Synthesis and characterization of 1,1′-bis[(N-methyl-N-phenyl)aminomethyl(ethyl)]ferrocenes. Crystal structures of [Fe{(η5-C5H4)-C(C6H 5){double bond, long}N-CH2C6H4CH3-4} 2] and 2[Fe{(η5-C5H4)-CH2N (CH3)...

Article abstract of DOI:10.1016/j.poly.2006.09.093

Title full: Synthesis and characterization of 1,1′-bis[(N-methyl-N-phenyl)aminomethyl(ethyl)]ferrocenes. Crystal structures of [Fe{(η⁵-C₅H₄)-C(C₆H ₅){double bond, long}N-CH₂C₆H₄CH₃-4} ₂] and 2[Fe{(η⁵-C₅H₄)-CH₂N (CH₃)-C₆H₄OCH₃-4}₂] · 1/4H₂O. Direct or catalytic condensation of diacylferrocenes (acyl = formyl, acetyl, and benzoyl) and anilines or benzylamines with titanium tetrachloride as a catalyst resulted in the corresponding diimines 1-3, respectively. Reduction of these imines with sodium borohydride or lithium aluminum hydride/aluminum chloride in THF yielded 1,1′-bis[(N-phenyl)aminomethyl(ethyl)]ferrocenes (4, 5) and 1,1′-bis[(N-benzyl)aminobenzyl]ferrocenes (6), respectively. Reductive methylation of 4-6 with aqueous formaldehyde, cyanoborohydride and acetic acid only afforded 1,1′-bis[(N-methyl-N-phenyl)aminomethyl(ethyl)]ferrocenes (7, 8). 1,1′-Bis[{(N-methyl-N-benzyl)amino}benzyl]ferrocenes (9) were not obtained, probably due to their debenzylation under the acidic conditions. The molecular structures of 3g and 7a were determined by single crystal X-ray analysis.

Full text of DOI:10.1016/j.poly.2006.09.093

Polyhedron 26 (2007) 1037–1044
www.elsevier.com/locate/poly
Synthesis and characterization of
1,10-bis[(N-methyl-N-phenyl)aminomethyl(ethyl)]ferrocenes. Crystal
structures of [Fe{(g5–C5H4)–C(C6H5)@N–CH2C6H4CH3-4}2]
and 2[Fe{(g5–C5H4)–CH2N(CH3)–C6H4OCH3-4}2] Æ 1/4H2O
a,
a
a
a
a
Hong-Xing Wang *, Ren-Qing Gao , Xiao-Li Yang , Li Wan , Hong-Fei Wu ,
a
b
Feng-Ying Geng , Rong Jin
a
Department of Chemistry, College of Sciences, Tianjin University, Tianjin 300072, People’s Republic of China
Department of Ultrasound, The First Central Hospital of Tianjin, Tianjin 300192, People’s Republic of China
b
Received 3 August 2006; accepted 27 September 2006
Available online 10 October 2006
Abstract
Direct or catalytic condensation of diacylferrocenes (acyl = formyl, acetyl, and benzoyl) and anilines or benzylamines with titanium
tetrachloride as a catalyst resulted in the corresponding diimines 1–3, respectively. Reduction of these imines with sodium borohydride or
lithium aluminum hydride/aluminum chloride in THF yielded 1,10-bis[(N-phenyl)aminomethyl(ethyl)]ferrocenes (4, 5) and 1,10-bis[(N-
benzyl)aminobenzyl]ferrocenes (6), respectively. Reductive methylation of 4–6 with aqueous formaldehyde, cyanoborohydride and acetic
acid only afforded 1,10-bis[(N-methyl-N-phenyl)aminomethyl(ethyl)]ferrocenes (7, 8). 1,10-Bis[{(N-methyl-N-benzyl)amino}benzyl]fer-
rocenes (9) were not obtained, probably due to their debenzylation under the acidic conditions. The molecular structures of 3g and
7a were determined by single crystal X-ray analysis.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Ferrocene; Acylferrocene; Amines; Reductive methylation; Crystal
1. Introduction
nation to produce cycloplatinated complexes [5], the
latter exhibit potential medical and biological activities
[5d]. As far as we know, although a few 1,10-disubstituted
nitrogen-containing ferrocenes have been described, they
are normally limited to 1,10-bis[(N,N-dimethylamino)-
methyl]- and 1,10-bisoxazolinylferrocenes. Recently, we
have reported the synthesis of monosubstituted tert-ferr-
ocenylamines by N-methylation of ferrocenylketimines by
methyl iodide to form iminum salts, followed by reduction
with sodium borohydride [6]; or reductive methylation of
sec-ferrocenylamines (ferrocenylaldimines) [7] with formal-
dehyde and sodium cyanoborohydride. It was found that
these tert-ferrocenylamines were good candidates for
ortho-metallations [8], particularly for ortho-palladation,
their ortho-palladated complexes exhibiting a high catalytic
efficiency in the Suzuki coupling of aryl chlorides and the
1,1-Disubstituted ferrocenes, especially those bearing
chelating nitrogen atoms, are a class of important ligands
in organic synthesis [1]. These nitrogen-containing com-
plexes not only serve as [N, N] bidentate ligands to coordi-
nate directly with transition-metals for studying structures
and mechanisms [2], but also are good precursors of the [N,
X] type of complexes (X = P, S, etc.) by phosphination [3],
etc. The [N, X] type of complexes have been successfully
used in asymmetric catalysis, e.g., allylic alkylation [4]. In
addition, some 1,10-disubstituted nitrogen-containing fer-
rocenes, e.g., 1,10-diaminoferrocenes, undergo cycloplati-
*
Corresponding author. Tel.: +86 22 27892355; fax: +86 22 27403475.
E-mail address: hongxing_wang@hotmail.com (H.-X. Wang).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.09.093

1038
H.-X. Wang et al. / Polyhedron 26 (2007) 1037–1044
Heck reaction [9]. Encouraged by our earlier results and in
order to explore new types of 1,10-diaminoferrocenes, in
this paper, we report the synthesis and characterization
of 1,10-bis[(N-methyl-N-phenyl)aminomethyl(ethyl)]ferroc-
enes starting from diacylferrocenes (acyl = formyl, acetyl)
and anilines. Additionally, the debenzylation phenomenon
observed in the synthesis of 1,10-bis[{(N-methyl-N-benzyl)-
amino}benzyl]ferrocenes, starting from dibenzoylferrocene
and benzylamines, will be also discussed.
9 are indeed produced in these reactions. The unsuccessful
isolation of 9 is probably attributed to the unique structure
of the benzylferrocenyl moiety, causing their debenzylation
(Scheme 2), and this result is consistent with Baltzly’s
observation [13]. As illustrated in Schemes 1 and 2, 7(8)
and 9 are in fact tert-amines and are easily protonated by
acetic acid, particularly for 9, to give ammonium salts A,
which is followed by elimination of a neutral benzylamine
to afford cations B, the latter are better stabilized by both
ferrocenyl and phenyl groups. Nucleophilic attack of
hydride on B will generate C. Similarly, the elimination
of a second benzylamine, yielding 1,10-dibenzylferrocene
(D), is in the same manner as that for the first one
2. Results and discussion
2.1. Synthesis of 1,10-bis[(N-methyl-N-phenyl)-
aminomethyl(ethyl)]ferrocenes 7(8)
(A ! C). Since
9
bear
a
1,10-bis[(N-methyl-N-ben-
zyl)amino-benzyl] group, the possible elimination of two
benzylamines at the same time to generate D is also not
excluded.
The synthetic pathway for 1,10-bis[(N-methyl-N-
phenyl)aminomethyl(ethyl)]ferrocenes 7(8) is outlined in
Scheme 1. Diimine complexes 1 are obtained directly by
condensation of diformyl ferrocene and anilines at room
temperature in methanol whereas 2(3) are synthesized by
condensation of diacetylferrocene (dibenzoylferrocene)
and anilines (benzylamines) in toluene using titanium tetra-
chloride as the catalyst. Although active aluminum oxide
as the catalyst in these reactions is also applicable [10],
the titanium catalyzed method shows some advantages
such as time savings and affording moderate yields of the
products, etc. Reduction of 1 with sodium borohydride
produce quantitatively the 1,10-bis[(N-phenylamino)-
methyl]ferrocenes (4). However, it is difficult to isolated 5
and 6 due to the incomplete reduction of 2 and 3 with
sodium borohydride. Thus, a catalytic reductive system
i.e., lithium aluminum hydride–aluminum chloride is cho-
sen to catalyze their reduction, and 5, 6 are obtained in
good yields. Reductive methylation of 4 and 5 with sodium
cyanoborohydride and aqueous formaldehyde in the pres-
ence of acetic acid [11] yield 7, 8, respectively, in moderate
yields. Surprisingly, N-methylation of 6 with the conditions
as mentioned above does not afford the corresponding
complexes 9, in contrast, a sole product, 1,10-dibenzyl
ferrocene [12], is isolated. The same product is also
obtained in the N-methylation reaction of 1,10-bis[(N-
phenylamino)benzyl]ferrocene.
2.2. Spectra characterization of 7(8)
Compounds 1, 3–8 are characterized by elemental anal-
1
ysis, IR and H NMR. The elemental analyses are in good
agreement with the proposed formula. In the IR spectra, 4
and 6 all display a weak or medium absorption approxi-
mate at m 3340 cmꢀ1, indicating that a N–H group is pres-
ent in these molecules and this assignment is further
1
confirmed by their H NMR where a singlet appears at
d ꢁ 3.90 ppm in 5 and d 2.30 ppm in 6 (the peak for a
N–H group in 4 is missing). In addition, a peak
d ꢁ 4.25 ppm in 4 is assigned to H4 (H4@H40@H5@H50).
The satellites correspond to H4 and H5 (H4@H40,
H5@H50) in 5 (a multiplet d ꢁ 3.15 ppm, a doublet
d ꢁ 1.44 ppm) and 6 (a singlet d ꢁ 4.37 ppm, H4@H40,
H5@H50@0). All of these confirm that diimines 1–3 are
converted into diamines 4–6, respectively. In the IR spectra
of 7, the absorptions at m 3340 cmꢀ1 observed in 4, 5 disap-
pear, meanwhile the absorptions at m 2960, 2870, 1460,
1380 cmꢀ1 are present, implying that a N–H group is
replaced by N–CH3 in 4 and 5, and this assignment is con-
1
sistent with their H NMR where H7(70) display a singlet
d ꢁ 2.80 ppm in 7 and d ꢁ 2.45 ppm in 8, and these d val-
ues are comparable to those of [(N-methyl-N-phenyl)ami-
nomethyl]ferrocenes (d ꢁ 2.70 ppm) [7]. In addition, the
protons in para-substituted phenyl rings in 1, 3–8 all dis-
play their corresponding splitting patterns.
We are puzzled by the above observations. Comparison
of the structures of 7(8) and 9 and consideration of the
acidic medium in our reactions, it is easily understood that
7
5
5
5
R'
R'
R'
6
R
1
6
R
1
6
R
R
1
H
4
4
4
O
2
N (CH2)n
2
N (CH2)n
2
N (CH2)n
3
3
3
(i)
(ii)
(iii)
Fe
Fe
2'
Fe
2'
Fe
2'
1'
1'
6'
6'
1'
6'
3'
3'
3'
N (CH2)n
O
(CH2)n
N
(CH2)n
N
4'
4'
4'
H
R
R
R
R
R'
R'
R'
5'
5'
5'
7'
R = H, n =0
R = CH3, n =0
R = Ph, n= 1
1
2
3
4
5
6
7
8
Scheme 1. Condition: (i) R0C6H4(CH2)nNH2/TiCl4, toluene, reflux for acetyl- and benzoylferrocenes; (ii) LiAlH4–AlCl3/THF; (iii) NaCNBH3,
37%HCHO, AcOH, CH3CN. n = 0, R0 = 4-CH3O (a), 4-CH3 (b), C6H5 (c), 3-Cl (d), 4-Cl (e); n = 1, R0 = 4-CH3 (f), H (g).

H.-X. Wang et al. / Polyhedron 26 (2007) 1037–1044
1039
Ph
Fe
Ph
H
+
N
Bz
Bz
N+ Bz
Ph
Ph
N
Ph
Ph
H+
-BzNH(CH3)
NaCNBH3
Fe
Fe
Fe
Fe
Bz
Bz
N
Bz
N
N
Ph
Ph
Ph
Ph
9
A
B
C
D
Scheme 2. The possible mechanism for the decomposition of 9.
2.3. X-ray analysis for the crystal structures of 3g and 7a
In order to better understand the structures of the 7(8),
complexes, the structures of 3g and 7a were determined by
X-ray single crystal diffraction. The crystal structures of 3g
and 7a are presented in Figs. 1 and 2, respectively. Crystal-
lographic data for 3g and 7a are given in Table 1, selected
bond lengths and angles are listed in Table 2.
Fig. 1 demonstrates that the crystal of 3g consists of
[Fe{(g5-C5H4)–C(C6H5)@NCH2C6H5}2]. However, the
crystal of 7a (Fig. 2) consists of two molecular units
[Fe{(g5-C5H4)–CH2N(CH3)C6H4OCH3-4}2], each being
located at a crystallographic center of symmetry. In
˚
Fig. 1, the bond lengths of N1–C11 (1.273(3) A) and N2–
˚
C25 (1.278(3) A) of 3g correspond to C@N double bonds
and are all in the normal range. The phenyl rings attached
directly to C11 and C25 are not coplanar with the C@N
planes due to the steric hindrance between the phenyl rings
and hydrogen atoms of the cyclopentadienyl (Cp) rings.
The related dihedral angles between the phenyl planes
and the corresponding Cp rings are 63.7ꢁ and 102.4ꢁ,
respectively. In Fig. 2, the bond lengths of N1–C6
(1.502(7) A) and N2–C20 (1.498(7) A) in the two molecular
units of 7a are nearly the same. The phenyl plane defined
by C8-C13 in one molecular unit is situated above the same
side Cp ring, and the dihedral angle between them is 78.5ꢁ.
A similar location of the phenyl ring and the dihedral angle
Fig. 2. Perspective view of the independent molecules of 7a with the
atomic numbering scheme (H atoms are omitted for clarity).
˚
˚
(with Cp ring, 77.1ꢁ) in the other molecular unit is also
observed. All of these data are nearly the same as those
of [(N-methyl-N-phenyl)aminomethyl]ferrocenes [14]. The
˚
average C–C bond length of the Cp rings in 3g (1.417 A)
˚
and 7a (1.453 A) are similar to the values reported for other
ferrocene derivatives [15]. The Fe–C(ring) bond distances
˚
range from 2.036 to 2.050 A in 3g and from 2.079 to
˚
2.098 A in 7a. The two Cp rings of the ferrocenyl fragment
in 3g and 7a are planar and nearly parallel (interplanar
angle 1.7ꢁ in 3g).
3. Experimental
3.1. Materials and instruments
Diformylferrocene [16], diacetylferrocene and dibenzoyl-
ferrocene [17] were prepared according to the literature
methods. Sodium borohydride, sodium cyanoborohydride
were used as received, anilines, titanium tetrachloride,
formaldehyde, acetic acid, lithium aluminum hydride, and
aluminum chloride were obtained commercially. All of the
solvents were purified according standard methods prior
to use. Melting points were obtained from a Yanaco micro
Fig. 1. Perspective view of the independent molecule of 3g with the atomic
numbering scheme (H atoms are omitted for clarity).

1040
H.-X. Wang et al. / Polyhedron 26 (2007) 1037–1044
Table 1
Crystallographic data for 3g and 7a
Compound
3g
7a
Empirical formula
M
C38H32FeN2
572.51
C28H32.25FeN2O2.13
486.66
Crystal dimensions (mm)
Crystal system, space group
0.26 · 0.20 · 0.18
monoclinic, P2(1)/c
10.763(7)
26.046(2)
10.487(7)
90
91.847(9)
90
2938(4)
0.24 · 0.22 · 0.14
monoclinic, P2(1)/c
27.347(1)
10.043(4)
9.350(4)
90
99.672(6)
90
2531.5(2)
4
1.277
0.623
1029
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
4
qcalcd (Mg mꢀ3
)
1.294
0.543
1200
l (mmꢀ1
F(000)
)
Reflections collected/unique [Rint
Data/restraints/parameters
Final R1, wR2
]
15775/5198 [0.0370]
5198/0/370
0.0353, 0.0781
0.188 and ꢀ0.218
11972/4409 [0.0906]
4409/6/307
0.0654, 0.1468
0.886 and ꢀ0.311
ꢀ3
˚
Largest difference in peak and hole (e A
)
1
Table 2
Selected bond lengths (A) and angles (ꢁ) for 3g and 7a
68.87; H, 5.33; N, 6.18%. Yield 81%. H NMR (CDCl3)
d: 3.81(s, 6H, OCH3), 4.08(s, 4H, H3, H30), 4.19(s, 4H,
H2, H20), 6.83(q, 8H, PhH), 8.01(s, 2H, H4, H40) ppm.
IR(KBr) m: 3075(w), 2991(w), 2931(w) 2833(m), 1622(s),
1598(m), 1511(s), 1458(s), 1240(s), 1176(s), 1164(m),
˚
3g
7a
˚
˚
Bond lengths
(A)
Bond lengths
(A)
N(2)–C(32)
C(11)–C(12)
C(25)–C(26)
C(5)–C(11)
C(6)–C(25)
N(1)–C(18)
C(4)–C(5)
1.467(3)
1.500(3)
1.502(3)
1.484(3)
1.467(3)
1.470(3)
1.424(3)
1.427(3)
C(5)–C(6)
C(19)–C(20)
N(1)–C(7)
N(2)–C(21)
N(1)–C(8)
N(2)–C(22)
C(4)–C(5)
C(18)–C(19)
1.544(7)
1.545(7)
1.466(8)
1.486(8)
1.406(7)
1.411(8)
1.452(7)
1.450(7)
1038(s), 819(vs), 691(w) cmꢀ1
.
3.2.1.2. [Fe{(g5-C5H4)–CH@N–C6H4CH3-4}2] (1b).
Dark-red solid. M.p. 98–100 ꢁC; Yield 81%. Anal. Calc. for
C26H24FeN2: C, 74.29; H, 5.76; N, 6.66. Found: C, 74.07;
1
H, 5.73; N, 6.64%. H NMR (CDCl3) d: 1.99(s, 6H, Ar–
C(6)–C(7)
CH3), 4.07(s, 4H, H3, H30), 4.18(s, 4H, H2, H20), 6.85(q,
8H, PhH), 8.01(s, 2H, H4, H40) ppm. IR(KBr) m:
3077(w), 3021(w), 2919(w), 2860(w), 1623(vs), 1596(s),
1506(s), 1467(m), 1367(w), 1217(m), 1187(w), 1039(m),
Bond angles
(ꢁ)
Bond angles
(ꢁ)
C(4)–C(5)–C(11)
C(7)–C(6)–C(25)
C(5)–C(11)–C(12)
C(6)–C(25)–C(26)
N(1)–C(11)–C(12)
N(2)–C(25)–C(26)
124.8(2)
125.6(2)
117.0(2)
116.8(2)
125.7(2)
125.1(2)
C(4)–C(5)–C(6)
C(18)–C(19)–C(20)
N(1)–C(6)–C(5)
N(2)–C(20)–C(19)
C(7)–N(1)–C(6)
C(21)–N(2)–C(20)
125.6(5)
124.9(5)
114.0(4)
113.9(4)
115.4(5)
114.8(5)
819(s), 778(m) cmꢀ1
.
3.2.1.3. [Fe{(g5-C5H4)–CH@N–C6H4Cl-3}2] (1d). Dark-
red solid. M.p. 80–82 ꢁC; Yield 83%. Anal. Calc. for
C24H18Cl2FeN2: C, 62.51; H, 3.93; N, 6.07. Found: C,
1
62.43; H, 3.91; N, 6.06%. H NMR (CDCl3) d: 4.08(s,
melting point apparatus and were uncorrected. Elemental
analyses were obtained from a Carlo Erba 1106 Elemental
4H, H3,H30), 4.21(s, 4H, H2, H20), 6.88(m, 8H, phH),
8.02(s, 2H, H4, H40) ppm. IR(KBr) m: 3083(w), 2937(w),
2891(w), 2811(w), 1625(s), 1596(vs), 1498(s), 1361(m),
1
analyzer. H NMR spectra were measured with a Bruker
AV-400 spectrometer by using CDCl3 as a solvent and
TMS as internal standard. IR spectra were taken on a
BIO-RAD 3000 spectrophotometer.
1251(m), 1094(m), 985(s), 920(w), 761(s), 682(m) cmꢀ1
.
3.2.2. Preparation of 4a–b, 4d from 1a–b, 1d
General procedure: the synthetic procedure for 4a–b, 4d
3.2. Preparation of 7a, 7b, 7d from diformylferrocene (I)
was the same as described previously [7].
3.2.1. Preparation of dialdimines 1a–b, 1d from I
General procedure: the synthetic procedure for 1a–b, 1d
was the same as described previously [7].
3.2.2.1. [Fe{(g5-C5H4)–CH2NH–C6H4OCH3-4}2] (4a).
Yellow liquid. Yield 90%. Anal. Calc. for C26H28FeN2O2:
C, 68.43; H, 6.18; N, 6.14. Found: C, 68.19; H, 6.16; N,
6.13%. IR(KBr) m: 3386(m), 3076(w), 2992(w), 2933(w)
2830(m), 1616(w), 1518(s), 1463(s), 1241(s), 1179(s),
1163(m), 1035(s), 818(vs), 692(w) cmꢀ1. 1H NMR (CDCl3)
3.2.1.1. [Fe{(g5-C5H4)–CH@N–C6H4OCH3-4}2] (1a).
Dark-red solid. M.p. 134–136 ꢁC; Yield 85%. Anal. Calc.
for C26H24FeN2O2: C, 69.04; H, 5.35; N, 6.19. Found: C,

H.-X. Wang et al. / Polyhedron 26 (2007) 1037–1044
1041
d: 3.75(s, 6H, OCH3), 4.01(s, 4H, H2, H20), 4.11(s, 4H, H3,
3.3. Preparation of 8a–c, 8e from diacetylferrocene (II)
H30), 4.24(s, 4H, H4, H40), 6.77(q, 8H, PhH) ppm.
3.3.1. Preparation of diketimines 2a–c, 2e from II
General procedure: to the stirred mixtures of diacetylfer-
rocene in toluene and titanium tetrachloride (3% mol),
were added 4 equivalents of anilines. The mixtures were
refluxed for 6–8 h under argon. After the reactions com-
pleted, the mixtures were washed with water three times
(3 · 100 ml). The organic phase was dried over anhydrous
sodium sulfate and filtered. The solvent was removed under
reduced pressure, and the residues were purified by flash
chromatography (silica gel, ethyl acetate/hexane = 1:5) to
give 2a–c, 2e.
3.2.2.2. [Fe{(g5-C5H4)–CH2NH–C6H4CH3-4}2] (4b).
Yellow solid. Yield 89%; m.p. 70–72 ꢁC. Anal. Calc. for
C26H28FeN2: C, 73.59; H, 6.65; N, 6.60. Found: C,
73.41; H, 6.62; N, 6.59%. IR(KBr) m: 3401(m), 3089(w),
2912(w), 2857(w), 1613(m), 1517(vs), 1461(w), 1315(m),
1246(m), 1183(w), 1032(w), 805(s) cmꢀ1
.
1H NMR
(CDCl3) d: 2.26(s, 6H, Ar–CH3), 3.96(s, 4H, H4, H40),
4.16(s, 4H, H2, H20), 4.24(s, 4H, H3, H30), 6.80 (q,
8H, PhH) ppm.
3.2.2.3. [Fe{(g5-C5H4)–CH2NH–C6H4Cl-3}2] (4d). Yel-
low solid. Yield 85%; m.p. 46–48 ꢁC. Anal. Calc. for
C24H22Cl2FeN2: C, 61.96; H, 4.77; N, 6.02. Found: C,
61.78; H, 4.71; N, 6.00%. IR(KBr) m: 3421(m), 3088(w),
2939(w), 2893(w), 2811(w), 1594(vs), 1557(m), 1495(s),
1362(m), 1251(m), 1098(m), 987(s) 920(w), 831(m), 760(s),
3.3.1.1. [Fe{(g5-C5H4)–C(CH3)@N–C6H4OCH3-4}2](2a).
Dark-red solid. Yield 65%; m.p. 182–184 ꢁC (dec.) (lit. [18],
>184 ꢁC). IR(KBr) m: 3097(w), 2963(w), 2856(w), 1622(vs),
1504(vs), 1465(m), 1361(m), 1236(vs), 1197(m), 1032(m),
850(m), 833(m) cmꢀ1
.
1
681(m) cmꢀ1. H NMR (CDCl3) d: 4.10(s, 4H, H2, H20),
3.3.1.2. [Fe{(g5-C5H4)–C(CH3)@N–C6H4 CH3-4}2] (2b).
Dark-red solid. Yield 65%; m.p. 144–146ꢁC (lit. [18], 147–
147.5 ꢁC). IR(KBr) m: 3015(w), 2965(w), 2857(w),
1624(vs), 1504(m), 1460(m), 1287(m), 1117(m), 1036(w),
4.14(s, 4H, H3, H30), 4.25(s, 4H, H4, H40), 6.62–7.15(m,
8H, PhH) ppm.
3.2.3. Preparation of 7a–b, 7d from 4–b, 4d
General procedure: the synthetic procedure for 7a–b, 7d
was the same as described previously [7].
809(s) cmꢀ1
.
3.3.1.3. [Fe{(g5-C5H4)–C(CH3)@N–C6H5}2] (2c). Dark-
red solid. Yield 62%; m.p. 138–140 ꢁC (lit. [18], 141.5–
142.5 ꢁC). IR(KBr) m: 3021(w), 2968(w), 2858(w),
1623(vs), 1502(m), 1458(m), 1285(m), 1117(m), 1035(w),
3.2.3.1. [Fe{(g5-C5H4)–CH2N(CH3)–C6H4OCH3-4}2] (7a).
Yellow solid. Yield 85%; m.p. 78–80 ꢁC. Anal. Calc. for
C28H32FeN2O2: C, 69.42; H, 6.66; N, 5.78. Found: C,
69.31; H, 6.60; N, 5.77%. IR(KBr) m: 2980(w), 2939(w),
2893(w), 1509(s), 1456(w), 1332(w), 1243(vs), 1183(m),
809(s) cmꢀ1
.
3.3.1.4. [Fe{(g5-C5H4)–C(CH3)@N–C6H4Cl-4}2] (2e).
Dark-red solid. Yield 58%, m.p. 183–185 ꢁC (lit. [18],
184.5–185.5 ꢁC). IR(KBr) m: 3023(m), 2969(w), 2861(w),
1623(s), 1494(vs), 1454(w), 1278(m), 1234(w), 1091(m),
1
1039(m), 917(w), 810(s), 697(m) cmꢀ1. H NMR (CDCl3) d:
2.73(s, 6H, H7, H70), 3.76(s, 6H, OCH3), 4.04(s, 4H, H2,
H20), 4.06(s, 4H, H3, H30), 4.15(s, 4H, H4, H40), 6.79(q,
8H, PhH) ppm.
825(m) cmꢀ1
.
3.2.3.2. [Fe{(g5-C5H4)–CH2N(CH3)–C6H4CH3-4}2] (7b).
Yellow solid. Yield 78%; m.p. 84–86 ꢁC. Anal. Calc. for
C28H32FeN2: C, 74.33; H, 7.13; N, 6.19. Found: C, 74.17;
H, 7.12; N, 6.18%. IR(KBr) m: 3067(w), 3009(w), 2911(w),
2853(w), 1619(m), 1522(s), 1373(m), 1332(m), 1253(m),
3.3.2. Preparation of 5a–c, 5e from 2a–c, 2e
General procedure: to the stirred solutions of 2a–c and
2e (10 mmol) in anhydrous THF (50 ml) was added alumi-
num chloride (3% mmol) and the resulted mixtures were
continuously stirred for 30 min at room temperature. Then
20 mmol of lithium aluminum hydride was added in one
portion and the mixtures were refluxed for 1 h under argon.
The solvent was evaporated under reduced pressure to dry-
ness, dichloromethane (120 ml) was then added and stirred
for 1 h. The extraction phase was dried over sodium sulfate
and filtered. Removal of solvent yielded residues which
were purified by column chromatography (silica gel, ethyl
acetate/hexane = 1:3) to yield 5a–c, 5e.
1
1189(m), 1101(w), 830(m), 802(s) cmꢀ1. H NMR (CDCl3)
d: 2.25(s, 6H, Ar–CH3), 2.80(s, 6H, H7, H70), 4.05(s, 4H,
H2, H20), 4.09(s, 4H, H3, H30), 4.22(s, 4H, H4, H40),
6.72(q, 8H, PhH) ppm.
3.2.3.3. [Fe{(g5-C5H4)–CH2N(CH3)–C6H4Cl-3}2] (7d).
Yellow liquid. Yield 72%. Anal. Calc. for C26H26Cl2FeN2:
C, 63.31; H, 5.31; N, 5.68. Found: C, 63.11; H, 5.29; N,
5.64%. IR (KBr) m: 3078(w), 2924(w), 2888(w), 1593(s),
1558(s), 1491(s), 1355(m), 1230(m), 1099(s), 986(s),
3.3.2.1. [Fe{(g5-C5H4)–CH(CH3)NH–C6H4OCH3-4}2](5a).
Yellow liquid. Yield 86%. Anal. Calc. for C28H32FeN2O2:
C, 69.42; H, 6.66; N, 5.78. Found: C, 69.31; H, 6.65; N,
5.78 %. IR(KBr) m: 3380(w), 3088(w), 2970(m), 2929(m),
2832(m), 1510(vs), 1469(m), 1408(w), 1232(s), 1182(m),
827(m), 756(m), 684(m) cmꢀ1 1H NMR (CDCl3) d:
.
2.89(s, 3H, H7), 2.96(s, 3H, H7, H70), 4.13(s, 4H, H2,
H20), 4.18(s, 4H, H3, H30), 4.28(s, 4H, H4, H40), 6.67-
7.19(m, 8H, PhH) ppm.

1042
H.-X. Wang et al. / Polyhedron 26 (2007) 1037–1044
1126(m), 1037(s), 819(s) cmꢀ1. 1H NMR (CDCl3) d: 1.43(d,
6H, H5, H50), 3.75(s, 6H, OCH3), 3.11(m, 2H, H4, H40),
3.88(s, 2H, NH), 4.04(s, 4H, H2, H20), 4.16(s, 4H, H3,
H30), 6.71(q, 8H, PhH) ppm.
4H, H3, H30), 4.93(m, 2H, H4, H40), 6.88(q, 8H, PhH)
ppm.
3.3.3.3. [Fe{(g5-C5H4)–CH(CH3)N(CH3)–C6H5}2] (8c).
Yellow liquid. Yield 56%. Anal. Calc. for C28H32FeN2: C,
74.33; H, 7.13; N, 6.19. Found: C, 74.19; H, 7.10; N,
6.17%. IR (KBr) m: 3032(w), 2975(w), 2924(w), 2873(w),
1601(vs), 1507(vs), 1439(m), 1346(s), 1224(m), 1188(m),
3.3.2.2. [Fe{(g5-C5H4)–CH(CH3)NH–C6H4CH3-4}2] (5b).
Yellow liquid. Yield 80%. Anal. Calc. for C28H32FeN2: C,
74.33; H, 7.13; N, 6.19. Found: C, 74.19; H, 7.12; N,
6.16%. IR(KBr) m: 3404(m), 3094(w), 3023(w), 2961(m),
2913(m), 1616(s), 1517(vs), 1449(m), 1298(m), 1241(m),
1
988(m), 750(s), 691(s) cmꢀ1. H NMR (CDCl3) d: 1.50(s,
6H, H5, H50), 2.51(s, 6H, H7, H70), 4.05(s, 4H, H2, H20),
4.11(s, 4H, H3, H30), 5.10(m, 2H, H4, H40), 6.95–7.21(m,
10H, PhH) ppm.
1134(m), 1024(w), 807(s) cmꢀ1 1H NMR (CDCl3) d:
.
1.44(d, 6H, H5, H50), 2.23(s, 6H, Ar–CH3), 3.15(m, 2H,
H4, H40), 3.89(s, 2H, NH), 4.06(s, 4H, H2, H20), 4.20(s,
4H, H3, H30), 6.90(q, 8H, PhH) ppm.
3.3.3.4. [Fe{(g5-C5H4)–CH(CH3)N(CH3)–C6H4Cl-4}2]
(8e). Yellow solid. Yield 53%; m.p. 78–80 ꢁC. Anal. Calc.
for C28H30Cl2FeN2: C, 64.51; H, 5.80; N, 5.37. Found:
C, 64.44; H, 5.80; N, 5.36%. IR (KBr) m:3035(w),
2978(w), 2920(w), 2873(w), 1598(s), 1505(s), 1437(m),
3.3.2.3. [Fe{(g5-C5H4)–CH(CH3)NH–C6H5}2] (5c). Yel-
low liquid. Yield 50%. Anal. Calc. for C26H28FeN2: C,
73.59; H, 6.65; N, 6.60. Found: C, 73.40; H, 6.62; N,
6.58%. IR (KBr) m: 3405(m), 3083(w), 3047(w), 2970(m),
2924(w), 2863(w), 1601(vs), 1502(vs), 1424(m), 1367(m),
1346(s), 1185(m), 986(m), 820(s), 691(s)cmꢀ1 1H NMR
.
(CDCl3) d: 1.47(d, 6H, H5, H50), 2.49 (s, 6H, H7, H70),
4.06(s, 4H, H2, H20), 4.19(s, 4H, H3, H30), 5.11(s, 2H,
H4, H40), 6.95(q, 8H, PhH) ppm.
1313(s), 1249(m), 1129(m), 1029(m), 748(s), 691(s) cmꢀ1
.
1H NMR (CDCl3) d: 1.45(s, 6H, H5, H50), 3.21(m, 2H,
H4, H40), 3.90(s, 2H, NH), 4.05(s, 4H, H2, H20), 4.13(s,
4H, H3, H30), 6.92(m, 10H, PhH) ppm.
3.4. Preparation of 6f–g from dibenzoylferrocene (III)
3.3.2.4. [Fe{(g5-C5H4)–CH(CH3)NH–C6H4Cl-4}2] (5e).
Yellow liquid. Yield 89%. Anal. Calc. for C26H26Cl2FeN2:
C, 63.31; H, 5.31; N, 5.68. Found: C, 63.17; H, 5.29; N,
5.66%. IR (KBr) m: 3411(m), 3083(w), 2965(m), 2924(w),
2868(w), 1598(s), 1497(s), 1393(m), 1315(m), 1239(m),
3.4.1. Preparation of diketimines 3f–g from III
General procedure: the synthetic procedure for 3f–g was
the same as that for 2.
3.4.1.1. [Fe{(g5-C5H4)–C(C6H5)@N–CH2C6H4CH3-4}2]
(3f). Dark-red solid. M.p.101–103 ꢁC; Yield 78%. Anal.
Calc. for C40H36FeN2: C, 80.00; H, 6.04; N, 4.66. Found:
C, 79.89; H, 6.03; N, 4.65%. IR (KBr) m: 3028(w),
2916(m). 2862(w), 1622(vs), 1503(m), 1458(m), 1285(m),
1115(m), 1034(w), 810(s). 1H NMR (CDCl3) d: 2.01(s,
6H, Ar–CH3), 3.67(q, 4H, H6, H60), 3.93(s, 4H, H3,
H30), 4.16(s, 4H, H2, H20), 6.71(q, 8H, PhH), 7.03(m,
10H, PhH) ppm.
1168(m), 1093(m), 814(s) cmꢀ1 1H NMR (CDCl3) d:
.
1.46(d, 6H, H5, H50), 3.10(q, 2H, H4, H40), 3.91(s, 2H,
NH), 4.08(s, 4H, H2, H20), 4.19(s, 4H, H3, H30), 7.03(q,
8H, ArH) ppm.
3.3.3. Preparation of 8a–c, 8e from 5a–c, 5e
General procedure: the synthetic procedure for 8a–c, 8e
was the same as described previously [7].
3.3.3.1. [Fe{(g5-C5H4)–CH(CH3)N(CH3)–C6H4OCH3-
4}2] (8a). Yellow solid. Yield 58%; m.p. 58–60 ꢁC. Anal.
Calc. for C30H36FeN2O2: C, 70.31; H, 7.08; N, 5.47.
Found: C, 70.18; H, 7.06; N, 5.45%. IR(KBr) m: 3083(w),
2964(m), 2925(m), 2831(m), 1514(vs), 1441(m), 1246(s),
3.4.1.2. [Fe{(g5-C5H4)–C(C6H5)@N–CH2C6H5}2] (3g).
Red-dark solid. M.p. 99–101 ꢁC; Yield 69%. Anal. Calc.
for C38H32FeN2: C, 79.72; H, 5.63; N, 4.89. Found: C,
79.67; H, 5.62; N, 4.89%. IR (KBr) m: 3024(w), 2918(w),
2858(w), 1623(vs), 1501(m), 1458(m), 1283(m), 1116(m),
1033(w), 821(m), 690(m). 1H NMR (CDCl3) d: 3.65(q,
4H, H6, H60), 3.91(s, 4H, H3, H30), 4.14(s, 4H, H2, H20),
7.01 (m, 20H, PhH) ppm.
1
1181(m), 1039(s), 817(s), 683(m) cmꢀ1. H NMR (CDCl3)
d: 1.42(d, 6H, H5, H50), 2.42(s, 6H, H7, H70), 3.78(s, 6H,
OCH3), 4.05(s, 4H, H2, H20), 4.17(s, 4H, H3, H30),
4.89(m, 2H, H4, H40), 6.78(q, 8H, PhH) ppm.
3.4.2. Preparation of 6f–g from 3f–g
The synthetic procedure for 6f–g was the same as that
for 5.
3.3.3.2. [Fe{(g5-C5H4)–CH(CH3)N(CH3)–C6H4CH3-4}2]
(8b). Yellow solid. Yield 55%; m.p. 46–48 ꢁC. Anal. Calc.
for C30H36FeN2: C, 74.99; H, 7.55; N, 5.83. Found: C,
74.88; H, 7.52; N, 5.82%. IR(KBr) m: 3093(w), 2975(m),
2922(m), 2852(m), 2801(m), 1617(s), 1519(vs), 1444(w),
3.4.2.1. [Fe{(g5-C5H4)–CH(C6H5)NH–CH2C6H4CH3-4}2]
(6f). Yellow liquid. Yield 76%. Anal. Calc. for
C40H40FeN2: C, 79.46; H, 6.67; N, 4.63. Found: C, 79.28;
H, 6.64; N, 4.62%. IR (KBr) m: 3394(m), 3083(w),
2917(w), 2859(w), 1515(vs), 1458(w), 1314(m), 1245(m),
1342(m), 1296(m), 1229(m), 1106(m), 804(s) cmꢀ1 1H
.
NMR (CDCl3) d: 1.45(d, 6H, H5, H50), 2.26(s, 6H, Ar–
CH3), 2.44(s, 6H, H7, H7’), 4.07(s, 4H, H2, H20), 4.18(s,

H.-X. Wang et al. / Polyhedron 26 (2007) 1037–1044
1043
1181(w), 1034(w), 806(s) cmꢀ1. 1H NMR (CDCl3) d: 2.15(s,
References
6H, Ar–CH3), 2.30(m, 2H, NH), 3.49(m, 4H, H6, H60),
3.90(s, 4H, H2, H20), 4.13(s, 4H, H3, H30), 4.37(s, 2H,
H4, H40), 6.66(q, 8H, PhH), 6.98(m, 10H, PhH) ppm.
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Yellow liquid. Yield 70%. Anal. Calc. for C38H36FeN2: C,
79.16; H, 6.29; N, 4.86. Found: C, 79.01; H, 6.25; N,
4.83%. IR (KBr) m: 3401(m), 3085(w), 3044(w), 2979(m),
2922(w), 2861(w), 1601(vs), 1500(vs), 1434(m), 1365(m),
1311(s), 1245(m), 1130(m), 1029(m), 748(s), 692(s) cmꢀ1.1H
NMR (CDCl3) d: 2.28(m, 2H, NH), 3.52(q, 4H, H6, H60),
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mixture of ethyl acetate and hexane at room temperature
over a period of 1 week. The single crystals of 3g and 7a
were mounted on a Bruker SMART CCD diffractometer
equipped with graphite-monochromated Mo Ka radiation
˚
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25.02ꢁ (7a) for data collection. Semi-empirical absorption
corrections were applied using the SABABS program [19].
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by the full-matrix least-squares procedure on F2 using the
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2
1=½r2ðF 2oÞ þ ð0:0376PÞ þ 0:2035Pꢂ where P ¼ ðF o2 þ 2F 2cÞ=
2
3 for 3g, w ¼ 1=½r2ðF o2Þ þ ð0:0587PÞ þ 2:9596Pꢂ where
P ¼ ðF 2o þ 2F 2cÞ=3 for 7a. Crystallographic data for 3g
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Supplementary material
CCDC 614253 and 613898 contain the supplementary
crystallographic data for 3g and 7a. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk.
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Acknowledgements
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We are grateful to the Natural Scientific Foundation of
Tianjin Metropolitan Council (Project No. 033609011),
People’s Republic of China and the Opening Fund from
the State Key Laboratory of Elemento-organic Chemistry,
Nankai University, People’s Republic of China for their
generous support for this project.
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