Ferrocenylamines 2. Reductive methylation of secondary ferrocenylamines and ferrocenylaldimines: Synthesis, characterization of [(N-methyl-N-aryl)amino] methylferrocenes (see abstract)

Article abstract of DOI:10.1016/j.jorganchem.2005.10.056

The reactions of ferrocenylaldimines (II) [(η⁵-C ₅H₅)Fe(η⁵-C₅H ₄CHNC₆H₄-R)] (R = 4-CH₃O (a), 4-CH₃ (b), H (c), 4-Cl (d), 3-Cl (e), 4-NO₂ (f), 3-NO ₂ (g)) and ferrocenylketimine (I) [(η⁵-C ₅H₅)Fe (η⁵-C₅H ₄CH₃CNC₆H₅)] with sodium borohydride in ethanol or lithium aluminum hydride in THF resulted in secondary ferrocenylamines 3, 4. Reductive methylation of 3 (or II) and 4 with aqueous formaldehyde and sodium cyanoborohydride all gave out corresponding N-methylated tertiary ferrocenylamines 5 [(η⁵-C₅H ₅)Fe(η⁵-C₅H₄CH ₂N(CH₃)C₆H ₄-R)] (R = same as above mentioned) and 2, respectively, in good yields. All these tertiary ferrocenylamines 3-5 were characterized structurally. The crystal structures of 3d and 5a were also determined. Compound 3d is monoclinic, space group P2(1)/n, with a = 9.7585(14) A?, b = 11.5267(17) A?, c = 13.0830(19) A? and β = 97.969(2)°. Compound 5a is orthorhombic, space group Pccn, with a = 13.752(2) A?, b = 22.095(3) A?, c = 10.6421(16) A?.

Full text of DOI:10.1016/j.jorganchem.2005.10.056

Journal of Organometallic Chemistry 691 (2006) 987–993
www.elsevier.com/locate/jorganchem
Ferrocenylamines 2. Reductive methylation of secondary
ferrocenylamines and ferrocenylaldimines: Synthesis, characterization
of [(N-methyl-N-aryl)amino]methylferrocenes,
1-[(N-methyl-N-phenyl)amino]ethylferrocene and crystal structures
of [(g5-C5H5)Fe(g5-C5H4CH2NHC6H4-Cl-4)] and
[(g5-C5H5)Fe(g5-C5H4CH2N(CH3)-C6H4-OCH3-4)]
a,b,
a
c
a
a
Hong-Xing Wang
Hui-Chao Zhou , Jian Xu , Ren-Qing Gao , Feng-Ying Geng
*, Ying-Jie Li , Rong Jin , Ji-Ru Niu , Hong-Fei Wu ,
a
a
a
a
a
Department of Chemistry, College of Sciences, Tianjin University, Tianjin 300072, PeopleÕs Republic of China
b
State Key Laboratory of Elemento-organic Chemistry, Nankai University, Tianjin 300071, PeopleÕs Republic of China
c
Department of Ultrasound, The First Central Hospital of Tianjin, Tianjin 300192, PeopleÕs Republic of China
Received 9 July 2005; received in revised form 4 October 2005; accepted 13 October 2005
Available online 15 December 2005
Abstract
The reactions of ferrocenylaldimines (II) [(g5-C5H5)Fe(g5-C5H4CH@NC6H4-R)] (R = 4-CH3O (a), 4-CH3 (b), H (c), 4-Cl (d), 3-Cl
(e), 4-NO2 (f), 3-NO2 (g)) and ferrocenylketimine (I) [(g5-C5H5)Fe (g5-C5H4CH3C@NC6H5)] with sodium borohydride in ethanol or
lithium aluminum hydride in THF resulted in secondary ferrocenylamines 3, 4. Reductive methylation of 3 (or II) and 4 with aqueous
formaldehyde and sodium cyanoborohydride all gave out corresponding N-methylated tertiary ferrocenylamines 5 [(g5-C5H5)Fe(g5-
C5H4CH2N(CH3)C6H 4-R)] (R = same as above mentioned) and 2, respectively, in good yields. All these tertiary ferrocenylamines
3–5 were characterized structurally. The crystal structures of 3d and 5a were also determined. Compound 3d is monoclinic, space group
˚
˚
˚
P2(1)/n, with a = 9.7585(14) A, b = 11.5267(17) A, c = 13.0830(19) A and b = 97.969(2)ꢀ. Compound 5a is orthorhombic, space group
˚
˚
˚
Pccn, with a = 13.752(2) A, b = 22.095(3) A, c = 10.6421(16) A.
ꢁ 2005 Elsevier B.V. All rights reserved.
Keywords: Ferrocenylimines; Ferrocenylamines; Reductive methylation; Crystal
1. Introduction
tion of ferrocenyl moiety into amine molecules render
ferrocenylamines, the [C,N] bidentate ligands, possess po-
tential planar chirality [1]. Researches of the planar chiral-
ity for ferrocene complexes, e.g., Ugi amines [3] on
asymmetric synthesis have already established an active
field in organometallic chemistry. The planar chirality
can be obtained normally by reactions of tertiary ferroce-
nylamines either with transition metals to form coordi-
nated complexes and then directed the metal to activate
ortho C–H bonds of the substrates to give out cyclometal-
lated compounds which are potential catalysts in Suzuki
Tertiary amines as one kind of important nitrogen-con-
taining ligands are widely used in organic synthesis [1]. Fer-
rocene since its discovery has attracted much attention in
asymmetric catalysis and drug designing owing to its un-
ique structure and low toxicity [1,2], thus, the incorpora-
*
Corresponding author.
E-mail address: hongxing_wang@hotmail.com (H.-X. Wang).
0022-328X/$ - see front matter ꢁ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.10.056

988
H.-X. Wang et al. / Journal of Organometallic Chemistry 691 (2006) 987–993
reaction [4], Heck reaction [5] as well as the other usages [6]
or by initial ortho-lithiation and followed by substitution to
yield [N,P] bidentate ligands. Now, researches on the nitro-
gen-containing ligands in asymmetric catalysis mainly
focus on oxazolinyl type [7–10] or imino form [11], in the
contrast, reports on amines in asymmetric catalysis except
Hayashi type [1,12] are still rare mostly because of the lack
of suitable tertiary ferrocenylamines and their synthetic
methods [13], though many of other aromatic tertiary
amines have been prepared [14,15]. Therefore, to assess
chemical properties of planar chirality of tertiary ferroce-
nylamines, the synthesis of suitable tertiary ferrocenylam-
ines is necessary. Our previous work [16] demonstrated
that tertiary ferrocenylamines could be synthesized by
methylation of ferrocenylketimines I [17] with methyl
iodide and followed by reduction of the corresponding
iminium salts 1 to give out tertiary ferrocenylamines 2
(Scheme 1). However, this method has some practical lim-
itations to the tertiary ferrocenylamines which bear elec-
tron-withdrawing groups on their phenyl rings. For
example, for the ferrocenylketimines bearing electron-
donating groups such as methoxy and methyl group, their
yields of corresponding ferrocenylamines are only moder-
ate, when the substituent is chlorine, the yield of corre-
sponding 2d is only 30%. However, replacement of
chlorine with nitro group, no corresponding product is ob-
tained. In order to find out a general method to prepare
tertiary ferrocenylamines and explore the scope and its lim-
itation, we wish to report here an alternative route in detail
to synthesize ferrocenylamines 5, 2 by reductive methyla-
tion [18] of secondary ferrocenylamines 3 (or ferrocenyl-
aldimines II), 4, respectively, with the system composed
by aqueous formaldehyde, sodium cyanoborohydride as
well as acetic acid (Scheme 2). Experiments show that this
method is applicable to prepare tertiary ferrocenylamines
no matter what kind of substituents on the phenyl rings.
In addition, the reaction condition is mild, and easy to
handle.
2. Synthesis and characterization of [(N-methyl-N-
aryl)amino]methylferrocenes
2.1. Synthesis of [(N-aryl)amino]methylferrocenes 3a–3g
and their N-methylated compounds 5a–5g
Initially, encouraged by the experiment results as
shown in Scheme 1, we tried to obtain tertiary ferrocenyl-
amines 5 with the same procedure as shown in Scheme 1,
CH3
N+
CH3
N
H3C
Fe
H3C
Fe
H3C
C
CH
C N
R
R
R
CH3I
abs. ethanol
NaBH4
ethanol
Fe
R = 4-CH3O(a), 4-CH3(b)-, H(c), 4-Cl(d), 4-Br(e), 3-CH3(f)
I
1
2
Scheme 1.
CH3
2
R'
3
R'
R'
C7H N
1
4
CH NH
C
N
8
9
6
5
R
R
R
12
10
HCHO/H+
NaCNBH3
NaBH4 or LiAlH4
ethanol or THF
Fe
Fe11
Fe
II R' = H, R = 4-MeO(a)
4-Me(b)
3
R' = H, R = 4-MeO(a)
4-Me(b)
5
R' = H, R = 4-MeO(a)
4-Me(b)
H(c)
H(c)
H(c)
4-Cl(d)
4-Cl(d)
4-Cl(d)
3-Cl(e)
3-Cl(e)
3-Cl(e)
4-NO2(f)
4-NO2(f)
4-NO2(f)
3-NO2(g)
3-NO2(g)
3-NO2(g)
I
R' = CH3, R = H
4
R' = CH3, R = H
2
R' = CH3, R = H
Scheme 2.

H.-X. Wang et al. / Journal of Organometallic Chemistry 691 (2006) 987–993
989
unfortunately, our effort was unsuccessful. An attempt to
isolate 5, 2 by the nucleophilic substitution of secondary
ferrocenylamines 3, 4 (Scheme 2) with methyl iodide, ethyl
bromide or benzyl chloride also failed. It is probably that
for the former reaction, replacement of methyl group with
a hydrogen atom in I could not sufficiently stabilize imin-
ium moiety (Scheme 1), hence, only a small amount of
products 5 were obtained. The explanation for the latter
unsuccessful substitution might be attributed to the weaker
nucleophicility of secondary ferrocenylamines 3, 4. Finally,
we had to turn our attention to search the other method,
i.e., reductive methylation [18] starting from secondary
amines 3, 4 with sodium cyanoborohydride, aqueous form-
aldehyde reagents as shown in Scheme 2.
Reductions of ferrocenylketimines II, I with sodium
borohydride in ethanol or lithium aluminum hydride [19]
in THF at room temperature proceeded smoothly. After
the reactions completed, in case, when lithium aluminum
hydride was used, degassed water was added to decompose
the excess reductive reagent. The mixture was extracted
with dichloromethane. The organic layer was dried over
anhydrous sodium sulfate and removed to give out 3, 4.
Reductive methylation of 3, 4 with the system composed
by sodium cyanoborohydride, aqueous formaldehyde were
carried out in acetonitrile solution, acetic acid was then
added to maintain the neutral pH value of the mixtures,
the reaction progresses were monitored by TLC. After
the reactions completed, solvent was removed under
reduced pressure. Purification of the crude products by
chromatography and further by recrystallization gave out
5, 2 as very good crystals.
tures of mono-substituted ferrocene derivatives [20]. A
sharp absorption band displayed around at 3400 cmꢀ1
for 3, 4 indicated that each molecule contained one N–H
bond which was indirectly supported by the fact that the
absence of N–H absorption band in 5, 2 are observed,
and this fact in turn indicated the conversion of 3, 4 into
5, 2 took place actually.
In their NMR spectra, ferrocenylamines 5 all displayed
a singlet appeared around at d2.87 ppm and this corre-
sponded to the methyl group attached directly to nitrogen
atom, on the contrary, the NMR of 3d gave a single peak
around d3.92 ppm which was indicative of a N–H group.
Two singlet appeared at d 4.08 and d 4.12 ppm, respec-
tively, in ferrocenylamines 3, 5 were assigned to the four
hydrogen atoms of the substituted cyclopentadienyl (Cp)
ring, a singlet displayed around at d4.15 ppm which repre-
sented five hydrogen atoms corresponded to the unsubsti-
tuted Cp ring. In addition, the hydrogen atoms in a
variety of substituted phenyl rings all displayed their corre-
sponding splitting patterns. All of these confirmed that 5, 2
were mono-substituted tertiary ferrocenylamines.
2.3. The crystal structures of 3d and 5a
The crystal structures and crystal packing diagrams of
3d and 5a were presented in Figs. 1–4, respectively. Crystal-
lographic data for 3d and 5a were given in Table 1, and
selected bond lengths and angles were listed in Tables 2
and 3, respectively.
Crystal structures of 3d, 5a showed that the bond length
˚
between C(10) and C(11) were nearly equal (1.499(3) A for
˚
It should be noted that reductive methylation of II with
the system as mentioned above also afforded tertiary
amines 5 (Scheme 3). On the contrary, the conversion from
I to 2 with reductive methylation method was unsatisfied,
because the reaction mixture was much complicated. Obvi-
ously, the conversion of II into 5 might proceed via second-
ary ferrocenylamines 3. In addition, when 3 and II were
used as starting material, experiments results showed that
the yields of 5 were nearly same.
3d and 1.502(4) A for 5a) and all of these data were in nor-
mal range. However, the bond length between N(1) and
˚
C(11) in 3d (1.450(3) A) was shorter than that in 5a
˚
(1.466(3) A), and all of these N(1)–C(11) bond lengths were
˚
shorter than that in 2d (1.473(3) A) [16]. In addition, the
˚
bond length between N(1)–C(12) in 3d (1.382(3) A) is
shorter than the bond length between N(1)–C(13) in 5a
˚
(1.399(3) A).
The dihedral angle of C(11)–N(1)–C(12)–C(17) in 3d
was ꢀ3.6(4)ꢀ, this indicated that the plane consisted of
C(12), N(1), C(11) fell in plane of the phenyl ring. In addi-
tion, the dihedral angle constructed by C(9)–C(10)–C(11)–
2.2. Spectral characterization of [(N-aryl)
amino]methylferrocenes 3a–3g and their N-methylated
compounds 5a–5g
Elemental analysis of compounds 5 are in consistence
with the proposed formulae (see Section 4). The IR spectral
features of 3–5 were similar to those as described in our
previous paper [17]. Two absorption bands appeared
around at m 1100 and 1000 cmꢀ1 corresponded to the struc-
NaCNBH3, HCHO
IIa-IIg
5a-5g
HOAc
Fig. 1. Molecular structure of 3d with numbering scheme (torsion angles:
C(9)–C(10)–C(11)–N(1): ꢀ86.6(3)ꢀ, C(11)–N(1)–C(12)–C(17): ꢀ3.6(4)ꢀ,
C(12)–N(1)–C(11)–C(10): 163.1(2)ꢀ).
R = 4-MeO(a), 4-Me(b)-, H(c), 4-Cl(d), 3-Cl(e), 4-NO2(f), 3-NO2(g)
Scheme 3.

990
H.-X. Wang et al. / Journal of Organometallic Chemistry 691 (2006) 987–993
Fig. 2. Crystal packing for compound 3d.
Table 1
Crystallographic data for 3d and 5a
Compound
Empirical formula
M
3d
C
325.61
5a
C19H21FeNO
335.22
17H16ClFeN
Crystal dimensions (mm)
0.48 · 0.24 · 0.20
0.36 · 0.24 · 0.20
Crystal system, space group Monoclinic, P2(1)/n Orthorhombic, Pccn
˚
a (A)
9.7585(14)
11.5267(17)
13.0830(19)
90.00
97.969(2)
90.00
1457.4(4)
4
1.484
13.752(2)
22.095(3)
10.6421(16)
90.00
90.00
90.00
3233.7(8)
8
1.377
˚
b (A)
˚
c (A)
a (ꢀ)
b (ꢀ)
c (ꢀ)
Fig. 3. Molecular structure of 5a with numbering scheme (torsion angles:
C(9)–C(10)–C(11)–N(1): 104.5(3)ꢀ, C(12)–N(1)–C(11)–C(10): 75.6(3)ꢀ,
C(13)–N(1)–C(11)–C(10): ꢀ70.0(3)ꢀ, C(11)–N(1)–C(13)–C(18): ꢀ28.4(4)ꢀ,
C(12)–N(1)–C(13)–C(18): ꢀ172.5(2)ꢀ, C(19)–O(1)–C(16)–C(17): 177.5(3)ꢀ).
3
˚
V (A )
Z
qcalcd (g cmꢀ3
)
l (mmꢀ1
)
1.206
0.934
Reflections collected:
total/independent/Rint
Data/restraints/parameters
Final R1, wR2
2974/2300/0.0289
2843/2052/0.0330
2974/0/181
0.0327, 0.0764
2843/0/201
0.0346, 0.0808
N(1) was ꢀ86.6(3)ꢀ, which mean that this plane was nearly
perpendicular to the substituted Cp ring. A similar confor-
mation in 5a was also observed. However, the influences of
substituents at para-position of phenyl rings on the bond
lengths of carbon–carbon double bond in phenyl rings were
not significant.
packing (Fig. 2), The distance between adjacent phenyl
˚
rings is 5.933 A, the dihedral angle between adjacent phe-
˚
The average Fe–C bond lengths in 3d (2.025 A for
nyl rings is 27.1ꢀ, in addition, the distance between interval
phenyl rings is 7.052 A, and the dihedral angle between
˚
˚
unsubstituted Cp ring, 2.037 A for substituted Cp ring)
˚
˚
and 5a (2.027 A for unsubstituted Cp ring, 2.031 A for
interval phenyl rings is 0ꢀ. The diameter of the helix is
˚
˚
substituted Cp ring) were shorter than that in 2d (2.039 A
for unsubstituted Cp ring, 2.043 A for substituted Cp ring)
0.948 A (The longer side of a right triangle when the dis-
˚
tance between Fe1E and Fe1F is defined as the hypote-
nuse). For compound 5a, the molecules were linked
through weak intermolecular interaction between H7 and
[17]. All of these indicated that the structures of 3d, 5a were
tightly packed than that of 2d.
For compound 3d, the molecules are linked with inter-
molecular Clꢁ ꢁ ꢁH (Cp ring) interaction to form a helix-like
˚
O1 (H7–O1, 2.692 A, C7–H7–O1, 171.2ꢀ) to form zig-zag
chains (Fig. 4).
Fig. 4. Crystal packing for compound 5a.

H.-X. Wang et al. / Journal of Organometallic Chemistry 691 (2006) 987–993
991
Table 2
4. Experimental
˚
Selected bond lengths (A) for compounds 3d and 5a
˚
˚
3d
(A)
5a
(A)
4.1. Materials and instruments
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–C(3)
Fe(1)–C(6)
Fe(1)–C(9)
Fe(1)–C(10)
C(1)–C(2)
2.027(3)
2.015(3)
2.015(3)
2.040(2)
2.031(2)
2.030(2)
1.428(5)
1.405(6)
1.425(3)
1.419(3)
1.499(3)
1.450(3)
1.382(3)
1.399(3)
1.373(3)
1.380(3)
1.377(3)
1.747(2)
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–C(3)
Fe(1)–C(6)
Fe(1)–C(9)
Fe(1)–C(10)
C(1)–C(2)
2.036(3)
2.031(3)
2.028(3)
2.028(3)
2.034(3)
2.036(2)
1.383(4)
1.394(4)
1.421(4)
1.415(4)
1.502(4)
1.466(3)
1.462(3)
1.399(3)
1.402(4)
1.372(4)
1.369(4)
1.387(4)
1.378(3)
1.420(3)
Ferrocenylaldimines and ferrocenylketimine were syn-
thesized according to the literature procedures [18,21], ani-
lines were obtained commercially and used without further
purification, sodium borohydride, sodium cyanoborohy-
dride and sodium aluminum hydride were purchased from
Aldrich. All of the solvents were purified with standard
method prior to use. Melting points were obtained from
Yanaco micro melting point apparatus and were uncor-
rected. Elemental analyses were obtained from Carlo Erba
C(2)–C(3)
C(2)–C(3)
C(6)–C(10)
C(9)–C(10)
C(10)–C(11)
N(1)–C(11)
N(1)–C(12)
C(12)–C(13)
C(15)–C(16)
C(13)–C(14)
C(14)–C(15)
Cl(1)–C(15)
C(6)–C(10)
C(9)–C(10)
C(10)–C(11)
N(1)–C(11)
N(1)–C(12)
N(1)–C(13)
C(13)–C(18)
C(15)–C(16)
C(17)–C(18)
C(16)–C(17)
O(1)–C(16)
O(1)–C(19)
1
1106 Elemental analyzer. H NMR spectra were measured
with Bruker AV-400 spectrometer by using CDCl3 as a sol-
vent and TMS as internal standard. IR spectra were taken
on BIO-RAD 3000 spectrophotometer.
4.2. Preparation of [(N-methyl-N-aryl)
amino]methylferrocenes (5a–5g) and 1-[(N-methyl-N-
phenyl)amino]ethyl-ferrocene (2)
4.2.1. Preparation of (N-arylamino)methylferrocenes
(3a–3g) and 1-(N-phenylamino)ehtylferrocene (4)
General procedure. To the solutions of ferrocenylaldi-
mines (5 mmol) in ethanol or tetrahydrofuran (20 ml), were
added 2.5 equivalents of sodium borohydride or lithium
aluminum hydride. When lithium aluminum hydride was
used as reductive reagent, 5 ml methanol was added. The
mixtures were stirred at room temperature for 12 h and
TLC monitored the reactions until they were completed.
Forty millilitres of degassed water was then added to
decompose the excess reductive reagent. The mixtures were
extracted with dichloromethane (3 · 30 ml), the organic
layer was dried with anhydrous sodium sulfate and filtered.
Solvent was removed to afford the crude product, and the
crude products were recrystallized from dichloromethane–
pentane or ethyl acetate–petroleum ether (60–90 ꢀC) and
then subjected to chromatography to give out very good
crystals.
Table 3
Selected bond angles (ꢀ) for compounds 3d and 5a
3d
(ꢀ)
5a
(ꢀ)
C(3)–C(2)–C(1)
106.1(3)
107.0(2)
125.9(2)
109.36(19)
123.7(2)
118.2(2)
121.0(2)
119.88(18)
119.13(18)
C(1)–C(2)–C(3)
109.7(3)
107.2(3)
126.9(2)
114.8(2)
113.6(2)
119.1(2)
117.8(2)
115.6(3)
117.9(3)
125.5(3)
116.6(3)
117.2(2)
C(9)–C(10)–C(6)
C(9)–C(10)–C(11)
N(1)–C(11)–C(10)
C(12)–N(1)–C(11)
C(17)–C(12)–C(13)
C(16)–C(15)–C(14)
C(16)–C(15)–Cl(1)
C(14)–C(15)–Cl(1)
C(9)–C(10)–C(6)
C(9)–C(10)–C(11)
N(1)–C(11)–C(10)
C(12)–N(1)–C(11)
C(13)–N(1)–C(11)
C(13)–N(1)–C(12)
C(14)–C(13)–C(18)
C(15)–C(16)–C(17)
C(15)–C(16)–O(1)
O(1)–C(16)–C(17)
C(16)–O(1)–C(19)
3. Conclusion
(N-p-Methoxyphenylamino)methylferrocene (3a): yel-
low solid. Yield 89%. M.p. 50–52 ꢀC. IR (KBr pellet):
3369 (s, N–H), 2992, 1614, 1513, 1460, 1408, 1232, 1180,
Reductive methylation of ferrocenylaldimines and
their reductive products, i.e., secondary ferrocenylamines
with the system composed by sodium cyanoborohydride,
aqueous formaldehyde and acetic acid produced N-meth-
ylated tertiary ferrocenylamines with higher yields.
Similarly, reductive methylation of secondary ferrocenyl-
amines derived from ferrocenylketimines with the above
system also resulted in the corresponding N-methylated
products. The synthesis of tertiary ferrocenylamines
[(g5-C5H5)Fe(g5-C5H4CHRN(CH3)-(CH2)nC6H4-R0)] 6–
10 (6, R = Me, n = 0; 7, R = Ph, n = 0; 8, R = H,
n = 1; 9, R = Me, n = 1; 10, R = Ph, n = 1), the ana-
logues of compounds 5 (and 2), and their corresponding
ferrocenylaminophosphines 11–15 as well as the reactions
with palladium reagents are now in progress in our
laboratory.
1092, 1003, 813 cmꢀ1
.
(N-p-Methylphenylamino)methylferrocene (3b): yellow
solid. Yield 87%. M.p. 62–64 ꢀC. IR (KBr pellet): 3396
(s, N–H), 3099, 2940, 1612, 1517, 1458, 1317, 1249, 1101,
810 cmꢀ1
.
(N-Phenylamino)methylferrocene (3c): yellow solid.
Yield 85%. M.p. 82–84 ꢀC. IR (KBr pellet): 3400 (s, N–
H), 3088, 2924, 1602, 1504, 1457, 1427, 1315, 1105, 999,
748 cmꢀ1
.
(N-p-Chlorophenylamino)methylferrocene (3d): yellow
solid. Yield 83%. M.p. 126–128 ꢀC. IR (KBr pellet): 3421
(s, N–H), 3097, 2936, 1595, 1499, 1463, 1400, 1320, 1284,
1102, 998, 818 cmꢀ1 1H NMR: d 3.92 (s, 3H, C(9)–H,
.
C(12)–H, NH), 4.18 (s, 2H, C(10)–H, C(11)–H), 4.21 (s,

992
H.-X. Wang et al. / Journal of Organometallic Chemistry 691 (2006) 987–993
5H, C5H5), 4.27 (s, 2H, C(7)–H), 6.58 (d, 2H, J = 8.8 Hz,
C(2)–H, C(6)–H), 7.15 (d, 2H, J = 8.8 Hz, C(3)–H, C(5)–
H) ppm.
C(2)–H, C(6)–H), 7.03 (d, 2H, J = 8.4 Hz, C(3)–H, C(5)–
H) ppm.
(N-methyl-N-phenylamino)methylferrocene (5c): yellow
rod. Yield 87%. M.p. 52–54 ꢀC. Anal. Found: C, 70.73;
H, 6.40; N, 4.79. Calc. For C18H19FeN: C, 70.84; H,
6.27; N, 4.59%. IR (KBr pellet): 3095, 1594, 1502, 1261,
(N-m-Chlorophenylamino)methylferrocene (3e): yellow
solid. Yield 85%. M.p. 78–80 ꢀC. IR (KBr pellet): 3416
(s, N–H), 1597, 1506, 1485, 1321, 1078, 1025, 816,
771 cmꢀ1
.
1190, 1101, 1031, 817, 784 cmꢀ1. H NMR: d 2.88 (s, 3H,
1
(N-p-Nitrophenylamino)methylferrocene (3f): yellow
solid. Yield 76%. M.p. 124–126 ꢀC. IR (KBr pellet): 3407
(s, N–H), 3080, 1598, 1499, 1454, 1356, 1296, 1262, 1185,
N-CH3), 4.09 (s, 2H, C(9)–H, C(12)–H), 4.15 (s, 2H,
C(10)–H, C(11)–H), 4.16 (s, 5H, C5H5), 4.28 (s, 2H,
C(7)–H), 6.71–7.24 (m, 5H, C(2)–H–(5)–H) ppm.
1112, 1052, 997, 817, 753 cmꢀ1
.
(N-methyl-N-p-chlorophenylamino)methylferrocene (5d):
yellow needle crystal. Yield 85%. M.p. 98–100 ꢀC. Anal.
Found: C, 63.80; H, 5.63; N, 4.29. Calc. For C19H18ClFeN:
C, 63.65; H, 5.34; N, 4.12%. IR (KBr pellet): 3095, 2941,
(N-m-Nitrophenylamino)methylferrocene (3g): yellow
solid. Yield 80%. M.p. 86–88 ꢀC. IR (KBr pellet): 3391
(s, N–H), 3092, 1530, 1478, 1350, 1297, 1260, 1100, 994,
811, 734 cmꢀ1
.
1595, 1502, 1373, 1329, 1253, 1198, 1102, 999, 804 cmꢀ1
.
1-(N-phenylamino)ethylferrocene (4). The starting
material was Ic, the quantity and procedure were the same
as that for preparation of 3a (82%), yellow solid. M.p. 68–
70 ꢀC. mmax (KBr) 3401 (s, N–H), 3089, 2941, 1508, 1498,
1H NMR: d 2.85 (s, 3H, N-CH3), 4.09 (s, 2H, C(9)–H,
C(12)–H), 4.13 (s, 2H, C(10)–H, C(11)–H), 4.15 (s, 5H,
C5H5), 4.24 (s, 2H, C(7)–H), 6.68 (d, 2H, J = 8.8 Hz,
C(2)–H, C(6)–H), 7.14 (d, 2H, J = 8.8 Hz, C(3)–H, C(5)–
H) ppm.
1350, 1296, 1260, 1100, 998, 748 cmꢀ1
.
(N-methyl-N-m-chlorophenylamino)methylferrocene (5e):
yellow needle crystal. Yield 87%. M.p. 82–84 ꢀC. Anal.
Found: C, 63.39; H, 5.56; N, 4.36. Calc. For
C19H18ClFeN: C, 63.65; H, 5.34; N, 4.12%. IR (KBr pel-
let): 3091, 2943, 1592, 1492, 1363, 1257, 1099, 985, 825,
4.2.2. Preparation of [(N-methyl-N-aryl)
amino]methylferrocenes 5a–5g (2) from secondary amines 3
(4)
General procedure. To a stirred solution of N-arylamino
methylferrocene (2 mmol) and 10 mmol of 37% aqueous
formaldehyde in 18 ml of acetonitrile was added 3.2 mmol
of sodium cyanoborohydride, 30 min later, glacial acid was
added dropwise until the pH value of the mixture reached
neutral. The mixture was stirred at room temperature for
6 h and TLC monitored the reaction until it completed.
The solvent was removed under reduced pressure, and
20 ml of 2 N NaOH was then added to the residue. The
mixture was extracted with diethyl ether (3 · 30 ml), and
the organic layer was dried over Na2SO4 and removed to
afford crude product, which was purified by recrystalliza-
tion and further by chromatography (silica gel, ethyl
acetate/hexane) to provide [(N-methyl-N-aryl)amino]meth-
ylferrocenes 5a–5g.
753 cmꢀ1 1H NMR: d 2.87 (s, 3H, N–CH3), 4.09 (s,
.
2H, C (9)–H, C(12)–H), 4.15 (s, 2H, C(10)–H, C(11)–
H), 4.16 (s, 5H, C5H5), 4.26 (s, 2H, C(7)–H), 6.65 (t,
2H, J = 8.0 Hz, J = 7.6 Hz, C(2)–H, C(4)–H), 6.73 (s,
1H, C(6)–H), 7.12 (t, 1H, J = 8.0 Hz, J = 8.4 Hz, C(5)–
H) ppm.
(N-methyl-N-p-nitrophenylamino)methylferrocene (5f):
yellow rod. Yield 76%. M.p. 160–162 ꢀC. Anal. Found:
C, 61.52; H, 5.31; N, 8.29. Calc. For C18H18FeN2O2: C,
61.74; H, 5.18; N, 8.00%. IR (KBr pellet): 3101, 2914,
1594, 1476, 1293, 1201, 1107, 997, 826, 752 cmꢀ1 1H
.
NMR: d 3.06 (s, 3H, N–CH3), 4.15 (s, 2H, C(9)–H,
C(12)–H), 4.19 (s, 2H, C(10)–H, C(11)–H), 4.21 (s, 5H,
C5H5), 4.38 (s, 2H, C(7)–H), 6.68 (d, 2H, J = 9.6 Hz,
C(2)–H, C(6)–H), 8.10 (d, 2H, J = 9.6 Hz, C(3)–H, C(5)–
H) ppm.
(N-methyl-N-p-methoxyphenylamino)methylferrocene
(5a): yellow needle crystal. Yield 88%. M.p. 82–84 ꢀC.
Anal. Found: C, 67.78; H, 6.55; N, 4.37. Calc. For
C19H21FeNO: C, 68.08; H, 6.31; N, 4.18%. IR (KBr pellet):
(N-methyl-N-m-nitrophenylamino)methylferrocene (5g):
yellow rod. Yield 83%. M.p. 94–96 ꢀC. Anal. Found: C,
61.48; H, 5.40; N, 8.10. Calc. For C18H18FeN2O2: C,
61.74; H, 5.18; N, 8.00%. IR (KBr pellet): 3090, 2943,
3081, 2934, 1512, 1475, 1243, 1180, 1092, 1028, 818 cmꢀ1
.
1H NMR: d 2.76 (s, 3H, N–CH3), 3.76 (s, 3H, OCH3),
4.07 (s, 2H, C(9)–H, C(12)–H), 4.10 (s, 2H, C(10)–H,
C(11)–H), 4.13 (s, 5H, C5H5), 4.17 (s, 2H, C(7)–H), 6.77
(d, 2H, J = 9.2 Hz, C(2)–H, C(6)–H), 6.82 (d, 2H,
J = 9.2 Hz, C(3)–H, C(5)–H) ppm.
1
1613, 1517, 1344, 1206, 1106, 994, 817, 739, 500 cmꢀ1. H
NMR: d 2.98 (s, 3H, N-CH3), 4.13 (s, 2H, C(9)–H,
C(12)–H), 4.17 (s, 2H, C(10)–H, C(11)–H), 4.20 (s, 5H,
C5H5), 4.33 (s, 2H, C(7)–H), 7.01 (d, 1H, J = 8.4 Hz,
C(2)–H), 7.31 (t, 1H, J = 8.4 Hz, J = 8.0 Hz, C(5)–H),
7.50 (d, 1H, J = 8.0 Hz, C(4)–H), 7.58 (s, 1H, C(6)–H)
ppm.
1-[(N-methyl-N-phenyl)amino]ethylferrocene (2). The
starting material was 4, the quantity and procedure were
the same as that for preparation of 5a (87%), yellow needle
crystal. M.p 74–76 ꢀC (lit. [16] 75–77 ꢀC). IR and NMR
spectra were the same as authentic sample.
(N-methyl-N-p-methylphenylamino)methylferrocene (5b):
yellow needle crystal. Yield 85%. M.p. 72–74 ꢀC. Anal.
Found: C, 71.39; H, 6.91; N, 4.60. Calc. For C19H21FeN:
C, 71.49; H, 6.63; N, 4.39%. IR (KBr pellet): 3089, 2939,
1613, 1517, 1188, 1096, 809 cmꢀ1 1H NMR: d 2.25 (s,
.
3H, Ar–CH3), 2.81 (s, 3H, N–CH3), 4.07 (s, 2H, C(9)–H,
C(12)–H), 4.13 (s, 2H, C(10)–H, C(11)–H), 4.14 (s, 5H,
C5H5), 4.22 (s, 2H, C(7)–H), 6.71 (d, 2H, J = 8.4 Hz,

H.-X. Wang et al. / Journal of Organometallic Chemistry 691 (2006) 987–993
993
4.2.3. Preparation of [(N-methyl-N-aryl)amino]
methylferrocenes 5a–5g from ferrocenylaldimines II
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˚
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2
with w ¼ 1=½r2ðF o2Þ þ ð0:0423PÞ þ 0:3954Pꢂ, where P ¼
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Crystallographic data (excluding structure factors) for
the structure of 3d, 5a in this paper have been deposited
with the Cambridge Crystallographic Data Centre as
supplementary publication Nos. CCDC 271789 and
271790. Copies of the data can be obtained, free of charge,
on application to CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: 144 0 1223 336033 or deposit@ccdc.cam.
ac.uk).
Acknowledgements
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5443;
We are grateful to the Natural Scientific Foundation of
Tianjin City, PeopleÕs Republic of China, for their generous
support for this Research (Grant No. 033609011). Partial
support for this Project from Opening Fund of Ministry
of Science and Technology, PeopleÕs Republic of China,
is also acknowledged.
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¨