Organometallics
Article
(70 eV): calcd for C13H13BrFeO2, 335.9448; found, 335.9449. Anal.
Calcd for C13H13BrFeO2: C, 46.33; H, 3.89. Anal. Calcd for a mixture
of C13H13BrFeO2 (336.99; 96%) and C13H14FeO2 (258.10; 4%): C,
46.90; H, 3.95. Found: C, 46.59; H, 3.87.
52.21; H, 3.89; N, 3.38. Anal. Calcd for a mixture of C18H16BrFeNO2
(414.08; 96%) and C18H17FeNO2 (335.18; 4%): C, 52.70; H, 3.94; N,
3.41. Found: C, 52.87; H, 3.61; N, 3.38.
Synthesis of 1-Amino-1′-bromoferrocene (5). Employing a known
procedure,22 Pd−C (0.99 g) was added to a solution of compound 4
(4.32 g, 10.5 mmol) in dry and deoxygenated iPrOH (160 mL) taken
in a Schlenk flask. After the reaction flask was purged with hydrogen
by six consecutive cycles of evacuation and refilling, a balloon, filled
with hydrogen gas, was placed on the well-stirred reaction mixture for
2.5 h. All the volatiles were removed under high vacuum, and the
resulting black solid was suspended in dry Et2O (100 mL). All
insoluble materials were filtered off by Schlenk filtration, resulting in a
bright yellow solution, which, after removal of all the volatiles, resulted
in a yellow crystalline solid. This yellow solid was dissolved in CH2Cl2
(75 mL), and the organic phase was washed by an aqueous NaOH
solution (6 M, 5 × 20 mL) and deionized water (20 mL). After drying
the organic phase over anhydrous Na2SO4, all volatiles were removed
under high vacuum to give a yellow solid, which according to 1H NMR
spectroscopy was composed of compound 5 (85%) and amino-
ferrocene (15%). Some of the aminoferrocene was removed by
sublimation (96 h; 38 °C oil bath temperature; p ≈ 10−2 mbar).
Further sublimation (24 h; 60 °C oil bath temperature; p ≈ 10−2
mbar) gave product 5 as a yellow, amorphous solid contaminated with
ca. 6% of aminoferrocene (2.03 g, 70%). 1H NMR (C6D6): δ 2.08 (bs,
2H, NH2), 3.57 (pst, 2H, CpBr), 3.68 (pst, 2H, CpNH2), 3.71 (pst, 2H,
CpNH2), 4.12 (pst, 2H, CpBr). 13C NMR (C6D6): δ 60.02 (C of
CpNH2), 65.68 (C of CpNH2), 67.54 (C of CpBr), 71.06 (C of CpBr),
79.86 (ipso-C-Br), 107.89 (ipso-C-NH2). MS (70 eV): m/z (%) 279
(100) [M+], 199 (10) [M+ − HBr]. HRMS (70 eV): calcd for
C10H10BrFeN, 278.9346; found, 278.9357. Anal. Calcd for
C10H10BrFeN: C, 42.90; H, 3.60; N, 5.00. Anal. Calcd for a mixture
of C10H10BrFeN (279.94; 94%) and C10H11FeN (201.05; 6%): C,
43.91; H, 3.72; N, 5.12. Found: C, 43.74; H, 3.74; N, 5.07.
Synthesis of 1-Bromo-1′-carboxyferrocene (2). Employing a
known procedure,29 compound 1 (8.56 g, 25.6 mmol) and KOH
(55.42 g, 987.8 mmol) were dissolved in a mixture of EtOH (780 mL)
and deionized water (80 mL). After the solution was heated under
reflux for 40 h, deionized water (100 mL) was added to the reaction
mixture at rt. The aqueous phase was washed with CH2Cl2 (4 × 200
mL; discarded) and acidified by concentrated HCl(aq) (60 mL) to
give a yellow precipitate, which was extracted by CH2Cl2 (3 × 100
mL). After the CH2Cl2 phase was dried over anhydrous Na2SO4, all
volatiles were removed in a rotary evaporator, resulting in product 2 as
an orange powder (6.05 g, 77%). Compound 2 contained ca. 4% of
1
[(HO2C)H4C5](C5H5)Fe as an impurity. H NMR (CDCl3): δ 4.20
(pst, 2H, CH-β of CpBr), 4.49 (pst, 2H, CH-α of CpBr), 4.51 (pst, 2H,
CH-β of CpCOOH), 4.91 (pst, 2H, CH-α of CpCOOH), 11.95 (bs, 1H,
COOH). 13C NMR (CDCl3): δ 69.29 (C-β of CpBr), 70.13 (ipso-C-
COOH), 71.88 (C-α of CpBr), 72.67 (C-α of CpCOOH), 74.62 (CH-β
of CpCOOH), 78.06 (ipso-C-Br), 176.12 (COOH). MS (70 eV): m/z
(%) 308 (100) [M+], 165 (57) [M+ − CpBr]. HRMS (70 eV): calcd
for C11H9BrFeO2, 307.9135; found, 307.9127. Anal. Calcd for
C11H9BrFeO2: C, 42.77; H, 2.94. Anal. Calcd for a mixture of
C11H9BrFeO2 (308.94; 96%) and C11H10FeO2 (230.04; 4%): C, 43.36;
H, 3.00. Found: C, 43.50; H, 2.89.
Synthesis of 1-Azidocarbonyl-1′-bromoferrocene (3). Employing
a known procedure,21 (COCl)2 (1.6 mL, 19 mmol) was added
dropwise to a solution of 2 (1.82 g, 5.95 mmol) in CH2Cl2 (35 mL),
followed by the addition of DMF (four drops). After stirring the
solution for 3 h, all the volatiles were removed under high vacuum. To
a solution of the so-obtained red solid in CH2Cl2 (35 mL), nBu4NBr
(0.015 g, 0.046 mmol) and an aqueous solution of NaN3 (0.575 g, 8.84
mmol in 7.0 mL of deionized water) were added. The biphasic
solution was stirred for 16 h at rt, followed by the addition of
deionized water (100 mL). The aqueous phase was removed by a
separatory funnel, and the organic phase was washed with deionized
water (4 × 200 mL) and dried over anhydrous Na2SO4. All volatiles
were removed by a rotary evaporator, resulting in compound 3 as a
brown powder (1.83 g, 93%). Compound 3 contained ca. 4% of
Synthesis of 1-Bromo-1′-(trimethylsilylamino)ferrocene (6). Em-
ploying a known procedure,23 compound 5 (0.28 g, 1.0 mmol) was
suspended in hexanes (20.0 mL), and NEt3 (1.2 mL, 8.6 mmol) was
added, followed by addition of a solution of chlorotrimethylsilane
(0.20 mL, 1.6 mmol) in hexanes (4.0 mL). After stirring the solution
for 20 h at rt, all the insoluble materials were removed by Schlenk
filtration, resulting in a red solution. After removal of all the volatiles
under high vacuum, compound 6 was left behind as a red oil (0.32 g,
92%). Product 6 contained ca. 6% of [(Me3SiNH)H4C5](C5H5)Fe as
1
[(N3OC)H4C5](C5H5)Fe as an impurity. H NMR (CDCl3): δ 4.19
(pst, 2H, CH-β of CpBr), 4.49 (pst, 2H, CH-α of CpBr), 4.54 (pst, 2H,
CH-β of CpCON3), 4.87 (pst, 2H, CH-α of CpCON3). 13C NMR
(CDCl3): δ 69.28 (C-β of CpBr), 70.25 (ipso-C-COON3), 72.01 (C-α
of CpBr), 72.33 (C-α of CpCON3), 75.07 (CH-β of CpCON3), 78.37
(ipso-C-Br), 175.92 (COON3). MS (70 eV): m/z (%) 333 (13) [M+],
305 (29) [M+ − N2]. HRMS (70 eV): calcd for C11H8BrFeN3O,
332.9200; found, 332.9198. Anal. Calcd for C11H8BrFeN3O: C, 39.56;
H, 2.41; N, 12.58. Anal. Calcd for a mixture of C11H8BrFeN3O
(333.95; 96%) and C11H9FeN3O (255.06; 4%): C, 40.05; H, 2.46; N,
12.74. Found: C, 39.94; H, 2.20; N, 12.64.
1
an impurity. H NMR (CDCl3): δ 0.23 (s, 9H, SiMe3), 2.42 (bs, 1H,
NH), 3.85 (pst, 2H, CH of CpNHSiMe3), 3.88 (pst, 2H, CH of
CpNHSiMe3), 3.99 (pst, 2H, CH of CpBr), 4.25 (pst, 2H, CH of CpBr).
13C NMR (CDCl3): δ 0.18 (SiMe3), 59.64 (C of CpNHSiMe3), 65.24 (C
of CpNHSiMe3), 67.62 (C-β of CpBr), 70.87 (C-α of CpBr), 79.07 (ipso-
C-Br), 109.34 (ipso-C-NHSiMe3). MS (70 eV): m/z (%) 353 (76)
[M+], 273 (16) [M+ − Br]. HRMS (70 eV): calcd for C13H18BrFeNSi,
350.9741; found, 350.9745. Note: Due to technical difficulties in
analyzing liquids, an elemental analysis could not be performed for
species 6.
Synthesis of Benzyl N-(1′-Bromoferrocen-1-yl)carbamate (4).
Employing a known procedure,22 a solution of 3 (3.05 g, 9.22
mmol) in PhCH2OH (15.0 mL) was heated at 90 °C for 2 h, resulting
in a color change from burgundy red to yellow. The yellow solution
was cooled to rt, and all volatiles were removed under high vacuum.
The mixture was further purified by column chromatography on silica
gel (hexanes/CH2Cl2/NEt3; 15:83:2 by volume). The product was
obtained as a golden yellow crystalline solid (3.35 g, 88%). Compound
4 contained ca. 4% of [{PhCH2O(O)CNH}H4C5](C5H5)Fe as an
impurity. 1H NMR (CDCl3): δ 4.04 (s, 2H, CH-β of CpNHCOOBz), 4.09
(s, 2H, CH-β of CpBr), 4.38 (s, 2H, CH-α of CpBr), 4.52 (s, 2H, CH-α
of CpNHCOOBz), 5.18 (s, 2H, CH2), 6.00 (bs, 1H), 7.25−7.42 (m, 5H,
Ph). 13C NMR (CDCl3): δ 62.77 (CH2), 66.69 (C-β of CpNHCOOBz),
67.02 (ipso-C-NH), 67.93 (C-β of CBr), 69.11 (C-α of CpNHCOOBz),
71.09 (C-α of CpBr), 78.93 (ipso-C-Br), 128.23 (C of Ph), 128.30
(ipso-C of Ph), 128.59 (C of Ph), 136.16 (CO). MS (70 eV): m/z
Synthesis of 2,2-Dimethyl-1-trimethylsilyl-1,2-azasila[2]-
ferrocenophane, 7SiMe2. nBuLi (0.40 mL, 1.0 mmol) was added
dropwise to a −78 °C cooled solution of 6 (0.17 g, 0.49 mmol) in thf
(24.0 mL), resulting in a color change from pale yellow to bright
orange. After the reaction mixture was stirred for 40 min at −78 °C,
the cold bath was replaced by an ice bath, followed by stirring of the
reaction mixture at 0 °C for 1 h. The resulting deep red solution was
cooled to −78 °C, and a solution of Me2SiCl2 (0.064 g, 0.50 mmol) in
thf (5.0 mL) was added dropwise over 5 min. The reaction mixture
was warmed to ambient temperature and stirred for 4 h. After all
volatiles were removed under high vacuum, the product was dissolved
in hexanes (15.0 mL) and LiCl was removed by Schlenk filtration.
From this red solution, solvents were removed under high vacuum,
resulting in a red, sticky solid. Product 7SiMe2 was obtained by vacuum
sublimation (45 °C oil bath temperature; p ≈ 10−2 mbar) in the form
of red crystals (0.085 g, 53%). 1H NMR (C6D6): δ 0.07 (s, 9H,
Me3Si), 0.43 (s, 6H, Me2Si), 3.80 (pst, 2H, CH of CpNSiMe3), 4.23 (pst,
2H, CH of CpNSiMe3), 4.27 (pst, 2H, CH of CpSiMe2), 4.63 (pst, 2H,
(%) 413 (37) [M+], 335 (2) [M+ − HPh], 278 (26) [M+
−
NHCOOCH2Ph]. HRMS (70 eV): calcd for C18H16BrFeNO2,
412.9714; found, 412.9700. Anal. Calcd for C18H16BrFeNO2: C,
E
Organometallics XXXX, XXX, XXX−XXX