Preparation and characterization of carboximidate iron(II) complexes

Article abstract of DOI:10.1016/j.inoche.2004.10.019

The reactions of C₅H₄NCH=NNHC(=O)Ph with Fe(II) chloride gave dinuclear [Fe₂(C₅H₄NC(OEt)=NNHC(= O)Ph)₂(μ-OR)₂Cl₂]) in alcohol and mononuclear complex [C₅H₄NCH=NNHC(=O)Ph]FeCl₂ in THF, in which the ferrous ion assisted the transformation of CHN group into carboximide ester of the ligand. The reactions of C₅H ₄NCH=NNHC(=O)Ph (1) with Fe(II) chloride gave [Fe₂(C ₅H₄NC(OEt)=NNHC(=O)Ph)₂(μ-OEt) ₂Cl₂]) (2) in ethanol and [Fe₂(C ₅H₄NC(OMe)=NNHC(=O)Ph)₂(μ-OMe) ₂Cl₂] (3) in methanol as well as [Fe(C₅H ₄NCH=NNHC(=O)Ph)Cl₂] (4) in tetrahydrofuran, respectively. The X-ray diffraction analysis reveals their structures and complex 4 is proposed as an intermediate of formation of complexes 2 and 3.

Full text of DOI:10.1016/j.inoche.2004.10.019

Inorganic Chemistry Communications 8 (2005) 41–43
www.elsevier.com/locate/inoche
Preparation and characterization of carboximidate
iron(II) complexes
a
Liyi Chen , Wen Zhang , Shuping Huang , Xianglin Jin , Wen-Hua Sun
a
b
c
a,
*
a
Laboratory of Engineering Plastics, Joint Laboratory of Polymer Science and Materials, The Chinese Academy of Sciences,
Institute of Chemistry, Zhongguancun, Beiyijie, Beijing 100080, PR China
b
School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006, PR China
c
Institute of Physical Chemistry, Peking University, Beijing 100871, PR China
Received 4 January 2004; accepted 24 October 2004
Available online 24 November 2004
Abstract
The reactions of C5H4NCH@NNHC(@O)Ph (1) with Fe(II) chloride gave [Fe2(C5H4NC(OEt)@NNHC(@O)Ph)2(l-OEt)2Cl2])
(2) in ethanol and [Fe2(C5H4NC(OMe)@NNHC(@O)Ph)2(l-OMe)2Cl2] (3) in methanol as well as [Fe(C5H4NCH@NNHC(@O)
Ph)Cl2] (4) in tetrahydrofuran, respectively. The X-ray diffraction analysis reveals their structures and complex 4 is proposed as
an intermediate of formation of complexes 2 and 3.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Carboximidate; Fe(II) complex; Crystal structure
Imino-containing compounds have drawn much
attention due to their biological activities and organic
synthesis considerations [1–3]. Because of the pharma-
ceutical applications, the structure unit of carboximide
ester has recently been explored as a useful intermediate
in organic syntheses [4–7]. A distinct example was form-
ing copper complexes containing benzoylpyridin-2-yl-
methylene-hydrazide derivatives [8]. In this paper, the
extensive reactions of C5H4NCH@NNHC(@O)Ph (1)
[9] with Fe(II) chloride in various solvents give three
complexes 2–4 (Scheme 1).
Benzoylpyridin-2-yl-methylene-hydrazide (1) reacted
with stoichiometric amount of FeCl2 Æ 4H2O to form
complexes 2 in ethanol, 3 in methanol and 4 in tetra-
hydrofuran (THF), respectively. The complex 4 reacted
with alcohol to form the complexes 2 and 3. Their crys-
tals were obtained by diffusing ethyl ether into the reac-
tant solution.
All complexes were carefully investigated by elemen-
tal analysis, spectral characterization as well as single-
1
crystal determination. According to complexes 2 and
2
3 , the infrared spectra showed the lower frequency
1
Complex 2. Brown crystals, 11%. C34H40N6O6Fe2Cl2 Calc.
(found): C, 50.33 (50.27); H, 4.97 (4.74); N, 10.36 (10.34). IR (cmÀ1
,
KBr): 2964 (w), 2931 (w), 2878 (w, CH3, CH2), 1632 (s) (C@O), 1511
(m, C@N), 1371 (s), 1322 (s, CAOAC). Mp: >300 °C. leff = 4.40 lB.
M = 811.32, orthorhombic, a = 18.535(4), b = 10.503(2), c = 18.433(4)
3
˚
˚
A, V = 3588.4(12) A , T = 293(2) K, Space group Pbcn, Z = 4, number
of collected reflections = 21837, number of independent reflec-
tions = 4060, R (F2) = 0.0388, wR = 0.0552. Full crystallographic detail
was deposited at the Cambridge Crystallographic Data Centre with
number CCDC 220810.
2
Complex 3. Brown crystals, 33%. C30H32N6O6Fe2Cl2 Calc.
(found): C, 47.71 (47.72); H, 4.27 (3.98); N, 11.13 (11.02). IR (cmÀ1
,
KBr): 2958 (w), 2922 (w), 2818 (w, CH3), 1631 (s, C@O), 1511 (m,
C@N), 1375 (s), 1335 (s, CAOAC). Mp: >300 °C. leff = 4.46 lB
M = 755.22, monoclinic, a = 11.125(2), b = 9.2402(18), c = 16.402(3)
3
˚
˚
A, b = 100.67(3), V = 1656.9(6) A , T = 293(2) K, Space group P2(1)/c,
Z = 2, number of collected reflections = 5076, number of independent
reflections = 2887, R (F2) = 0.0291, wR = 0.0232. Full crystallographic
detail was deposited at the Cambridge Crystallographic Data Centre
with number CCDC 220811.
*
Corresponding author. Tel.: 86 10 62557955; fax: +86 10
62618239.
E-mail address: whsun@iccas.ac.cn (W.-H. Sun).
1387-7003/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2004.10.019

42
L. Chen et al. / Inorganic Chemistry Communications 8 (2005) 41–43
H
N2, Ethanol
N
H
+
N
N
H
reflux, 6h
H2N
N
N
O
O
O
1
.
.
FeCl2 4H2O
FeCl2 4H2O
Alcohol, N2
THF, N2
R
N
R
O
O
H
N
Cl
O
HN
Alcohol
N
N
Fe
Fe
N
N
O
NH
O
R
O
Fe
Cl
Cl
O
Cl
N
R
H2O
2: R=Ethyl
3: R=Methyl
4
Scheme 1. Synthesis of compounds.
and intensity for m(C@O) of the complexes (1632 cmÀ1
for 2; 1631 cmÀ1 for 3) compared to the ligand 1 (1684
cmÀ1), this confirmed the coordination of C@O with
Fe(II). Due to the coordination of nitrogen atom in
the both complexes, the bands of m(C@N) also shift
(1532 cmÀ1 for 1; 1511 cmÀ1 for 2; 1511 cmÀ1 for 3).
In addition, several new absorptions appeared between
2800 and 2960 cmÀ1 (m(ACH3, ACH2)) and 1320–1375
cmÀ1 (m(CAO)) for the complexes. In their single crystal
structures, the complexes 2 and 3 both contained the
two six-coordinated Fe(II) cations bridged by two alk-
oxy groups (Figs. 1 and 2).
Looking at the ligand moiety, a substitution reaction
happens at C(6) atom by alkoxy group which is trans to
Fe(II) ion due to the coordination of pyridine moiety. In
the complex 2, as the example, the bond between C(6)
and N(1) atoms remains double bond (C(6)@N(1),
˚
1.284(3) A). Interestingly, the O(2)AC(6) bond length
˚
is 1.318(3) A, much shorter than the single bond length
˚
of O(2)AC(14) (1.441(3) A). The similar phenomena
were previously observed in carboximide ester [10].
Fig. 1. Structure of complex 2, 30% probability ellipsoids, H atoms
˚
Fig. 2. Structure of complex 3, 30% probability ellipsoids, H atoms
˚
omitted for clarity. Selected bond lengths (A) and angles (°): Fe(1)–
omitted for clarity. Selected bond lengths (A) and angles (°): Fe(1)–
O(3) 1.9642(18), Fe(1)–O(3A) 2.0639(19), O(1)–C(7) 1.290(3), O(2)–
C(6) 1.318(3), O(2)–C(14) 1.441(3), N(1)–C(6) 1.284(3), N(1)–N(2)
1.386(3), N(2)–C(7) 1.319(3) and O(1)–Fe(1)–N(1) 74.41(9), O(3)–
Fe(1)–N(3) 102.69(9), N(1)–Fe(1)–N(3) 74.02(10), O(3A)–Fe(1)–Cl(1),
169.41(6).
O(2) 1.936(2), Fe(1)–O(2A) 2.058(3), O(1)–C(8) 1.299(5), O(3)–C(6)
1.344(5), O(3)–C(16) 1.464(4), N(2)–C(6) 1.257(5), N(2)–N(3) 1.384(5),
N(3)–C(8) 1.332(6) and O(2)–Fe(1)–O(1) 106.40(12), O(1)–Fe(1)–N(2)
76.66(15), O(2)–Fe(1)–N(1) 102.46(14), N(2)–Fe(1)–N(1) 72.83(16),
O(2A)–Fe(1)–Cl(1), 169.95(9).

L. Chen et al. / Inorganic Chemistry Communications 8 (2005) 41–43
43
˚
Fig. 3. Structure of complex 4, 30% probability ellipsoids, H atoms omitted for clarity. Selected bond lengths (A) and bond angles (°): Fe(1)–O(1)
2.003(3), Fe(1)–N(2) 2.106(3), Fe(1)–O(2) 2.113(3), Fe(1)–N(3) 2.137(3), Fe(1)–Cl(1) 2.2335(12), Fe(1)–Cl(2) 2.3217(14), O(1)–C(1) 1.274(4), N(1)–
C(1) 1.330(5), N(1)–N(2) 1.373(4), N(2)–C(8) 1.272(5) and O(1)–Fe(1)–N(2) 74.23(12), N(2)–Fe(1)–N(3) 74.35(13), O(2)–Fe(1)–Cl(1) 88.72(9).
˚
The bond length of O(1)AC(7) (1.290(3) A) is between
Acknowledgement
3
˚
the typical single bond C(sp )AO (1.34 A) and double
bond C(sp2) = (1.21 A) [11]. In addition, the
The project was supported by NSFC No. 20272062.
˚
˚
˚
N(1)AN(2) (1.386(3) A) and N(2)AC(7) (1.319(3) A)
have part characters of double bonds, which is similar
to its Cu(II) analogue reported by Pal et al. [8]. There-
fore extended conjugated system is present in the result-
ant iron complex.
Appendix A. Supplementary data
Supplementary data associated with this article can
be found, in the online version at doi:10.1016/
j.inoche.2004.10.019.
3
The complex 4 (Fig. 3) was formed in the stoichio-
metrical reaction of the ligand 1 with FeCl2 in THF. The
complex 4 is mononuclear with a coordinated water
molecule. The complex 4 reacted with ethanol or meth-
anol to yield the complexes 2 and 3. Therefore complex
4 is postulated as an intermediate in forming complexes
2 and 3 with nucleophilic attack of alkoxy on ACH@N
of complexes 4. The effective magnetic moment leff of
complexes 2, 3 and 4 were measured with the values of
4.40, 4.46 and 5.46 lB, respectively. It proved that those
iron complexes were all high-spin species having the
configuration (t2g)4(eg)2.
References
[1] R. Bloch, Chem. Rev. 98 (1998) 1407.
[2] S. Kobayashi, H. Ishitani, Chem. Rev. 99 (1999) 1069.
[3] G.K. Friestad, Tetrahedron 57 (2001) 5461.
[4] R.H.B. Galt, P.B. Hitchcock, S.J. Mccarthy, D.W. Young,
Tetrahedron Lett. 37 (1996) 8035.
[5] K. Unegama, J. Hao, H. Amii, Tetrahedron Lett. 39 (1998) 4079.
[6] S. Kim, C.J. Lim, C. Song, W. Chung, J. Am. Chem. Soc. 124
(2002) 14306.
In general, hydrazine-derived Schiff-base ligands
could easily coordinated with transition metals, and
the polarity of HAC bond in HAC@NAM is increased
for easy substitution with alkoxy group. This helps to
understand the formation of carboximide ester in the
copper complexes [8], and more importantly the exten-
siveness to other transition metals. Therefore this pro-
vides a convenient method for the transformation of
ACH@N group into carboximide ester.
[7] P.E. Maligres, S.A. Weissman, V. Upadhyay, S.J. Cianciosi,
R.A. Reamer, R.M. Purick, J. Sager, K. Rossen, K.K. Eng, D.
Askin, R.P. Volante, P.J. Reider, Tetrahedron 52 (1996) 3327.
[8] S. Pal, N.R. Sangeetha, S.N. Pal, Polyhedron 19 (2000) 2713.
[9] D.G. Paschalidis, I.A. Tossidis, M. Gdaniec, Polyhedron 19
(2000) 2629.
[10] C.S. Chin, D. Chong, B. Lee, H. Jeong, G. Won, Y. Do, Y.J.
Park, Organometallics 19 (2000) 638.
[11] J. March, Advanced Organic Chemistry, fourth ed., Wiley-
Interscience, New York, 1992, p. 21.
3
Complex 4. Red crystals, 20%. C13H11N3OFeCl2 Calc. (found): C,
44.36 (44.28); H, 3.15 (3.25); N, 11.94 (11.84). IR (cmÀ1, KBr): 1624(s,
C@O), 1523 (s, C@N). Mp: 132 °C (Dec.). meff = 5.46 mB. C13H11Cl2Fe
N3O Æ H2O, M = 370.01, monoclinic, a = 14.390(3), b = 7.1480(14),
3
˚
˚
c = 15.002(3) A, b = 106.70(3)°, V = 1478.0(5) A , T = 123(2) K,
Space group P2(1)/n, Z = 4, number of collected reflections = 5827,
number of independent reflections = 2593,
wR = 0.0867. Full crystallographic detail was deposited at the Cam-
bridge Crystallographic Data Centre with number CCDC 220812.
R
(F2) = 0. 0491,