Syntheses and crystal structures of ferrocene-containing enaminones and their copper complexes

Article abstract of DOI:10.1016/j.poly.2003.08.017

Six ferrocene-containing enaminones [C₅H₅FeC ₅H₄C(O)CH=C-(NHAr)R] (HL¹, R=CH₃, Ar=C₆H₅; HL², R=CH₃, Ar=2-CH ₃C₆H₄

Full text of DOI:10.1016/j.poly.2003.08.017

Polyhedron 23 (2004) 15–21
www.elsevier.com/locate/poly
Syntheses and crystal structures of ferrocene-containing
enaminones and their copper complexes
a,
a
b
a
a
Yao-Cheng Shi *, Hua-Mei Yang , Wen-Bin Shen , Chao-Guo Yan , Xiao-Ya Hu
a
School of Chemistry, Yangzhou University, Yangzhou 225002, PR China
b
Analytical Center, China Pharmaceutical University, Nanjin 210009, PR China
Received 2 July 2003; accepted 29 August 2003
Abstract
Six ferrocene-containing enaminones [C5H5FeC5H4C(O)CH ¼ C–(NHAr)R] (HL1, R ¼ CH3, Ar ¼ C6H5; HL2, R ¼ CH3,
Ar ¼ 2-CH3C6H4; HL3, R ¼ CH3, Ar ¼ 2,6-(CH3)2C6H3; HL4, R ¼ C6H5, Ar ¼ C6H5; HL5, R ¼ C6H5, Ar ¼ 2-CH3C6H4; HL6,
R ¼ C6H5, Ar ¼ 2,6-(CH3)2C6H3) and their copper(II) complexes (I, L12Cuꢀ2H2O; II, L22Cu; III, L23Cu; IV, L42Cuꢀ2H2O; V,
L52Cuꢀ2H2O) have been synthesized and characterized by elemental analyses, 1HNMR, IR and UV spectroscopies. Their structures
have been determined by the X-ray crystallography of enaminone HL6 and complex I.
Ó 2003 Elsevier Ltd. All rights reserved.
Keywords: Ferrocene; Enaminone; Ligand; Copper; Complex; X-ray crystallography
1. Introduction
nones has appeared, and herein we report the syntheses
and structures of the ferrocenyl enaminones and their
copper complexes.
In the last few decades enaminones and enamine-
carbaldehydes have been widely investigated because of
their applications in the synthesis of heterocyclic com-
pounds [1] and plentiful reaction chemistry [2] and co-
ordination chemistry [3]. Therefore, enaminones of the
type [R0C(O)CHC(NHAr)R] constitute an important
class. Recently non-metallocene complexes of Group IV
metals have attracted much interest as possible
alternatives for olefin polymerization catalysts using N4-
macrocycles, porphrins, tripodal amides, mixed cyclo-
pentadienyl-amides and Schiff0 bases as spectator ligands
[5–7]. Because the anions [R C(O)CHC(NAr)R]ꢁ gen-
erated from the above enaminones offer potential iso-
electronic alternatives to the cyclopentadienyl-based
anion and can be used as good chelating ligands for
copper complexes that exhibit catalytic activity [3,8],
organometallic enaminones of the new type [C5H5FeC5
H4C(O)CH ¼ C(NHAr)R] have been studied. To our
knowledge, so far no article on organometallic enami-
2. Experimental
2.1. Reagents and general procedures
All chemicals used were of reagent grade. Toluene
and THF were distilled from Na/benzophenone under
dinitrogen atmosphere. Absolute ethanol for sodium
ethoxide was distilled from Na/diethyl phthalate. DMF,
ethyl acetate and ethyl benzoate were redistilled before
use. Other commerial chemicals were used without fur-
ther purification. Acetylferrocene was synthesized from
ferrocene according to the literature method [9]. Pro-
gress of the reactions was monitored by TLC. 1H NMR
spectra were determined with a Bruker Avance 500
spectrometer using TMS as external standard in CDCl3.
IR spectra were recorded on a Perkin–Elmer 402 as KBr
disks in the range of 400–4000 cmꢁ1. UV spectra were
measured with a Shimadzu UV-240 spectrometer using a
solution in DMF. Analyses for C, H and N were per-
formed on an Elementa Vario EL III instrument.
* Corresponding author. Tel.: +86-514-7857939; fax: +86-514-
7857939.
E-mail address: yzssyc@yzcn.net (Y.-C. Shi).
0277-5387/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2003.08.017

16
Y.-C. Shi et al. / Polyhedron 23 (2004) 15–21
Melting points were measured on a Yanagimoto appa-
ratus and were uncorrected.
(0.9) (B-band), 333 (1.2) (K-band). 1H NMR (CDCl3): d
1.99 (s, 3H, CH3), 2.33 (s, 3H, CH3), 4.21 (s, 5H, C5H5),
4.41 (s, 2H, 2 (H3, H4) of C5H4 ring), 4.79 (s, 2H, 2 (H2,
H5) of C5H4 ring), 5.54 (s, 1H, CH), 7.12–7.27 (m, 4H,
C6H4), 12.44 (s, 1H, NH).
2.2. Syntheses of enaminones
2.2.1. Syntheses of b-diketones 1 and 2
[C5H5FeC5H4C(O)CH ¼ C(NHAr)CH3] (Ar ¼ 2,6-
(CH3)2C6H3, HL3). The similar reaction of 2,6-dime-
thylaniline (2.42 g, 20 mmol) and b-diketone 1 (10 mmol)
afforded 2.99 g (80%) of HL3 as a red crystalline solid.
M.p. 114–116 °C. Anal. Found: C, 70.81; H, 6.04; N,
3.27. Calc. for C22H23FeNO: C, 70.79; H, 6.21; N, 3.75%.
IR (KBr disk): m(NH) 3079 (w), m(C ¼ O) 1603 (vs),
Modified literature syntheses were used [10,11]. A
solution of sodium ethoxide (8.85 g, 130 mmol), acetyl-
ferrocene (16.42 g, 72 mmol) and ethyl acetate (11.45 g,
130 mmol) in 60 ml of THF was refluxed under nitrogen
for 2 h. The yellow solid was filtered, washed with THF
and acidified with aqueous acetic acid to give the b-di-
ketone 1 (16.14 g, 83%) as a red solid. M.p. 97 °C (lit: 97–
97.5 °C) [10]. UV (nm, in DMF): kmaxðe ꢂ 104) 261
(1.02), 308 (1.12).
The similar reaction of sodium ethoxide (4.08 g, 60
mmol), acetylferrocene (7.98 g, 35 mmol) and ethyl
benzoate (5.56 g, 37 mmol) in 60 ml of THF for 2 h after
the above-mentioned workup and extraction with
CH2Cl2 (three times, each 20 ml) gave the combined
organic layer. The mixture was dried with anhydrous
CaCl2 and then the solvent of the filtrate was removed
to give a purple–red oil, which was separated with the
eluant (CH2Cl2: petroleum ether, 2:1) by vacuum liquid
chromatography (VLC). A main band was collected to
afford the b-diketone 2 (5.81 g, 50%) as a purple–red
solid. M.p. 106 °C (lit: 106–107 °C) [11]. UV (nm, in
DMF): kmax(e ꢂ 104) 268 (0.85), 332 (0.64), 360 (0.65).
m(C ¼ C) 1553 (vs) cmꢁ1
. UV (nm, in DMF):
k
max(e ꢂ 104) 265 (1.51) (B-band), 330 (1.36) (K-band).
1H NMR (CDCl3): d 1.73 (s, 3H, CH3), 2.26 (s, 6H,
2CH3 of benzene ring), 4.21 (s, 5H, C5H5), 4.41 (s, 2H, 2
(H3, H4) of C5H4 ring), 4.82 (s, 2H, 2 (H2, H5) of C5H4
ring), 5.57 (s, 1H, CH), 7.10–7.15 (m, 3H, C6H3), 12.03
(s, 1H, NH).
[C5H5FeC5H4C(O)CH ¼ C(NHAr)C6H5] (Ar ¼ C6H5,
HL4). The similar reaction of aniline (0.93g, 10 mmol)
and b-diketone 2 [C5H5FeC5H4C(O)CH2C(O) C6H5]
(1.66 g, 5 mmol) afforded 1.71 g (84%) of HL4 as a deep
red crystalline solid. M.p. 118–120 °C. Anal. Found: C,
73.29; H, 5.00; N, 3.02. Calc. for C25H21 FeNO: C, 73.72;
H, 5.20; N, 3.44%. IR (KBr disk): m(NH) 3087 (s),
m(C ¼ O) 1589 (vs), m(C ¼ C) 1567 (vs) cmꢁ1. UV (nm, in
DMF): kmaxðe ꢂ 104) 369 (1.06) (K-band). 1H NMR
(CDCl3): d 4.25 (s, 5H, C5H5), 4.57 (s, 2H, 2 (H3, H4) of
C5H4 ring), 4.87 (s, 2H, 2 (H2, H5) of C5H4 ring), 5.77 (s,
1H, CH), 6.75–7.13 (3m, 5H, NC6H5), 7.27–7.44 (m, 5H,
C6H5), 12.43 (s, 1H, NH).
2.2.2. Syntheses of enaminones
[C5H5FeC5H4C(O)CH ¼ C(NHAr)CH3] (Ar ¼ C6H5,
HL1). Aniline (1.86 g, 20 mmol) was added to a solution
of b-diketone 1 [C5H5FeC5H4C(O)CH2C(O) CH3] (2.7
g, 10 mmol) and a catalytic trace amount of p-TsOH
(ꢃ10 mg) in 20 ml of toluene, and then the mixture was
refluxed with a Dean-Stark apparatus to remove water
for 2 h. The solvent was evaporated under vacuum, and
the residue was recrystallized from petroleum ether (60–
90 °C) to afford 2.76 g (80%) of HL1 as a red crystalline
solid. M.p. 120–121 °C. Anal. Found: C, 69.60; H, 5.52;
N, 3.72. Calc. for C20H19NFeO: C, 69.58; H, 5.55; N,
4.06%. IR (KBr disk): m(NH) 3084 (s), m(C ¼ O) and
m(C ¼ C) 1582 (vs, br) cmꢁ1. UV (nm, in DMF):
[C5H5FeC5H4C(O)CH ¼ C(NHAr)C6H5] (Ar ¼ 2-
CH3C6H4, HL5). The similar reaction of 2-methylani-
line (1.07 g, 10 mmol) and b-diketone 2 (5 mmol) af-
forded 1.71 g (81%) of HL5 as a light red crystalline
solid. M.p. 138–140 °C. Anal. Found: C, 73.98; H, 5.22;
N, 2.88. Calc. for C26H23FeNO: C, 74.12; H, 5.50; N,
3.32%. IR (KBr disk): m(NH) 3082 (s), m(C ¼ O) 1591
(vs), m(C ¼ C) 1567 (vs) cmꢁ1. UV (nm, in DMF):
k
max(e ꢂ 104) 274 (1.32) (B-band), 369 (1.03) (K-band).
1H NMR (CDCl3): d 2.48 (s, 3H, CH3), 4.27 (s, 5H,
C5H5), 4.50 (s, 2H, 2 (H3, H4) of C5H4 ring), 4.90 (s, 2H,
2 (H2, H5) of C5H4 ring), 5.70 (s, 1H, CH), 6.40–7.50
(4m, 9H, (C6H4, C6H5)), 12.26 (s, 1H, NH).
k
max(e ꢂ 104) 259 (8.7), 275 (1.5) (B-band); 328 (1.9)
1
(K-band). H NMR (CDCl3): d 2.15 (s, 3H, CH3), 4.24
(s, 5H, C5H5), 4.58 (s, 2H, 2 (H3, H4) of C5H4 ring), 4.83
(s, 2H, 2 (H2, H5) of C5H4 ring), 5.54 (s, 1H, CH), 7.10–
7.37 (m, 5H, C6H5), 12.64 (s, 1H, NH).
[C5H5FeC5H4C(O)CH ¼ C(NHAr)C6H5] (Ar ¼ 2,6-
(CH3)2C6H3, HL6). The similar reaction of 2,6-dime-
thylaniline (1.21 g, 10 mmol) and b-diketone 2 (5 mmol)
was refluxed for four days. After removal of the solvent,
the deep-red oil obtained was chromatographed on a
silica gel column with CH2Cl2and petroleum ether (3:1).
The second band was collected and further recrystallized
from petroleum ether (60–90 °C) afforded 1.31 g (46%)
of HL6 as a deep red crystalline solid. M.p. 153–154 °C.
Anal. Found: C, 74.89; H, 5.67; N, 2.79. Calc. for
C27H25FeNO: C, 74.49; H, 5.79; N, 3.22%. IR (KBr
[C5H5FeC5H4C(O)CH ¼ C(NHAr)CH3] (Ar ¼ 2-CH3
C6H4, HL2). The similar reaction of 2-methylaniline
(2.14 g, 20 mmol) and b-diketone 1 (10 mmol) afforded
2.83 g (80%) of HL2 as a red crystalline solid. M.p. 96–97
°C. Anal. Found: C, 70.24; H, 5.70; N, 3.85. Calc. for
C21H21FeNO: C, 70.21; H, 5.89; N, 3.90%. IR (KBr
disk): m(NH) 3080 (s), m(C ¼ O) 1601 (vs), m(C ¼ C)
1554 (vs) cmꢁ1. UV (nm, in DMF): kmax(e ꢂ 104) 274

Y.-C. Shi et al. / Polyhedron 23 (2004) 15–21
17
disk): m(NH) 3080 (w), m(C ¼ O) 1586 (vs), m(C ¼ C) 1567
(vs) cmꢁ1. UV (nm, in DMF): kmax(e ꢂ 104) 365 (1.45)
(K-band). 1H NMR (CDCl3): d 2.21 (s, 6H, 2CH3), 4.24
(s, 5H, C5H5), 4.46 (s, 2H, 2 (H3, H4) of C5H4 ring), 4.87
(s, 2H, 2 (H2, H5) of C5H4 ring), 5.70 (s, 1H, CH), 6.93–
7.33 (2m, 8H, (C6H3, C6H5)), 12.22 (s, 1H, NH).
and ethanol. X-ray data of both compounds were
measured on an Enraf–Nonius CAD4 diffractometer
using graphite-monochromated Mo Ka radiation
ꢀ
(k ¼ 0:71073 A) at 293 K. The structures were solved by
direct methods and refined by full-matrix least-squares
methods based on F2 with anisotropic thermal param-
eters for all non-hydrogen atoms [12]. A summary of the
data collection and structure refinement parameters is
2.3. Syntheses of copper complexes
ꢀ
given in Table 1. Selected bond distances (A) and angles
A solution of 1 mmol of the appropriate ligand (ex-
cept enaminone HL6) in absolute ethanol (10 ml) was
added dropwise to a stirred solution of 0.5 mmol of
hydrated copper acetate in the same solvent (10 ml). The
mixture was stirred for 24 h at room temperature and
then filtered to afford the crude product. The resulting
solid was recrystallized from CH2Cl2 and petroleum
ether to give the corresponding complex.
(°) are listed in Tables 2 (enaminone HL6) and 3 (com-
plex I).
3. Results and discussion
3.1. Syntheses of enaminones and their complexes
Complex I as a black solid, yield: 0.335 g (85%). M.p.
201–202 °C (dry sample). Anal. Found: C, 60.82; H,
4.71; N, 3.14. Calc. for C40H40N2O4Fe2Cu: C, 60.97; H,
5.12; N, 3.55%. IR (KBr disk): m(OH) 3436 (m, br),
m(C ¼ O) 1562 (s), m(C ¼ C) 1513 (vs) cmꢁ1. UV (nm, in
DMF): kmax(e ꢂ 104) 275 (2.5), 358 (3.4) (K-band), 450
(0.49) (CT-band).
Complex II as a black red solid, yield: 0.312 g (80%).
M.p. 209.5–210.5 °C. Anal. Found: C, 64.75; H, 5.21; N,
3.33. Calc. for C42H40N2O2Fe2Cu: C, 64.67; H, 5.17; N,
3.59%. IR (KBr disk): m(C ¼ O) 1561 (s), m(C ¼ C) 1512
(vs) cmꢁ1. UV (nm, in DMF): kmax(e ꢂ 104) 275 (2.9),
355 (4.3) (K-band), 447 (0.50) (CT-band).
Complex III as a purple red solid, yield: 0.331 g (82%).
M.p. 213–214.5 °C. Anal. Found: C, 65.30; H, 5.16; N,
3.04. Calc. for C44H44N2O2Fe2Cu: C, 65.40; H, 5.49; N,
3.47%. IR (KBr disk): m(C ¼ O) 1557 (s), m(C ¼ C) 1513
(vs) cmꢁ1. UV (nm, in DMF): kmax(e ꢂ 104) 278 (2.4),
351 (3.2) (K-band), 447 (0.37) (CT-band).
Syntheses of enaminones and their complexes are
represented in Schemes 1 and 2. Reaction of the b-di-
ketone 1 or 2 [C5H5FeC5H4C(O)CH2C(O)R] (R ¼ CH3,
C6H5) and an excess of an appropriate aniline [H2NAr]
(Ar ¼ Ph, 2-CH3C6H4, 2,6-(CH3)2C6H3) in the presence
of a catalytic trace amount of p-toluenesulfonic acid in
refluxing toluene via removal of water using a Dean–
Stark apparatus affords the corresponding enaminones
in satisfactory yields. For enaminones HL4, HL5 and
HL6, in view of the electronic and steric effects of the
phenyl and ferrocenyl groups, it may be expected that
the anilines attack the carbonyl with the Ph substituent.
This conclusion is further supported by X-ray diffraction
analysis on the enaminone HL6 (see below). Also be-
cause of steric hindrance from the N-phenyl and
C-phenyl groups, reaction of the b-diketone 2 with 2,6-
dimethylaniline is incomplete and accordingly enami-
none HL6 is obtained only in moderate yield. Except
HL6, each enaminone can react with the copper(II) ion
forming the corresponding neutral complex with the
release of HOAc. TLC analyses of all the complexes
show that each exists as a single isomer. However, be-
cause of the steric hindrance of HL6, all attempts to
synthesize the corresponding complex L62CuꢀxH2O were
unsuccessful and the starting materials were recovered.
Analytical data of all the new complexes listed in
Section 2 suggest that they may be formulated as
L12Cuꢀ2H2O, L22Cu, L23Cu, L24Cuꢀ2H2O and L25Cuꢀ2H2O,
respectively.
Complex IV as a black solid, yield: 0.379 g (83%).
M.p. 203.5–205 °C (dry sample). Anal. Found: C, 65.51;
H, 4.47; N, 3.14. Calc. for C50H44N2O4Fe2Cu: C, 65.84;
H, 4.86; N, 3.07%. IR (KBr disk): m(OH) 3439 (w, br),
m(C ¼ O) 1550 (m), m(C ¼ C) 1509 (vs) cmꢁ1. UV (nm, in
DMF): kmax(e ꢂ 104) 379 (3.5) (K-band).
Complex V as a black red solid, yield: 0.376 g (80%).
M.p. 222.5–223.5 °C (dry sample). Anal. Found: C,
66.85; H, 5.06; N, 3.18. Calc. for C52H48N2O4Fe2Cu: C,
66.43; H, 5.15; N, 2.98%. IR (KBr disk): m(OH) 3430
(w, br), m(C ¼ O) 1580 (m), m(C ¼ C) 1513 (vs) cmꢁ1. UV
(nm, in DMF): kmax(e ꢂ 104) 378 (2.67) (K-band).
1
3.2. H NMR spectra of enaminones
1
2.4. Crystal structure determinations
The H NMR spectral data of the enaminones are
presented in Section 2. The spectra of the free ligands
display two singlets at d 4.41–4.58 and 4.79–4.90 ppm,
with the integration corresponding to 2H attributed to
the H3/H4 and H2/H5 protons of the substituted cyclo-
pentadienyl ring. Another singlet signal with the inte-
gration corresponding to 5H at d 4.21–4.27 ppm is due
Single crystals of enaminone HL6 for X-ray analysis
were obtained by slow evaporation of its solution in
CH2Cl2 and petroleum ether at room temperature.
Single crystals of complex I for structure determination
were obtained by further recrystallization from CH2Cl2

18
Y.-C. Shi et al. / Polyhedron 23 (2004) 15–21
Table 1
Crystallographic data for HL6 and I
HL6
I
Formula
C
435.33
27H25FeNO
C40H40Fe2N2O4Cu
787.98
Formula weight
Crystal size (mm)
Crystal system
Space group
0.30 ꢂ 0.30 ꢂ 0.20
monoclinic
P21/c
0.3ꢂ0.3 ꢂ 0.2
orthorhombic
Pbcn
Unit cell dimensions
ꢀ
a(A)
ꢀ
8.3000(17)
13.320(3)
12.910(3)
19.280(4)
b(A)
ꢀ
c(A)
20.410(4)
90.00
27.620(6)
90.00
a(°)
b(°)
c(°)
101.66(3)
90.00
2209.9(8)
90.00
90.00
6875(2)
3
ꢀ
V (A )
Z
4
1.308
8
1.521
Dc(g cmꢁ1
F(0 0 0)
T (K)
)
912
293(2)
3176
293(2)
l(Mo Ka) (mmꢁ1
Scan mode
h Range (°)
Limiting indices
)
0.700
x ꢁ 2h
1.487
x ꢁ 2h
1.84; 24.97
0 6 h 6 9, 0 6 k 6 15, -24 6 l 6 23
PSI-scan
2.16; 24.96
0 6 h 6 15, 0 6 k 6 22, 0 6 l 6 32
PSI-scan
Absorption correction
Reflections collected
4158
3872
5996
5996
Independent reflections ½I > 2:0r (I)]
Refinement method
full-matrix least-squares on F 2
271
full-matrix least-squares on F 2
436
Number of parameters refined
Final R indices ½I > 2:0r (I)]
R indices (all data)
Goodness-of-fit
Largest difference peak and hole (e A
R1, 0.0485; wR2, 0.1427
R1, 0.1059; wR2, 0.1690
1.016
R1, 0.0944; wR2, 0.1910
R1, 0.3446; wR2, 0.3014
0.931
ꢁ3
ꢀ
)
0.228 and )0.221
0.546 and )0.552
Table 2
Table 3
6
ꢀ
ꢀ
Selected bond distances (A) and angles (°) for HL
Selected bond distances (A) and angles (°) for I
Bond distances
Bond distances
H–N
0.85(0)
C(1)–C(15)
C(2)–C(13)
C(3)–C(45)
C(5)–C(34)
C(14)–N
1.516(7)
1.473(8)
1.493(5)
1.482(5)
1.443(8)
Cu–O(1)
Cu–N(1)
1.92(1)
1.95(1)
1.28(2)
1.31(1)
1.45(2)
Cu–O(2)
Cu–N(2)
1.89(1)
1.99(1)
1.31(2)
1.31(2)
1.42(2)
N–C(3)
C(3)–C(4)
C(4)–C(5)
O–C(5)
1.349(5)
1.367(5)
1.408(5)
1.250(4)
N(1)–C(2)
O(1)–C(4)
N(1)–C(14)
N(2)–C(6)
O(2)–C(8)
N(2)–C(26)
Bond angles
N–C(3)–C(4)
C(3)–C(4)–H
C(3)–C(4)–C(5)
C(5)–C(4)–H
C(3)–N–C(14)
C(3)–N–H
Bond angles
121.2(3)
117.9(3)
124.2(3)
117.9(3)
127.3(3)
116.3(3)
N–C(3)–C(45)
O–C(5)–C(4)
O–C(5)–C(34)
C(4)–C(5)–C(34)
N–Hꢀ ꢀ ꢀO
118.4(3)
123.0(3)
119.0(3)
117.9(3)
135
O(1)–Cu–O(2)
O(1)–Cu–N(1)
O(1)–Cu–N(2)
O(2)–Cu–N(1)
O(2)–Cu–N(2)
N(1)–Cu–N(2)
154.1(5)
92.1(5)
93.1(5)
91.6(5)
94.1(5)
155.5(5)
C(2)–N(1)–Cu
C(2)–N(1)–C(14)
C(14)–N(1)–Cu
C(6)–N(2)–Cu
C(6)–N(2)–C(26)
C(26)–N(2)–Cu
124.9(1)
117.4(1)
117.5(1)
123.1(1)
118.4(1)
118.4(1)
to the unsubstituted cyclopentadienyl ring protons. For
enaminones HL1, HL2 and HL3, the methyl protons
of the C(O)CHC(NHAr)CH3 moiety show a singlet
corresponding to 3H at d 1.73–2.15 ppm. The methyl
protons of the NHAr moiety also show a singlet corre-
sponding to 3H and 6H for HL2 and HL5 and for HL3
and HL6 at d 2.21–2.48 ppm, respectively. For each li-
gand, the vinylic proton as a singlet appears at d 5.54–
5.70 ppm, and the relative integrated intensity ratio of
this peak to other peaks shows that there is only one H
atom bonded to the a-C atom in the C(O)CaHC(N-
HAr)R moiety. The aromatic protons of the ligands
exhibit multiplets corresponding to 5H, 4H and 3H for
HL1, HL2 and HL3 and 10H, 9H and 8H for HL4, HL5
and HL6 at d 6.40–7.44 ppm, respectively. The spectra
of all ligands display a singlet signal at d 12.03–12.64
ppm, which is assigned to the enamino NH and disap-
pears in the presence of D2O. The downfield position of
this signal may mainly arise from the intramolecular
hydrogen bonding as shown in Scheme 1. Obviously, the
above evidence is in agreement with the proposed
structure of the ligands and also supported by the crystal
structure of enaminone HL6 [2a,3c].

Y.-C. Shi et al. / Polyhedron 23 (2004) 15–21
19
C(sp2) ¼ O ꢃ1.20, C(sp2)–C(sp2) ꢃ 1.48, C(sp2) ¼ C(sp2)
2
2
6
ꢀ
ꢃ 1.33 and C(sp )–N (sp ) ꢃ 1.44 A, HL exhibits
partial delocalization of the O ¼ C–C ¼ C–N system.
ꢀ
That the Hꢀ ꢀ ꢀO distance of 1.971 A is significantly
ꢀ
shorter than the sum of the van der walls radii (2.60 A)
indicates the existence of intramolecular hydrogen
bonding; this is also in accordance with spectroscopic
data. The plane of the skeleton and the plane of the
substituted cyclopentadienyl ring only form a dihedral
angle of 13.6°, whereas the skeleton with the N-benzene
ring and C-benzene ring makes two angles of 74.4 and
116.9° to avoid the steric repulsions. Therefore, in the
solid state, neither the N-benzene ring nor the C-ben-
zene ring is involved in the conjugation of the skeleton,
whereas the substituted cyclopentadienyl ring may in
part conjugate with the enaminonic system [3c,4a].
Scheme 1. Syntheses of enaminones.
Scheme 2. Syntheses of complexes.
3.3. Crystal structure
3.3.2. Crystal structure of complex I
In view of cis or trans isomerism of donor atoms and
planar or tetrahedral coordination geometry of the
central metal ion, as well as anti or syn arrangement of
the ferrocenyl groups with respect to the plane with the
central metal ion and donor atoms, four-coordinate
copper(II) complexes may possess eight stereoisomers:
planar-cis-anti, planar-cis-syn, planar-trans-anti, planar-
trans-syn, tetrahedral-cis-anti, tetrahedral-cis-syn, tet-
rahedral-trans-anti and tetrahedral-trans-syn [13,14].
Therefore, to further establish their structures and to
provide more structural evidence for the new complexes,
the crystal structure of complex I was determined. The
molecular structure of the new copper complex I to-
gether with the atomic numbering is shown in Fig. 2.
The metal atom displays a tetrahedral coordination ge-
ometry surrounded by two nitrogen atoms and two
oxygen atoms of two deprotonated ligands (Lꢁ), so
complex I exists only in the tetrahedral-trans-syn form,
which is further supported by the above-described TLC.
More interestingly, against usual expectation, both
3.3.1. Crystal structure of HL6
As mentioned above, enaminones with the general
formula [R0C(O)CHC(NHAr)R] may have the following
four isomers: cis-s-cis, cis-s-trans, trans-s-cis and trans-s-
trans in which cis and trans refer to two possible geo-
metric arrangements for the carbon–carbon double
bond and s-cis and s-trans to both isomerisms about the
carbon–carbon single bond between the carbon–carbon
and carbon–oxygen double bonds [2a]. Owing to very
few X-ray diffraction studies, so far the structure of
enaminones [R0C(O)CHC(NHAr)R] has resulted in in-
consistencies and remains uncertain [2b,4]. Therefore, a
single crystal X-ray analysis on HL6 was carried out to
determine the structure of the new enaminones. The
molecular structure of HL6 together with the atomic
numbering is shown in Fig. 1. As seen from Fig. 1, HL6
in the solid state belongs to the cis-s-cis isomer. All at-
oms in the skeleton O ¼ C–C ¼ C–N can be regarded as
sp2 hybridized. As shown by the comparison of the
C ¼ O, C–C, C ¼ C and C–N distances (Table 2) with
the corresponding pure double or single bond distances
Fig. 2. Molecular structure of complex I together with the atomic
numbering. Hydrogen atoms and water molecules are omitted for
clarity.
Fig. 1. Molecular structure of enaminone HL6 together with the
atomic numbering. Hydrogen atoms are omitted for clarity.

20
Y.-C. Shi et al. / Polyhedron 23 (2004) 15–21
ferrocenyl groups in complex I are syn to each other. In
ꢀ
cmꢁ1 due to the presence of m(OH) of lattice water
molecules. Further, this has been confirmed by another
band appearing at about 600 cmꢁ1 [18,19]. Also this is
consistent with the above-described X-ray crystal
structure determination and elemental analyses data.
view of the Feꢀ ꢀ ꢀFe distance of 10.502 A, it may be
concluded that one ferrocenyl group in complex I does
not interact sterically with the other and therefore the
syn isomer can be isolated, whereas the corresponding
anti-isomer cannot be found. As expected, both
six-membered chelate rings are planar. Angles O(1)–Cu–
N(1) and O(2)–Cu–N(2), which are 92.1(5) and 94.1(5)°,
are slightly larger than the corresponding values ob-
served in related structures [15,16]. Values of angles
O(1)–Cu–O(2) and N(1)–Cu–N(2) are 154.1(5) and
155.5(5)°, therefore indicating that the coordination
geometry about the copper ion is tetrahedral as men-
tioned above. The bonds between the copper atom and
the donor sites of the deprotonated ligand are within the
range of values normally found for these bonds [15,16].
Interestingly, the Cu–O distances (Cu–O(1) ¼ 1.92(1);
3.5. UV spectra
The UV spectral data of the enaminones and the
complexes are listed in Section 2. In the UV spectra,
complexes I, II and III show three maxima at ꢃ275, 350
and 450 nm while for complexes IV and V each exhibits
one maxima at ꢃ378 nm. The shortest wavelength ab-
sorption which is due to the B-band of cyclopentadienyl
or benzene rings, displays a red shift compared with the
corresponding ligand [20]. Unlike other ligands, only
HL1 exhibits the respective B-band for the cyclopenta-
dienyl ring and benzene ring. On the other hand, the
longer wavelength band in the region 350–379 nm may
be attributed to the ðp ! pꢄÞ transition (viz. K-band)
while the corresponding absorption in each ligand is
observed in the region 328–369 nm. Therefore, com-
pared with those absorptions of the corresponding li-
gands, the K-bands of all the complexes also show red
shifts. Because deprotonated ligands bonded to the
central metal ions strengthen the conjugative effect of
the skeleton as shown in Fig. 3, red shifts of K-bands in
the complexes are observed, whereas slightly decreased
bonding of the cyclopentadienyl groups of the com-
plexes results in a bathochromic shift of the B-band of
the cyclopentadienyl group, which is also supported by
the X-ray crystallography of enaminone HL6 and
complex I [20,21]. Furthermore, unlike the correspond-
ing ligands, complexes I, II and III exhibit an intense
absorption band in the region 450–447 nm which may be
assignable to a ligand-to-metal charge transfer transi-
tion [22]. However for complexes IV and V no charge
transfer transitions are observed. Finally, because weak
d–d transtions in ferrocene-containing complexes are
obscured by much more intense UV transitions from a
different nature, the ligand field absorptions in these
complexes cannot be resolved.
ꢀ
Cu–O(2) ¼ 1.89(1) A) are significantly different from
each other whereas the Cu–N distances (Cu–
ꢀ
N(1) ¼ 1.95(1); Cu–N(2) ¼ 1.99(1) A) are similar. The
structural features of two Lꢁ ions (Table 3) are as fol-
lows. One exhibits N(1)–C(2), C(2)–C(3), C(3)–C(4) and
O(1)–C(4) bond distances of 1.28(2), 1.42(2), 1.35(2) and
ꢀ
1.31(2) A, and the other shows N(2)–C(6), C(6)–C(7), C
(7)–C(8) and O(2)–C(8) bond distances of 1.31(2),
ꢀ
1.42(2), 1.36(2) and 1.31(2) A whereas the corresponding
bond distances of HL6 are 1.349(5), 1.367(5), 1.408(5)
ꢀ
and 1.250(4) A. These suggest that the O ¼ C–C ¼ C–N
system of the complex has more delocalization than that
of the corresponding ligand [16]. It should be pointed
out that the water molecules in complex I are non-
coordinate and disordered.
3.4. IR spectra
The important IR data of the enaminones and the
complexes are given in Section 2. The band at ꢃ3080
cmꢁ1 in the spectrum of each ligand is due to m(NH) and
does not occur in that of the corresponding complex.
This suggests that the enaminones are bonded to copper
ions in the monoanionic form. Moreover, the strong
bands assignable to stretching vibrations of the skeleton
C ¼ O and C ¼ C groups, which are observed at 1585–
1603 and 1552–1567 cmꢁ1 in the ligands, are all red-
shifted to the region 1550–1580 and 1510–1513 cm ꢁ1 in
the complexes [3c,7a]. This is because the complexes
possess resonance forms as shown in Fig. 3, which lead
to a decrease in double bond character of the C ¼ O and
C ¼ C groups [17]. As expected, the spectra of complexes
I, IV and V display a broad and weak band at ꢃ3430
4. Conclusion
Reaction of the ferrocene-containing b-diketone
[C5H5FeC5H4C(O)CH2C(O)R] (1, R ¼ CH3; 2, R ¼ C6
H5) and the corresponding aniline [H2NAr] (Ar ¼ Ph,
2-CH3C6H4, 2,6-(CH3)2C6H3) in the presence of a cat-
alytic amount of p-toluenesulfonic acid yields a series of
cis-s-cis enaminones [C5H5FeC5H4C(O)CH ¼ C(NH
Ar)R] (HL1–HL6). Reaction of enaminones HL1–HL5
and copper acetate affords tetrahedral-trans-syn com-
plexes I–V in which each of the enaminones coordinates
to the copper ion as a monoanionic bidentate ligand via
Fig. 3. Resonance forms of copper complexes.

Y.-C. Shi et al. / Polyhedron 23 (2004) 15–21
21
[4] (a) P. Gilli, V. Bertolasi, V. Ferretti, G. Gilli, J. Am. Chem. Soc.
122 (2000) 10405;
carbonyl oxygen and enamine nitrogen atoms after de-
protonation.
(b) G.O. Dudek, G.P. Volpp, J. Am. Chem. Soc. 85 (1963)
2697.
[5] G.J.P. Britovsek, Angew. Chem., Int. Ed. Engl. 38 (1999) 428.
[6] M.J. Bochmann, J. Chem. Soc., Dalton Trans. (1996) 255.
[7] (a) A.A. Osowole, J.A.O. Woods, O.A. Odunola, Synth. React.
Inorg. Met. Org. Chem. 32 (2002) 783;
5. Supplementary material
Full crystallographic data (CCDC No. 200938 for
enaminone HL6 and CCDC No. 207417 for complex I)
have been deposited at the Cambridge Crystallographic
Database Centre and are available on request from the
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (Fax: +44-1223-336-033; Email:deposit@ccdc.
cam.ac.uk or http://www.ccdc.cam.ac.uk).
(b) J. Kim, J.W. Hwang, Y. Kim, M.H. Lee, Y. Han, Y. Do, J.
Organomet. Chem. 620 (2001) 1;
(c) S. Doherty, R.J. Errington, N. Housley, J. Ridland, W. Clegg,
M.R.J. Elsegood, Organometallics 18 (1999) 1018.
[8] C.W. Ho, W.C. Cheng, M.C. Cheng, S.M. Peng, K.F. Cheng,
C.M. Che, J. Chem. Soc., Dalton Trans. (1996) 405.
[9] P.J. Graham, G.W. Parshall, M.L. Peterson, G.M. Whitman,
J. Am. Chem. Soc. 79 (1957) 3416.
[10] V. Weinmayr, Naturwiss 45 (1958) 311.
[11] (a) C.E. Cain, T.A. Mashburn Jr., C.R. Hauser, J. Org. Chem. 26
(1960) 1030;
Acknowledgements
(b) C.R. Hauser, J.K. Lindsay, J. Org. Chem. 22 (1957) 482.
[12] G.M. Sheldrick, SHLXTL, Software Reference Manual, Bruker
Analytical X-ray Systems, Madison, WI, USA, 1996.
[13] G.E. Gurr, Inorg. Chem. 3 (1964) 614.
We thank the National Nature Science Foundation
of China (No. 20175023) and Yangzhou University (No.
D0009107) for financial support of this work.
[14] R.D. Archer, Inorg. Chem. 2 (1963) 292.
[15] J.P. Costes, J.F. Serra, F. Dahan, J.P. Laurent, Inorg. Chem. 25
(1986) 2790.
[16] M.B. Cingi, A.C. Villa, A.G. Manfredotti, C. Guastini, M.
Nardelli, Acta Crystallogr. Sect. B 28 (1972) 1075.
[17] Y.C. Shi, W.B. Shen, H.M. Yang, H.B. Song, X.Y. Hu,
Polyhedron 22 (2003), in press.
References
€
[1] (a) L.F. Tietze, A. Bergmann, G. Brill, K. Bruggemann, U.
[18] M.A. El-Gahami, Synth. React. Inorg. Met.-Org. Chem. 32 (2002)
1143.
Hartfiel, E. Vob, Chem. Ber. 122 (1989) 83;
(b) H. Iida, Y. Yuasa, C. Kibayashi, J. Chem. Soc., Chem.
Comm. (1981) 114.
[19] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, third ed., John Wiley, New York,
1978.
[2] (a) J.V. Greenhill, Chem. Soc. Rev. 6 (1977) 277;
(b) L. Kozerski, Tetrahedron 32 (1976) 1299.
[3] (a) J. Mrosset, C. Floriani, M. Mazzanti, A.C. Villa, C. Guastini,
Inorg. Chem. 29 (1990) 3991;
[20] Y.C. Shi, Q.B. Song, X.L. Wu, Y.X. Ma, Polyhedron 13 (1994)
2101.
[21] Y.C. Shi, Y.M. Liang, X.L. Wu, Q.B. Song, G.S. Huang, Y.X.
Ma, J. Coord. Chem. 33 (1994) 295.
(b) M. Kwiatkowski, A. Olechnowicz, J. Mrozinski, D.M. Ho, E.
Deutsch, Inorg. Chim. Acta 158 (1989) 37;
[22] B.N. Figgis, Introduction to Ligand Fields, John Wiley, New
York, 1976.
(c) H. Iida, Y. Yuasa, C. Kibayashi, Y. Iitaka, J. Chem. Soc.,
Dalton Trans. (1981) 2212.