272
B.D. Humphrey et al. / Inorganica Chimica Acta 368 (2011) 271–274
Table 1
UV–Vis spectral data summary for compounds 1, 2, and 3 (acetonitrile as solvent).
Compound
kmax, nm (
e
, L molÀ1 cmÀ1
)
1
2
3
sh 209 (12 900)
222 (13 600)
222 (14 900)
230 (15 800)
364 (719)
364 (682)
366 (790)
sh 209 (13 500)
272 (13 900)
sh: shoulder.
IR (KBr): 3117, 3070, 3041, 2980, 2920, 2862, 2166, 2140, 2115,
2000, 1962, 1735, 1591, 1475, 1382, 864, 842, 671 cmÀ1
.
Elemental Anal. Calc. for C32H32N3FePF6 – 659.436: C, 58.29; H,
4.89; N, 6.37. Found: C, 58.16; H, 5.09; N, 6.38%.
Scheme 1.
2.2. Electrochemistry
Elemental Anal. Calc. for C20H32N3FePF6 – 515.304: C, 46.62; H,
6.26; N, 8.15. Found: C, 46.41; H, 6.16; N, 8.08%.
Cyclic voltammetry was performed using a BAS 100 A electro-
chemical analyzer and a standard three electrode electrochemical
cell configuration with
a platinum working electrode (BAS
2.1.2. Preparation of Tris–cyclohexyl isocyanide cyclopentadiene
iron(II) hexafluorophosphate, [FeCp(cyclohexyl isocyanide)3][PF6] (2)
To a stirring solution of ferrocene (1095.2 mg, 5.888 mmol) in
100 mL reagent grade ethanol was added cerric ammonium nitrate
(3225.5 mg, 5.883 mmol). After stirring for 10 min solution turned
from clear orange to clear blue. To this blue solution was added
cyclohexyl isocyanide (2.2 mL, 1931.6 mg, 17.69 mmol). After stir-
ring overnight the resulting light brown solution had solvent re-
moved in vacuo. The residue was washed with hexane (3 Â
10 mL). The dried residue was dissolved in 30 mL acetone to this
stirred solution was added tetra-methyl ammonium hexafluoro-
phosphate (1302.8 mg, 5.946 mmol). After stirring overnight the
resulting brown solution was filtered through celite. The solvent
was removed in vacuo and the resulting residue was washed with
methylene chloride (3 Â 5 mL). The residue was purified by col-
umn chromatography on silica gel (acetone) then recrystallized
from ethanol. Yield: 38.7%.
3.0 mm diameter), platinum wire counter electrode, and a Ag/AgCl
reference electrode. The experiments were carried out under inert
atmosphere (N2 or Ar) at room temperature in dry acetonitrile con-
taining 0.10 M tetra-butyl ammonium perchlorate (TBAP) as sup-
porting electrolyte. A scan rate of 0.2 V/s was used for all
experiments and ferrocene was added as an internal potential
reference.
3. Results and discussion
3.1. Synthesis
The synthetic route leading to the formation of the ferrocene
piano-stool complexes is shown in Scheme 1.
1.0
1H NMR (d, CDCl3): 4.73 (s, 5H), 3.98 (br m, 3H), 1.89 (br m, 6H),
1.67 (br m, 12H), 1.46 (br m, 12H).
13C NMR (d, CDCl3): 81.9, 55.5, 32.7, 24.9, 22.7.
UV–Vis (CH3CN) kmax
IR (KBr): 3118, 2936, 2869, 2183, 2140, 2048, 1449, 1364, 1323,
1270, 1235, 1152, 1129, 1020, 931, 842, 660, 557 cmÀ1
(e) = 222 (14 900), 364 nm (682).
.
Elemental Anal. Calc. for C26H38N3FePF6 – 593.418: C, 52.63; H,
6.45; N, 7.08. Found: C, 52.47; H, 6.41; N, 7.07%.
2.1.3. Preparation of Tris–2,6-dimethylphenyl isocyanide cyclopenta-
diene iron(II) hexafluorophosphate, [FeCp(2,6-dimethylphenyl isocy-
anide)3][PF6] (3)
To a stirring solution of ferrocene (1006.59 mg, 5.410 mmol) in
75 mL reagent grade ethanol was added cerric ammonium nitrate
(3037.7 mg, 5.541 mmol). After stirring for 10 min the solution
turned from clear orange to clear blue. To this clear blue solution
was added 2,6-dimethylphenyl isocyanide (1970 mg, 15.02 mmol).
After stirring overnight the resulting red/brown solution had sol-
vent removed in vacuo. The residue was washed with hexane
(3 Â 5 mL). The dried residue was dissolved in 25 mL acetone. To
this stirred solution was added tetra-methyl ammonium hexa-
fluorophosphate (1198.5 mg, 5.470 mmol). After stirring overnight
the resulting brown solution was filtered through celite. The sol-
vent was removed in vacuo and the resulting residue washed with
methylene chloride (3 Â 5 mL) affording yellow/golden crystals
after recrystallization from ethanol. Yield: 49.2%.
0
200
300
400
500
1H NMR (d, CDCl3): 7.18 (br m, 9H), 5.28 (s, 5H), 2.44 (s, 18H).
Wavelength, nm
13C NMR (d, CDCl3): 136.0, 130.3, 129.1, 86.1, 19.2.
UV–Vis (CH3CN) kmax (e) = sh 209 (13 500), 230 (15 800), 272
Fig. 1. Normalized UV–Vis absorption spectra of compounds 1 (dashed line) and 3
(13 900), 366 nm (790).
(solid line).