Synthesis, reactivity and magnetochemical studies on copper(II) complexes derived from N-salicylidenearoylhydrazines. X-ray structure of [mononitratoOO( - 1 ) (N-salicylidenatobenzoylhydrazine)-ONO( - 1 )]copper(II) monohydrate

Article abstract of DOI:10.1016/S0277-5387(00)00340-5

A series of new mononuclear and binuclear copper(II) complexes derived from N-salicylidenearoylhydrazines (H₂L) of the types K₂[{Cu(L) (OH)}₂]·nH₂O, [Cu(HL)CI·H₂O]·nH₂O, [{Cu(HL)CI}₂], [Cu(HL)NO₂]·H₂O, [{Cu(HL)}₂]·2NO₃, [{Cu(HL)H₂O}₂]·2NO₃·nH₂O and [Cu(HL)NCS]·H₂O have been prepared and characterized. The X-ray crystal and molecular structure of [Cu(HSBzh)NO₃]·H₂O, where HSBzh refers to the mononegative N-salicylidenebenzoylhydrazine anion, has been determined. The complex is monomeric with the copper(II) adopting a (4 + 1) distorted square pyramidal coordination, with the ONO aroylhydrazone tridentate anion and an oxygen atom of the unsymmetric bidentate nitrate ion occupying the basal plane. The fifth coordination site is occupied by the other oxygen of the nitrate ion. The magnetic susceptibilities of both mononuclear and binuclear complexes were measured within the temperature range 4.2-298 K. All binuclear copper(II) complexes show strong antiferromagnetic interactions, and the singlet-triplet separation (-2J) recorded for μ-dihydroxy bridged complexes K₂[{Cu(L)OH}₂}]·nH₂O are within the range 172-276 cm^-1, while (-2J) for binuclear complexes [{Cu(HL)Cl}₂], [{Cu(HL)}₂]·2NO₃ and [{Cu(HL)H₂O}₂]·2NO₃·nH₂O are respectively within the range 400-460, ca. 340 and ca. 390 cm^-1. There are no appreciable exchange interactions between copper(II) ions in the monomeric complexes [Cu(HL)Cl·H₂O]·nH₂O, [Cu(HL)NO₂]·H₂O and [Cu(HL)NCS]·H₂O. The IR spectra of the prepared complexes are also discussed. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(00)00340-5

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 949–958
Synthesis, reactivity and magnetochemical studies on copper(II)
complexes derived from N-salicylidenearoylhydrazines. X-ray structure
of [mononitratoOO(y1)(N-salicylidenatobenzoylhydrazine)-
ONO(y1)]copper(II) monohydrate
a
b
b
c
c
M.F. Iskander a, , T.E. Khalil , R. Werner , W. Haase , I. Svoboda , H. Fuess
*
a Chemistry Department, Faculty of Science, Alexandria University, P.O. Box 426, Ibrahimia, Alexandria 21321, Egypt
b
¨
¨
Institut fur physikalische Chemie, AG Kondensierte Materie, Fachbereich Chemie, Technische Universitat Darmstadt, Petersenstrasse 20,
D-64287 Darmstadt, Germany
Institut fur Strukturforschung, Fachbereich Materialwissenschaft, Petersenstrasse 24, D-64287 Darmstadt, Germany
c
¨
Received 22 November 1999; accepted 21 February 2000
Abstract
A series of new mononuclear and binuclear copper(II) complexes derived from N-salicylidenearoylhydrazines (H2L) of the types
K2[{Cu(L)(OH)}2]PnH2O, [Cu(HL)ClPH2O]PnH2O, [{Cu(HL)Cl}2], [Cu(HL)NO2]PH2O, [{Cu(HL)}2]P2NO3, [{Cu(HL)-
H2O}2]P2NO3PnH2O and [Cu(HL)NCS]PH2O have been prepared and characterized. The X-ray crystal and molecular structure of
[Cu(HSBzh)NO3]PH2O, where HSBzh refers to the mononegative N-salicylidenebenzoylhydrazine anion, has beendetermined.Thecomplex
is monomeric with the copper(II) adopting a (4q1) distorted square pyramidal coordination, with the ONO aroylhydrazone tridentate anion
and an oxygen atom of the unsymmetric bidentate nitrate ion occupying the basal plane. The fifth coordination site is occupied by the other
oxygen of the nitrate ion. The magnetic susceptibilities of both mononuclear and binuclear complexes were measured within the temperature
range 4.2–298 K. All binuclear copper(II) complexes show strong antiferromagnetic interactions, and the singlet–triplet separation (y2J)
recorded for m-dihydroxy bridged complexes K2[{Cu(L)OH}2}]PnH2O are within the range 172–276 cmy1, while (y2J) for binuclear
complexes [{Cu(HL)Cl}2], [{Cu(HL)}2]P2NO3 and [{Cu(HL)H2O}2]P2NO3PnH2O are respectively within the range 400–460, ca.
340 and ca. 390 cmy1. There are no appreciable exchange interactions between copper(II) ions in the monomeric complexes
[Cu(HL)ClPH2O]PnH2O, [Cu(HL)NO2]PH2O and [Cu(HL)NCS]PH2O. The IR spectra of the prepared complexes are also discussed.
q2000 Elsevier Science Ltd All rights reserved.
Keywords: N-salicylidenearoylhydrazines; Copper(II) complexes; X-ray crystal structures; Molecular structures; Magnetic properties; Infrared spectra
1. Introduction
ization of some new mononuclear and dinuclear copper(II)
complexes with N-salicylidenearoylhydrazines.
N-salicylideneacylhydrazines (1) (H2L) can act either as
neutral, mononegative or dinegative ONO tridentate ligands
[1–20]. A large number of monomeric and dimeric cop-
per(II) complexes have been prepared and characterized[1–
20]. Most recent studies have been directed towards struc-
tural studies and a number of X-ray crystal and molecular
structures have been reported [16–20]. Less attention, how-
ever, has been directed towards magnetochemical studies
[13–18]. In this paper we report the synthesis and character-
The single X-ray structure of the monomeric
[Cu(HBzh)NO3]PH2O has been determined and the mag-
netic measurements recorded for the prepared complexeswill
be discussed. Hereafter, N-salicylidenebenzoylhydrazine
* Corresponding author. Tel.: q20-3-5423323; fax: q20-3-4911794;
e-mail: iskandar@alexcomm.net
0277-5387/00/$ - see front matter q2000 Elsevier Science Ltd All rights reserved.
PII S0277-5387(00)00340-5
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M.F. Iskander et al. / Polyhedron 19 (2000) 949–958
and the corresponding p-methyl-, p-methoxy- and p-
chlorobenzoylhydrazine are abbreviated as H2SBzh,
H2Sp-CH3Bzh, H2Sp-CH3Obzh and H2Sp-ClBzh, respec-
tively.
dinegative anion of 5-chloro-2-hydroxo acetophenone sali-
cylhydrazide from DMF gave the correspondingDMFadduct
of the formula [Cu(L)DMF] where L referstothedinegative
hydrazone anion [16,17]. Neutral monodentate nitrogen
Lewis bases such as diethylamine [(Et)2NH] can also affect
the rupture of the Cu–O–Cu bridges in 2 and eventually
gave the corresponding monomeric ternary complex
[Cu(L)HNEt2] (3, RsC6H5).
2. Results and discussion
The reaction of the neutral dimeric copper(II) complexes
[{Cu(L)}2] (2, RsC6H5, p-CH3C6H4 and p-CH3OC6H4)
with a large excess of KOH in dry methanol afforded the
corresponding m-hydroxo bridged copper(II) complexes of
general formula K2[{Cu(L)(OH)}2] (4, RsC6H5, p-
CH3C6H4 and p-CH3OC6H4). The isolated hydroxo com-
plexes are soluble in methanol, ethanol and acetonitrile. In
water, these complexes are readily hydrolysed giving the
parent neutral dimer (2). The isolated hydroxo complexes
together with elemental analysis are given in Table 1.
On the other hand, treatment of a suspension of
[{Cu(L)}2] (2, RsC6H5, p-CH3C6H4, p-CH3OC6H4 and
p-ClC6H4) in absolute ethanol with an equivalent amount of
aqueous hydrogen chloride afforded the hydrated mono-
chloro complex [Cu(HL)ClPH2O]PnH2O (5, RsC6H5, p-
CH3C6H4, p-CH3OC6H4 and p-ClC6H4) (HL refers to the
mononegative N-salicylidenearoylhydrazine anion). These
2.1. Synthesis and stoichiometry
In methanol, the reaction of copper(II) acetate with N-
salicylidenearoylhydrazines (H2L) (1, RsC6H5, p-CH3-
C6H4, p-CH3OC6H4 and p-ClC6H4) afforded the binuclear
neutral copper(II) complexes [{Cu(L)}2] (2, RsC6H5, p-
CH3C6H4, p-CH3OC6H4 and p-ClC6H4). These binuclear
copper(II) complexes were insoluble in water, alcohols, halo-
genated aliphatic hydrocarbons and aromatic hydrocarbons
but soluble in DMSO or DMF. The dissolution of these bi-
nuclear complexes proceeded with the rupture of Cu–O–Cu
bridges giving the solvated monomeric species [Cu(L)S] or
[Cu(L)S2] where S refers to the solvent molecule [12]. A
similar behaviour was previously reported and recrystalliza-
tion of the anhydrous dimeric copper(II) complexes with the
Table 1
Elemental analyses of copper(II) complexes derived from N-salicylidenearoylhydrazines
Complex
R
Found (calculated) (%)
n
C
H
N
Cu
K2[{Cu(L)OH}2]PnH2O (4)
C6H5
p-CH3C6H4
2
2
1
44.55 (44.73)
46.17 (46.20)
45.06 (45.39)
3.07 (3.49)
3.84 (3.88)
3.60 (3.55)
7.20 (7.45)
7.00 (7.18)
6.86 (7.06)
16.73 (16.90)
16.52 (16.30)
16.25 (16.01)
p-CH3OC6H4
[Cu(HL)ClPH2O]PnH2O (5)
C6H5
p-CH3C6H4
p-CH3OC6H4
p-ClC6H4
47.16 (47.20)
48.08 (48.65)
44.01 (44.56)
40.46 (41.14)
3.59 (3.68)
3.50 (4.08)
3.69 (4.24)
2.75 (3.45)
7.83 (7.86)
7.48 (7.57)
6.81 (6.93)
7.07 (6.85)
17.57 (17.84)
17.00 (17.16)
15.87 (15.72)
15.41 (15.55)
1
1
[{Cu(HL)Cl}2] (5)
C6H5
p-CH3C6H4
49.57 (49.71)
51.08 (51.14)
3.18 (3.28)
3.71 (3.72)
8.43 (8.28)
8.25 (7.95)
18.53 (18.79)
17.87 (18.04)
[Cu(HL)(NO3)]PnH2O
C6H5
1
1
43.15 (43.93)
3.24 (3.42)
10.91 (10.98)
16.72 (16.60)
[{Cu(HL)}2]P2NO3 (7)
C6H5
p-CH3OC6H4
46.14 (46.09)
45.61 (45.63)
2.94 (3.04)
3.24 (3.32)
11.50 (11.52)
10.75 (10.64)
17.50 (17.42)
16.24 (16.09)
[{Cu(HL)(H2O)}2]P2NO3PnH2O (7a)
p-CH3C6H4
CH3
44.88 (44.39)
33.62 (33.70)
3.43 (3.97)
3.55 (3.46)
10.72 (10.35)
12.73 (13.10)
15.40 (15.66)
20.02 (19.81)
[Cu(HL)(NCS)]PnH2O (8)
C6H5
p-CH3C6H4
p-CH3OC6H4
p-ClC6H4
1
2
47.23 (47.55)
50.95 (51.95)
48.92 (49.16)
41.52 (41.77)
3.33 (3.46)
3.44 (3.50)
3.32 (3.35)
3.04 (3.27)
11.09 (11.09)
11.19 (11.21)
10.94 (10.75)
9.35 (9.74)
16.41 (16.77)
17.01 (16.95)
16.41 (16.26)
14.42 (14.73)
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951
complexes were also prepared in situ from the reaction of
salicylaldehyde with the corresponding aroylhydrazine (1:1
molar ratio) in the presence of copper(II) chloride in ethanol
or methanol. However, direct reaction of N-salicylidene-
aroylhydrazine (1, RsC6H5 and p-CH3C6H4) with 1 equiv.
of copper(II) chloride in absolute ethanol afforded the anhy-
drous brown chloro complexes [Cu(HL)Cl]2 (6, RsC6H5
and p-CH3C6H4). This reaction usually gave salicylaldehyde
azine (HOC6H4CH_N–N_CHC6H4OH) as a side reaction
product. Meanwhile, the direct reaction of p-methoxy- and
p-chlorobenzoylhydrazones (1, Rsp-CH3OC6H4 and p-
ClC6H4) with copper(II) chloride in ethanol or methanol
gave the hydrated copper(II) complexes [Cu(HL)ClPH2O]
(5, Rsp-CH3OC6H4 and p-ClC6H4) and attempts to prepare
the corresponding anhydrous binuclear complexes were
unsuccessful. Similar to the reaction of N-salicylidenearoyl-
hydrazines with copper(II) chloride, the reaction of cop-
per(II) nitrate gave either monomeric and/or dimeric nitrate
complexes. The reaction of 1 (Rsp-CH3C6H4) with cop-
per(II) nitrate trihydrate in boiling absolute ethanol afforded
the
hydrated
binuclear
complex
[{Cu(HSp-
CH3Bzh)H2O}2](NO3)2PH2O (7, Rsp-CH3C6H4), while
the reaction with 1 (RsC6H5, p-CH3OC6H4) gave the cor-
responding anhydrous complexes [{Cu(HSBzh)}2]P2NO3
and [{Cu(HSp-CH3OBzh)2]P2NO3 (7a, RsC6H5 and p-
CH3OC6H4), respectively. However, the in situ preparation,
using benzoylhydrazine, gave the monomeric complex
[Cu(HSBzh)(NO3)]PH2O. The prepared mononuclear and
binuclear copper(II) chloride and nitrate complexestogether
with elemental analysis are included in Table 1.
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The reaction of eithermononuclearorbinuclearcopper(II)
chloride and nitrate complexes with an equivalent amount of
NH4SCN in methanol afforded the corresponding thio-
cyanato complexes [Cu(HL)SCN]PnH2O (8, RsC6H5, p-
CH3C6H4, p-OCH3C6H4) and p-ClC6H4), implying the ease
y
of displacement of either Cly or NO3 by the thiocyanate
ion. However, in the presence of large excess of NH4SCN,
the reaction proceeded by the reduction of copper(II) and
copper(I) thiocyanate [CuSCN]2 was precipitated. On the
other hand, the reaction of thiocyanate with either m-hydroxo
bridged complexes (5) or the neutral binuclear copper(II)
complexes [{Cu(L)}2] (2) failed to give the corresponding
thiocyanato complexes, suggesting that the SCNy cannot
affect the rupture of Cu–O–Cu bridges in these complexes.
The isolated thiocyanato complexes [Cu(HL)SCN]PnH2O
together with elemental analysis are also given in Table 1.
Fig. 1. ORTEP drawing of [Cu(HSBzh)NO3]PH2O.
2.2. X-ray crystal structure of [mononitratoOO9(y1)(N-
salicylidenebenzoylhydrazinato)ONO9(y1)]copper(II)
monohydrate complex [Cu(HSBzh)(NO3)]PH2O
Table 3
˚
Selected bond lengths (A) and bond angles (8) for [Cu(HSBzh)-
(NO3)]PH2O
The crystal data and structure refinement for
[Cu(HSBzh)(NO3)]PH2O are collected in Table 2. The
molecular structure together with the numberingschemeused
are shown in Fig. 1. Some selected bond distances and bond
angles are listed in Table 3. In [Cu(HBzh)(NO3)]PH2O,
Copper(II) polyhedron
O(1)–Cu(1)
O(2)–Cu(1)
N(1)–Cu(1)
O(3)–Cu(1)
O(4)–Cu(1)
1.881(3)
1.947(3)
1.913(3)
1.993(3)
2.480(3)
O(1)–Cu(1)–N(1)
O(1)–Cu(1)–O(2)
O(1)–Cu(1)–O(3)
O(2)–Cu(1)–O(3)
O(4)–Cu(1)–O(3)
N(1)–Cu(1)–O(2)
N(1)–Cu(1)–O(3)
92.99(14)
174.31(13)
91.71(14)
93.64(13)
55.50(13)
81.49(13)
172.33(14)
Table 2
Crystal data and structure refinement for [Cu(HSBzh)NO3]PH2O
Tridentate ligand
C(1)–O(2)
C(1)–N(2)
C(1)–C(9)
C(2)–N(1)
C(3)–C(8)
C(8)–O(1)
N(1)–N(2)
N(2)–H(2N)
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
C14H13CuN3O6
382.84
300(2)
0.71093
orthorhombic
P212121
1.252(5)
1.336(5)
1.488(6)
1.283(5)
1.427(6)
1.305(6)
1.383(5)
1.20(4)
C(1)–N(2)–N(1)
C(1)–O(2)–Cu(1)
C(1)–N(2)–H(2N)
C(2)–N(1)–N(2)
C(2)–N(1)–Cu(1)
C(8)–O(1)–Cu(1)
N(1)–C(2)–C(3)
N(1)–N(2)–H(2N)
N(2)–N(1)–Cu(1)
N(2)–C(1)–C(9)
O(1)–C(8)–C(3)
O(2)–C(1)–N(2)
O(2)–C(1)–C(9)
113.9(3)
113.1(3)
133.3(3)
119.1(3)
128.9(3)
127.8(3)
122.9(4)
113(2)
112.0(2)
119.5(4)
124.3(4)
119.5(4)
120.9(4)
˚
Unit cell dimensions
˚
a (A)
5.331(2)
16.231(2)
17.185(3)
90
90
90
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
3
˚
Volume (A )
1487.0(6)
Z
4
Nitrate ligand
N(3)–O(3)
N(3)–O(4)
N(3)–O(5)
Density (calculated) (Mg my3
)
1.710
1.435
80
1.288(5)
1.231(5)
1.208(5)
O(4)–N(3)–O(3)
O(5)–N(3)–O(3)
O(5)–N(3)–O(4)
N(3)–O(3)–Cu(1)
115.3(4)
119.9(4)
124.8(4)
105.4(3)
Absorption coefficient (mmy1
F(000)
Crystal size (mm)
)
0.88=0.15=0.13
Theta range for data collection (8) 1.73–25.98
Index ranges
y6FhF6, y1FkF19, y1FlF21
Reflections collected
Independent reflections
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices (I)2s(I))
R indices (all data)
3543
the N-salicylidenebenzoylhydrazinato anion behaves as a
mononegative tridentate ligand and is coordinated to the
Cu(II) via the deprotonated phenolic oxygen O(1), azome-
thine nitrogen N(1) and the ketoamide oxygen O(2). The
2908 (Rints0.0291)
full-matrix least-squares on F2
2908/0/250
1.068
˚
˚
R1s0.0418, wR2s0.1093
R1s0.0596, wR2s0.1194
0.02(2)
Cu–O(1) (1.881 A), Cu–N(1) (1.913 A) and Cu–O(2)
˚
(1.97 A) bond distances are within the range reported for
Absolute structure parameter
other copper(II) complexes derived from N-salicylidene-
acylhydrazines [10,11,18–21]. The fourth coordinate site of
the basal plane is occupied by the oxygen atom O(3) of the
Largest difference peak, hole
0.639, y0.942
y3
˚
(e A
)
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953
nitrate group. The Cu(II) lies in the ligand plane and shows
˚
a slight deviation of 0.037 A from the least square plane. The
nitrate ion in this complex behaves as a bidentate ligand, and
the fifth coordinate site is weakly bonded with the O(4) of
the nitrate group. This bidentate nitrate is characterized by
˚
one short Cu–O(3) (1.993 A) distance and a second much
˚
˚
longer Cu–O(4) (2.480 A) with a difference of 0.487 A
which falls within the range reported for the unsymmetrically
coordinated bidentate nitrate group [22–25]. The small
O(3)–Cu–O(4) angle (55.58) is also in agreement with the
bidentate nature of the nitrate ion in this complex.
The coordination polyhedron around the copper(II) is bet-
ter described as (4q1) distorted square pyramidal asevident
from the tetragonality parameter of Addison et al. [26],
ts(bya)/60s0.033, where a and b are the N(1)–Cu–
O(3) (172.338) and O(2)–Cu–O(1) (174.318) angles,
respectively. The uncoordinated water molecule O(6) is
involved in strong hydrogenbondingwiththeN(2)hydrogen
Fig. 2. Magnetic susceptibilities x (d) and magnetic moments (o) vs.
temperature for K2[{Cu(Sp-CH3Bzh)OH}2]P2H2O. Solid lines represent
the best least squares fit to Eq. (1), with Jsy138, gs2.10 and Xps4.1%.
Xp represents the fraction of a possible magnetically dilute
copper(II) impurity (Ss1/2), Na is the temperature inde-
pendent paramagnetism (60=10y6 cm3 moly1 per cop-
per(II) ion) and the other symbols have their usual meaning
and a non-linear regression analysis was carried out with J,
g, and Xp as floating parameters. The obtained best fit para-
meters for the di-m-hydroxo-bridged copper(II) complexes
(4, RsC6H5, p-CH3C6H4 and p-CH3OC6H4) are listed in
Table 4. The recorded y2J values are within the range
reported for other bis-m-hydroxy bridged dicopper com-
plexes with nearly planar Cu2O2 [28–33] and a binuclear
structure (4) can be proposed for these complexes.
˚
atom (O(6)∆H(2)N) (1yx, y0.5qy, 1.5yz) (1.55 A).
2.3. Magnetic measurements
At room temperature, the binuclear copper(II) complexes
[{Cu(L)}2] (2, RsC6H5, p-CH3C6H4, p-CH3OC6H4 and
p-ClC6H4) show subnormalmagneticmoments(1.2–1.6mB)
and their electronic spectra agree with a square planar con-
figuration [1–3,27]. The magnetic susceptibility measure-
ments within the temperature range 97–297 K showed strong
antiferromagnetic interactions. The exchange coupling con-
stant (y2J) of these neutral dimeric complexes were found
to vary from 594 to 680 cmy1 [27] in agreement with the
formation of dimeric copper(II) complexes with Cu–O–Cu
bridges [28]. Recent X-ray studies on binuclear copper(II)
complexes with N-salicylideneacylhydrazines show that
dimerization takes place via the phenolic oxygen rather than
the deprotonated enolic oxygen [18–21].
For di-m-hydroxo dicopper(II) complexes with almost
planar Cu2O2, the 2J values were found to decrease linearly
with increasing either Cu–O–Cu angle w (8) or Cu∆Cu
˚
separation rCu–Cu (A), and least square regression analyses
of the available data gave [28]:
2Jsy77.6wq7555 cmy1 (Rsy0.95)
2Jsy46.0rCu∆Cuq13389 cmy1 (Rsy0.95)
(2)
(3)
Substitution of the 2J values, recorded for 4 (RsC6H5,
p-CH3C6H4 and p-OCH3C6H4), in Eq. (2) gave 99.6, 100.9
and 100.78 for the values of Cu–O–Cu angles, respectively.
While 2.948, 2.971 and 2.967 A are, respectively, the values
calculated from Eq. (3) for the Cu∆Cu separation.
The newly prepared di-m-hydroxo-bridged binuclear cop-
per(II) complexes K2[{Cu(L)OH)}2] (4, RsC6H5, p-
CH3C6H4 and p-OCH3C6H4) also show subnormal magnetic
moments (1.50–1.65 mB) at room temperature. The variation
of xM and meff, recorded for K2[{Cu(Sp-CH3Bzh)OH}2](4,
Rsp-CH3C6H4), as a function of temperature (4.2–298 K)
is shown in Fig. 2. The remarkable decrease in meff (per
copper atom) from 1.5 mB at 290 K to about 0.4 mB at 4.5 K
suggests strong antiferromagnetic exchange interaction.
Similar behaviour was also observed for the other di-m-
hydroxo-bridged copper(II) complexes (4, RsC6H5,
and p-CH3OC6H4). The experimental data were fitted to the
modified Bleaney–Bowers equation Eq. (1),
˚
The green hydrated chloro complexes [Cu(HL)ClP
H2O]PnH2O (5, RsC6H5, p-CH3C6H4, p-CH3OC6H4, and
p-ClC6H4) show normal magnetic moments (1.80–1.84mB),
Table 4, and the temperature dependent magnetic suscepti-
bilities measured for these hydrated complexes, assuming
Curie–Weiss behaviour, suggest a very weak antiferromag-
netic coupling with u values in the range of ca. y1.5 K.
These mononuclear chloro complexes may adopt a square
pyramidal coordination, the four in-plane donor atoms are
provided by the tridentate ONO hydrazone and an oxygen
from a coordinated water while the axial site is occupied by
the chloride ion. A similar structure has been reported for
[Cu(HSAch)ClPH2O]PH2O, where HSAc refers to the
mononegative N-salicylideneacetylhydrazine anion (1,
RsCH3) [21]. On the other hand, the brown anhydrous
2 NL g2m2b exp(2J/kT)
xMs(1yXp)
kT
1q3 exp(2J/kT)
(1)
2NLg2m2
qX
b S(Sq1)q2Na
p 3k(Tyu)
where 2J is the singlet–triplet splitting or exchange integral,
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Table 4
The magnetic parameters recorded for the prepared copper(II) complexes derived from N-salicylidenearoylhydrazones
Complex
R
meff (mB) (298 K)
u (K)
y2J (cmy1
)
g
Xp (%)
n
[{Cu(L)(OH)}2]PnH2O (4)
C6H5
p-CH3C6H4
2
2
1
1.65
1.54
1.52
171
276
261
2.05
2.12
2.10
6.75
4.20
4.10
p-CH3OC6H4
[Cu(HL)Cl.H2O]PnH2O (5)
C6H5
p-CH3C6H4
p-CH3OC6H4
p-ClC6H4
1.80
1.83
1.83
1.84
y16.8
y15.4
y17.2
y16.7
1
1
[{Cu(HL)Cl}2] (6)
C6H5
p-CH3C6H4
1.12
1.21
452
406
2.20
2.19
1.56
1.80
[Cu(HL)(NO3)]PnH2O
C6H5
1
1.85
1.30
y8.5
[{Cu(HL)(H2O)}2](NO3)2 (7a)
C6H5
390
2.21
1.70
[{Cu(HL)(H2O)}2](NO3)2PnH2O (7)
CH3
p-CH3C6H4
1.30
1.45
340
338
2.20
2.21
0.50
1.60
1
1
[Cu(HL)NCS]PnH2O (8)
C6H5
p-CH3C6H4
1.87
1.89
1.89
1.35
1.75
3.15
p-CH3OC6H4
chloro complexes [{Cu(HL)Cl}2] show, at room tempera-
ture, low lying magnetic moments within the range1.12–1.21
mB. A plot of xM and meff, measured for [{Cu(HSp-
CH3Bzh)Cl}2], as a function of temperature, Fig. 3, suggests
strong antiferromagnetc interaction. Fitting the data to the
Bleaney–Bowers equation gives Jsy203 cmy1, gs2.19,
and Xps0.0179. These values are comparable with those
previously reported for [{Cu(HSBzh)Cl}2] (6, RsC6H5)
[18]. The obtained y2J values, Table 4, are within the range
reported for bis-m-aryloxo bridged dicopper complexes
[18,28]. The copper(II) in these complexes has a distorted
(4q1) tetragonal pyramidal coordination where the apical
site is occupied by a chloride ion. Dimerization is achieved
by sharing of phenoxy oxygen from each ligand through two
copper atoms [18].
Similar to the chloro complexes [{Cu(HL)Cl}2] (6,
RsC6H5, p-CH3C6H4), the isolated binuclear nitrate com-
plexes [{Cu(HSBzh)}2]P2NO3, [{Cu(HSp-CH3Bzh)P
H2O}2]PH2OP2NO3 and [{Cu(HSp-CH3OBzh)}2]P2NO3
show subnormal magnetic moments (1.30–1.45 mB) at room
temperature. A plot of the magnetic susceptibility data meas-
ured for [{Cu(HSBzh)2]P2NO3 as a function of temperature
(5–298 K), Fig. 4, indicates strong antiferromagnetic
exchange coupling. Similar behaviour was also observed
for both [{Cu(HSp-CH3Bzh)PH2O}2]PH2OP2NO3 and
Fig. 3. Magnetic susceptibilities x (d) and magnetic moments (o) vs.
temperature for [{Cu(HSp-CH3Bzh)Cl}2]. Solid lines represent the best
least squares fit to Eq. (1), with Jsy203, gs2.19 and Xps1.8%.
Fig. 4. Magnetic susceptibilities x (d) and magnetic moments (o) vs.
temperature for [{Cu(Sp-Bzh)}2]P2NO3. Solid linesrepresentthebestleast
squares fit to Eq. (1), with Jsy195, gs2.21 and Xps1.7%.
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955
[{Cu(HSp-OCH3Bzh)}2]P2NO3. Thebest fitparameters(J,
g and Xp) obtained by fitting the variable temperature mag-
netic susceptibility data to the Bleaney–Bowers equation are
bridged thiocyanate cannot be ruled out, since no magnetic
interactions between the copper(II) centres was observed in
polymeric [Cu(bheg)NCS]PH2O (where Hbheg is N,N
bis(2-hydroxyethylglycine)) [34]. The actual structure of
these isothiocyanate complexes must remain in doubt until
complete X-ray molecular structures are available.
listed in Table 4. The obtained y2J values (338–390 cmy1
)
suggest strong antiferromagnetic exchange interaction via
bridged phenoxy oxygens [28]. Recently, the preparation
and X-ray crystal and molecular structure of the analogous
dinuclear complex [{Cu(HSAc)H2O}2]P2NO3 have been
reported [20]. This complex is a centrosymmetric (planar)
dimer, the monomeric units being bridged through the phen-
oxy oxygen. The copper atom has a square-pyramidal geom-
etry with the basal donor atoms coming from the ONO
mononegative tridentate ligand and the symmetry related
phenolate oxygen, while the fifth coordination site is occu-
pied by water oxygen. The nitrate ions are not coordinated
and act as counter ions [20]. Unfortunately, no variable-
temperature magnetic data have been reported for this com-
plex. In the present work, the room temperature magnetic
moment of the dinuclear complex [{Cu(HSAc)H2O}2]P
2NO3 was found to be 1.29 mB which is more or less similar
to the value reported previously by Chan et al. (1.28 mB)
[20]. Fitting the variable temperature susceptibility data
recorded for [{Cu(HSAc)H2O}2]P2NO3 to a modified Ble-
aney–Bowers equation gives Jsy340 cmy1, gs2.20 and
Xps 2.2%. The obtained (y2J) is comparable to that
reported for [{Cu(HSp-CH3Bzh)PH2O}2]PH2OP2NO3 and
a similar dimeric structure (7, Rsp-CH3C6H4) can be pro-
posed forthiscomplex, wherethecopper(II)isweaklybound
to the oxygen of the coordinated water molecule. The anhy-
drous dimeric [{Cu(HSBzh)2]P2NO3 and [{Cu(HSp-
OCH3Bzh)}2]P2NO3 complexes, on the other hand, show
relatively higher y2J values (ca. 392 cmy1) implying
stronger antiferromagnetic exchange interaction between the
two copper(II) centres. It seems that coordination of a water
molecule in 7a (Rsp-CH3C6H4) results in a slight distortion
from planarity and decreases the strength of antiferromag-
netic interactions relative to the more planar anhydrous
dimers.
The thiocyanate complexes [Cu(HL)SCN]PnH2O, Table
1, have room temperature magnetic moments in excess of 1.8
mB, Table 4, suggesting that the paramagnetic centres are
quite shielded by the diamagnetic matrix, and if the copper
centres are spin coupled, exchange is likely to be weak. The
magnetic moments of these complexes are more or less con-
stant (ca. 1.87 mB) within the temperature range (35–300
K), but decrease below 35 K and drop to ca. 1.74 mB at 10
K, suggesting weak antiferromagnetic interactions. Assum-
ing Curie–Weiss behaviour, plots of inverse magnetic sus-
ceptibility for 8 (RsC6H5, p-CH3C6H4 and p-ClC6H4)
versus temperature gave Curie–Weiss constants usy1.35,
y1.75 and y3.20, respectively. This magnetic behaviour
can rule out the possible formation of a binuclear structure
with phenoxy bridges similar to that reported for the corre-
sponding chloride or nitrate complexes and a monomeric
structure (8) can be proposed for these thiocyanate com-
plexes. However, dimeric or polymeric structures with
2.4. Infrared spectra
The IR spectra of N-salicylidenearoylhydrazines, Table 5,
show a series of bands at ca. 3200, 1670, 1600 and 1340
cmy1, respectively due to n(N–H), n(C_O) (amide I),
n(C_N), d(N–H) (amide II), and n(C–N) (amide III).
The spectra of the corresponding binuclear complexes
[{Cu(L)}2] (2) and K[{Cu(L)(OH)}2]PnH2O (4) lack
any absorption which can be attributed to n(N–H), n(C_O)
or d(N–H), but show an intense absorption due to n(C_N–
N_C) as well as the amide III band, implying the deproton-
ation of the enolimine tautomer of the hydrazone ligand
[1,2,35,36]. However, the spectra of the mononuclear
complexes of the types [Cu(HL)ClPH2O]PnH2O (5),
[Cu(HSBzH)NO2]PH2O, and [Cu(HL)NCS]PnH2O (8)
as well as the binuclear complexes [{Cu(HL)Cl}2] (6),
[{Cu(HL)H2O}2](NO3)2PnH2O (7) [{Cu(HL)}2]-
(NO3)2 (7a), Table 5, show a series of bands at ca. 3180,
1615, 1600, 1540 and 1320 cmy1 due to n(N–H), n(C_O),
n(C_N), d(N–H) and n(C–N), respectively. The presence
of n(N–H), n(C_O) and d(N–H) in the IR spectra of these
complexes indicate that the hydrazone molecule reacts in the
ketoamine form. Moreover, the stoichiometry of these com-
plexes as well as the pronounced shift in both n(C_O) and
n(C_N) to lower frequenciesrelativetothoseofcorrespond-
ing uncoordinated hydrazones suggest that these aroylhydra-
zones act as mononegative ONO tridentate ligands
[1,2,35,36]. The IR spectrum of the mononuclear complex
[Cu(HSBzH)NO2]PH2O, Fig. 1, displays three bands at
1510, 1290 and 1000 cmy1, respectively due to the n(N_O),
nasym(NO2) and nsym(NO2), in agreement with the unsym-
metric bidentate nature of the coordinated nitrate. The spectra
of the binuclear nitrate complexes [{Cu(HL)H2O}2]-
(NO3)2PnH2O (7) and [{Cu(HL)}2](NO3)2 (7a), on the
other hand, show an intense band at ca. 1380 cmy1 charac-
teristic of ionic nitrate [22,37]. The spectraofthethiocyanate
complexes 8 show an intense band at 2085 cmy1 indicating
that the thiocyanate group acts as monodentate ligand, most
probably through the nitrogen atom [37].
3. Experimental
3.1. Preparation of aroylhydrazines and N-salicylidene-
aroylhydrazines
Aroylhydrazines were prepared, as previously described
[38], by the hydrazinolysis of aromatic carboxylic methyl
esters in methanol. The corresponding N-salicylidene aroyl-
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Table 5
Selected IR spectral bands (cmy1) for N-salicylidenearoylhydrazines and their corresponding copper(II) complexes
Compound
R
n(N–H)
n(C_O) (amide I)
n(C_N), n(C_C)
d(N–H)
n
(amide II)
(amide III)
[H2L] (1)
C6H5
p-CH3C6H4
p-CH3OC6H4
p-ClC6H4
3250 m
3200 m
3200 m
3205 m
I675 s
1635 s
1540 s
1540 s
1555 s
1560 s
1355 m
1362 m
1355 s
1365 s
1675 s
1670 sh
1646 s
1640 s, 1620 s
1636 s, 1604 s
1620 s
[{Cu(L)}2}] (2)
C6H5
p-CH3C6H4
p-CH3OC6H4
p-ClC6H4
1618 s, 1594 s
1619 s, 1595 s
1618 s, 1597 s
1619 s, 1593 s
1340 s
1342 m
1342 s
1342 s
K2[{Cu(L)OH}2]PnH2O (4)
C6H5
p-CH3C6H4
p-CH3OC6H4
p-ClC6H4
2
2
1
1612s
1612s
1615s
1614s
1340 s
1340 m
1343 m
1338 s
[Cu(HL)Cl.H2O]PnH2O (5)
C6H5
p-CH3C6H4
p-CH3OC6H4
p-ClC6H4
3120 m
3195 m
3200 m
1620 s
1618 s
1620 s
1600 s, 1590 sh
1605 s
1605 s, 1590 s
1590 s
1545 m
1535 s
1555 s
1540 s
1340 s
1335 m
1330 m
1318 m
1
1
[{Cu(HL)Cl}2] (6)
C6H5
p-CH3C6H4
3125 m
3130 m
1615 s
1618 s
1595 s
1590 s
1550 s
1543 s
1344 m, 1312 m
1326 m, 1308 m
[Cu(HL)NO3]PnH2O
C6H5
1
3195m
1622s
1603 s
1545 m
1335 m
[{Cu(HL)}2](NO3)2 (7a)
C6H5
p-CH3OC6H4
3180 m
3170 m
1618 s
1620 s
1595 s
1597 s
1545 m
1540 m
1300m
1305m
[{Cu(HL)PH2O}2](NO3)2PnH2O (7)
p-CH3C6H4
1
1
3170 m
1620 s
1602 s, 1570
1545 m
1330 m
[Cu(HL)(NCS)]PnH2O (8)
C6H5
p-CH3C6H4
3146 m
3195 m
3210
1620 s
1620 s
1623 s
1605 s, 1590 s
1605 s
1605 s
1544 s
1538 s
1540 m
1327 m
1335 m
1335 s
p-CH3OC6H4
hydrazines were prepared by the condensation of salicylal-
dehyde with aroylhydrazines in methanol [38–40](H2SBzh,
m.p.s1828C; H2Sp-MeBzh, m.p.s1958C; H2Sp-MeOBzh,
m.p.s1738C; H2Sp-ClBzh, m.p.s2088C).
green complex, [Cu(L)]2, was filtered, washed with hot
methanol and then dried in vacuo.
3.2.2. Preparation of K2[{Cu(L)OH}2]PnH2O (4, RsC6H5,
p-CH3C6H4 and p-OCH3C6H4)
3.2. Preparation of copper(II) complexes of N-salicylidene-
aroylhydrazines
To a suspension of [{Cu(L)}2] complex (2, RsC6H5,
p-CH3C6H4 and p-OCH3C6H4) (0.01 mol) in hot absolute
ethanol (50 cm3), an excess amount of KOH (0.025 mol)
was added and the reaction mixture was refluxed until com-
plete dissolutionof[{Cu(L)}2]complex. Theresultingsolu-
tion was filtered and then evaporated to half its volume. On
cooling the formed green complex K2[{Cu(L)OH}2]P
nH2O, Table 1, was isolated and then dried over CaCl2.
3.2.1. Preparation of [{Cu(L)}2] (2, RsC6H5, p-CH3C6H4,
p-CH3OC6H4 and p-ClC6H4)
To a solution of N-salicylidenearoylhydrazine (H2L) (1,
RsC6H5, p-CH3C6H4, p-CH3OC6H4 and p-ClC6H4) (0.01
mol) in dry methanol (30 cm3), an equivalent amount of
Cu(CH3COO)2P2H2O (0.012 mol) in dry methanol (50
cm3) was added dropwise with constantstirring. Duringaddi-
tion a green precipitate started to appear and after complete
addition of copper acetate, the reaction mixture was refluxed,
with constant stirring, for ca. 30 min. On cooling the formed
3.2.3. Preparation of [Cu(HL)Cl]PnH2O (5, RsC6H5,
p-CH3C6H4, p-OCH3C6H4 and p-ClC6H4)
A solution of CuCl2P2H2O (0.01 mol)inethanol(20cm3)
was added to a solution of salicylaldehyde (0.01 mol) in
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957
ethanol (50 cm3). The reaction mixture was heated for a few
minutes and then an equivalent amount of aroylhydrazine
(0.01 mol) was added dropwise with constant stirring. The
resulting mixture was then refluxed for ca. 15 min and the
isolated green complex [Cu(HL)ClPH2O]PnH2O (5, Rs
C6H5, p-CH3C6H4, p-CH3OC6H4 and p-ClC6H4) which was
separated on cooling, was filtered, washed with ethanol then
dried in vacuo.
reading was made with polystyrene film. Solid samples were
examined as KBr discs. Magnetic susceptibilities of pow-
dered dried samples were recorded on a Faraday-type mag-
netometer using a sensitive computer controlled D-200 Cahn
RG microbalance in the temperature range 4.2–298 K. The
magnetic field applied was ;1.5 T. Details of the apparatus
have been described elsewhere [41,42]. Experimental sus-
ceptibility data were corrected for the underlying diamagne-
tism. The elemental analyses (C, H and N) were performed
at the microanalytical laboratory, Faculty of Science, Alex-
andria University and/or at the Darmstadt Technical Univer-
sity, Germany. The copper(II) content of the prepared
complexes was determined volumetrically by titration with
EDTA using PAN as indicator and/or by atomic absorption
technique.
3.2.4. Preparation of [{Cu(HL)Cl}2]PnH2O (6, RsC6H5
and p-CH3C6H4)
To a solution of N-salicylidenearoylhydrazine (H2L) (1,
RsC6H5 or p-CH3C6H4) (0.01 mol) in absolute ethanol (30
cm3), an equivalent amount of CuCl2P2H2O (0.01 mol) in
hot absolute ethanol (20 cm3) was added dropwise with
constant stirring, then refluxed for 1 h. On cooling the pre-
cipitated copper(II) complex (2.34, RsC6H5 or p-CH3-
C6H4) was filtered, washed with absolute ethanol and then
dried in vacuo.
3.4. X-ray crystal and molecular structure
Suitable crystals were sealed in a fine focus glass capillary
tube and mounted on a Nonius CAD-4 [43] diffractometer.
Intensity data were collected at room temperature in the v–u
scan mode, using graphite monochromatized Mo Ka radia-
tion. Lattice constants were determined by full-matrix least-
squares refinement. The solution of the crystal structures was
carried out by using both SHELXS-86 [44] and SHELXL-
93 [45] programs. The SHELXL-93 program was also used
for structure refinement and for the evaluation of data. The
Steo-REDU4 [46] and StoeX-RED [46] programs were
used for computing data reductions. The graphics plotting of
the molecular and crystal structures was carried out using the
PLUTON-93 [47] program as well as ORTEP [48] method.
The form factors for Cu(0) were taken from the international
tables [49] and those for the other atoms are included as
saved values in used programs.
3.2.5. Preparation of [Cu(HSBz)NO3]PH2O
A solution of CuNO3P6H2O (0.01 mol) in ethanol (20
cm3) was added to a solution of salicylaldehyde (0.01 mol)
in ethanol (50 cm3). The reaction mixture was heated for a
few minutes and then an equivalent amountofaroylhydrazine
(0.01 mol) was added dropwise with constant stirring. The
resulting mixture was refluxed for ca. 1 h. On cooling, the
separated copper(II) complex [Cu(HL)NO3]PH2O was fil-
tered, washed with ethanol and then dried in vacuo.
3.2.6. Preparation of [{Cu(HL)NO3}2]PnH2O (7, RsC6H5,
p-CH3C6H4, and p-CH3OC6H4)
To a solution of N-salicylidenearoylhydrazine H2L (1,
RsC6H5, p-CH3C6H4 and p-CH3OC6H4) (0.01 mol) in
absolute ethanol (30 cm3), an equivalent amount of
Cu(NO3)2P6H2O (0.015 mol) in absolute ethanol (50 cm3)
was added dropwise with constant stirring. The brownish-
green nitrate complex, [Cu(HL)NO3]2PnH2O, which was
formed, was filtered off, washed with ethanol and then dried
in vacuo.
Supplementary data
Atomic coordinates, equivalent isotropic displacement
parameters, hydrogen coordinates, isotropic displacement
parameters, anisotropic displacement parameters and com-
plete lists of bond distancesand bond angleshavebeendepos-
ited with the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK (fax: q44-1223-
336033; e-mail: deposit@ccdc.cam.ac.uk) and are available
on request quoting no. CCDC 136950.
3.2.7. Preparation of [Cu(HL)SCN]PnH2O (8, RsC6H5,
p-CH3C6H4, p-CH3OC6H4 and p-ClC6H4)
To a suspension of either copper chloride or copper nitrate
copper(II) complexes (0.01 mol) in methanol (30 cm3), the
equivalent amount of NH4SCN (0.015 mol) as a solid or in
methanol (10 cm3) was added dropwise and the reaction
mixture was stirred at room temperature or refluxed for ca.
2 h. The green precipitate, which was formed, was isolated
and washed with methanol, then dried in vacuo.
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M.F. Iskander et al. / Polyhedron 19 (2000) 949–958
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