Iron Carbene and Alkylidene Complexes
Organometallics, Vol. 15, No. 25, 1996 5407
stirring (18 h). The solvent was removed in vacuo, and the
solid residue was extracted with pentane. After removal of
the solvent and drying in vacuo, the complex 5 was obtained
as a red powder in 45% yield (0.50 g, 0.77 mmol). Anal. Calcd
(C39H46FeOP2): C, 72.22; H, 7.15. Found: C, 72.35; H, 7.23.
[F e(η5-C5Me5)(d p p e)(CHMe)][P F 6] (6). To a solution of
0.10 g (0.155 mmol) of complex 5 in 40 mL of diethyl ether
cooled to -80 °C was added 35 µL of hexafluorophosphoric acid
(0.24 mmol). The mixture was allowed to warm to 20 °C, and
a pale-orange precipitate was formed. After filtration and
washing with 3 × 20 mL of diethyl ether, 0.11 g (0.144 mmol,
95%) of a pale-orange powder of the complex 6 was obtained.
Anal. Calcd (C38H43F6FeP3): C, 59.86; H, 5.68. Found: C,
60.08; H, 5.72.
X-r a y Cr ysta llogr a p h y for 6. Suitable crystals for single
crystal X-ray diffraction studies were obtained from a dichlo-
romethane-diethyl ether mixture at 20 °C. The data were
measured on CAD-4 Enraf Nonius automated diffractometer.
All the calculations were performed on a Digital MicroVax
3100 computer with the MOLEN package.73 Crystal data
collection and refinement parameters are collected in Table
2. The unit cell parameters were determined by least-squares
fit of a set of 25 high-θ reflections. After Lorenz-polarization
corrections, the structure was solved by direct methods, which
revealed the Fe and the two P atoms. The remaining non-
hydrogen atoms of the cation, the PF6 anion, and the diethyl
ether molecule were found after successive scale factor and
Fourier differences. The PF6 anion appeared as disordered
between two positions (F(1)F(2)F(3) and F(4)F(5)F(6)). After
isotropic (R ) 0.10) and then anisotropic refinements (R )
0.085), all hydrogen atoms were found with a Fourier differ-
ence map (between 0.45 and 0.18 e Å-3). The whole structure
was refined by the full-matrix least-square techniques (use of
F magnitudes; x, y, z and bij values for Fe, P, C, and O atoms,
transition state that the heterochiral coupling is favored.
This fits very well with the experimental results.
In summary, we have synthesized and structurally
characterized the first thermally stable iron ethylidene
complex. We have also shown that 17-electron iron(III)
vinyl radicals can be stabilized at low temperature and
that they undergo oxidative coupling to produce diiron
µ-bis(methoxycarbene) or µ-bis(ethylidene) complexes in
good yields, all the resulting compounds being thermally
stable. The coupling reaction is sensitive to steric effects
of the ancillary ligands at the metal center, and both
the meso and the dl couple of the bis(carbene) dimers
were diastereoselectively produced and their separation
readily achieved. These results open the route for the
synthesis of new diiron(II) µ-bis(vinyl) complexes, and
the study of their interesting redox properties which will
be the subject of future reports from our group.
Exp er im en ta l Section
Gen er a l Da ta . Reagent grade tetrahydrofuran (THF),
diethyl ether, and pentane were dried and distilled from
sodium benzophenone ketyl prior to use. Pentamethylcyclo-
pentadiene was prepared according to the published proce-
dure,72 and other chemicals were used as received. All the
manipulations were carried out under argon atmosphere using
Schlenk techniques or in a J acomex 532 drybox filled with
nitrogen. Routine NMR spectra were recorded using a Bruker
AW 80 MHz. High-field NMR spectra experiments were
performed on a multinuclear Bruker 300 MHz instrument.
Chemical shifts are given in part per million relative to
1
tetramethylsilane (TMS) for H and 13C NMR spectra and H3-
PO4 for 31P NMR spectra. Cyclic voltammograms were re-
corded by using a PAR 263 instrument. X-Band ESR spectra
were recorded on a Bruker ESP-300E spectrometer at 77 K in
liquid nitrogen. Elemental analyses were performed at the
Center for Microanalyses of the CNRS at Lyon-Solaise, France.
[Cp *F e(P Me3)(CO)(dC(OMe)(Me))][SO3CF 3] (2b). To a
suspension of Cp*Fe(PMe3)(CO)(COMe) (4) (0.44 g, 1.3 mmol)
in 20 mL of CH2Cl2 at -80 °C was added CH3SO3CF3 (1.45
mmol, 160 µL). At room temperature, the solvent was
concentrated in vacuo to 5 mL and 100 mL of diethyl ether
was added to precipitate 2b (0.52 g) as an orange powder (80%
yield, 1.04 mmol). Anal. Calcd (C18H30F3FeO5PS): C, 43.04;
H, 6.02. Found: C, 43.14; H, 6.05.
[Cp *F e(d p p e)(dC(OMe)(Me))][SO3CF 3] (2c). dppe (1.1
mmol, 0.44 g) was added to a solution of the carbene complex
1 (1.1 mmol, 0.50 g) in CH2Cl2 (210 mL), and the mixture was
photolyzed in a quartz vessel for 2 h. The solvent was removed
in vacuo and the crude residue washed with diethyl ether (4
× 25 mL). After drying in vacuo, the complex 2c is isolated
as an orange powder in 97% yield (0.85 g, 1.07 mmol). Anal.
Calcd (C40H45F3FeO4P2S): C, 60.31; H, 5.69. Found: C, 60.33;
H, 5.90.
B
iso values for F atoms, x, y, z for H atoms of the cation and x,
y, z fixed for H atoms of the solvent molecule; 602 variables
and 3685 observations).
[Cp *F e(L1)(L2)(C(R)dCH2)] (7a , R ) OMe, L1 ) CO,
L2 ) P P h 3; 7b, R ) OMe, L1 ) CO, L2 ) P Me3; 7c, R )
OMe, L1, L2 ) d p p e; 7d , R ) H, L1, L2 ) d p p e). To a -80
°C THF solution of the appropriate carbene complex [7a , 2.138
g (3.1 mmol); 7b, 0.440 g (0.87 mmol); 7c, 1.635 g (2.05 mmol);
7d , 0.356 g (0.47 mmol)] was added 2 equiv of potassium tert-
butoxide (7a , 0.70 g; 7b, 0.19 g; 7c, 0.46 g; 7d 0.11 g). After
30 min of stirring, the solution was allowed to warm and the
solvent removed in vacuo. The solid residue was extracted
with pentane (3 × 15 mL), and microcrystals were obtained
by removal of the solvent in vacuo [7a , 89%, 1.48 g (2.75 mmol);
7b, 85%, 0.26 g (0.74 mmol); 7c, 80%, 1.06 g (1.64 mmol); 7d ,
85%, 0.25 g (0.40 mmol)]. Anal. Calcd for 7a (C32H35FeO2P):
C, 71.38; H, 6.55. Found: C, 71.13; H, 6.81. Calcd for 7c
(C39H44FeOP): C, 72.45; H, 6.86. Found: C, 72.82; H, 7.00.
[{(η5 -C 5 Me 5 )F e (C O )(P P h 3 )}2 µ-(dC (O Me )(C H 2 )2 -C -
(OMe)d)][P F 6]2 (8a ). In a Schlenk tube was dissolved 547
mg (1.01 mmol) of complex 7a in a minimum of degassed
dichloromethane. The solution was cooled to -80 °C, and
0.319 g (0.95 equiv) of ferrocenium salt was added under argon.
The mixture was stirred at -80 °C for 6 h and then precipi-
tated with pentane cooled at -80 °C. After filtration at -80
°C of the resulting liquor, the residue was dried in vacuo and
allowed to warm to room temperature overnight. The crude
residue was washed with 2 × 20 mL of diethyl ether, 2 × 3
mL of CH2Cl2, and 2 x 2 mL of acetone. The complex 8a was
isolated as an orange-yellow powder of a pure diastereoisomer
Cp *F e(P Me3)(CO)(COMe) (4). To a suspension of [Cp*Fe-
(PMe3) (CO)2][PF6] (1.38 g, 2.96 mmol) in 30 mL of THF at
-80 °C was added 1.2 equiv of MeLi. The mixture was slowly
allowed to warm to room temperature (16 h). The solvent was
evaporated to dryness in vacuo and the residue was dissolved
in toluene and hydrolyzed with a H2O/NaHCO3 solution. The
solvent was removed in vacuo, and the crude residue was
extracted with pentane. After evaporation of the solvent, the
complex Cp*Fe(PMe3)(CO)(COMe) was isolated with an overall
in 60% yield (0.41 g, 0.30 mmol). Anal. Calcd (C64H70F12
Fe2O4P4): C, 56.24; H, 5.16. Found: C, 56.38; H, 5.14.
[{(η -C 5 Me 5 )F e (C O )(P Me 3 )}2 µ-(dC (O Me )(C H 2 )2 -C -
(OMe)d)][P F 6]2 (8b). In a Schlenk tube was dissolved 0.40
g (1.13 mmol) of complex 7b in a minimum of CH2Cl2. The
-
yield of 50% (0.500 mg, 1.48 mmol). Anal. Calcd (C16H27
FeO2P): C, 56.82; H, 8.05. Found: C, 56.63; H, 7.92.
-
5
Cp *F e(d p p e){CH(OMe)Me} (5). To a -80 °C THF solu-
tion (20 mL) of 2b (1.35 g, 1.7 mmol) is added 1.7 mmol (0.14
g) of NaBH4. The mixture was allowed to warm to 20 °C under
(73) Enraf-Nonius molecular structure determination package,
MOLEN, Delft, The Netherlands, 1990.
(72) Kohl, F. X.; J utzi, P. J . Organomet. Chem. 1983, 243, 119.
Mahias, Virginie
