Oxime-functionalized diazamesocyclic derivates and their metal complexes: Effect of the ligand backbones and anions on the generation of novel monomeric and mono-μ-Cl dimeric CuII complexes

Article abstract of DOI:10.1016/j.ica.2005.07.034

Two oxime-functionalized diazamesocyclic derivates, namely, N,N′-bis(acetophenoneoxime)-1,4-diazacycloheptane (H₂L ¹) and N,N′-bis(acetophenonoxime)-1,5-diazacyclooctane (H ₂L²), have been prepared and characterized. Both ligands (obtained in the hydrochloride form) can form stable metal complexes with Cu^II and Ni^II salts, the crystal structures of which were determined by X-ray diffraction technique. The reactions of H₂L ¹ with Cu(ClO₄)₂ and Ni(ClO₄) ₂ afford a penta-coordinated mononuclear complex [Cu(H ₂L¹)Cl]·ClO₄ (1) and a four-coordinated monomeric [Ni(HL¹)]·ClO₄ (2), in which the ligand is monodeprotonated. The ligand H₂L² also forms a quite similar mononuclear [Ni(HL²)]·ClO₄ complex with Ni(ClO₄)₂, according to our previous work. However, reactions of different Cu^II salts [Cu(ClO₄)₂, CuCl₂ and Cu(NO₃)₂ for 3, and CuSO₄ for 4] with H₂L² in the presence of NaClO₄ yield two unusual mono-μ-Cl dinuclear Cu^II complexes [Cu ₂(HL²)₂Cl]·(ClO₄) (3), and [Cu₂(H₂L²)(HL²)Cl]·(ClO ₄)₂·(H₂O)(4). These results indicate that the resultant Cu^II complexes (1, 3 and 4) are sensitive to the backbones of diazamesocycles and even auxiliary anions.

Full text of DOI:10.1016/j.ica.2005.07.034

Inorganica Chimica Acta 358 (2005) 4481–4488
www.elsevier.com/locate/ica
Oxime-functionalized diazamesocyclic derivates and their
metal complexes: Effect of the ligand backbones and anions on
the generation of novel monomeric and mono-l-Cl dimeric
CuII complexes
b
b
b
a,
*
Xiao-Jun Zhao a,b, Miao Du , Ying Wang , Jian-Hua Guo , Xian-He Bu
a
Department of Chemistry, Nankai University, Tianjin 300071, PR China
College of Chemistry and Life Science, Tianjin Normal University, Tianjin 300074, PR China
b
Received 8 April 2005; received in revised form 13 July 2005; accepted 22 July 2005
Available online 31 August 2005
Abstract
Two oxime-functionalized diazamesocyclic derivates, namely, N,N0-bis(acetophenoneoxime)-1,4-diazacycloheptane (H2L1) and
N,N0-bis(acetophenonoxime)-1,5-diazacyclooctane (H2L2), have been prepared and characterized. Both ligands (obtained in the
hydrochloride form) can form stable metal complexes with CuII and NiII salts, the crystal structures of which were determined
by X-ray diffraction technique. The reactions of H2L1 with Cu(ClO4)2 and Ni(ClO4)2 afford a penta-coordinated mononuclear com-
plex [Cu(H2L1)Cl] Æ ClO4 (1) and a four-coordinated monomeric [Ni(HL1)] Æ ClO4 (2), in which the ligand is monodeprotonated. The
ligand H2L2 also forms a quite similar mononuclear [Ni(HL2)] Æ ClO4 complex with Ni(ClO4)2, according to our previous work.
However, reactions of different CuII salts [Cu(ClO4)2, CuCl2 and Cu(NO3)2 for 3, and CuSO4 for 4] with H2L2 in the presence
of NaClO4 yield two unusual mono-l-Cl dinuclear CuII complexes [Cu2(HL2)2Cl] Æ (ClO4) (3), and [Cu2(H2L2)(HL2)Cl] Æ
(ClO4)2 Æ (H2O) (4). These results indicate that the resultant CuII complexes (1, 3 and 4) are sensitive to the backbones of diazames-
ocycles and even auxiliary anions.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Oxime-functionalized diazamesocycles; Crystal structures; Monomeric CuII and NiII complexes; Mono-l-Cl CuII dimers
1. Introduction
diazacyclooctane (DACO) and 1,4-diazacycloheptane
(DACH) are most typical; the former always takes the
‘‘boat-chair’’ conformation when coordinated to the me-
tal ion, while the latter can take different configurations
[1]. As described in many other publications from this
laboratory [3–12], we are exploring the coordination
chemistry of such interesting diazamesocyclic systems,
especially DACO, and a series of heterocycle-, phenol-,
thiol- and carboxyl-functionalized derivates have been
designed and synthesized, which are proven to be good
building blocks for constructing polymeric coordination
complexes with unique structures and properties.
Mesocyclic ligands and their functional derivates oc-
cupy a vital position in the field of coordination chemis-
try, located between acyclic and macrocyclic ligands,
with regard to the unique conformations, exceptionally
strong ligand fields and potential ability for further
functionalization [1,2]. Mesocyclic diamines, possessing
only two nitrogen donors, are the smallest members
in the family of cyclic polyamines. Among them, 1,5-
*
Corresponding author. Tel.: +86 22 23502809; fax: +86 22
Oximes play an important role in the development of
transition metal coordination chemistry due to their
23502458.
E-mail address: buxh@nankai.edu.cn (X.-H. Bu).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.07.034

4482
X.-J. Zhao et al. / Inorganica Chimica Acta 358 (2005) 4481–4488
N
N
N
N
N
N
N
N
HO
HO
OH
OH
H2L1
H2L2
Chart 1.
versatile bonding modes [13]. Thus, we anticipated that
the design of new ligands by introducing the oxime
groups onto the backbone of diazamesocycles would cre-
ate novel metal complexes. Recently, we have reported a
new oxime-functionalized DACO ligand, N,N0-bis(acet-
ophenonoxime)-1,5-diazacyclooctane (H2L2) and its NiII
complex [Ni(HL2)] Æ ClO4 [14], in which both deproto-
nated and protonated oxime groups have only N-binding
mode with NiII. To further develop the understanding of
the coordination chemistry of such systems, we will de-
scribe herein the preparation of a new ligand (see Chart
1) N,N0-bis(acetophenone-oxime)-1,4-diazacycloheptane
(H2L1) and four related metal complexes, including
cmꢀ1): 3461s, 3048w, 2954w, 2931w, 2857w, 1685m,
1460vs, 1317m, 1302w, 1231w, 1159w, 1146w, 1095m,
1073m, 1029s, 1003m, 976m, 948s, 849s, 764s, 695s,
648m, 600m.
2.3. Synthesis of complexes 1–4
2.3.1. [Cu(H2L1)Cl] Æ ClO4 (1)
The ligands H2L1 Æ 2HCl (44.1 mg, 0.1 mmol) and Na-
ClO4 (48.7 mg, 0.4 mmol) were dissolved in methanol
(20 mL). After stirring for 30 min, the above suspension
was filtered and treated with Cu(ClO4)2 Æ 6H2O
(37.5 mg, 0.1 mmol), resulting in a clear blue solution.
ThepHvalueofthissolutionwasadjustedto6byaddition
of several drops of triethylamine. The stirring was contin-
ued for 1 h with reflux and the solution was filtered after
cooling to room temperature. Vapor diffusion of diethyl
ether to this filtrate yielded X-ray quality deep-blue block
crystals in 75% yield. Anal. Calc. for C21H26N4O6Cl2Cu:
C, 44.65; H, 4.64; N, 9.92. Found: C, 44.41; H, 4.97; N,
9.67%. FT-IR (KBr pellet, cmꢀ1): 3434s(br), 2910w,
1644s, 1561s, 1540m, 1499m, 1455s, 1428m, 1352m,
1294s, 1150m, 1110vs, 1104vs, 1066 vs, 1029m, 923m,
861m, 827m, 774m, 679s, 624s, 593m, 552m.
[Cu(H2L1)Cl] Æ ClO4
(1),
[Ni(HL1)] Æ ClO4
(2),
[Cu2(HL2)2Cl] Æ (ClO4) (3), and [Cu2(H2L2)(HL2)Cl] Æ
(ClO4)2 Æ (H2O) (4), which were structurally character-
ized by single-crystal X-ray diffraction. Significantly,
the structures of these CuII complexes can be influenced
by the modification of the ligand backbones and anions.
2. Experimental
2.1. Materials and general methods
All reagents and solvents for synthesis and analysis
were obtained commercially with the analytical grade
and used as received. FT-IR spectra (KBr pellets) were
taken on an FT-IR 170SX (Nicolet) spectrometer. Ele-
mental analyses of carbon, hydrogen and nitrogen were
2.3.2. [Ni(HL1)] Æ ClO4 (2)
The same synthetic procedure as for 1 was used ex-
cept that Cu(ClO4)2 Æ 6H2O was replaced by Ni(-
ClO4)2 Æ 6H2O, resulting in yellow prism single crystals
suitable for X-ray diffraction in 80% yield. Anal. Calc.
for C21H25N4O6ClNi: C, 48.17; H, 4.81; N, 10.70.
Found: C, 48.33; H, 4.62; N, 10.59%. FT-IR (KBr pel-
let, cmꢀ1): 3431m, 3101w, 3057w, 3024w, 2933w,
2875w, 1590w, 1575w, 1543w, 1495m, 1460m, 1442s,
1373w, 1320w, 1285w, 1232w, 1191m, 1154m, 1092vs,
1027m, 990w, 953w, 912w, 865w, 835w, 798w, 760s,
687s, 636m, 623s, 596m, 546w.
1
performed on a Perkin–Elmer 240C analyzer. H NMR
spectra were recorded on a Bruker AC-P 300 spectrom-
eter (300 MHz) at room temperature with tetramethylsi-
lane as the internal reference.
2.2. Preparation of the ligands
The ligand H2L2 Æ 2HCl was prepared according to
our previous work [14]. The new ligand H2L1 was also
obtained in its dihydrochloride form utilizing the same
synthetic procedure as for H2L2, except that the starting
material DACO was replaced by DACH. Yield: 59%
(light-yellow powder). Anal. Calc. for C21H26ꢀ
N4O2 Æ 2HCl: C, 57.41; H, 6.42; N, 12.75. Found: C,
57.66; H, 6.28; N, 13.01%. 1H NMR (CD3OD): d
1.65–1.67 (m, 2H), 2.62–2.70 (m, 8H), 3.53 (s, 4H),
7.32–7.37 (m, 6H), 7.63–7.67 (m, 4H). IR (KBr pellet,
2.3.3. [Cu2(HL2)2Cl] Æ (ClO4) (3)
The same synthetic procedure as for 1 was used
except that H2L1 was replaced by H2L2, giving block
blue-black single crystals suitable for X-ray diffraction
in 65% yield. Complex 3 could also be isolated by apply-
ing the same synthetic procedure using CuCl2 or
Cu(NO3)2 as the source of copper (II). Anal. Calc. for
C44H54Cl2Cu2N8O8: C, 51.76; H, 5.33; N, 10.98. Found:
C, 51.65; H, 5.21; N, 11.24%. FT-IR (KBr pellet, cmꢀ1):

X.-J. Zhao et al. / Inorganica Chimica Acta 358 (2005) 4481–4488
4483
3440b, 3058w, 2913w, 2858w, 1618w, 1587w, 1495m,
1445s, 1405w, 1365w, 1320w, 1300w, 1225w, 1122vs,
1093vs, 1035m, 994m, 962w, 922w, 855w, 823w, 769m,
751m, 695m, 623s, 588m, 556w.
All structures were solved by direct methods using
SHELXS program of the SHELXTL-97 package and refined
with SHELXL [16]. CuII and NiII centers were located from
the E-maps and other non-hydrogen atoms were located
in successive difference Fourier syntheses. The final
refinements were performed by full matrix least-squares
methods with anisotropic thermal parameters for non-
hydrogen atoms on F2. The hydrogen atoms of the
ligand were placed in the geometrically calculated posi-
tions (the hydrogen atoms of the oxime groups were first
found in a different electron density map, and then
placed in the calculated sites) and included in the final
refinement in the riding model approximation with fixed
displacement parameters. Hydrogen atoms of the disor-
dered lattice water molecule in 4 could not be located.
Perchlorate counter anions in complexes 2–4 were trea-
ted with the disorder model. Molecular graphics were
drawn with the program XP. Further crystallographic
data and experimental details for structural analyses
and selected bond lengths and angles with their esti-
mated standard deviations for complexes 1–4 are sum-
marized in Tables 1 and 2, respectively.
2.3.4. [Cu2(H2L2)(HL2)Cl] Æ (ClO4)2 Æ (H2O) (4)
The same synthetic procedure as for 3 was used ex-
cept that Cu(ClO4)2 Æ 6H2O was replaced by CuSO4,
producing block blue crystals suitable for X-ray diffrac-
tion in 40% yield. Anal. Calc. for C44H57Cl3Cu2N8O13:
C, 46.38; H, 5.04; N, 9.83. Found: C, 46.51; H, 4.85;
N, 9.67%. FT-IR (KBr pellet, cmꢀ1): 3448b, 2913w,
1774w, 1624m, 1495m, 1446s, 1404w, 1364w, 1303w,
1250w, 1121vs, 1090vs, 1015m, 992s, 964w, 927w,
855w, 823w, 767s, 695s, 624s, 591m.
Caution: Although no problem was encountered in
this study, transition metal perchlorate complexes are
potentially explosive, and should be handled with proper
precautions.
2.4. X-ray crystallographic data collection and refinement
Single-crystal X-ray diffraction study of complexes
1–4 was performed on a Bruker Smart 1000 CCD dif-
fractometer equipped with a graphite crystal monochro-
mator situated in the incident beam for data collection.
Data collections were performed with Mo Ka radiation
3. Results and discussion
3.1. Crystal structures of complexes 1–4
˚
(k = 0.71073 A) by - scan mode in the range of
1.92ꢁ < h < 26.39ꢁ (for 1), 1.99ꢁ < h < 25.00ꢁ (for 2),
2.03ꢁ < h < 25.03ꢁ (for 3), and 2.19ꢁ < h < 25.00ꢁ (for
4) at 293(2) K. All data were corrected by semi-empirical
method using SADABS program. The program SAINT [15]
was used for integration of the diffraction profiles.
3.1.1. [Cu(H2L1)Cl] Æ ClO4 (1)
The crystal structure of 1 consists of a discrete mono-
nuclear [Cu(H2L1)Cl]+ cation and a perchlorate counter
anion. The ORTEP view of the coordination cation in 1
with atom labeling scheme is shown in Fig. 1(a). Each
Table 1
Crystallographic data and structure refinement summary for complexes 1–4
Formula
C
564.90
21H26Cl2CuN4O6
C21H25ClNiN4O6
523.61
C44H54Cl2Cu2N8O8
1020.93
0.35 · 0.30 · 0.20
monoclinic
P21/n
14.990(4)
10.748(3)
28.047(8)
90
91.104(5)
90
4518(2)
4
C44H57Cl3Cu2N8O13
1139.41
0.22 · 0.14 · 0.10
triclinic
Formula weight
Crystal size (mm)
Crystal system
Space group
0.22 · 0.20 · 0.18
monoclinic
C2/c
28.492(8)
11.983(4)
17.391(6)
90
126.820(4)
90
4753(3)
8
0.40 · 0.12 · 0.10
orthorhombic
P212121
9.690(3)
12.258(4)
18.549(6)
90
ꢀ
P1
˚
a (A)
11.114(4)
14.641(4)
16.984(6)
77.585(6)
73.908(6)
79.272(5)
2569.5(14)
2
1.473
1.052
1180
13098
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90
90
3
˚
V (A )
2203.4(13)
4
1.578
1.049
1088
Z
Dcalc (g cmꢀ3
)
1.579
1.189
2328
13267
1.501
1.122
2120
36672
l (mmꢀ1
F(000)
N
)
9296
Nind
Parameters
4866
309
3871
337
7772
583
8942
696
R indices (I > 2r(I))
Goodness-of-fit on F2
0.0559, 0.1372
1.045
0.886 and ꢀ0.438
0.0548, 0.0599
0.975
0.460 and ꢀ0.352
0.0620, 0.1224
1.038
0.652 and ꢀ0.441
0.0641, 0.1316
1.045
0.651 and ꢀ0.499
ꢀ3
˚
Dqmax,min (e A
)

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X.-J. Zhao et al. / Inorganica Chimica Acta 358 (2005) 4481–4488
Table 2
Table 2 (continued)
˚
Selected bond lengths (A) and angles (ꢁ) for complexes 1–4
Cu(1)–N(1)
Cu(1)–Cl(3)
Cu(2)–N(7)
Cu(2)–N(6)
Cu(1)–N(4)
Cu(1)–N(2)
Cu(2)–N(8)
Cu(2)–N(5)
Cu(2)–Cl(3)
2.008(5)
2.533(6)
1.997(5)
2.010(5)
1.984(5)
2.026(5)
1.961(6)
2.006(6)
2.515(6)
Complex 1
Cu(1)–N(4)
Cu(1)–N(1)
Cu(1)–N(3)
Cu(1)–N(2)
Cu(1)–Cl(1)
1.975(3)
2.012(3)
2.334(4)
1.999(3)
2.2736(13)
N(4)–Cu(1)–N(2)
N(4)–Cu(1)–N(1)
N(2)–Cu(1)–N(1)
N(4)–Cu(1)–N(3)
Cl(1)–Cu(1)–N(3)
N(4)–Cu(1)–Cl(1)
N(2)–Cu(1)–Cl(1)
N(1)–Cu(1)–Cl(1)
N(1)–Cu(1)–N(3)
N(2)–Cu(1)–N(3)
81.25(14)
160.23(14)
79.79(14)
120.64(14)
92.50(11)
92.41(11)
151.90(11)
101.70(11)
72.95(13)
114.35(14)
N(3)–Cu(1)–N(4)
N(4)–Cu(1)–N(1)
N(4)–Cu(1)–N(2)
N(3)–Cu(1)–Cl(3)
N(1)–Cu(1)–Cl(3)
N(8)–Cu(2)–N(7)
N(7)–Cu(2)–N(5)
N(7)–Cu(2)–N(6)
N(8)–Cu(2)–Cl(3)
N(5)–Cu(2)–Cl(3)
Cu(2)–Cl(3)–Cu(1)
N(3)–Cu(1)–N(1)
N(3)–Cu(1)–N(2)
N(1)–Cu(1)–N(2)
N(4)–Cu(1)–Cl(3)
N(2)–Cu(1)–Cl(3)
N(8)–Cu(2)–N(5)
N(8)–Cu(2)–N(6)
N(5)–Cu(2)–N(6)
N(7)–Cu(2)–Cl(3)
N(6)–Cu(2)–Cl(3)
98.7(2)
157.1(2)
81.3(2)
98.1(2)
104.0(2)
98.5(2)
81.5(2)
156.4(2)
100.5(2)
98.2(2)
126.2(3)
83.4(2)
163.0(2)
90.20(19)
98.3(2)
98.7(2)
161.2(2)
82.6(2)
90.0(2)
96.2(2)
106.8(2)
Complex 2
Ni(1)–N(4)
Ni(1)–N(2)
Ni(1)–N(3)
Ni(1)–N(1)
1.854(4)
1.879(4)
1.824(4)
1.869(4)
N(4)–Ni(1)–N(3)
N(4)–Ni(1)–N(2)
N(4)–Ni(1)–N(1)
N(3)–Ni(1)–N(1)
N(3)–Ni(1)–N(2)
N(2)–Ni(1)–N(1)
99.7(2)
88.3(2)
173.3(2)
87.0(2)
172.3(3)
85.1(2)
Complex 3
Cu(1)–N(4)
Cu(1)–N(2)
Cu(1)–Cl(1)
Cu(2)–N(8)
Cu(2)–N(7)
Cu(1)–N(3)
Cu(1)–N(1)
Cu(2)–N(5)
Cu(2)–N(6)
Cu(2)–Cl(1)
1.943(5)
1.998(5)
2.4972(15)
1.933(5)
1.971(6)
1.952(6)
1.996(5)
1.924(6)
1.963(5)
2.5405(15)
CuII center coordinates to two oxime nitrogen donors
(Cu–N lengths: 2.012(3) and 1.999(3) A), a pair of nitro-
gen atoms from DACH ring (Cu–N lengths: 2.334(4)
and 1.975(3) A) and one chloride ion (Cu–Cl length:
˚
˚
˚
2.2736(13) A). The coordination geometry around the
CuII center could be described as a distorted square pyr-
amid with a value of 0.14 for s parameter, which is usu-
ally used to describe the degree of distortion of the metal
ion in penta-coordinated complexes (s = 1 for an ideal
trigonal-bipyramid and s = 0 for an ideal square-pyra-
mid) [17]. For all related complexes based on doubly
substituted (referring to pendant arms) DACO or
DACH derivates [3–12], in which the metal center has
a square-pyramidal or square-planar geometry, two
nitrogen (or oxygen) donors from the pendants and
two diazamesocyclic nitrogens are always in cis arrange-
ment, forming the basal plane of the coordination poly-
hedron. In each case of square pyramid, the axial site of
the coordination sphere is finished by a chloride ion or
water ligand. Significantly for 1, the equatorial plane
of the square pyramid is composed of two DACH nitro-
gen atoms (N1 and N2), one oxime N4 atom and one
chloride ion. The CuII center is deviated from this mean
N(4)–Cu(1)–N(3)
N(3)–Cu(1)–N(2)
N(3)–Cu(1)–N(1)
N(4)–Cu(1)–Cl(1)
N(2)–Cu(1)–Cl(1)
N(5)–Cu(2)–N(8)
N(8)–Cu(2)–N(6)
N(8)–Cu(2)–N(7)
N(5)–Cu(2)–Cl(1)
N(6)–Cu(2)–Cl(1)
Cu(1)–Cl(1)–Cu(2)
N(4)–Cu(1)–N(2)
N(4)–Cu(1)–N(1)
N(2)–Cu(1)–N(1)
N(3)–Cu(1)–Cl(1)
N(1)–Cu(1)–Cl(1)
N(5)–Cu(2)–N(6)
N(5)–Cu(2)–N(7)
N(6)–Cu(2)–N(7)
N(8)–Cu(2)–Cl(1)
N(7)–Cu(2)–Cl(1)
97.1(2)
82.4(2)
157.1(2)
101.42(17)
101.69(18)
96.3(2)
159.9(2)
83.3(2)
94.91(16)
101.14(16)
142.42(6)
156.3(2)
81.7(2)
89.7(2)
103.39(18)
99.24(16)
84.1(2)
161.5(2)
90.0(2)
98.85(16)
103.47(17)
˚
basal plane by 0.346 A. The oxime N3 atom occupies the
apex position with a considerably long Cu–N distance
Complex 4
Cu(1)–N(3)
1.964(5)

X.-J. Zhao et al. / Inorganica Chimica Acta 358 (2005) 4481–4488
4485
a
3.1.2. [Ni(HL1)] Æ ClO4 (2)
X-ray single-crystal structure determination reveals
that complex 2 is composed of a discrete mononuclear
[Ni(HL1)]+ cation and a perchlorate anion. The ORTEP
view of the monomeric cation in 2 with atom labeling
scheme is shown in Fig. 2, in which each NiII center
coordinates to two oxime nitrogen atoms and two nitro-
gens from DACH that are in the expected cis positions,
to form a square-planar geometry. Four adjacent N–Ni–
N angles are in the range of 88.3(2)–99.7(2)ꢁ, and two
diagonal N–Ni–N angles are 173.3(2)ꢁ and 172.3(3)ꢁ,
respectively. The NiII ion is deviated from the mean
coordination plane generated by N(1)–N(2)–N(3)–N(4)
1
b
˚
by only 0.0113 A. The Ni–N bond distances lie in the
˚
range of 1.824(4)–1.879(4) A, all being normal for such
coordination bonds. The lengths of Ni–NDACH bonds
are longer than those of Ni–Noxime (see Table 2), indicat-
ing weaker coordination of DACH rings compared with
the oxime groups, which is also the case for other similar
mononuclear NiII complexes based on functionalized
diazamesocyclic ligands [14,20,21].
Fig. 1. (a) ORTEP structure of the [Cu(H2L1)Cl]+ cation drawn with
30% thermal ellipsoid probability with atom labeling scheme in
complex 1; (b) the hydrogen-bonding supramolecular dimer in 1. The
hydrogen bonds are indicated by dashed lines in this and the
subsequent figures.
For the ligand HL1, one oxime group is deproto-
nated, forming a single directed intramolecular O(1)–
H(1)ꢁ ꢁ ꢁO(2) hydrogen bond that stabilizes this discrete
˚
monomeric motif. The Oꢁ ꢁ ꢁO separation is 2.454 A
and the bond angle is 164ꢁ. The dihedral angle of two
phenyl planes of the oxime pendants is 31.8ꢁ. The
N(4)–O(2) and N(3)–O(1) bond lengths in the oxime
II
˚
(2.334(4) A). This unusual environment of Cu may be
fixed and stabilized by the intramolecular O(2)–
˚
H(2)ꢁ ꢁ ꢁCl(1) hydrogen bond (Fig. 1(a)). The Oꢁ ꢁ ꢁCl sep-
groups are 1.325(5) and 1.339(5) A, which are compara-
˚
aration is 3.053 A and the O–Hꢁ ꢁ ꢁCl bond angle is 138ꢁ.
ble to those in the related complex [Ni(HL2)] Æ ClO4 [14].
The DACH ring in this structure also takes the normal
boat configuration, giving rise with the NiII center to
two five-membered chelate rings N(1)–C(6)–C(7)–
N(3)–Ni(1) and N(2)–C(14)–C(15)–N(4)–Ni(1). In addi-
tion, the NDACHꢁ ꢁ ꢁNDACH non-bonding distance
For the ligand, the DACH ring adopts the normal boat
configuration, and gives rise with the CuII center to two
five-membered chelate rings [N(1)–C(6)–C(7)–N(3)–
Cu(1)] and [N(2)–C(14)–C(15)–N(4)–Cu(1)], being in-
clined to each other with a dihedral angle of 63.1ꢁ.
Two oxime pendants coordinate to CuII ion with only
N-binding mode and make a dihedral angle of 85.0ꢁ be-
tween two benzene planes. The N(4)–O(2) and N(3)–
O(1) bond lengths in oximes are 1.378(5) and
˚
(2.533 A) is significantly shorter than that of Noximeꢁ ꢁ ꢁ
˚
Noxime (2.811 A). Consequently, the bite angle of
N
DACH–Ni–NDACH (85.1(2)ꢁ) is significantly smaller
than that of Noxime–Ni–Noxime (99.7(2)ꢁ) due to the ste-
reochemical requirement. It is worthy to note that com-
plex 2 is composed of spontaneously resolved chiral
crystals, crystallizing in the acentric space group
˚
1.399(5) A, which are comparable to those in a related
CuII complex [18].
Analysis of the crystal packing of 1 in the unit cell
shows that two perchlorate anions bridge a pair of
[Cu(H2L1)Cl]+ cations via strong O–Hꢁ ꢁ ꢁO and weak
C–Hꢁ ꢁ ꢁO interactions to result in a dimeric motif.
As depicted in Fig. 1(b), each perchlorate anion
acts as the acceptor of one intramolecular O(1)–
H(1)ꢁ ꢁ ꢁO(3)
and
one
intermolecular
C(14)–
H(14A)ꢁ ꢁ ꢁO(5)i (i = ꢀx + 1, ꢀy + 1, ꢀz + 1) hydrogen
bonds, connecting two adjacent monomeric cations in
(l2, g2) mode to form a supramolecular dimer, within
˚
which the Cuꢁ ꢁ ꢁCu separation is 10.252 A. The Oꢁ ꢁ ꢁO
˚
and Cꢁ ꢁ ꢁO separations are 2.804 and 3.395 A, respec-
tively, and the bond angles are 164ꢁ and 149ꢁ, falling
into the normal range of such hydrogen-bonding
interactions [19].
Fig. 2. ORTEP view of the [Ni(HL1)]+ cation in complex 2, drawn
with 30% thermal ellipsoid probability with atom labeling scheme.

4486
X.-J. Zhao et al. / Inorganica Chimica Acta 358 (2005) 4481–4488
P212121. The Flack parameter in this structure was re-
fined to 0.00(2) (near zero), indicating the correct abso-
lute configuration and a single enantiomer for each
individual crystal in the solid state [22].
a
3.1.3. [Cu2(HL2)2Cl] Æ (ClO4) (3) and
[Cu2(H2L2)(HL2)Cl] Æ (ClO4)2 Æ (H2O) (4)
The crystal structure of complex 3 consists of a
monochloro-bridged dimeric [Cu2(HL2)2Cl]+ cation, of
which the ORTEP view including the atomic numbering
scheme is given in Fig. 3(a), and a perchlorate counter
anion. It should be noted that monochloro-bridged CuII
dimers are quite unusual compared with the common di-
chloro-bridged dinuclear complexes and only a few
examples are documented so far [10]. Within the dimeric
cation, both Cu(1) and Cu(2) centers are penta-coordi-
nated (CuN4Cl sphere) to four nitrogen atoms of the
mono-deprotonated diazamesocycle ligand HL2, and
the shared bridging chloride anion at the apical site.
The coordination polyhedron for Cu(1)/Cu(2) could be
best described as a slightly distorted square-pyramid in
which two oxime nitrogens and two DACO nitrogen do-
nors are in the cis positions, which is reflected by the s
value (0.013 for Cu(1) and 0.027 for Cu(2)) as defined
b
˚
by Addison et al. [17]. Cu(1) atom is 0.392 A above
the mean basal plane defined by N(1)–N(2)–N(3)–N(4)
toward the apical Cl(1), and for Cu(2) the corresponding
˚
value is 0.322 A above the mean N(5)–N(6)–N(7)–N(8)
plane. The Cu–N bond distances lie in the range of
˚
1.924(5)–1.998(5) A, all being normal for such coordina-
tion bonds. The lengths of Cu–NDACO bonds are longer
than those of Cu–Noxime (see Table 2), indicating weaker
coordination of DACO rings compared with the oxime
groups, which is also observed in other related CuII
complexes [3,4,6]. The Cu–Cl bond lengths (2.4972(15)
˚
and 2.5405(15) A) are comparable to the related mono-
chloro-bridged CuII dimers [10], and significantly short-
er than those in the dichloro-bridged dinuclear motifs
˚
(normally, in 2.7–3.0 A range), and the Cu(1)–Cl(1)–
Cu(2) bridging angle is 142.42(6)ꢁ. The intramolecular
˚
Cu(1)ꢁ ꢁ ꢁCu(2) distance is 4.770 A, being comparable to
the related monochloro-bridged CuII dimers, and signif-
icantly longer than those in the dichloro-bridged dinu-
clear complexes [10]. The shortest intermolecular
separations for Cu(1)ꢁ ꢁ ꢁCu(2) (symmetry code: x,
y + 1, z), Cu(1)ꢁ ꢁ ꢁCu(1) (symmetry code: ꢀx, ꢀy + 1,
ꢀz) and Cu(2)ꢁ ꢁ ꢁCu(2) (symmetry code: ꢀx + 1,
Fig. 3. ORTEP structure with atom labeling of the: (a)
[Cu2(HL2)2Cl]+ cation in 3; (b) [Cu2(H2L2)(HL2)Cl]2+ cation in 4,
drawn with 30% thermal ellipsoid probability.
ligand [14]. The dihedral angle between two phenyl-
groups of the oxime pendants in the ligand bound to
Cu(1) is 155.6ꢁ and that for the other ligand bound to
Cu(2) is 47.7ꢁ. The N(3)–O(1), N(4)–O(2), N(5)–O(3)
and N(8)–O(4) bond distances in the oxime pendants
˚
ꢀy + 1, ꢀz) are 7.759, 7.858, and 9.614 A, respectively.
Both ligands in this structure are mono-deprotonated,
and as expected, a pair of O(1)–H(1)ꢁ ꢁ ꢁO(2) and O(3)–
H(3)ꢁ ꢁ ꢁO(4) hydrogen bonds is generated that stabilizes
this discrete dimeric motif. Both Oꢁ ꢁ ꢁO separations are
˚
are 1.343(6), 1.374(6), 1.333(6) and 1.349(6) A, respec-
2.434 A, and the bond angles are 167ꢁ and 163ꢁ, respec-
tively. Similarly, each DACO ring gives rise with a CuII
center to two five-membered chelate rings. The non-
bonding separations of NDACOꢁ ꢁ ꢁNDACO (2.816 and
˚
tively. The DACO ring binding to Cu(1) adopts the nor-
mal boat-chair conformation, while that to Cu(2) takes
the boat-boat style, similar to the NiII complex of this
˚
2.784 A) are also shorter than those of Noximeꢁ ꢁ ꢁNoxime

X.-J. Zhao et al. / Inorganica Chimica Acta 358 (2005) 4481–4488
4487
can observe that two CuII monomers in 4 are bridged
by the chloride ion in a cis-arrangement, while those
in 3 are in a trans-style.
˚
(2.919 and 2.872 A). As a result, the bite angles of
NDACO–Cu–NDACO (89.7(2)ꢁ and 90.0(2)ꢁ) are smaller
than those of Noxime–Cu–Noxime (97.1(2)ꢁ and 96.3(2)ꢁ)
due to the stereochemical effect.
Complex 4 has a similar structure to 3, consisting of a
monochloro-bridged [Cu2(H2L2)(HL2)Cl]2+ cation, as
illustrated in Fig. 3(b), two perchlorate anions and one
lattice water. Both CuII centers are also penta-coordi-
nated in the distorted square-pyramidal geometries with
the shared chloride bridge at the apical positions, having
s values of 0.098 for Cu(1) and 0.080 for Cu(2). Cu(1) is
3.2. Preparation and general characterization
The ligands H2L1 and H2L2 were prepared using the
same procedure with moderate yields and all the analyti-
cal data are in good agreement with the theoretical
requirements. The syntheses of complexes 1–4 were
achieved by reactions of the acid-free ligands with CuII
or NiII salts. Since the corresponding ligands are the
HCl salts, they must be neutralized with triethylamine
prior to complexation. Although the synthetic proce-
dures for the four complexes are almost the same, quite
different products were obtained. For mononuclear com-
plexes 1 and 2, CuII and NiII centers have square-pyrami-
dal and square-planar geometries, respectively. The
ligand for 2 is mono-deprotonated and for 1 is not depro-
tonated, in which an unexpected O–Hꢁ ꢁ ꢁCl bond is
generated. Complexes 3 and 4 are unusual monochloro-
bridged CuII dimers, while their NiII analogue [Ni-
(HL1)] Æ ClO4 is a four-coordinated monomer. That is,
the choice of metal center or the backbone of the ligand
is clearly critical in determining the molecular structures
of the resultant complexes. Of further interest, complexes
3 and 4 were produced differently only arising from the
anions of CuII salts [Cu(ClO4)2, CuCl2 and Cu(NO3)2
for 3, and CuSO4 for 4], which are in fact not involved
in the final structures. The IR spectra for all the com-
plexes show absorption bands resulting from the skeletal
vibrations of benzene rings in the 1400–1600 cmꢀ1 region.
The characteristic bands due to the oxime ligands [mOH
and mNO] appear in 3434 and 1150 cmꢀ1 for 1, 3431 and
1154 cmꢀ1 for 2, 3440 and 1122 cmꢀ1 for 3, and 3448
and 1121 cmꢀ1 for 4. Additionally, the very strong bands
that appear at ca. 1100 and 623 cmꢀ1 suggest the presence
of the perchlorate anions in all the complexes.
˚
0.337 A above the mean basal plane of N(1)–N(2)–
N(3)–N(4) toward the apical Cl(3) bridge, and for
˚
Cu(2) center the value is 0.359 A above the N(5)–
N(6)–N(7)–N(8) least-squares plane. The Cu–N bond
˚
distances lie in the range of 1.961(6)–2.026(5) A, with
the Cu–NDACO distances longer than those of Cu–
Noxime (see Table 2), suggesting weaker coordination
interactions. The two Cu–Cl bond lengths (2.533(6)
˚
and 2.515(6) A) are comparable to those of complex 3
and other related monochloro-bridged CuII dimers.
The Cu–Cl–Cu bridging angle is 126.2(3)ꢁ, however, it
represents the smallest one in such complexes. The intra-
˚
molecular Cu(1)ꢁ ꢁ ꢁCu(2) distance is 4.500 A, being com-
parable to 3 and other monochloro-bridged CuII dimers.
The
shortest
intermolecular
separations
for
Cu(1)ꢁ ꢁ ꢁCu(2) (symmetry code: x, y ꢀ 1, z),
Cu(1)ꢁ ꢁ ꢁCu(1) (symmetry code: ꢀx, ꢀy + 1, ꢀz + 1)
and Cu(2)ꢁ ꢁ ꢁCu(2) (symmetry code: ꢀx + 1, ꢀy + 2,
˚
ꢀz) are 8.797, 6.295 and 9.359 A, respectively. Two crys-
tallographically independent ligands in this structure are
different: the ligand binding to Cu(2) is mono-deproto-
nated and the other is not deprotonated. For the former,
one intramolecular O(3)–H(3)ꢁ ꢁ ꢁO(4) bond between two
oxime groups is formed with the Oꢁ ꢁ ꢁO separation and
˚
bond angle of 2.708 A and 157ꢁ. While the latter gener-
ates one similar O(2)–H(2C)ꢁ ꢁ ꢁO(1) bond and one O(1)–
H(1C)ꢁ ꢁ ꢁO(4) interaction with the deprotonated oxime
group in the former ligand, as indicated in Fig. 3(b).
˚
The Oꢁ ꢁ ꢁO separations are 2.603 and 2.494 A, and the
bond angles are 161ꢁ and 174ꢁ, respectively. The DACO
rings in both ligands adopt the normal boat-chair
conformation and similarly, each of them gives rise
with CuII to two five-membered chelate rings. The
NDACOꢁ ꢁ ꢁNDACO non-bonding distances (2.857 and
4. Conclusion and comments
A series of CuII and NiII complexes 1–4 based on two
oxime-functionalized diazamesocyclic derivates have
been prepared and structurally characterized by X-ray
diffraction analyses. The oxime groups have three poten-
tial coordination modes, that is, only N-, only O- and
both N- and O-binding sites, and solely the N-binding
mode is encountered in all our results, even though some
oxime groups are deprotonated which would make the
coordination of the O-donor of oxime facile. Addition-
ally, the resultant structures of these complexes are pro-
foundly influenced by the metal centers (CuII or NiII),
the backbones of the ligands (DACO or DACH), and
even the auxiliary anions (for 3 and 4). Further studies
on other oxime-functionalized diazamesocyclic derivates
˚
2.840 A) are also shorter than those of Noximeꢁ ꢁ ꢁNoxime
˚
(2.995 and 2.999 A), and thus, the bite angles of
NDACO–Cu–NDACO (90.20(19)ꢁ and 90.0(2)ꢁ) are smaller
than those of Noxime–Cu–Noxime (98.7(2)ꢁ and 98.5(2)ꢁ)
due to the stereochemical effect. The dihedral angle be-
tween two phenyl-groups of oximes in the ligand bound
to Cu(1) is 27.2ꢁ and that for the other ligand bound to
Cu(2) is 81.1ꢁ. The N(3)–O(1), N(4)–O(2), N(7)–O(3)
and N(8)–O(4) bond distances in oximes are 1.371(6),
˚
1.381(6), 1.380(6) and 1.407(6) A, respectively. Addi-
tionally, comparing both dimeric motifs of 3 and 4, we

4488
X.-J. Zhao et al. / Inorganica Chimica Acta 358 (2005) 4481–4488
[3] X.H. Bu, M. Du, Z.L. Shang, R.H. Zhang, D.Z. Liao, M.
Shionoya, T. Clifford, Inorg. Chem. 39 (2000) 4190.
[4] X.H. Bu, M. Du, L. Zhang, Z.L. Shang, R.H. Zhang, M.
Shionoya, J. Chem. Soc., Dalton Trans. (2001) 729.
[5] X.H. Bu, M. Du, L. Zhang, D.Z. Liao, J.K. Tang, R.H. Zhang,
M. Shionoya, J. Chem. Soc., Dalton Trans. (2001) 593.
[6] X.H. Bu, M. Du, Z.L. Shang, L. Zhang, Q.H. Zhao, R.H. Zhang,
M. Shionoya, Eur. J. Inorg. Chem. (2001) 1551.
[7] M. Du, X.H. Bu, Y.M. Guo, L. Zhang, D.Z. Liao, J. Ribas, M.
Monfort, Chem. Commun. (2002) 1478.
(e.g., replacing the phenyl in this work by alkyl, amido
or hydroxyl group) and their metal complexes are
underway in our laboratory, which may open new
perspectives of the coordination chemistry of the diaza-
mesocyclic system.
5. Supplementary materials
[8] M. Du, X.H. Bu, Y.M. Guo, J. Ribas, M. Monfort, Chem.
Commun. (2002) 2550.
[9] M. Du, Y.M. Guo, X.H. Bu, J. Ribas, M. Monfort, New J.
Chem. 26 (2002) 645.
[10] M. Du, Y.M. Guo, X.H. Bu, J. Ribas, M. Monfort, New J.
Chem. 26 (2002) 939.
[11] M. Du, X.H. Bu, Y.M. Guo, J. Ribas, Chem. Eur. J. 10 (2004)
1345.
Crystallographic data for the crystal structures re-
ported in this paper have been deposited with the Cam-
bridge Crystallographic Data Center (CCDC Nos.
266595/96/97/98). This material can be obtained free
of charge via www.ccdc.cam.ac.uk/conts/retrieving.html
(or from the CCDC, 12 Union Road, Cambridge CB2
1EZ, UK; fax: +44 1223 336033; e-mail: deposit@
ccdc.cam.ac.uk).
[12] M. Du, X.J. Zhao, J.H. Guo, X.H. Bu, J. Ribas, Eur. J. Inorg.
Chem. (2005) 294.
[13] V.Y. Kukushkin, A.J.L. Pombeiro, Coord. Chem. Rev. 181
(1999) 147.
[14] X.J. Zhao, M. Du, Y. Wang, X.H. Bu, J. Mol. Struct. 687 (2004)
119.
Acknowledgements
[15] A.X.S. Bruker, SAINT Software Reference Manual, Madison, WI,
1998.
[16] G.M. Sheldrick, SHELXTL NT Version 5.1. Program for Solution
and Refinement of Crystal Structures, University of Go¨ttingen,
Germany, 1997.
[17] A.W. Addison, T.N. Rao, J. Reedijk, J. Van Rijn, G.C.
Verschoor, J. Chem. Soc., Dalton Trans. (1984) 1349.
[18] V. Pavlishchuk, F. Birkelbach, T. Weyhermuller, K. Wieghardt,
P. Chaudhuri, Inorg. Chem. 41 (2002) 4405.
This work was financially supported by the National
Natural Science Funds for Distinguished Young Schol-
ars of China (No. 20225101), the National Natural Sci-
ence Foundation of China (No. 20401012), the Key
Project of Tianjin Natural Science Foundation (No.
043804111) and Tianjin Normal University.
[19] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Struc-
tural Chemistry and Biology, Oxford University Press, 1999.
[20] M. Du, Q. Xu, Y.M. Guo, L.H. Weng, X.H. Bu, Chin. J. Chem.
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[21] Y.M. Guo, M. Du, X.H. Bu, Inorg. Chim. Acta 358 (2005) 1887.
[22] H.D. Flack, Helv. Chim. Acta 86 (2003) 905.
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