E.O. Changamu, H.B. Friedrich / Journal of Organometallic Chemistry 693 (2008) 3351–3356
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[Cp(CO)2Fe{(CH2)4I}] (0.60 g, 1.67 mmol) in CH2Cl2 (5 mL) in a
Schlenk tube and the mixture allowed to stand for 4 h under nitro-
gen at room temperature. After 2 h, a solid started precipitating in
the Schlenk tube, but the reaction mixture was allowed to stand
until IR monitoring showed the reaction to be complete (the start-
ing materials shows two strong IR bands at around 1956 and
1941 cmÀ1, while the cationic products show two strong bands
at around 2075 and 2039 cmÀ1). In the complex, where n = 4, the
mother liquor was removed through a cannula and the solid
washed with two 3 ml portions of CH2Cl2 and dried under reduced
pressure. The cationic products did not initially precipitate from
solution where n > 4. Thus, when the reaction was deemed com-
plete, the reaction mixture was filtered by cannula into a clean,
pre-weighed, Schlenk tube and diethyl ether added to precipitate
the product, usually as a yellow solid. The mother liquor was then
removed through a cannula and the solid dried under reduced
pressure. The reactions of the bromoalkyl complexes required ca.
1 h longer to go to completion than the iodoalkyl analogues. The
yields, melting/decomposition temperatures, IR and elemental
analysis data are given in Table 1. 1H NMR and 13C NMR spectro-
scopic data are given in Tables 2–5.
spectra at intervals of 5 min until there was no further change in
the spectra. Free PPh3 showed a double multiplet at 7.30 ppm.
After 5 min of reaction the1H NMR spectrum showed a new double
multiplet at 7.88 ppm due to the phosphonium ion phenyl protons
and a new singlet at 5.08 ppm due to Cp of the phoshonium adduct
complex. These continued increasing in intensity with time. As
these were growing, the originally observed starting material sig-
nals decreased. This procedure was repeated with [Cp(CO)2-
Fe{CH2CH(CH2)2I}]PF6 and [Cp(CO)2Fe{CH2CH(CH2)3I}]PF6.
The reaction of [Cp(CO)2Fe{CH2CH(CH2)3I}]PF6 with PPh3 was
followed for a longer period. After about 1 h of reaction a third
PPh3 signal started growing at 7.60 ppm along with another singlet
at 5.62 ppm. These were due to the PPh3 and Cp group,
respectively, of the complex [Cp(CO)2Fe(PPh3)]+ formed by the
decomposition
of
the
phosphonium
adduct
[Cp(CO)2-
Fe{CH2CH(PPh3)- (CH2)3I}]PF6. At the same time signals character-
istic of the displaced iodo-olefin started growing in the olefinic
proton regions. The reaction mixture was left standing overnight
in the NMR tube at 5 °C. The 1H NMR spectrum recorded after this
showed peaks attributable to the starting material, the phospho-
nium adduct salt and [Cp(CO)2Fe(PPh3)]+.
[Cp(CO)2Fe{CH2CH(PPh3)(CH2)2Br}]PF6 1H NMR (d, acetone-d6):
7.8 (dm, P-phenyl), 5.21 (s, C5H5), 3.85, 2.60 (m, CH(PPh3)CH2, dia-
stereotopic), 4.21 (m, CH-P), 3.55 (t, CH2Br), 3.16, 1.84 (m,
CH2CH2Br, diastereotopic). [Cp(CO)2Fe{CH2CH(PPh3)(CH2)2I}]PF6
1H NMR (d, nitromethane-d3): 7.80 (dm, P-phenyl) 5.05 (s, C5H5),
3.81 (m CH-P), 3.61, 2.50 (m, CH(PPh3)CH2, diastereotopic), 3.28
(m, CH2I), 2.82, 1.86 (m, CH2CH2I, diastereotopic). [Cp(CO)2-
Fe{CH2CH(PPh3)(CH2)3I}]PF6 1H NMR (d, acetone-d6): 7.90 (dm, P-
phenyl), 5.18 (s, Cp), 4.20 (m, CH-P), 3.80, 2.40 (m, CH(PPh3)CH2,
diastereotopic), 3.54 (m, CH2I), 2.32, 1.86 (m, CH2CH2I, diastereo-
topic), 2.40, 1.58 (m, FeCH2, diastereotopic). [Cp(CO)2FePPh3]),
7.60 (dm, phenyl protons), 5.6 (s, Cp of [Cp(CO)2FePPh3]). The unre-
acted cationic complex [Cp(CO)2Fe{CH2CH(PPh3)(CH2)3I}]PF6 was
also observed (see Table 2 for spectral data).
4.3. Reactions of the complexes [Cp(CO)2Fe{CH2CH(CH2)nBr}]PF6
(n = 2, 6, 7) with NaI
About 10 mg of a given complex was dissolved in nitrogen sat-
urated acetone-d6 in an NMR tube and the 1H NMR spectrum was
recorded. About 10 mg of NaI was added to the tube and the reac-
tion followed by recording spectra at intervals of 5 min until there
was no further change in the spectra. It was noticed that the iodide
ion displaced the
a-bromoalkene and formed the complex
[Cp(CO)2FeI]. Some halide exchange was also noticed because a
growing triplet at around 3.30 ppm due to the CH2I protons was
observed. The intensity of the CH2Br triplet of the starting material
decreased as the triplet due to the CH2Br of the displaced olefin
grew.
The reaction of [Cp(CO)2Fe{CH2CH(CH2)6Br}]PF6 gave the alkene
CH2@CH(CH2)6Br. 1H NMR (d, acetone-d6): 5.80 (m, CH2@CH), 4.98
(d, J = 17.3 Hz, CH2@CH), 4.89 (d, J = 9.3 Hz, CH2@CH), 3.50 (t,
CH2Br), 2.08 (m, @CHCH2), 1.83 (m, CH2CH2Br), 1.32–1.45 (brm,
–(CH2)3). The iodo alkene also present was recognized by the dis-
tinct triplet due to the CH2I protons at 3.26 ppm. The reaction of
[Cp(CO)2Fe{CH2CH(CH2)7Br}]PF6 gave CH2@CH(CH2)7Br. 1H NMR
(d, acetone-d6): 5.80 (m, CH2@CH), 4.98 (d, J = 17.3 Hz, CH2@CH),
4.89 (d, J = 9.3 Hz, CH2@CH), 3.52 (t, CH2Br), 2.08 (m, @CHCH2),
1.88 (m, CH2CH2Br), 1.45–1.51(brm, (CH2)4). The iodo analogue
also present was identified by the distinct triplet at 3.25 ppm.
The reaction of [Cp(CO)2Fe{CH2CH(CH2)2Br}]PF6 with NaI and sub-
sequent standing for 5 h gave a mixture of CH2@CH(CH2)4Br and
CH2@CH(CH2)4I; 1H NMR (d, acetone-d6): 5.81 (m, CH2@CH), 5.00
(d, J = 17.0 Hz, CH2@CH), 4.93 (d, J = 10.2 Hz, CH2@CH), 3.48 (t,
CH2Br), 2.09 (m, @CHCH2, very close to solvent peak), 1.83 (m,
CH2CH2Br) and 1.50 (m, @CHCH2CH2), 3.27 (m, CH2I). 13C NMR (d,
acetone-d6): 214.6 (CO of [Cp(CO)2FeI]), 85.6 (Cp of [Cp(CO)2FeI];
138.8 (CH2@CH), 114.9 ((CH2@CH), 33.5 (CH2Br), 33.1 (@CHCH2),
32.7 (CH2CH2Br), 28.9 (CHCH2CH2Br).
4.5. Reaction of [Cp(CO)2Fe{CH2CH(CH2)6I}]PF6 with Na[Cp(CO)2Fe]
The complex [Cp(CO)2Fe{CH2CH(CH2)6I}]PF6 (0.1 g, 0.18 mmol)
was dissolved in 10 cm3 CH2Cl2 and cooled in a dry ice-acetone
bath to À78 °C. A solution of Na[Cp(CO)2Fe] (0.1 g 0.18 mmol) in
THF was added dropwise to the solution while stirring, upon which
the solution turned maroon in colour. The mixture was maintained
at À78 °C for 20 min and then allowed to warm up to room tem-
perature (1 h). The solvent mixture was removed under reduced
pressure and a maroon paste obtained. 1H NMR of the crude prod-
uct showed that it consisted of only the iron dimer [Cp(CO)2Fe]2
and the iodo-octene CH2@CH(CH2)6I identified as follows: 1H
NMR (d, acetone-d6): 4.94 (s, Cp of [Cp(CO)2Fe]2); CH2@CH(CH2)6I
1H NMR (d, acetone-d6): 5.80 (m, CH2@CH), 4.98 (d, J = 17.3 Hz,
CH2@CH), 4.89 (d, J = 9.3 Hz, CH2@CH), 3.15 (t, CH2I), 2.16 (m,
@CHCH2), 1.80 (m, CH2CH2I) and 1.34 (m br, –(CH2)3–).
4.6. Reaction of the complexes [Cp(CO)2Fe{CH2CH(CH2)nBr}]PF6 (n = 2,
10) with Et3N
This reaction was carried out by following the procedure of Cut-
ler et al. [13]. Thus, a solution of [Cp(CO)2Fe{CH2CH(CH2)2Br}]PF6
(0.31 g, 0.68 mmol) in CH2Cl2 was cooled to À50 °C, and triethyl-
amine (0.1 g, 0.99 mmol) was added with stirring. The solution
was allowed to warm up to room temperature and the reaction
was followed with IR until it was complete (about 20 min). The sol-
vent was then removed under reduced pressure, and the residue
extracted thrice with 20 ml portions of diethyl ether. The extracts
were concentrated and chromatographed on activity III neutral
alumina with methylene chloride-ether (1:l) to give the product,
4.4. Reaction of [Cp(CO)2Fe{CH2CH(CH2)2Br}]PF6 with PPh3
About 10 mg of the complex was dissolved in nitrogen satu-
rated acetone-d6 or nitromethane-d3 in an NMR tube and the 1H
NMR spectrum was recorded. The spectrum showed characteristic
peaks at 5.95 (s, Cp), 4.22 (d, cis FeCH2), 3.72 (d, trans FeCH2), and
5.17 (m, FeCH2CH), whose disappearance was followed during the
course of the reaction of the complex with PPh3. About 10 mg of
PPh3 was added to the tube and the reaction followed by recording