiMe2R]2, R=Me (1), Ph (2). The
two metal centers are held together via a dimethylsi-
lylene unit bridging two cyclopentadienyl ligands, thus
the inherent closeness of the two reaction centers might
produce new chemistry.
Fp–SiMe2SiMe3“Fp–SiMe3+[SiMe2]
(1)
(2)
Fp–SiMe2SiMe2SiMe2SiMe3“Fp–Si(SiMe3)3
2. Results and discussion
The proposed silyl(silylene) intermediates have been
observed spectroscopically by low-temperature matrix
isolation [14], and isolated, and structurally character-
ized, as intramolecularly base- and metal-stabilized spe-
cies and observed as intermolecularly HMPA-stabilized
complexes [15–18].
The photochemistry of oligosilyl complexes contain-
ing two metal centers produces distinctive results. Irra-
diation of FpSiMe2SiMe2Fp resulted in no silylene
expulsion; mono- and bis-bridging silylene diiron com-
plexes were formed sequentially [19–22]. Our recent
observation that photochemical treatment of
The reaction between the chlorodisilanes ClSiMe2-
SiMe2R (R=Me, Ph) and [(h5, h5-C5H4Me2SiC5H4)-
Fe2(CO)4]2− 2Na+ yielded moderate to good yields of
the corresponding (disilyl)iron complexes (SiMe2)[(h5-
C5H4)Fe(CO)2SiMe2SiMe2R]2 (R=Me (1), Ph (2)) (Eq.
(3)). The spectroscopic data for 1 and 2 are in accord
with the proposed structures [4,24].
* Corresponding author. Fax: +1-915-747-5748.
E-mail address: kpannell@utep.edu (K. H. Pannell).
(3)
0022-328X/01/$ - see front matter © 2001 Published by Elsevier Science B.V.
PII: S0022-328X(01)01094-4

Y. Zhang et al. / Journal of Organometallic Chemistry 634 (2001) 102–108
103
Photolysis of 1 in C6D6 resulted in the formation of
(SiMe2)[(h5-C5H4)Fe(CO)2SiMe3]2 (3b) after 25 h.
NMR monitoring indicated the intermediacy of
[Me3Si(CO)2Fe(h5 - C5H4)(SiMe2)(h5 - C5H4)Fe(CO)2-
SiMe2SiMe3] (3a), indicating the photo-reaction is step-
wise (Eq. (4)). Along with 3a, irradiation of 1 resulted
in the formation of a minor product (20%) exhibiting
29Si-NMR signals at 31.3 and −8.9 ppm.
SiMe2Ph] (4a) and [Me3Si(CO)2Fe(h5-C5H4)(SiMe2)(h5-
C5H4)Fe(CO)2SiMe2SiMe2Ph] (4b), with the former
dominant over the course of the photolysis. Continued
irradiation led to the complete disappearance of 2, 4a
and 4b and the formation of the monosilyl iron com-
plexes
[Me3Si(CO)2Fe(h5-C5H4)(SiMe2)(h5-C5H4)-
Fe(CO)2SiMe2Ph] (4c), [Me2PhSi(CO)2Fe(h5-C5H4)-
(4)
The photolysis of 2 was both more rapid and com-
plex, Scheme 1. Initially formed were [PhMe2Si-
(CO)2Fe(h5 - C5H4)(SiMe2)(h5 - C5H4)Fe(CO)2SiMe2-
(SiMe2)(h5-C5H4)Fe(CO)2SiMe2Ph] (4d) and 3b,
1:8:1.
Scheme 1.

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Y. Zhang et al. / Journal of Organometallic Chemistry 634 (2001) 102–108
The presence of HMPA [(Me2N)3PO] during photol-
ysis of Fp–disilanes is an effective route for stabilizing
the iron–silylene intermediates [18]. After 10 h irradia-
tion a C6D6 solution of 1 and 2.5 equivalents of HMPA
showed the complete disappearance of 1 and the forma-
tion of HMPA-coordinated silyl(silylene) complexes 5
and 6, Eq. (5). Further irradiation for 15 h resulted in
the complete disappearance of 5 and almost quantita-
tive formation of 6 further supporting the stepwise
nature of the reaction, Scheme 1. The 29Si-NMR spec-
trum of 6 exhibited six resonances at −9.23, −9.13,
31.09, 31.17, 116.66 and 116.70 ppm which are assigned
to two isomers 6a and 6b (meso and rac relative peak
ratios of 10:8). In the 13C-NMR spectrum of 6, bridged
silicon methyl groups exhibited three resonances. Two
resonances of equal intensity observed at −0.95 and
1.71 ppm are assigned to the meso isomer with a mirror
symmetry about the SiMe2 bridge, and the remaining
resonance observed at 0.56 ppm is assigned to the rac
isomer with a C2 axis about the SiMe2 bridge.
Similar irradiation of 2 as a C6D6 solution containing
HMPA resulted in the ultimate formation of a single
HMPA-coordinated silyl(silylene) complex 8 via the
transient formation of 7, Eq. (5). All spectroscopic data
are in accord with the proposed structures. For exam-
ple, the 29Si-NMR spectrum of 8 exhibited six reso-
nances at −9.20, −9.24, 29.44, 29.57, 115.70 and
115.80 ppm which are assigned to two isomers 8a and
8b (meso/rac=10/8.5). Two 13C resonances of equal
intensity observed at −1.08 and 1.11 ppm for bridged
silicon methyl groups were similarly assigned to the
meso isomer 8a, while the third resonance at −0.11
ppm for bridged silicon methyl groups was assigned to
the rac isomer 8b.
Fig. 1. Molecular structure of 4d. Hydrogen atoms are omitted for
clarity.
Overall, the photolysis of 1 and 2 led to similar
results to those of their non-bridged analogs Fp–
SiMe2SiMe2R, (R=Me, Ph) involving silylene elimina-
tion, and the predominant formation of FeSiMe2Ph
compounds where possible. Although it seems that the
proximity of the two Fe centers has little impact upon
the chemistry at each center, the unknown and highly
labile species formed along with 3 during the irradiation
of 1 suggests a minor new pathway. With the 29Si-
NMR chemical shifts of 31.3 and −8.85 ppm this may
well be a disilyl bridged diiron complex derived from
the association of two silylene transients. At present we
have been unable to further study this material; how-
ever, changing the various groups associated with the
Fe atoms may be useful to tease out this new chemistry
and we are pursuing this aspect of the project.
The ORTEP drawing of 4d is shown in Fig. 1. The
molecule consists of two (h5-C5H4)Fe(CO)2SiMe2Ph
groups linked a SiMe2 bridge. The Fe–Si bond lengths
,
(mean 2.330 A) are well within the range of 2.312–
,
2.378 A [25–29] for such bonds, Table 2. The Ph group
(5)
During irradiation of 2 we did not observe the for-
mation of the other possible HMPA-coordinated
silyl(silylene) complexes containing the (Fe=SiMePh·
HMPA) fragments despite the fact that photolysis with-
is trans to two CO groups possibly to reduce steric
repulsion and the two Cp rings are almost perpendicu-
lar to each other with a dihedral angle of 82.2°.

Y. Zhang et al. / Journal of Organometallic Chemistry 634 (2001) 102–108
105
out HMPA resulted in two transient intermediate prod-
ucts 4a and 4b. This result indicates that the silyl(si-
lylene)iron intermediates, once formed, are immediately
coordinated by HMPA before they have time to partic-
ipate in 1,3-aryl migrations. This result contrasts the
behavior of Cp*(OC)Fe(ꢀSiMe2·HMPA)SiMe3 where
exchange between the diastereotopic methyl groups in
the Fe(ꢀSiMe2·HMPA) unit was observed [18], but is in
line with the chemistry of Cp(OC)2W(SiMe3)-
(ꢀSiMe2·HMPA) [30].
(bridged-SiMe2), 17.05 (SiMe2); IR w(CO) 1994 (s),
1943 (s).
Using the same procedure as above, (SiMe2)[(h5-
C5H4)Fe(CO)2SiMe2SiMe2Ph]2 (2, oil) and (SiMe2)[(h5-
C5H4)Fe(CO)2SiMe2Ph]2 (4d, m.p. 78–80 °C) were
prepared in 37 and 67% yields, respectively. 2: Anal.
Calc. (Found) C, 54.26 (54.21); H, 6.07(5.85)%; 1H-
NMR l 0.38 (s, 6H, bridged-SiMe2), 0.47 (s, 12H,
SiMe2Ph), 0.56 (s, 12H, Fe–SiMe2), 4.12, 4.23 (s, s, 4H,
4H, Cp), 7.21 (m, 6H, Ph), 7.51(m, 4H, Ph); 13C-NMR
l −2.31 (SiMe2Ph), −1.06 (bridged-SiMe2), 4.00 (Fe–
SiMe2), 86,49, 88.56, 89.91 (Cp), 128.41, 128.92, 134.31,
3. Experimental
141.45 (Ph), 215.93 (CO); 29Si-NMR
l
−15.10
(SiMe2Ph), −10.07 (bridged-SiMe2), 17.09 (Fe–
SiMe2); IR w(CO) 1993 (s), 1943 (s). 4d: Anal. Calc.
(Found) C, 56.47 (56.81); H, 5.33 (5.41)%; H-NMR l
3.1. General data
1
All manipulations were carried out under an argon
atmosphere or in vacuo. THF was distilled under nitro-
gen from sodium benzophenone ketyl prior to use. The
following reagents were used as received, silica gel
(grade 950, 60–200 mesh) MCB; PhMe2SiCl,
Me3SiSiMe3, Gelest; HMPA [(Me2N)3PO], Aldrich.
Other reagents were synthesized by literature proce-
dures: PhMe2SiSiMe2Cl [31], Me3SiSiMe2Cl [32],
(SiMe2)[(h5-C5H4)Fe(CO)2]2 [33]. NMR spectra were
recorded on a Bruker ARX-300 FT spectrometer in
C6D6; IR spectra were obtained on a Perkin–Elmer
1600 series FT-IR spectrometer in hexane. Elemental
analyses were performed by Galbraith Laboratories.
0.23 (s, 6H, bridged-SiMe2), 0.64 (s, 12H, SiMe2Ph),
3.89, 4.11 (s, s, 4H, 4H, Cp), 7.06–7.18 (m, 6H, Ph),
7.53–7.56 (m, 4H, Ph); 13C-NMR l −1.19 (bridged-
SiMe2), 5.84 (Fe–SiMe2Ph), 88.65, 88.26 (Cp), 127.88,
128.52, 133.04, 147.60 (Ph), 216.18 (CO); 29Si-NMR l
−10.04 (bridged-SiMe2), 35.62 (Fe–SiMe2Ph); IR
w(CO) 1994 (s), 1943 (s).
3.3. Photolysis of 1: formation of
(SiMe2)[(p5-C5H4)Fe(CO)2SiMe3]2 (3b)
A 5 mm Pyrex NMR tube was charged 0.15 g (0.22
mmol) of 1 and 0.8 ml of C6D6. After three freeze–
pump–thaw cycles it was sealed under vacuum and
irradiated with 450 W medium-pressure Hg lamp at a
distance of 2 cm. After 3 h, NMR monitoring showed
the formation of a major product 3a, along with traces
of 3b. Further irradiation for 22 h resulted in the
complete disappearance of 1 and 3a and the formation
of 3b, along with a minor product with two 29Si-NMR
resonances (31.33, −8.85 ppm), which we have not yet
to identify. The reaction mixture was placed upon a
1.0×20 cm silica gel column. Elution with hexanes
developed a light yellow band which was collected and
subsequent to solvent removal afforded a yellow oil
which after several days in a refrigerator formed 3b as
a brown yellow crystalline solid (50 mg, 0.09 mmol,
41%), m.p. 68–70 °C.
3.2. Synthesis of (SiMe2)[(p5-C5H4)Fe(CO)2Si2Me5]2
(1)
To 50 ml of
a
THF solution of [(h5,h5-
C5H4Me2SiC5H4)Fe2(CO)4]2−2Na+ (prepared from
1.50 g (3.66 mmol) of (SiMe2)[(h5-C5H4)Fe(CO)2]2 and
an excess of Na–Hg amalgam in THF) 1.22 g (7.32
mmol) of ClMe2SiSiMe3 was added at 0 °C. The solu-
tion was stirred at 0 °C for 30 min and then permitted
to warm to room temperature (r.t.) and stirred
overnight. The solvent was removed under vacuum and
the residue was extracted with methylene chloride. The
solution was filtered through a short silica gel column
and concentrated to 5 ml and placed upon a 2.5×30
cm silica gel column. Elution with a mixture of hexane/
methylene chloride (10:1) developed a yellow band
which was collected and subsequent to solvent removal
afforded a yellow oil. The oil was put in the refrigerator
for several days and slowly solidified to form 1 as a
brown yellow crystalline solid (0.92 g, 1.37 mmol, 37%),
m.p. 38–40 °C. Anal. Calc. (Found) C, 46.42 (46.45);
1
3a: H-NMR l 0.20 (s, 9H, SiMe2SiMe3), 0.41 (s,
6H, bridged-SiMe2), 0.47 (s, 9H, Fe–SiMe3), 0.52 (s,
6H, SiMe2SiMe3), 4.17, 4.34, 4.42 (s, s, s, 2H, 4H, 2H,
Cp); 13C-NMR l −1.04 (bridged-SiMe2), −0.31
(SiMe2SiMe3), 3.69 (SiMe2SiMe3), 7.98 (Fe–SiMe3),
86.50, 87.26, 88.52, 88.76, 89.43, 89.92 (Cp), 215.91,
216.05 (CO); 29Si-NMR l −11.49 (SiMe2SiMe3),
−10.08 (bridged-SiMe2), 17.00 (SiMe2SiMe3), 41.28
(Fe–SiMe3).
1
H, 6.59 (6.92)%; H-NMR l 0.21 (s, 18H, SiMe3), 0.44
(s, 6H, bridged-SiMe2), 0.53 (s, 12H, SiMe2), 4.34, 4.43
(s, s, 4H, 4H, Cp); 13C-NMR l −1.06 (bridged-SiMe2),
−0.33 (SiMe3), 3.68 (SiMe2), 86,54, 88.53, 89.83 (Cp),
215.94 (CO); 29Si-NMR l −11.47 (SiMe3), −10.04
3b: Anal. Calc. (Found) C, 47.49 (47.68); H, 4.80
1
(3.98)%; H-NMR l 0.42 (s, 6H, bridged-SiMe2), 0.51
(s, 18H, SiMe3), 4.14, 4.34 (s, s, 4H, 4H, Cp); 13C-NMR

106
Y. Zhang et al. / Journal of Organometallic Chemistry 634 (2001) 102–108
l −0.98 (bridged-SiMe2), 7.95 (SiMe3), 3.68 (SiMe2),
87.26, 88.80, 89.44 (Cp), 216.16 (CO); 29Si-NMR l
−10.13 (bridged-SiMe2), 41.28 (SiMe2); IR w(CO) 1995
(s), 1943 (s).
2JP–C=5.1 Hz, HMPA), 80.04, 80.51, 80,76, 81.01,
85.47, 85.52, 86.51, 87.52, 87.44, 87.58 (Cp), 220.80,
220.89 (CO); 29Si-NMR l 6a: −9.23 (bridged-SiMe2),
31.09 (SiMe3), 116.66 (d, 2JP–Si=27.3 Hz,
FeꢀSiMe2·HMPA); 6b: −9.13 (bridged-SiMe2), 31.17
(SiMe3), 116.70 (d, 2JP–Si=28.5 Hz, FeꢀSiMe2·HMPA).
When hexane was utilized as the solvent instead of
C6D6, brown–yellow crystals of 6 was formed directly
in the NMR tube over the course of irradiation. We did
not isolate this compound due to its extreme sensitivity
toward air and moisture.
3.4. Photolysis of 2
As described above, 0.30 g (0.38 mmol) of 2 in 1 ml
of C6D6 was irradiated and the reaction monitored by
NMR spectroscopy. The formation of a major product
4a, along with traces of 4b was observed after 2 h.
Further irradiation for 12 h resulted in the complete
disappearance of 2, 4a and 4b and the formation of
three products 4c, 4d and 3b (1:8:1) along with traces of
unidentified products. Complexes 3b and 4d were iden-
tified by comparison with the spectroscopic data of
authentic samples.
3.6. Photolysis of 2 in the presence of HMPA
As above a solution of 2 (0.18 g, 0.23 mmol) and
HMPA (112 mg, 0.63 mmol) was irradiated and the
reaction monitored by NMR spectroscopy. After 3 h
formation of [PhMe2SiMe2Si(CO)2Fe(h5-C5H4)(SiMe2)-
(h5-C5H4)Fe(CO)(SiMe2Ph)(ꢀSiMe2·HMPA)] 7 was ob-
served along with traces of di-HMPA coordinated
silyl(silylene) complex 8, existing as a mixture of meso
(8a) and trans (8b) isomers. Further irradiation, 22 h
resulted in the complete disappearance of 2 and 7 and
almost quantitative formation of 8a and 8b (8a/8b=10/
8.5).
[PhMe2Si(CO)2Fe(h5 - C5H4)(SiMe2)(h5 - C5H4)Fe-
(CO)2SiMe2SiMe2Ph], 4a: 13C-NMR l −2.34 (Fe–
SiMe2SiMe2Ph), −1.14 (bridged-SiMe2), 3.97 (Fe–
SiMe2SiMe2Ph), 5.83 (Fe–SiMe2Ph), 88.45, 88.52,
88.61, 89.21, 89.87 (Cp), 128.18, 128.36, 128.46, 128.88,
132.98, 134.25, 141.40, 147.53 (Ph), 215.87, 216.10
(CO); 29Si-NMR l −15.10 (SiMe2SiMe2Ph), −10.10
(bridged-SiMe2), 17.02 (Fe–SiMe2SiMe2Ph), 35.58
(Fe–SiMe2Ph).
7: 13C-NMR
l
−2.28 (SiMe2SiMe2Ph), 0.51
[Me3Si(CO)2Fe(h5 - C5H4)(SiMe2)(h5 - C5H4)Fe(CO)2-
SiMe2SiMe2Ph], 4b: 29Si-NMR l −15.10 (SiMe2-
SiMe2Ph), −10.11 (bridged-SiMe2), 17.04 (Fe–
SiMe2SiMe2Ph), 41.27 (Fe–SiMe3). [Me3Si(CO)2Fe(h5-
C5H4)(SiMe2)(h5-C5H4)Fe(CO)2SiMe2Ph], 4c: 29Si-
NMR l −10.10 (bridged-SiMe2), 35.58 (Fe–SiMe2Ph),
41.26 (Fe–SiMe3)
(bridged-SiMe2), 3.88 (SiMe2SiMe2Ph), 8.50 (Fe–
SiMe2Ph), 13.24, 13.28 (FeꢀSiMe2·HMPA) 36.77 (d,
2JP–C=4.4 Hz, HMPA), 79.08, 82.20, 83.98, 85.74,
86.25, 86.32, 88.66, 88.82, 89.70, 94.31 (Cp) 125.87,
127.21, 128.32, 128.87, 133.73, 134.23, 141.58, 156.40
(Ph), 216.57, 216.66, 220.75 (CO); 29Si-NMR l −15.4
(SiMe2SiMe2Ph),
(SiMe2SiMe2Ph), 29.03 (Fe–SiMe2Ph), 115.10 (d, JP–
Si=30.0 Hz, FeꢀSiMe2·HMPA).
SiMe2[(h5-
−9.57
(bridged-SiMe2),
16.4
2
3.5. Photolysis of 1 in the presence of HMPA
C5H4)Fe(CO)(SiMe2Ph)(ꢀSiMe2·HMPA)]2 8a and 8b:
13C-NMR l −1.08, −0.11, 1.11 (bridged-SiMe2), 8.75,
8.90, 8.94, 8.97, 10.20, 10.42 (SiMe2Ph), 13.33, 13.36,
In a sealed 5 mm NMR tube a mixture of 1 (0.1g,
0.15 mmol) and HMPA (54 mg, 0.3 mmol) was irradi-
ated and monitored by NMR spectroscopy. After 3 h
the transient Me3SiMe2Si(CO)2Fe(h5-C5H4)(SiMe2)(h5-
C5H4)Fe(CO)(SiMe3)(ꢀSiMe2·HMPA), 5 was formed
(29Si-NMR l −11.69 (SiMe2SiMe3), −9.56 (bridged-
SiMe2), 16.44 (SiMe2SiMe3), 31.00 (Fe–SiMe3), 116.26
(d, 2JP–Si=28.8 Hz, FeꢀSiMe2·HMPA)) along with
traces of di-HMPA coordinated silyl(silylene) complex
6, existing as a mixture of meso (6a) and trans (6b).
Further irradiation, 22 h, resulted in the complete
disappearance of 1 and 5 and almost quantitative for-
mation of 6a and 6b (6a/6b=10/8). SiMe2[(h5-
C5H4)Fe(CO)(SiMe3)(ꢀSiMe2·HMPA]2 6a and 6b:
1H-NMR l 0.72, 0.75 (s, 6H, bridged-SiMe2), 0.58, 0.60
(s, 18H, SiMe3), 0.63, 0.80 (s, 12H, FeꢀSiMe2·HMPA),
2
13.42, 13.46 (FeꢀSiMe2·HMPA) 36.61, 36.65 (d, d, JP–
C=5.1 Hz, 2JP–C=4.9 Hz, HMPA), 79.78, 80.29,
81.04, 81.97, 85.61, 85.70, 87.70, 88.24, 88.40 (Cp),
125.70, 125.73, 127.10, 133.85, 133.96, 156.69 (Ph),
220.97, 221.11 (CO); 29Si-NMR l 8a: −9.24 (bridged-
2
SiMe2), 29.44 (SiMe2Ph), 115.70 (d, JP–Si=28.2 Hz,
FeꢀSiMe2·HMPA); 8b: −9.20 (bridged-SiMe2), 29.57
(SiMe2Ph), 115.80 (d, 2JP–Si=28.2 Hz, FeꢀSiMe2·
HMPA).
3.7. X-ray crystal structure determination of 4d
Crystals suitable for X-ray diffraction analysis were
obtained from a hexane solution. Intensity data were
collected on a Nicolet–Siemens R3m/V four-circle dif-
fractometer at room temperature, using graphite-mono-
2
2.24 (d, 36H, JP–H=9.9 Hz, HMPA), 4.23–4.28, 4.46,
4.51, 4.67, 4.72 (m, 8H, Cp); 13C-NMR l −0.95, 0.56,
,
1.71 (bridged-SiMe2), 11.30, 11.36 (SiMe3), 13.47, 13.51
(FeꢀSiMe2·HMPA), 36.65, 36.68 (d, d, JP–C=5.1 Hz,
chromated Mo–Ka radiation (u=0.71073 A). The
ꢀ-scan technique was applied in the 2q range 3.55
2

Y. Zhang et al. / Journal of Organometallic Chemistry 634 (2001) 102–108
107
Table 1
166567 for 4d. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44-
1233-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
Summary of X-ray diffraction data
4d
Formula
C
32H36Fe2O4Si3
Formula weight
Space group
Crystal system
Z
680.59
P21/c
Monoclinic
4
Acknowledgements
Unit cell dimensions
This research has been supported by the Robert A.
Welch Foundation, Houston, TX.
,
a (A)
18.527(5)
11.582(3)
16.815(5)
90
109.76(2)
90
3395.7(16)
1.331
9.89
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
References
3
,
V (A )
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Dcalc (g cm−1
)
v (cm−1
F(000)
)
146
Crystal size (mm3)
0.20×0.20×0.30
4639
4454
0.025
3304
0.0545
0.071
0.0728
1.57
No. of reflections collected
No. of independent reflections
Rint
No. of observed data [F\4.0|(F)]
Robs
Rw
Rtot
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Goodness-of-fit
Largest difference peak and hole (e A
−3
,
)
0.79 and −0.55
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Table 2
,
Selected bond lengths (A) and bond angles (°) for 4d
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1435.
Bond lengths
Fe(1)–Si(1)
Fe(1)–C(13)
Fe(2)–C(23)
C(13)–O(1)
C(23)–O(3)
2.329(2)
1.730(10)
1.738(6)
1.162(8)
1.150(6)
Fe(2)–Si(3)
Fe(1)–C(14)
Fe(2)–C(24)
C(14)–O(2)
C(24)–O(4)
2.331(2)
1.728(8)
1.732(7)
1.148(8)
1.154(7)
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2011.
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959.
Bond angles
C(13)–Fe(1)–C(14)
Si(1)–Fe(1)–C(13)
Si(3)–Fe(2)–C(23)
Fe(1)–Si(1)–C(17)
C(1)–Si(2)–C(6)
94.6(3)
83.5(2)
86.8(2)
109.9(2)
106.0(2)
C(23)–Fe(2)–C(24)
Si(1)–Fe(1)–C(14)
Si(3)–Fe(2)–C(24)
Fe(2)–Si(3)–C(27)
C(11)–Si(2)–C(12)
92.3(3)
86.8(2)
84.7(2)
109.5(2)
110.7(4)
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1435.
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1.
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252 (1983) 127 and references therein.
2q545.0° with variable scan speeds. The structures
were refined by anisotropic, full-matrix least-squares.
Hydrogen atomic positions were generated from the
assumed geometry. Crystallographic data are summa-
rized in Table 1, and selected bond distances and angles
in Table 2.
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4. Supplementary material
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4620.
Crystallographic data (excluding structure factors)
for the structural analysis have been deposited with the
Cambridge Crystallographic Data Centre, CCDC No.

108
Y. Zhang et al. / Journal of Organometallic Chemistry 634 (2001) 102–108
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