Structural and redox properties of novel spirocyclic 1-sila-3- ferracyclobutanes, [(η5-C5H4)Fe(L 2)CH2SiMe2], L2 = P-P (diphosphine)

Article abstract of DOI:10.1021/om061141y

Photochemical treatment of the 1-dimethylsila-3-ferracyclobutane [(η⁵-C₅H₄)Fe(CO)₂CH ₂SiMe₂] (1) with diphosphine ligands Ph ₂P(CH₂)_nPPh₂, n = 1, 2, 3 (P-P), results in the formation of [η⁵-C₅H ₄)Fe(P-P)CH₂SiMe₂] (3-5) spirocyclic complexes. The new l-dimethylsila-3-ferracyclobutanes do not ring-open to form polymeric materials, although the X-ray structural analysis of [(η⁵-C ₅H₄)Fe(Ph₂PCH₂CH₂PPh ₂)CH₂SiMe₂] indicates the same ring strain as noted for analogues of 1 that do polymerize. Cyclic voltammetric studies of these complexes reveal a reversible one-electron redox process.

Full text of DOI:10.1021/om061141y

Organometallics 2007, 26, 3005-3009
3005
Structural and Redox Properties of Novel Spirocyclic
1-Sila-3-ferracyclobutanes, [(η5-C5H4)Fe(L2)CH2SiMe2], L2 ) P-P
(diphosphine)
Mukesh Kumar, Francisco Cervantes-Lee,† Hemant K. Sharma, and Keith H. Pannell*
Department of Chemistry, UniVersity of Texas at El Paso Texas, El Paso, Texas 79968-0513
ReceiVed December 18, 2006
Photochemical treatment of the 1-dimethylsila-3-ferracyclobutane [(η5-C5H4)Fe(CO)2CH2SiMe2]
(1) with diphosphine ligands Ph2P(CH2)nPPh2, n ) 1, 2, 3 (P-P), results in the formation of
[(η5-C5H4)Fe(P-P)CH2SiMe2] (3-5) spirocyclic complexes. The new 1-dimethylsila-3-ferracyclo-
butanes do not ring-open to form polymeric materials, although the X-ray structural analysis of
[(η5-C5H4)Fe(Ph2PCH2CH2PPh2)CH2SiMe2] indicates the same ring strain as noted for analogues of 1
that do polymerize. Cyclic voltammetric studies of these complexes reveal a reversible one-electron redox
process.
Introduction
Sila-metallacyclobutanes containing a transition metal atom
have been explored in terms of their synthesis and reactivity.1
For example, Cp2M-CH2-SiMe2-CH2 (M ) Ti, Zr, Hf, Nb,
Mo, Ir) undergo ring expansion chemistry via insertion of such
reagents as paraformaldehyde, isocyanides, and carbon mon-
oxide into the M-C bond. More recently we reported the syn-
Figure 1. Schematic representation for four-membered met-
allcycles.
thesis and ring-opening behavior of 1-sila-3-ferracyclobutanes,2
(η5-C5H4)Fe(CO)2CH2SiR2, and related 1,2-disilaferracyclobu-
exhibit reversible redox behavior, the utility of the new organo-
metallic polymers derived from this metal fragment is limited.
In an attempt to outline the potential for transforming
the metal center of the polymer precursor 1-sila-3-ferra-
cyclobutanes into conducting species, we now report the
synthesis, characterization, and reversible redox properties of
tanes,3 (η5-C5H4)Fe(CO)2SiR2SiR2 (A and B in Figure 1). Such
metallacycle ring-opening is reminiscent of the chemistry of
[1]-silaferrocenophanes4 (C in Figure 1), which provides an
interesting synthetic route for a new class of conducting organo-
metallic polymers due to the presence of the redox-active ferro-
cenylene group in the polymer backbone.5 Such polymers have
also been studied in nanoparticle synthesis and as magnetic ma-
terials.6 However, since the (η5-C5H5)Fe(CO)2 fragment does not
(η5-C5H4)Fe(P-P)CH2SiMe2 (3-5), P-P ) Ph2P(CH2)nPPh2
(n ) 1, 2, 3).
Results and Discussion
* Corresponding author. E-mail: kpannell@utep.edu.
The photochemical substitution of labile CO groups in [(η5-
C5H5)Fe(CO)2] complexes with mono- and diphosphine ligands
† Dr. Francisco (Paco) Jose Cervantes-Lee: 11/21/1950-2/15/2007.
(1) (a) Sharma, H. K.; Pannell, K. H. In Metal-Containing and Metallo
Supramolecular Polymers and Materials; Schubert, U. S.; Newkome, G.
R., Manners, I., Eds.; Oxford University Press: Washington, DC, 2006; p
457. (b) Tikkanen, W. R.; Liu, J. Z.; Egan, J. W.; Petersen, J. L.
Organometallics 1984, 3, 825. (c) Tikkanen, W. R.; Liu, J. Z.; Egan, J.
W.; Petersen, J. L. Organometallics 1984, 3, 1646. (d) Tikkanen, W. R.;
Petersen, J. L. Organometallics 1984, 3, 1651. (e) Berg, F. J.; Petersen, J.
L. Organometallics 1989, 8, 2461. (f) Petersen, J. L.; Egan, J. W.
Organometallics 1987, 6, 2007. (g) Andreucci, L.; Diversi, P.; Ingrosso,
G.; Lucherini, A.; Marchetti, F.; Adovasio, V.; Nardelli, M. J. Chem. Soc.,
Dalton Trans. 1986, 477.
(5) (a) Espada, L.; Pannell, K. H.; Papkov, V.; Larissa, L.; Bukalov, S.;
Suzdalev, I.; Tanaka, M.; Hayashi, T. Organometallics 2002, 21, 3758. (b)
Pannell, K. H.; Imshennik, V. I.; Maksimov, Yu. V.; Il’ina, M. N.; Sharma,
H. K.; Papkov, V. S.; Suzdalev, I. P. Chem. Mater. 2005, 17, 1844. (c)
Papkov, V. S.; Gerasimov, M. V.; Dubovik I. I.; Sharma, S.; Dementiev,
V. V.; Pannell, K. H. Macromolecules 2000, 33, 7107. (d) Tanaka, M.;
Hayashi, T. Bull. Chem. Soc. Jpn. 1993, 66, 334. (e) Rulkens, R.; Resendes,
R.; Varma, A.; Manners, I.; Muti, K.; Fossum, E.; Miller, P.; Matyjaszewski,
K. Macromolecules 1997, 30, 8165. (f) Bakueva, L.; Sargent, E. H.;
Resendes, R.; Bartole, A.; Manners, I. J. Mater. Sci.: Mater. Electron. 2001,
12, 21.
(2) Sharma, H. K.; Cervantes-Lee, F.; Pannell, K. H. J. Am. Chem. Soc.
2004, 126, 1326.
(3) Sharma, H. K.; Pannell, K. H. Chem. Commun. 2004, 2556.
(4) (a) Foucher, D. A.; Tang, B-Z.; Manners, I. J. Am. Chem. Soc.
1992, 114, 6246. (b) Nguyen, M. T.; Diaz, A. F.; Dementiev, V. V.;
Sharma, H.; Pannell, K. H. SPIE Proceedings 1993, 1910, 230. (c)
Flinckh, W.; Tang, B.; Foucher, D. A.; Zamble, D. B.; Ziembinski, R.;
Lough, A.; Manners, I. Organometallics 1993, 12, 823. (d) Nguyen, M.
T.; Diaz, A. F.; Dementiev, V. V.; Pannell, K. H. Chem. Mater. 1993, 5,
1389.
(6) (a) Clendenning, S. B.; Fournier-Bidoz, S.; Pietrangelo, A.; Yang,
G.; Han, S.; Brodersen, P. M.; Yip, C. M.; Lu, Z.-H.; Ozin, G. A.; Manners,
I. J. Mater. Chem. 2004, 14, 1686. (b) Wang, X.-S.; Winnik, M. A.;
Manners, I. Angew. Chem., Int. Ed. 2004, 43, 3703. (c) MacLachlan, M.
J.; Ginzburg, M.; Coombs, N.; Coyle, T. W.; Raju, N. P.; Greedan, J. E.;
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H.; Coombs, N.; Winnik, M. A.; Manners, I. J. Am. Chem. Soc. 2005, 127,
8924.
10.1021/om061141y CCC: $37.00 © 2007 American Chemical Society
Publication on Web 05/04/2007

3006 Organometallics, Vol. 26, No. 12, 2007
Kumar et al.
a
Scheme 1
a
dppm ) bis(diphenylphosphino)methane, dppe ) bis(diphenylphosphino)ethane, dppp ) bis(diphenylphosphino)propane.
is well-established.7 Thus, irradiation of a freshly prepared THF
solution of 1 in the presence of the appropriate phosphine ligand
results in the formation of mono- (for Ph3P) (2) and disubstituted
derivatives, 3-5 (Scheme 1). The use of excess Ph3P and
prolonged irradiation failed to replace both the CO groups.
Compounds 2-5 were isolated as red-orange solid materials
soluble in common organic solvents, and they were purified by
that of the starting iron dicarbonyl metallacycle 1 and were noted
in the range -5.0 to -7.0 ppm. 31P NMR signals in these
compounds were observed downfield as compared to the
uncoordinated phosphine ligands, exhibiting ∆δ (ppm) values
of 88 (2), 69 (3), 119 (4), and 83 (5). This behavior is in accord
with the literature evidence for phosphorus-coordinated com-
pounds.9
X-ray Structure of 4. The molecular structure of 4 was
confirmed by single-crystal X-ray analysis of crystals formed
from a benzene/hexane solvent mixture, Figure 2. The crystal-
lographic data and selected bond lengths and angles are
summarized in Tables 1 and 2, respectively. The molecule
crystallizes in the orthorhombic crystal system with space group
P(2)2(1)2(1). Structural analyses of several 1-metalla-3-silacy-
clobutanes1 are reported in the literature; however, the presence
of both the four (Fe-C-Si-C) and five (Fe-P-C-C-P)
membered spirocyclic rings presents some novelty. The Si-
C6 and Si-C1 bond distances of 4, 1.830(4) and 1.860(5) Å,
respectively, are in the range for such metallacycles. The C1-
Si-C6 angle of 95.41(17)° is small for a tetrahedral angle and
together with the C1-Fe-C6 bond angles of 80.39(16)° il-
lustrates a degree of ring strain for this new structural arrange-
ment. However, the sum of the four inner ring angles (359.9°)
1
recrystallization and have been characterized by H, 13C, and
29Si NMR spectroscopy, X-ray crystallography (for 4), and
elemental analysis.
The 1H NMR spectrum of 2 exhibited ABX quartet at -2.00
to -2.12 ppm (3JA-B ) 11.2 Hz, 3JA-X ) 12.6 Hz, 3JB-X ) 1
Hz), corresponding to two diastereotopic CH2 hydrogens.8 The
13C NMR spectrum exhibits a phosphorus-coupled doublet at
-50.2 ppm (2JP-C ) 12.9 Hz) for the FeCH2 group, a doublet
at 223.5 ppm (2JP-C ) 30.2 Hz) for the CO group, but singlets
for the carbon atoms of the substituted cyclopentadienyl ring.
1
The H NMR spectrum of the diphosphine complexes 3-5
exhibit triplets for the CH2 protons at δ -2.51 (3JP-H ) 6.0
Hz) (3), -3.20 (3JP-H ) 6.0 Hz) (4), and -2.53 (3JP-H ) 6.0
Hz) (5). The 13C NMR spectra exhibit the expected high-field
CH2 triplets at δ -48.7 (2JP-C ) 17.3 Hz) (3), -51.2 (2JP-C
)
17.2 Hz) (4), and δ -54.1(2JP-C ) 15.3 Hz) (5). 29Si NMR
values of 2-5 were not changed significantly (2-3 ppm) from
(9) (a) Montigny, F.; Argouarch, G.; Costuas, K.; Halet, J.; Roisnel, T.;
Toupet, L.; Lapinte, C. Organometallics 2005, 24, 4558. (b) Weyland, T.;
Lapinte, C.; Frapper, G.; Calhorda, M. J.; Halet, J.; Toupet, L. Organo-
metallics 1997, 16, 2024. (c) Scott, F.; Kruger, G. J.; Cronje, S.; Lombard,
A.; Raubenheimer, H. G. Organometallics 1990, 9, 1071.
(7) (a) King, R. B.; Pannell, K. H. Inorg. Chem. 1968, 7, 1510. (b)
Treichel, P. M.; Shubkin, R. L.; Barnett, K. W.; Reichard, D. Inorg. Chem.
1966, 5, 1177.
(8) Pannell, K. H. Chem. Commun. 1969, 1346.

NoVel Spirocyclic 1-Sila-3-ferracyclobutanes
Organometallics, Vol. 26, No. 12, 2007 3007
Figure 2. Molecular structure of [η5-C5H4Fe(Ph2P(CH2)2Ph2P)CH2SiMe2] (4). Thermal ellipsoids are shown at 30% probability. H atoms
are omitted for clarity.
Table 1. Summary of Crystallographic Data of 4
Table 2. Selected Bond Lengths and Angles of 4
source
synthesis
Bond Lengths (Å)
cryst color
red
chunk
Fe-C1
Fe-P1
Si-C6
Si-C1
2.095(4)
2.1540(10)
1.830(4)
1.860(5)
Fe-C6
Fe-P2
Si-C7
Si-C8
2.134(4)
2.1716(10)
1.860(5)
1.868(4)
cryst habit
cryst size/mm3
a/Å
0.30 × 0.30 × 0.20
12.3293(17)
b/Å
c/Å
12.9894(18)
18.476(3)
90
90
90
2959.0(7)
orthorhombic
Bond Angles (deg)
C1-Fe-C6
Si-C6-Fe
P1-Fe-P2
C7-Si-C1
C7-Si-C8
80.39(16)
91.89(16)
87.56(4)
109.3(3)
108.8(3)
Si-C1-Fe
C6-Si-C1
C6-Si-C7
C6-Si-C8
C1-Si-C8
92.25(16)
95.41(17)
115.6(2)
114.5(2)
112.7(2)
R/deg
â/deg
γ/deg
volume/Å3
cryst syst
space group
Z
P2(1)2(1)2(1)
4
1.326
0.68
Bruker SADABS program
23(2)
0.71073 Å
A comparison of the structural data of 4 with those of
Dc/g cm-3
µ/mm-1
abs corr
temp/°C
wavelength
[(η5-C5H4)Fe(CO)(Ph3P)CH2Si(n-Bu)2]2 [Fe-C(methylene) )
2.113(6) Å, C(methylene)-Si ) 1.839(3) Å, Si-C (Cp) )
1.871(3) Å, C(Cp)-Si-C(methylene) ) 94.06(11)°] and 1-si-
laferrocenophane, (η5-C5H4)2FeSiMe24 [Fe-C(Cp) ) 2.001(8)
Å, 1.990(8) Å, C(Cp)-Si ) 1.865(9), 1.851(9) Å, C(Cp)-Si-
C(Cp) ) 95.7(4)°], reflects the great similarity of the Fe-C-
Si-C ring distances and angles. Thus, we conclude that the
much greater disposition of the ferrocenophanes to ring-open
is mainly driven by the ferrocenylene portion of the molecular
geometry associated with the nonparallel character of the two-
cyclopentadienyl rings.
Cyclic Voltammetric Studies. Electrochemical studies of the
1-dimethylsila-3-ferracyclobutanes 1-5 reveal that, with scan
rates in the range 50/100 mV s-1, the parent dicarbonyl complex
1 exhibits a completely irreversible oxidation (Figure 3a), the
monophosphine-substituted 2 exhibits a slightly reversible
process (Figure 3b), and the disubstituted phosphine complexes
3-5 undergo a reversible one-electron redox process, Figure
4. The reversibility of the diphosphine-substituted systems is
monochromator
diffractometer
no. of reflns collected
no. of indep reflns
struct solution technique
struct solution program
refinement technique
refinement program
function minimized
goodness-of-fit on F2
R1,a wR2b [I > 2s(I)]
R1,a wR2b (all data)
graphite
Bruker SMART with Apex CCD
8805
2825 [R(int) ) 0.0397]
direct methods
SHELXS-97 (Sheldrick, 1990)
full-matrix least-squares on F2
SHELXS-97 (Sheldrick, 1997)
2
∑w(Fo2 - Fc )2
1.147
0.0601, 0.1218
0.0691, 0.1259
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) {∑[w(Fo2 - Fc )2]/∑[w(Fo )2]}1/2
.
b
2
2
reveals the planarity in the ring. The bite angle (P2-Fe-P1)
for the P2 moiety is 87.6° with Fe-P distances 2.1540(10) and
2.1716(10) Å. The bite angles (P-Fe-P) for related compounds
such as Cp*(dppe)Fe-CtC-9,10-ant-CtC-FeCp*(dppe)9a
[85.4(1)°], [Cp*Fe(dppe)]3(CtC)3(µ-1,3,5-C6H3)9b [84.7(1)°,
83.7(4)°, 85.7(1)°], and Fc-CtC-CpFe(dppe)10c [86.7(2)°]
[dppe ) bis(diphenylphosphino)ethane] are smaller than that
in 4. This may be an effect of the other four-membered ring
present in the molecule involving the same iron atom.
(10) (a) Connelly, N. G.; Geiger, W. E. In AdVances in Organometallic
Chemistry; Stone, F. G. A., West, R., Eds.; Academic Press Inc: New York,
1984; Vol. 23, p 1. (b) Treichel, P. M.; Molzahn, D. C.; Wagner, K. P. J.
Organomet. Chem. 1979, 174, 191. (c) Sato, M.; Hayashi, Y.; Kumakura,
S.; Shimizu, N.; Katada, M.; Kawata, S. Organometallics 1996, 15, 721.
(d) Tilset, M.; Fjeldahl, I.; Hamon, J.; Hamon, P.; Toupet, L.; Saillard, J.;
Costuas, K.; Haynes, A. J. Am. Chem. Soc. 2001, 123, 9984.

3008 Organometallics, Vol. 26, No. 12, 2007
Kumar et al.
Table 3. Cyclic Voltammetric Data of 1-5 in CH2Cl2 (0.1 M
[Bu4N]BF4]; sweep rate 0.100 V s-1 a
)
compound
E
ox (V)
Ered (V)
E1/2 (V)
∆Ep (V)
1
2
3
4
5
1.79
0.512
-0.096
-0.037
-0.032
-0.237
-0.127
-0.175
-0.166
-0.082
-0.103
0.141
0.090
0.143
a References with AgCl/Ag.
(CtC)}2-C6H4] (Eox ) -0.060 V, Ered ) -0.140 V, E1/2
-0.100 V, ∆EP ) 0.80 V).9b
)
The redox potentials of these compounds change in a
systematic manner, Table 3. In the sequence Fe(CO)2 (1) f
Fe(CO)(P) (2) f Fe(P-P) (3, 4, 5) the oxidation potentials
progressively decrease in line with the systematic increase of
electron density on the iron atom as the highly retrodative
electron-withdrawing CO groups are replaced by the phosphine
ligands. The more subtle changes noted for 3, 4, and 5 possibly
reflect the progressively favorable ring size of the chelating
ligand complex from the strained four-membered ring to the
six-membered ring. A comparison of the E1/2 values for Fc-
CtC-CpFe(dppm) (-0.50 V) and for Fc-CtC-CpFe(dppe)
(-0.47 V), Fc ) (η5-C5H5)Fe(η5-C5H4), indicates a slight
decrease in E1/2 by increasing the ring size.10c However, in our
study we found that the E1/2 values exhibited considerable
variation, -0.166 V (3), -0.082 V (4), -0.103 V (5).
Attempts to isolate a chemically oxidized 17-electron species
by treatment of 3, 4, or 5 with silver tetrafluoroborate, as
suggested by literature precedents,10b led to black materials that
were insoluble in all common solvents. Whether they are
molecular or ring-opened species is unknown.
Figure 3. Cyclic voltammograms of 1 (a) and 2 (b).
Attempted Ring-Opening Polymerization of 4. As a
representative example, a toluene solution of 4 was treated with
Pt(0) and Pd(0) catalysts (7-10 mol %) at both room temper-
ature and elevated temperatures. No evidence of ring-opening
of the metallacycle was observed on the basis of NMR
spectroscopic analysis. In other attempts, THF solutions of 4
were treated with anionic reagents, n-BuLi and LDA (5-10
mol %). In neither case was ring-opening observed. However,
on prolonged stirring (>24 h), small amounts of an intractable
precipitate were obtained. Both reaction conditions used have
been shown to result in ring-opening of the parent dicarbonyl
metallacycle 1.
Attempts to perform carbonyl substitution reactions directly
with the ring-opened polymers have yielded a complex mixture
of cross-linked materials involving both carbonyl insertion
products and the direct carbonyl substitution reactions of the
type noted here. Studies on these systems are currently in
progress.
Experimental Section
All experiments were performed under an atmosphere of dry
N2 using Schlenk techniques. THF and hexanes were freshly
distilled from sodium benzophenone ketyl immediately prior to use;
Figure 4. Cyclic voltammograms of 3 (a), 4 (b), and 5 (c).
(η5-C5H4)Fe(CO)2CH2SiMe2 (1) was prepared according to the
published procedure.2 Triphenylphosphine, 1,2-bis(diphenylphos-
phino)methane, 1,2-bis(diphenylphosphino)ethane, and 1,2-bis-
(diphenylphosphino)propane were purchased from Aldrich and used
as received. Cyclic voltammetric measurements were performed
using a Perkin-Elmer potentiostat/galvanostat CV (model # 263A)
analyzer. The electrochemical cell comprised a platinum wire
working electrode, a silver wire reference electrode, and a silver
wire counter electrode. All measurements were made in a dry N2
in accord with published studies on related (η5-C5R5)Fe(P)2X
systems.9a,b,10 In the case of the reversible processes for 3, 4,
and 5 the expected (iPa/iPc) ratio of unity is observed and the
∆EP separation is in the range 90-145 mV. The electrochemical
data are summarized in Table 3, and that for 4 (Eox ) -0.037
V, Ered ) -0.127 V, E1/2 ) -0.082 V, ∆EP ) 0.090 V)
resembles that of the first redox process for [{Fe(Cp*)(dppe)-

NoVel Spirocyclic 1-Sila-3-ferracyclobutanes
Organometallics, Vol. 26, No. 12, 2007 3009
atmosphere; oxidation potentials were referenced to Ag/AgCl
couple. Infrared spectra were obtained in THF solution on an ATI
CH2, 2JP-H ) 6.0 Hz), 0.15 (s, 6H, SiMe2), 2.21 (t, 4H, P(CH2)2P,
2JP-H ) 3.9 Hz), 4.18 (m, 2H, Cp), 4.54 (m, 2H, Cp), 7.70-7.23
1
Mattson infinity series FTIR; H, 13C, 29Si, and 31P NMR spectra
2
(m, 20H Ph). 13C NMR (CDCl3): δ -51.2 (t, CH2, JP-C ) 17.2
Hz), 0.99 (SiMe2), 27.4 (t, P(CH2)2P, 1JP-C ) 21.7 Hz), 65.7, 76.6,
87.2 (Cp), 128.3, 130.1, 133.6, 139.2 (Ph). 29Si NMR (C6D6): δ
-6.6. 31P NMR (C6D6): δ 108.2.
were recorded on a Bruker DPX-300 at 300, 75.4, 59.6, and 121.5
MHz, respectively. Elemental analyses were performed at Galbraith
Laboratories.
5. Mp: 182-5 °C. Anal. Calcd for C35H38P2FeSi: C 69.53, H
Synthesis. Isolation of [η5-C5H4Fe(CO)2CH2SiMe2] (1). 1 was
prepared in solution as reported previously.2 The THF was reduced
slowly to ∼10 mL and placed on a silica column packed in hexanes.
Elution with hexanes produced a yellow band, which was collected
and dried. The resulting orange semisolid was further purified by
passing through a second silica column, and removal of the solvent
resulted in the isolation of 1 as a semisolid in 50% yield. The
compound is stable for several weeks stored in a refrigerator under
N2. Anal. Calcd for C10H12O2FeSi: C 48.19, H 4.81. Found: C
1
6.29. Found: C 68.82, H 6.37. H NMR (C6D6): δ -2.53 (t, 2H,
CH2, J ) 6 Hz), 0.19 (s, 6H, SiMe2), 1.93 (t, 4H, PCH2CH2CH2P,
2JP-H ) 12.6 Hz), 2.19 (m, 2H, PCH2CH2CH2P), 4.11 (m, 2H, Cp),
4.41 (m, 2H, Cp), 7.21-7.37 (m, 20H, Ph). 13C NMR (CDCl3): δ
2
-54.1 (t, CH2, JP-C ) 15.3 Hz), 0.75 (SiMe2), 20.3 (PCH2CH2-
CH2P), 26.8 (t, PCH2CH2CH2P, 1JP-C ) 12.5 Hz), 66.0, 80.2, 85.4
(Cp), 127.6, 129.3, 131.8, 138.0, 142.5 (Ph). 29Si NMR (C6D6): δ
-5.84. 31P NMR (C6D6): δ 67.2.
1
47.53, H 4.75. IR (THF, cm-1): 2003, 1945 (ν CO). H NMR
Attempted Ring-Opening Polymerization of 4. In a typical
experiment a 5 mL toluene solution of 4 (0.100 g) was charged
into a two-neck flask fitted with a N2 inlet tube. To the clear solution
was added 7 mol % of the Karstedt’s catalyst. No change in the
(C6D6): δ -1.39 (s, 2H, FeCH2), 0.14 (s, 6H, SiMe2), 4.31, 4.59
(4H, Cp). 13C NMR (C6D6): δ -50.0 (FeCH2), -1.21 (SiMe2),
74.5, 85.2, 92.6 (Cp), 217.8 (CO). 29Si NMR (C6D6): δ -4.8.
1
viscosity of the solution and no changes in the H and 13C NMR
Synthesis of [(η5-C5H4)Fe(Ph3P)(CO)CH2SiMe2] (2). To a 30
mL THF solution of 1 (0.011 mol) in a quartz tube was added
2.89 g (0.011 mol) of PPh3, and the contents were degassed twice.
The solution was then irradiated by a Hanovia 450 W medium-
pressure lamp at a distance of 4 cm for 20 h. The progress of the
photochemical reaction was monitored by infrared spectroscopy
following the disappearance of the CO frequencies of 1. After
completion of reaction the solvent was removed under vacuum.
The solid material obtained was extracted with a hexanes/toluene
mixture and recrystallized from that solution to yield 2 as a red
solid compound in 68% yield, mp 143-5 °C. Anal. Calcd for
C27H27OPFeSi: C 67.21, H 5.60. Found: C 66.62, H 5.50. IR (THF,
spectral data were observed after 18 h . However, prolonged stirring,
>36 h, resulted in a very small amount of insoluble precipitate.
Related experiments using Pd(Ph3P)4 yielded similar results, even
after heating at 75 °C for 24 h.
Treatment of 1 with Pd(PPh3)4 under identical conditions noted
above, 75 °C for 24 h, led to ring-opened polymerization and to
polymers identical to that originally reported.2
In separate experiments similar solutions of 4 were treated with
n-BuLi/LDA (5 mol %). The solution was then stirred at room
temperature for 24 h. A small amount of an insoluble precipitate
formed; however, NMR spectral analysis provided no evidence of
the ring opening. The starting material was recovered in >90%
yield in each case.
1
cm-1): 1911 (ν CO). H NMR (CDCl3): δ -2.0 to -2.12 (2H,
3
3
3
CH2, JA-B ) 11.2 Hz, JA-X ) 12.6 Hz, JB-X ) 1 Hz), 0.02 (s,
3H, SiMe), 0.19 (s, 3H, SiMe), 3.70 (m, 1H, Cp), 4.49 (m, 1H,
Cp), 4.60 (m, 1H, Cp), 4.89 (m, 1H, Cp), 7.36 (m, 15H, Ph). 13C
NMR (CDCl3): δ -50.2 (d, CH2, 2JP-C ) 12.9 Hz), -1.24 (SiMe),
1.33 (SiMe), 71.7, 80.6, 87.6, 90.5, 95.1 (Cp), 129.6, 130.6, 132.4,
X-ray Crystallography. A crystal of 4 suitable for X-ray
analysis was mounted on a Bruker APEX CCD diffractometer
equipped with monochromatized Mo KR radiation. Crystallographic
measurement was carried out at 296(2) K. The details of crystal
data and refinement parameters are described in Table 1. The
structure was solved by direct methods and refined by full-matrix
least-squares on F2 values for all reflections using the SHELXL-
97 (Sheldrick, 1997) program. All non-hydrogen atoms were
assigned anisotropic displacement parameters and hydrogen atoms
were constrained to ideal geometries with fixed isotropic displace-
ment parameters.
2
133.7 (Ph), 223.5 (d, CO, JP-C ) 30.2 Hz). 29Si NMR (CDCl3):
δ -6.4. 31P NMR (CDCl3): δ 83.9.
In a similar manner we obtained [(η5-C5H4)Fe(Ph2PCH2PPh2)-
CH2SiMe2] (3), [(η5-C5H4)Fe(Ph2P(CH2)2)Ph2P)CH2SiMe2] (4), and
[(η5-C5H4)Fe(Ph2P(CH2)3PPh2)CH2SiMe2] (5) in 60%, 65%, and
68% yields, respectively.
3. Mp: 152-6 °C. Anal. Calcd for C33H34P2FeSi: C 68.75, H
1
5.90. Found: C 68.22, H 5.74. H NMR (C6D6): δ -2.51 (t, 2H,
Acknowledgment. Financial support from the Welch Foun-
dation (Grant #AH-546) is gratefully acknowledged.
2
CH2, JP-H ) 6.0 Hz), 0.41 (s, 6H, SiMe2), 2.31 (s, 2H, PCH2P),
4.61 (m, 2H, Cp), 4.69 (m, 2H, Cp), 6.99-7.46 (m, 20 H, Ph). 13
C
2
NMR (C6D6): δ -48.7 (t, CH2, JP-C ) 7.3 Hz), 2.40 (SiMe2),
44.0 (PCH2P), 65.1, 73.6, 86.1 (Cp), 129.5, 130.1, 138.5, 142.0
(Ph). 29Si NMR (C6D6): δ -6.11. 31P NMR (C6D6): δ 48.4.
4. Mp: 175-8 °C. Anal. Calcd for C34H36P2FeSi: C 69.03, H
Supporting Information Available: Crystallographic data in
CIF format (CCDC no. 631129). This material is available free of
charge via the Internet at http://pubs.acs.org.
1
6.09. Found: C 68.89, H 6.01. H NMR (C6D6): δ -3.20 (t, 2H,
OM061141Y