Chemistry - A European Journal
10.1002/chem.201701905
FULL PAPER
observed, as well as of the hypothetic, diastereomers. Most
strikingly the inversion of the central phosphorus center, P2,
affects the interaction σP-X* (X:Cl, Br) LUMO with the neighboring
phosphorus lone pairs, stabilizing the occupied and destabilizing
the unoccupied orbitals, changing the HOMO from an iron
centered (in the cis isomer) to a phosphorus centered orbital (in
the trans isomer). These theoretical findings were confirmed by
electrochemical investigations which revealed irreversible
processes for the diasteromeric mixtures, however are well
resolved for compounds occurring as single isomers such as 7.
The latter results, moreover, hint at subsequent transformations
occurring with rates in the range of the speed of the sweep voltage
which we would like to explore in the future with respect to radical
formation and small molecule activation.
Synthesis of 3b
To a stirred mixture of 2.37 g (6.5 mmol) Fc‘(PHtBu)
2
1 and 3.7 mL (26.7
mmol) NEt in 100 mL pentane 0.9 g (6.5 mmol) PCl were added dropwise
3
3
at room temperature. After continued stirring for 2 h, all volatiles were
removed under reduced pressure. The residue was extracted with 20 mL
pentane and filtered off. From the resulting orange solution the solvent was
removed in vacuo yielding a yellow-orange crystalline solid which could be
further purified by recrystallization from pentane at – 20°C. Yield: 2.7 g
(97%) crude product.
1
NMR: the spectra consist of signals from two diastereomers (A and B) H
(400 MHz, C D
6 6
): A δ 1.30–1.35 (m, 18H, tBu CH
3
), 3.93 (m, 2H, Cp), 4.13
(m, 2H, Cp), 4.47 (m, 2H, Cp), 4.97 (m, 2H, Cp) ppm; B δ 1.28-1.32 (m,
1
(
8H, tBu CH
3
), 3.92 (m, 2H, Cp), 3.95 (m, 2H, Cp), 4.22 (m, 2H, Cp), 4.29
): A δ 30.42 (m, tBu CH ), 33.64 (m,
), 69.56 (m, Cp), 72.94 (m, Cp), 76.12 (m, Cp), 79.44 (m, Cp Cipso),
0.13 (m, Cp) ppm; B δ 30.09 (m, tBu CH ), 32.67 (m, tBu C ), 72.36 (m,
Cp), 72.61 (s, Cp), 73.42 (m, Cp), 78.23 (m, Cp), 79.44 (m, Cp C ) ppm.
m, 2H, Cp) ppm. 13C (100 MHz, C
D
6 6
3
tBu C
8
q
3
q
Experimental Section
ipso
31
1
1
1
6 6
P{ H} (202 MHz, C D ): A δ 18.2 (d, JPP = 375 Hz, P-tBu), 18.2 (d, JPP
1
1
All experiments were carried out under exclusion of moisture and air under
an inert argon atmosphere. All solvents were dried over sodium potassium
alloy and distilled prior to use. Starting materials were purified and stored
= 375 Hz, P-tBu), 147.7 (dd, JPP = 377 Hz, JPP = 372 Hz, P-Cl) ppm; B δ
4.2 (d, 1JPP = 170 Hz, P-tBu), 61.8 (t, JPP = 170 Hz, P-Cl) ppm. MS (EI)
m/z: 426.22 (30%, M ), 313.02 (100%, [M+H] - 2tBu).
1
+
+
under argon. Fc’(PHtBu)
procedures. PCl (NEt
2 2
2
1
was synthesized according published
) is readily accessible using phosphorus trichloride
and two equivalents of diethylamine and purification via distillation. tert-
butyl dichlorophosphane (tBuPCl ) was prepared reacting phosphorus
[
6]
Synthesis of 3c
2
To a stirred mixture of 0.83 g (2.3 mmol) Fc‘(PHtBu)
3 3
mmol) NEt in 80 mL pentane 1.08 g (2.3 mmol) PBr were added dropwise
2
1 and 0.9 mL (6.5
trichloride with one equivalent of tert-butyl lithium in pentane at -80°C in
quantitative yields. Subsequently, the resulting colorless liquid was purified
via distillation to end up with a colorless solid. H-, 13C-, 19F- and 31P-NMR
spectra were recorded on a Varian VNMRS-500 MHz or MR-400 MHz
spectrometer at room temperature using TMS as the external reference for
1H and 13C cores. Even for single crystalline samples microanalytic
measurements resulted in too low carbon values suggesting metal carbide
formation which could not be suppressed using standard additives such as
at room temperature. After continued stirring for 2 h, all volatiles were
removed under reduced pressure. The residue was extracted with 20 mL
pentane and filtered off. From the resulting yellow solution the solvent was
removed in vacuo yielding a yellow crystalline solid which could be further
purified by recrystallization from pentane at – 20°C. Yield: 0.98 g (90%)
crude product.
1
2 5
V O . For all highly moisture and air sensitive compounds it was necessary
1
NMR: the spectra consist of signals from two diastereomers (A and B) H
(
(
to use EI-MS techniques for which we developed a method as inert as
possible or were recorded via vAPCI-MS using iASAP on a Advion
expressionS CMS. Thus, for these compounds it was not possible to
measure high resolution mass spectra. The APCI-MS spectrum for
compound 7 has been recorded on a ThermoQuest Finnigan LCQ Deca.
400 MHz, C
m, 2H, Cp), 4.45 (m, 2H, Cp), 5.15 (m, 2H, Cp) ppm; B δ 1.27-1.34 (m,
8H, tBu CH ), 3.91 (m, 2H, Cp), 3.95 (m, 2H, Cp), 4.21 (m, 2H, Cp), 4.27
m, 2H, Cp) ppm. 13C (126 MHz, C
): A δ 30.19-30.44 (m, tBu CH ),
4.01 (m, tBu C ), 69.74 (m, Cp), 72.71 (m, Cp), 75.00 (m, Cp), 79.54 (m,
Cp Cipso), 80.23 (m, Cp) ppm; B δ 30.17-30.31 (m, tBu CH ), 32.91 (m, tBu
), 72.38 (m, Cp), 72.53 (m, Cp), 72.92 (m, Cp), 78.10 (m, Cp), 79.54 (m,
6 6 3
D ): A δ 1.29–1.36 (m, 18H, tBu CH ), 3.93 (m, 2H, Cp), 4.14
1
3
(
D
6 6
3
3
q
3
C
q
31
1
1
6 6
Cp Cipso) ppm. P{ H} (202 MHz, C D ): A δ 19.1 (d, JPP = 375 Hz, P-tBu),
Synthesis of 3a
19.1 (d,
1
JPP = 375 Hz, P-tBu), 135.0 (dd,
1
JPP = 378 Hz,
1
JPP = 374 Hz, P-
PP = 171 Hz, P-Br)
ppm. MS (EI) m/z: 469.82 (8%, M ), 412.74 (5%, M -tBu), 356.72 (23%,
Br) ppm; B δ 5.8 (d, 1JPP = 171 Hz, P-tBu), 44.0 (t,
1
J
+
+
To a stirred suspension of 0.5 g (2.8 mmol) SbF
3
in 10 mL toluene a
+
+
solution of 1.2 g (2.8 mmol) Cl[3]Fc 3b in 10 mL toluene were added
dropwise at room temperature. After stirring over night, all volatiles were
removed in vacuo, extracted with 10 mL pentane and filtered off. The
yellow crystalline product was obtained via crystallization at -20°C from
pentane. Yield: 0.7 g (60%).
[M+H] - 2tBu), 56.89 (100%, tBu ).
Synthesis of 3d
0
.44 g (1.0 mmol) Cl[3]Fc 3b were stirred in 30 mL pentane at room
temperature. To this solution 0.21 g (1.0 mmol) TMSI were added dropwise
and stirring continued for 40 h at room temperature. From the resulting red
solution all volatiles were removed under reduced pressure. The residue
was recrystallized from pentane at -20 °C affording the product as bright
red needles. Yield: 0.21 g (40%).
NMR: 1H (500 MHz, C
.12 (m, 2H, Cp), 4.48 (m, 2H, Cp), 4.55 (m, 2H, Cp) ppm. 13C (126 MHz,
C D ): δ 30.58 (m, tBu CH ), 32.29 (m, tBu C ), 69.64 (m, Cp), 72.90 (m,
6 6 3 q
Cp), 76.19 (m, Cp), 78.27 (m, Cp Cipso), 79.92 (m, Cp) ppm. 19F (376 MHz,
6
6 3
D ): δ 1.29 (m, 18H, tBu CH ), 3.96 (m, 2H, Cp),
4
C
6
D
D
6
): δ -209.0 (dt, 1JFP = 936 Hz, 2JFP = 94 Hz) ppm. 31P{ H} (202 MHz,
1
C
6
6
): δ 14.2 (dd, 1JPP = 358 Hz, 2JPF = 94 Hz, P-tBu), 14.2 (dd, 1JPP = 358
Hz, JPF = 94 Hz, P-tBu), 247.2 (ddd, 1JPF = 936 Hz, 1JPP = 359 Hz, 1JPP
57 Hz, P-F) ppm. MS (APCI) m/z: 411.0 (20%, [M+H] ), 363.1 (100%,
1
NMR: the spectra consist of signals from two diastereomers (A and B) H
2
=
6 6 3
(500 MHz, C D ): A δ 1.28 (m, 18H, tBu CH ), 3.92 (m, 2H, Cp), 4.17 (m,
+
3
[
2H, Cp), 4.44 (m, 2H, Cp), 5.38 (m, 2H, Cp) ppm; B δ 1.36 (m, 18H, tBu
Fc’(PHtBu)
2
+H]+).
CH
3
), 3.89 (m, 2H, Cp), 3.96 (m, 2H, Cp), 4.23 (m, 2H, Cp), 4.26 (m, 2H,
Cp) ppm. 13C (126 MHz, C
): A δ 29.99 (m, tBu CH ), 34.07 (m, tBu C ),
6 6
D
3
q
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