Stability and reactivity of ferrocenyl(2,4,6-trimethoxyphenyl)carbenium salts

Article abstract of DOI:10.1016/S0022-328X(98)00925-5

Ferrocenyl(phenyl)methanols, Fc-CHΦOH [Fc=Fe(η⁵-C₅H₅)(η⁵-C ₅H₄), Φ^a=2,4,6-(MeO)₃C₆H₂ (1a); Φ^b=2,6-(MeO)₂C₆H₃ (1b)], were prepared by the reactions of Fc-CHO with ΦLi. 1a reacted with only a slight excess of perchloric acid or tetrafluoroboric acid even in methanol and in 1 M HCl acid to give dark violet crystals of the carbenium salts, [Fc-CHΦ^a]X [X=ClO₄ (2a), BF₄ (2a′)]. 1b reacted with these acids in diethylether to give the carbenium salts, [Fc-CHΦ^b]X [X=ClO₄ (2b), BF₄ (2b′) (dark red-brown crystals)] in good yields. The pK_R+ values could be measured in HCl acid for 1a (3.0) and for 1b (1.6). 2a and 2b were labile in hot 2-propanol to give the reduced compounds, Fc-CH₂Φ. 1a and 1b reacted with 1,3,5-trimethoxybenzene, Φ^aH, in 2-methyl-2-propanol containing only a slight excess of HCl acid to give diphenyl(ferrocenyl)methanes, Fc-CHΦ^a₂ and Fc-CHΦ^aΦ^b, respectively. While 1a decomposed in neat 1,3-dimethoxybenzene, Φ^bH, in the presence of acid, 1b reacted to give 2,4-dimethoxyphenyl(2,6-dimethoxyphenyl)ferrocenylmethane, Fc-CHΦ^bΦ^d [Φ^d=2,4-(MeO)₂C₆H₃]. The ¹H-NMR spectrum of 2a was temperature-dependent and indicated that the free rotations of both Fc and Φ^a groups in 2a existed at r.t. but were frozen at -60°C.

Full text of DOI:10.1016/S0022-328X(98)00925-5

Journal of Organometallic Chemistry 574 (1999) 86–93
Stability and reactivity of ferrocenyl(2,4,6-trimethoxyphenyl)carbenium
saltsꢀ
Satoko Natsume, Hideaki Kurihara, Takuya Yamaguchi, Tatsuo Erabi, Masanori Wada *
Department of Materials Science, Faculty of Engineering, Tottori Uni6ersity, Koyama, Tottori 680-0945, Japan
Abstract
Ferrocenyl(phenyl)methanols, Fc–CHFOH [Fc=Fe(h5-C5H5)(h5-C5H4), Fa=2,4,6-(MeO)3C6H2 (1a); Fb=2,6-(MeO)2C6H3
(1b)], were prepared by the reactions of FcꢀCHO with FLi. 1a reacted with only a slight excess of perchloric acid or
tetrafluoroboric acid even in methanol and in 1 M HCl acid to give dark violet crystals of the carbenium salts, [FcꢀCHFa]X
[X=ClO4 (2a), BF4 (2a%)]. 1b reacted with these acids in diethylether to give the carbenium salts, [FcꢀCHFb]X [X=ClO4 (2b),
BF4 (2b%) (dark red–brown crystals)] in good yields. The pKR values could be measured in HCl acid for 1a (3.0) and for 1b (1.6).
+
2a and 2b were labile in hot 2-propanol to give the reduced compounds, FcꢀCH2F. 1a and 1b reacted with 1,3,5-trimethoxyben-
zene, FaH, in 2-methyl-2-propanol containing only a slight excess of HCl acid to give diphenyl(ferrocenyl)methanes, FcꢀCHF2a
and FcꢀCHFaFb, respectively. While 1a decomposed in neat 1,3-dimethoxybenzene, FbH, in the presence of acid, 1b reacted to
1
give 2,4-dimethoxyphenyl(2,6-dimethoxyphenyl)ferrocenylmethane, FcꢀCHFbFd [Fd=2,4-(MeO)2C6H3]. The H-NMR spectrum
of 2a was temperature-dependent and indicated that the free rotations of both Fc and Fa groups in 2a existed at r.t. but were
frozen at −60°C. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Iron; 2,4,6-Trimethoxyphenyl; 2,6-Dimethoxyphenyl; Ferrocenyl(phenyl) methanol; Ferrocenyl(phenyl)carbenium; Fer-
rocenyl(phenyl)methane
1. Introduction
carbenium salts, [FcꢀCHF]X [Fc=Fe(h5-C5H5)(h5-
C5H4); F=Fa, Fb, Ph; X=ClO4, BF4], on the physical
and chemical properties is examined. The reactions
mentioned below are summarized in Scheme 1.
The number of methoxy substituents on phenyl
groups influences the stability and reactivity of di- and
triphenylcarbenium salts. Thus, bis(2,4,6-trimethoxy-
phenyl)carbenium perchlorate, [Fa2CH]ClO4 (Fa=2,4,6-
(MeO)3C6H2), is recrystallizable even from methanol,
and triphenylmethanols bearing at least four o-methoxy
groups, such as Fb3COH and PhFb2COH [Fb=2,6-
(MeO)2C6H3], were highly basic to form isolable triaryl-
carbenium salts, [ArFb2C]X, even in secondary alcohols
and water [1–3]. The ferrocenyl group also has been
known to stabilize the carbenium salts [4–8]. In this
report, the influence of the number of methoxy sub-
stituents on the phenyl group in ferrocenyl(phenyl)
2. Results and discussion
2.1. Preparation of ferrocenyl(phenyl)carbenium salts
Ferrocenyl(phenyl)methanols, FcꢀCHFOH [F=Fa
(1a), Fb (1b), Ph (1c)], were prepared as yellow crystals
by the reactions of ferrocenylaldehyde with the corre-
sponding phenyllithium. Compounds 1a–c reacted with
a slight excess of 60% aqueous perchloric acid in di-
ethylether to give the carbenium salts, [FcꢀCHF]X
(X=ClO4, 2a–c) almost in quantitative yields even in
the absence of a dehydration reagent, such as acetic
anhydride as used by Allenmark et al. [7]. Using 42%
ꢀ Dedicated to the memory of the late Professor Rokuro Okawara.
* Corresponding author. Tel.: +81-857-31-5248; fax: +81-857-
31-0881; e-mail: wada@chem.tottori-u.ac.jp.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)00925-5

S. Natsume et al. / Journal of Organometallic Chemistry 574 (1999) 86–93
87
Scheme 1.
taining a slight excess of acid to give FcꢀCH2Fb (3b)
and FcꢀCH2Ph (3c), respectively, although the latter
yield was poorer. Such a reduction by alcohols is one of
the characteristic reactions observed for carbenium salts
bearing Fa or Fb groups, and the aldehyde or ketone
were detected as the by-product [1–3,10].
tetrafluoroboric acid also gave analogous salts (X=
BF4, 2a%–c%), although the yields decreased in the order
of 2a%\2b%\2c% due probably to the presence of larger
amount of water. These salts are deeply colored in dark
violet (2a, 2a%), dark red–brown (2b, 2b%) or dark brown
(2c, 2c%).
Fortunately, it was found that 1a was soluble in
concentrated hydrochloric acid (1 mmol/2 ml) to give a
dark violet solution of 2a (X=Cl). It could be diluted
to 1 M hydrochloric acid solution without the loss of
violet color. An addition of only a slight excess of
aqueous tetrafluoroboric acid resulted to give the pre-
cipitates of 2a in good yield. When the solution of la in
l M hydrochloric aeid was neutralized by aqueous
The electronic spectra (Table 1) of 1a–c in 1,2-
dichloroethane showed a band with umax at the
analogous region (440–445 nm; log m=2.1–2.3) to
those of ferrocene (440 nm) and phenylferrocene (446
nm) [9]. In contrast, the spectra of 2a–c showed two
bands in the region of 330–530 nm, of which the molar
absorbances were much larger (log m=3.5–4.2). The
bands shifted to lower wavelengths in the order 2a\
2b\2c. A carbenium salt, [Fa2CH]ClO4, showed a
strong band at 521 nm (log m=4.71) [3]. Thus, the two
bands of 2a–c are tentatively assigned to charge trans-
fers from the Fa group and ferrocenyl group to the
cationic carbon, respectively.
Table 1
UV–vis spectral data of ferrocenyl(phenyl)methane derivativesa
Compounds l (nm) (log o)
The carbenium salt 2c decomposed in methanol very
fast to give the precipitates of methyl ether,
FcꢀCHPhOMe. In contrast, 2a dissolved in methanol
to give a violet solution, even at 4×10−4 M, and the
color disappeared below 1×10−4 M. The high stability
of 2a in methanol is astonishing, and in fact, crystals of
2a and 2a% could be obtained in methanol by the
reactions of 1a with only a slight excess of 60% aqueous
perchloric acid or 42% aqueous tetrafluoroboric acid at
a concentration of 1×10−1 M. These salts could also
be obtained in ethanol in analogous manners. Com-
pound 2b was less stable in methanol than 2a, and the
red–brown color disappeared at ca. 3×10−3 M.
The solubility of 2a in 2-propanol was very poor.
When it was heated at 50°C for 1 h at 1×10−1 M, it
was reduced to give FcꢀCH2Fa (3a). Compounds 1b
and even 1c were also reduced in hot 2-propanol con-
1a
1b
1c
440(2.30), 320(2.18, sh), 255(3.70, sh), 236(4.03)
445(2.15), 320(2.18, sh), 260(3.65, sh), 233(3.95)
444(2.18), 320(2.15, sh), 265(3.65, sh), 233(3.83)
2a
2b
2c
532(3.83), 397(4.24), 320(sh), 260(3.96, sh), 227(4.08)
450(3.75)b, 362(4.09)b, 260(3.95, sh), 236(4.02)
410(3.54)b, 336(4.12)b, 310(3.78, sh), 242(4.04)
3a
3b
3c
444(2.04), 325(2.08, sh), 255(3.70, sh), 235(4.02)
450(2.04), 320(2.00, sh), 255(3.70, sh), 233(3.96)
432(2.08), 320(2.18, sh), 255(3.60, sh), 233(3.74)
4a
4b
4c
427(2.15), 320(2.40, sh), 265(3.81, sh), 236(4.26)
445(2.23), 325(2.48, sh), 270(3.79, sh), 233(4.23)
445(2.11), 320(2.40, sh), 260(3.71, sh), 233(4.13)
5b
5c
440(2.11), 320(2.00, sh), 273(3.73, sh), 233(4.19)
442(2.08), 325(2.00, sh), 275(3.65, sh), 234(4.17)
a In 1,2-dichloroethane.
b In 1,2-dichloroethane containing CF3COOH [0.1% (v/v)].

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S. Natsume et al. / Journal of Organometallic Chemistry 574 (1999) 86–93
Table 2
1H-NMR spectral data for ferrocenyl(phenyl)methane derivativesa
C5H5
C5H4
CcentralꢀH
Others
1a
1b
4.11 sb
4.11 sb
4.42 m, 4.11b, 3.99 m, 3.92 m 6.05 d (11)
6.16 s (2H, 3,5-H), 3.91 d (11) (1H, OH), 3.83 s (6H, 2,6-MeO), 3.82 s
(3H, 4-MeO)
7.20 t (8) (1H, 4-H), 6.59 d (8) (2H, 3,5-H), 4.08 d (11) (1H, OH), 3.85 s
(6H, 2,6-MeO)
4.43 dt (2, 1), 4.11b, 4.00 dt
(2, 2), 3.96 m
6.13 d (11)
1c
2a
4.22 s
4.78 s
4.19 m (4H)
5.47 d (3)
8.55 s
8.45 s
8.29 s
8.40 s
7.40–7.25 m (5H, Ph), 2.45 d (3) (1H, OH)
6.18 s (2H, 3,5-H), 4.01 s (9H, 2,4,6-MeO)
6.01 s (2H), 5.12 br (2H)
6.02 s, 5.93 s, 5.36 s, 4.76b
6.31 s, 6.24 s, 5.37 s, 4.79 s
6.45 s, 6.29 s, 5.38 s, 4.99 s
2ac 4.76 sb
6.15 s and 6.08 s (2H, 3,5-H), 4.07 s, 3.99 s and 3.89 s (9H, 2,4,6-MeO)
7.62 t (8) (1H, 4-H), 6.63 d (8) (2H, 3,5-H), 3.98 s (6H, 2,6-MeO)
7.84 d (7) (2H, 2,6-H), 7.65 t (7) (1H, 4-H) and 7.50 t (8) (2H, 3,5-H)
6.11 s (2H, 3,5-H), 3.82 s (6H, 2,6-MeO), 3.78 s (3H, 4-MeO)
7.10 t (8) (1H, 4-H), 6.51 d (8) (2H, 3,5-H), 3.83 s (6H, 2,6-MeO)
7.28–7.16 m (5H, Ph)
6.07 s (2H, 3,5-H), 3.77 s (6H, 4-MeO), 3.60 s (12H, 2,6-MeO)
7.07 t (8) (1H,4%-H), 6.48 d (8) (2H, 3%,5%-H), 6.07 s (2H, 3,5-H), 3.77 s
(3H, 4-MeO), 3.60 s (12H, 2,6-MeO and 2%,6%-MeO)
7.14–7.06 m (5H, Ph), 6.16 s (2H, 3,5-H), 3.82 s (3H, 4-MeO), 3.66 br
(6H, 2,6-MeO)
2b
2c
3a
3b
3c
4a
4b
4.98 s
4.92 s
4.10 s
4.10 s
4.11 sb
4.01 s
4.01 s
4.14 t (2) (2H), 3.94 t (2) (2H) 3.59 s (2H)
4.17 t (2) (2H), 3.95 t (2) (2H) 3.67 s (2H)
4.11b, 4.08 br (2H)
3.95 s (4H)
3.69 s (2H)
5.93 s
6.00 s
3.97 br (4H)
4c
5b
3.99 s
4.12–4.07 m (4H)
4.08 br (4H)
5.82 s
6.01 s
4.03 br
7.14 t (8) (1H, 4%-H), 7.03 d (9) (1H, 6-H), 6.56 d (8) (2H, 3%,5%-H), 6.31 d
(1H, 5-H) and 6.30 s (1H, 3-H)c, 3.73 s, 3.69 br and 3.64 s (12H, 2,4-
MeO, 2%,6%-MeO)
5c
4.01 s
4.12 br (2H), 4.03 br (1H),
3.92 br (1H)
5.50 s
7.26–7.10 m (5H, Ph), 6.89 d (8) (1H, 6-H), 6.42 d (2) (1H, 3-H), 6.38 dd
(8, 2) (1H, 5-H), and 3.77 s (6H, 2,4-MeO)
a In CDCl3 (l), 270 MHz; coupling constants (JHH (Hz)) are given in parentheses; s, singlet; d, doublet; t, triplet; dd, double doublets; dt, double
triplets; m, multiplet; br, broad.
b Overlapped.
c At −60°C.
sodium hydroxide, 1a was recovered as precipitates
almost in quantitative yield.
Compound 1b also was soluble in concentrated HCl
to give a red–brown solution, and it could be diluted to
a 3 M HCl solution without the loss of the red–brown
color.
propanol, and the reactions were performed for 1a–c in
the presence of HCl or trifluoroacetic acid. Thus, 1a
was treated with 1,3,5-trimethoxybenzene (FaH) in 2-
methyl-2-propanol containing only a slight excess of 1
M HCl, and yellow crystals of bis(2,4,6-trimethoxy-
phenyl)ferrocenylmethane, FcꢀCHFa2 (4a), were ob-
tained in quantitative yield. Both 1b and 1c also rea-
cted with FaH in the presence of acid to give analo-
gous compounds, FcꢀCHFaFb (4b) and FcꢀCHFaPh
(4c).
When 1a–c were treated with 1,3-dimethoxybenzene
in an analogous manners as above, however, complex
mixtures containing a compound having two FcꢀCHF
moieties, possibly 1,3-dimethoxy-4,6-bis[ferrocenyl
(phenyl)methyl]benzene, 1,3-(MeO)2-4,6-(CHFcF)2C6
H2. When the reaction of 1a was performed in neat
1,3-dimethoxybenzene, the GC–MS spectra showed the
formation of FaH and possibly FcꢀCHFd2, of which
pure isolation has not been achieved. When 1b was
treated in neat 1,3-dimethoxybenzene containing acid,
yellow crystals of 2,4-dimethoxyphenyl(2,6-dimethoxy-
phenyl)ferrocenylmethane, FcꢀCHFbFd (5b), were ob-
tained in a good yield. Compound 1c also reacted with
1,3-dimethoxybenzene in the presence of acid to give an
analogous compound, FcꢀCHPhFd (5c), although the
yield was less.
Thus, the pKR value of 1a and 1b could be mea-
+
sured for the solutions in these aqueous HCl solutions
by titration using aqueous sodium hydroxide to give
values of +3.0 and +1.6, respectively. These values
may be compared with those reported for 1c (+0.49),
FcꢀCH(4-MeOC6H4)OH (+1.37) and Fc2CHOH (+
4.08) [6–8,11]. It is concluded that 1a is slightly less
basic than Fc2CHOH.
2.2. Reactions of ferrocenyl(phenyl)carbenium salts with
methoxybenzenes
The authors have reported that [Ar2CH]+ salts
(Ar=Fa, Fb) reacted with 1,3,5-trimethoxybenzene
and 1,3-dimethoxybenzene to give the triphenyl-
methanes, such as Fa3CH [3] or Fb2FdCH [Fd=
2,4-(MeO)2C6H3]
[10].
Ferrocenyl(phenyl)carben-
ium salts are also expected to react with these
methoxybenzenes [12–14]. Unfortunately, 2a–c and
2a%–c% were only slightly soluble in 2-methyl-2-

S. Natsume et al. / Journal of Organometallic Chemistry 574 (1999) 86–93
89
Fig. 1. 1H-NMR spectra of 2a in CDCl3 at (a) 25°C, (b) −10°C, (c) −20°C, (d) −60°C.
2.3. NMR spectra
proton resonances of the central CꢀH bond were ob-
served in regions l 6.2–5.5 for 1a–c and l 3.7–3.6 for
3a–c, while those of 2a–c were observed at a low
magnetic field l 8.6–8.2, also reflecting the cationic
character of the latter compounds. The coupling con-
stant of the central CꢀH with the hydroxide proton
(JHH) is significantly larger for 1a,b (11 Hz) than for 1c
(3 Hz). There is evidence that the spectra of
FcꢀCHFOH, where F is 2-methoxyphenyl or 2,5-
dimethoxyphenyl, show a value of 5 Hz, indicating that
the value is influenced by the number of methoxy
groups at the 2,6-positions of the phenyl group (F). The
methoxy proton resonances of 2a,b were also observed
at lower magnetic fields than those of 1a,b and 3a,b,
respectively.
1
The H-NMR spectrum of 1a (Table 2) showed a 5H
singlet attributable to C5H5 protons at 4.11, while that
of 2a showed a 5H singlet at much lower magnetic field
(l 4.78) reflecting the cationic character. Analogous
low-field shifts were observed for 2b, as well as for 2c.
The pattern of proton resonance of the C5H4 moiety
depends largely on the type of compound. Those of 1a
and 1b were observed as four multiplets, which reflect
the lack of symmetry in these compounds. In contrast,
the C5H4 proton resonances of 2a were observed as two
broad resonances, while four broad singlets were ob-
served for 2b and 2c. The spectrum of 2c has been
explained by the lack of free rotation around the
C5H4ꢀC bond [15], but the spectrum of 2a seems to
indicate the presence of free rotation (see below). The
With a hope to confirm the presence of free rotation
around the C5H4ꢀC bond in 2a at r.t., the spectrum was

90
S. Natsume et al. / Journal of Organometallic Chemistry 574 (1999) 86–93
Table 3
13C-NMR spectral data for ferrocenyl(phenyl)methane derivativesa
C5H5
C5H4
Ccentral
Others
1a 69.3 (176)
92.7, 68.3, 68.2,
67.7,67.6
66.4 (147)
161.0 (2,6-C), 158.9 (4-C), 113.0 (1-C), 91.7 (3,5-C), 56.2 and 56.0 (MeO)
1b 69.3 (174)
1c 69.1 (174)
92.4, 68.2, 67.7, –b 66.6 (149)
158.2 (2,6-C), 129.2 (4-C), 120.2 (1-C), 105.1 (3,5-C), 56.3 (2,6-MeO)
144.0 (1-C), 128.8 (3,5-C), 128.1 (2,6-C), 126.9 (4-C)
94.9, 72.8, 68.7,
68.1, 66.7
72.7 (145)
2a 78.8 (182)
2b 81.4 (182)
94.9, 89.3, 80.0
102.4, 93.8, 92.1,
83.0, 79.4
138.3 (162)
122.9 (164)
170.8 (2,6-C), 164.0 (4-C), 108.5 (1-C), 93.0 (3,5-C), 57.43 and 57.37 (MeO)
160.8 (2,6-C), 137.2 (4-C), 113.2 (1-C), 105.5 (3,5-C), 57.0 (2,6-MeO)
3a 69.1 (174)
3b 69.2 (176)
3c 69.3 (174)
4a 69.6 (176)
4b 68.9 (174)
89.9, 69.5, 67.4
89.4, 69.6, 67.4
88.7, 68.2, –b
94.9, 66.8, –b
93.7, 69.23, 69.17, 32.9 (127)
68.9, 66.4
22.9 (130)
23.2 (129)
36.8 (128)
32.5 (129)
160.1 (2,6-C), 159.2 (4-C), 112.0 (1-C), 91.2 (3,5-C), 56.2 and 56.0 (MeO)
158.7 (2,6-C), 127.6 (4-C), 119.3 (1-C), 104.4 (3,5-C), 56.2 (2,6-MeO)
142.3, 129.1, 128.9, 126.6
160.1, 159.5, 115.2, 91.9, 56.3, 55.7
160.0, 159.5, 129.6, 128.8, 127.1, 122.3, 114.8, 105.3, 91.7, 56.3, 56.2, 55.7
4c 69.2
5b 69.2
5c 69.3
91.3, 70.8, 69.7,
67.5, 67.4
91.8, 70.2, 70.0,
67.5, 67.1
92.7, 69.9, 69.2,
68.3, 67.9
40.1
36.6
44.0
160.3, 159.5, 146.7, 128.9, 127.7, 125.4, 115.7, 92.1, 56.1, 55.8
159.4, 159.1, 158.2, 132.4, 127.8, 127.6, 122.2, 105.7, 104.0, 98.5, 56.3, 56.2, 55.8
159.7, 157.8, 145.7, 130.6, 129.4, 128.3, 127.5, 126.3, 104.5, 99.0, 56.0, 55.9
a In CDCl3 (l), 68 MHz; coupling constants (JH/Hz) are given in parentheses.
b Not detected or overlapped.
measured at low temperatures. The spectrum observed
The 13C-NMR spectral resonances of 1a–c, 2a,b,
at −60°C clearly showed three well-formed singlets at
l 6.02, 5.93 and 5.36 attributable to C5H4 protons
(Fig. 1). The fourth singlet seemed to be overlapped
with the strong peak of C5H5 protons at l 4.76, as is
expected from the spectra of 2b and 2c. Of special
interest is the observation that the methoxy proton
resonance at l 4.01 split into three peaks with identi-
cal intensities at −60°C (Fig. 1). The 3,5-proton reso-
nance of the Fa group also split into two peaks. These
observations clearly indicate that the free rotations of
both Fc and Fa groups in 2a exist at r.t. but are
frozen at −60°C, possibly with the C5H4 and Fa
groups in almost the same plane. The coalescence tem-
perature was −10°C for both Fc and Fa protons. The
spectrum of 2b is understood by the presence of free
rotation of the Fb group and lack of free rotation of
the C5H4 group around their bonds to the central
carbon.
3a,b and 4a,b were assigned by measuring the coupling
constants [JH]. The spectrum of 1a (Table 3) showed a
resonance attributable to C5H5 carbons at l 69.3 with
a large magnetic coupling (JH=176 Hz). The spec-
trum of 2a showed the resonance at a much lower
magnetic field, l 78.8 (JH=182 Hz) reflecting the
cationic character. In accordance with the lack of sym-
metry, five resonances due to C5H4 carbons were ob-
served for 1a. The spectrum of 2a showed only three
resonances attributable to C5H4 carbons in agreement
with the presence of a free rotation around the FcꢀC
bond at r.t., while that of 2b showed five resonances.
The spectra of 1a–c showed the central carbon reso-
nance at l 66–73, with a magnetic coupling with the
proton (JH=145–149 Hz), while those of 2a and 2b
showed the resonance at a lower magnetic field l
138.3 and 122.9, respectively, with a larger magnetic
coupling (JH=ca. 160 Hz) with the proton. The reso-
nances
for
alkyl(ferrocenyl)carbenium
salts,
[FcꢀCRR%]X (R, R%=H or alkyl), have been observed
in a wide range l 87 (R, R%=H, H) to l 161 (Me, Et)
[16]. The spectrum of 2c could not be measured pre-
cisely due to its lability, and no data has been re-
ported in the literature [15,16].
Thus, the authors conclude that both resonances A
and B in Scheme 2 contribute to the stabilization of
2a in competition with each other, and that resonance
A contributes more than B for the stabilization of 2b.
Scheme 2.

S. Natsume et al. / Journal of Organometallic Chemistry 574 (1999) 86–93
91
2.4. GC–MS spectra
calc. for C19H20FeO3. Found: C, 64.53; H, 5.86%. Calc.:
C, 64.79; H, 5.72%.
1c: M.p. 75–77°C (reported, 81–82°C [17], 78–80°C
[18]).
The GC–MS spectra of 1a–c show that they decom-
posed during the measurement of GC at 300°C. For an
example, the spectrum of an acetone solution of 1a
showed the formation of 6-(2,4,6-trimethoxyphenyl)ful-
vene in addition to at least three compounds, Fcꢀ
CFaO, 3a and possibly FcꢀCHFaꢀCH2CMeO. No evi-
dence of decomposition was observed by GC spectra of
3a–c, 4a–c and 5b,c, of whose mass spectra showed
very strong parent peaks, respectively.
3.3. Reactions of ferrocenyl(phenyl)methanols with acid
(HClO4, HBF4) to gi6e ferrocenyl(phenyl)carbenium
salts
To a yellow suspension of 1a (0.382 g, 1 mmol) in
diethylether (10 ml), 60% aqueous perchloric acid (0.12
ml, 1.1 mmol) was added. The resultant dark violet
suspension was stirred at 0°C for 15 min to give dark
violet crystals of [FcꢀCHFa]ClO4 (2a) in 94% yield.
In a similar way to above but using 1b or 1c, crystals
of [FcꢀCHFb]ClO4 (2b) or [FcꢀCHPh]ClO4 (2c) were
obtained in 97 and 86% yields, respectively.
3. Experimental
3.1. General
In similar ways as well, but using 42% aqueous
tetrafluoroboric acid (a slight excess), crystals of
The NMR spectra were recorded for solutions in
CDCl3 using a JEOL model JNM-GX-270 spectrome-
ter. IR spectra were recorded for Nujol® mulls using a
Shimadzu FTIR-4200 spectrophotometer. GC–MS
spectra were recorded using a Shimadzu QP-5000 mass
spectrometer for acetone solutions. UV–vis spectra
were recorded using a Shimadzu UV-160 spectrophoto-
meter, and the spectral data are summarized in Table 1.
[FcꢀCHFa]BF4
(2a%),
[FcꢀCHFb]BF4
(2b%)
or
[FcꢀCHPh]BF4 (2c%) were obtained in 96, 73 or 22%
yields, respectively.
To suspensions of 1a (1 mmol) in methanol (10 ml)
or ethanol (10 ml), 60% aqueous perchloric acid (0.12
ml, 1.1 mmol) was added. The mixtures were stirred at
0°C for 15 min and were cooled to −30°C to give dark
violet crystals of 2a in 86 or 98% yields, respectively.
When 42% aqueous tetrafluoroboric acid (a slight ex-
cess) was used in methanol or ethanol, 2a% was obtained
in 71 or 80% yields, respectively. The crystals obtained
from ethanol were served for the elemental analysis
without recrystallization.
Compound 1a (1 mmol) dissolved in 12 M HCl (2
ml) to form a dark violet solution. It was immediately
diluted with water (22 ml) to give a 1 M HCl solution,
which kept the dark violet color for a prolonged period.
To this solution, 42% aqueous tetrafluoroboric acid (1.1
mmol) was added to give 2a% in 80% yield.
When an analogous solution of 1a in 1 M HCl was
neutralized by 5 M NaOH, yellow crystals of 1a were
recovered in 91% yield. The purity of each product
obtained above was confirmed by 1H-NMR and IR
spectra.
1
The H- and 13C-NMR spectral data for compounds
1–5 are summarized in Tables 2 and 3, respectively.
3.2. Preparation of ferrocenyl(phenyl)methanols
To a 15% hexane solution of butyllithium (4.4 ml, 7
mmol), diethylether (10 ml), 1,3,5-trimethoxybenzene
(1.34 g, 8 mmol), and N,N,N%,N%-tetramethylethylenedi-
amine (0.1 ml) were added at 0°C under argon. The
mixture was stirred at 0°C for 2 h to give a white
suspension of FaLi. To the suspension, a solution of
ferrocenylaldehyde (1.07 g, 5 mmol) in diethylether (40
ml) was added, and the mixture was stirred at r.t. for 24
h to give a yellow suspension. Toluene (100 ml) was
added, the mixture was washed with water (50 ml) and
the organic layer was concentrated to ca. half volume.
Hexane (30 ml) was added and the solution was cooled
to −30°C to give yellow crystals of FcꢀCHFaOH (1a)
in 79% yield. This compound is very soluble in chloro-
form, soluble in toluene, acetone, hot methanol, and
hot 2-propanol, and poorly soluble in diethylether and
hexane. The analytical sample was obtained by recrys-
tallization from toluene.
2a: M.p. 130°C, decomposed, IR 1100 cm−1 (ClO4−).
2a%: Dark violet crystals, m.p. 121°C, decomposed;
IR 1055 cm−1 (BF4−). Found: C, 53.02; H, 4.48%.
Calc. for C20H21BF4FeO3: C, 53.14; H, 4.68%.
2b: Dark red–brown crystals, m.p. 103°C, decom-
posed, IR 1100 cm−1 (ClO4−).
In essentially the same way as above but using 1,3-
dimethoxybenzene or bromobenzene, yellow crystals of
FcꢀCHFbOH (1b) or FcꢀCHPhOH (1c) were obtained
in 89 and 81% yields, respectively.
2b%: Dark red–brown crystals, m.p. 73°C, decom-
posed, IR 1055 cm−1 (BF4−).
2c: Dark brown crystals, m.p. 120°C, decomposed,
IR 1100 cm−1 (ClO4−).
2c%: Dark brown crystals, m.p. 69–70°C; IR 1055
cm−1 (BF4−). This compound has been reported [5,7].
The solubilities were studied for 0.1 mmol of samples
in solvents.
1a: M.p. 159–161°C, IR 3580 cm−1 (OH). Anal.
calc. for C20H22FeO4. Found: C, 62.73; H, 5.79%. Calc.:
C, 62 85; H, 5.80%.
1b: M.p. 139–140°C, IR 3540 cm−1 (OH). Anal.

92
S. Natsume et al. / Journal of Organometallic Chemistry 574 (1999) 86–93
2a was very soluble in acetonitrile to give a violet
3a: M.p. 137–140°C, MS m/z (relative intensity) 366
(100, M+). Anal. calc. for C20H22FeO3. Found: C,
65.42; H, 6.05%. Calc.: C, 65.59; H, 6.05%. This com-
pound is very soluble in toluene, chloroform, acetone
and methanol, soluble in hot 2-propanol and di-
ethylether, and poorly soluble in hexane.
solution, even at 10−3 M, while 2b gave dark red–
brown solution at 10−2 M and a light brown solution
at 10−3 M.
2a dissolved in dimethyl sulfoxide to give dark brown
solutions at 10−1 and 10−2 M, but gave a light brown
solution at 10−3 M, while 2b gave a light brown
solution at 10−2 M.
3b: M.p. 103–104°C, MS m/z (relative intensity) 336
(100, M+). Anal. calc. for C19H20FeO2. Found: C,
67.63; H, 6.00%. Calc.: C, 67 88; H, 6 00%.
2a dissolved in acetone to give dark violet solutions
both at 10−1 and 10−2 M, but on standing for a few
hours, the color changed to dark green (10−1 M) or
orange (10−2 M). 2b dissolved in acetone to give dark
red–brown solutions at 10−1 and 10−2 M, but on
standing for a few hours, the color changed to green.
In methanol, 2a was partly soluble at 10−1 M and
almost soluble at 10−2 M to give dark violet solutions.
The violet color was observed even at 10−3 M but
disappeared below 10−4 M. 2b also was partly soluble
at 10−1 M and soluble at 10−2 M to give light brown
solutions. Analogous results were observed in ethanol.
When 10−1 M suspensions of 2a in methanol or in
ethanol were heated to 50–60°C for 1 h, they decom-
posed to give mixtures containing 1,3,5-trimethoxyben-
zene (FaH) and FcꢀCHO (1H-NMR and GC–MS
spectra). Both 2a and 2b were poorly soluble in 2-
propanol at r.t. When 10−1 M suspensions of 2a were
heated at 50°C, it was reduced to give FcꢀCH2Fa (3a)
(see Section 3.4).
3c: M.p. 71–73°C (reported, 70–74°C [17]), MS m/z
(relative intensity) 276 (100, M+).
3.5. Reactions of ferrocenyl(phenyl)carbenium salts with
1,3,5-trimethoxybenzene to gi6e
diphenyl( ferrocenyl)methanes
To a yellow suspension of 1a (1 mmol) in 2-methyl-2-
propanol (10 ml), 1,3,5-trimethoxybenzene (0.202 g, 1.2
mmol) and 12 M HCl (0.1 ml, 1.2 mmol) were added.
The resulting dark brown suspension was stirred at r.t.
for 2 h to give a yellow suspension. Hexane (6 ml) was
added and the mixture was cooled to 5°C to give yellow
crystals of FcꢀCHFa2 (4a) in 96% yield. The analytical
sample was obtained by recrystallization from hexane.
In an analogous way as above but using 1b or 1c,
yellow crystals of FcꢀCHFaFb (4b) or FcꢀCHFaPh (4c)
were obtained in 83 and 90% yields, respectively.
4a: M.p. 164–165°C, MS m/z (relative intensity) 532
(100, M+).
2c (0.374 g, 1 mmol) decomposed in methanol (10
ml) during mixing to give FcꢀCHPhOMe in 77% yield;
4b: M.p. 189–191°C, MS m/z (relative intensity) 502
(100, M+).
1
m.p. 106–107°C (reported, 111–112°C [17]); H-NMR
4c: M.p. 129–130°C, MS m/z (relative intensity) 442
(100, M+).
(CDCl3) l 7.40–7.25 m (6H, Ph and CHCl3), 5.00 s
(1H, CcentralꢀH), 4.26 s, 4.13 s, 4.04 s (C5H5) and 3.95 s
(9H, C5H4) and 3.29 s (3H, OMe).
3.6. Reactions of ferrocenyl(phenyl)carbenium salts with
1,3-dimethoxybenzene to gi6e
diphenyl( ferrocenyl)methanes
3.4. Reactions of ferrocenyl(phenyl)carbenium salts in
2-propanol to gi6e ferrocenyl(phenyl)methanes
To a brown suspension of 1b (1 mmol) in 1,3-
dimethoxybenzene (5 ml), trifluoroacetic acid (0.08 ml,
1.1 mmol) was added at 0°C. The resulting dark brown
suspension was stirred at 0°C for 1 h to give a dark
green–brown solution. It was filtered through Florisil.
To the filtrate, hexane (5 ml) was added and the
mixture was cooled to −30°C to give yellow crystals of
FcꢀCHFbFd (5b) in 90% yield. The analytical sample
was obtained by recrystallization from hexane.
In an analogous way but using 1c, yellow crystals of
FcꢀCHPhFd (5c) were obtained in 52% yield.
5b: M.p. 163–164°C, MS m/z (relative intensity) 472
(84, M+), 121 (100, Cp2Fe+). Anal. calc. for
C27H28FeO4. Found: C, 68.77; H, 6.02%. Calc: C, 68
65; H, 5.97%.
A suspension of 2a (0.466 g, 1 mmol) in 2-propanol
(10 ml) was heated at 50°C for 1 h to give a dark green
suspension. Water (40 ml) was added, and the precipi-
tates were dissolved in acetone (20 ml). The acetone
solution was filtered through Florisil, and the filtrate
was concentrated under reduced pressure to give yellow
crystals of FcꢀCH2Fa (3a) in 83% yield. The analytical
sample was obtained by recrystallization from
diethylether.
To a suspension of 1b (0.352 g, 1 mmol) in 2-
propanol (10 ml) was added 60% perchloric acid (0.12
ml, 1.1 mmol) to give a dark suspension. It was heated
at 50°C for 1 h to give a green suspension, which was
treated as above to give yellow crystals of FcꢀCH2Fb
(3b) in 89% yield. The analytical sample was obtained
by recrystallization from diethylether. In an analogous
manner but using 1c, yellow crystals of FcꢀCH2Ph (3c)
were obtained in 36% yields.
5c: M.p. 121–122°C MS m/z (relative intensity) 412
(83, M+), 121 (100, Cp2Fe+), 56 (93, Fe+). Anal. calc.
for C25H24FeO2. Found: C, 72.94; H, 5.93%. Calc.: C,
72:83; H, 5.87%.

S. Natsume et al. / Journal of Organometallic Chemistry 574 (1999) 86–93
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Acknowledgements
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This work was supported by the Grant-in-Aid for
Scientific Research (No. 08455492) from the Ministry
of Education, Science and Culture, Japan.
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