Structurally diverse copper(II)-carboxylato complexes: Neutral and ionic mononuclear structures and a novel binuclear structure

Article abstract of DOI:10.1021/ic991476q

The copper complexes with the commercial auxin herbicides MCPA, 2,4-D, and 2,4,5-T in the presence of a nitrogen donor heterocyclic ligand, phen or bipyam, were prepared and characterized. The available evidence supports a dimeric structure for the 2,4-D complex in the presence of bipyam while phen leads to monomeric forms. The EPR spectrum of Cu₂(2,4-D)₄(bipyam)₂ at 4 K in the solid state exhibits an axial signal which corresponds to almost isolated S = 1/2 magnetic ions. Magnetic data for the dimer show a weak antiferromagnetic interaction between the two metal ions with J = -0.8 cm^-1. The crystal structures of tetrakis[(2,4-dichlorophenoxy)acetato]bis(2,2'-bipyridylamine)dicopper(II), 1, bis(1,10-phenanthroline)[(2,4,5-trichlorophenoxy)acetato]copper(II) chloride, 2, and aqua(1,10-phenanthroline)bis[((2-methyl-4-chlorophenoxyacetato]copper(II), 3, were determined and refined by least-squares methods using three-dimensional MoKα data. 1 crystallizes in space group P1, in a cell of dimensions a = 10.813(1) A, b = 12.138(1) A, c = 11.909(1) A, α = 86.448(3)°, β = 80.127(3)°, and γ = 63.982(3)°, and V = 1383.7(2) A³, with Z = 1.2 crystallizes in space group I2/a, in a cell of dimensions a = 29.958(9) A, b = 11.342(3) A, c = 21.196(7) A, β = 107.94(1)°, and V = 6852.2(4) A³, with Z = 8. 3 crystallizes in space group P1, in a cell of dimensions a = 8.7419(8) A, b = 12.512(1) A, c = 14.598(1) A, α = 110.737(1)°, β = 95-742(2)°, γ = 103.286(2)°, V = 1424.1(2) A³, with Z = 2.

Full text of DOI:10.1021/ic991476q

3042
Inorg. Chem. 2000, 39, 3042-3048
Structurally Diverse Copper(II)-Carboxylato Complexes: Neutral and Ionic Mononuclear
Structures and a Novel Binuclear Structure
George Psomas,† Catherine P. Raptopoulou,‡ Lykourgos Iordanidis,§
Catherine Dendrinou-Samara,† Vassilis Tangoulis,‡ and Dimitris P. Kessissoglou*,†
Department of General and Inorganic Chemistry, Aristotle University of Thessaloniki,
Thessaloniki 54006, Greece, Institute of Materials Science, NCSR “Demokritos”,
Aghia Paraskevi Attikis 15310, Greece, and Department of Chemistry,
Michigan State University, East Lansing, Michigan 48824-1322
ReceiVed December 22, 1999
The copper complexes with the commercial auxin herbicides MCPA, 2,4-D, and 2,4,5-T in the presence of a
nitrogen donor heterocyclic ligand, phen or bipyam, were prepared and characterized. The available evidence
supports a dimeric structure for the 2,4-D complex in the presence of bipyam while phen leads to monomeric
forms. The EPR spectrum of Cu2(2,4-D)4(bipyam)2 at 4 K in the solid state exhibits an axial signal which
corresponds to almost isolated S ) 1/2 magnetic ions. Magnetic data for the dimer show a weak antiferromagnetic
interaction between the two metal ions with J ) -0.8 cm-1. The crystal structures of tetrakis[(2,4-dichlorophenoxy)-
acetato]bis(2,2′-bipyridylamine)dicopper(II), 1, bis(1,10-phenanthroline)[(2,4,5-trichlorophenoxy)acetato]copper-
(II) chloride, 2, and aqua(1,10-phenanthroline)bis[((2-methyl-4-chlorophenoxyacetato]copper(II), 3, were determined
and refined by least-squares methods using three-dimensional MoKR data. 1 crystallizes in space group P1h, in a
cell of dimensions a ) 10.813(1) Å, b ) 12.138(1) Å, c ) 11.909(1) Å, R ) 86.448(3)°, â ) 80.127(3)°, and
γ ) 63.982(3)°, and V ) 1383.7(2) Å3, with Z ) 1. 2 crystallizes in space group I2/a, in a cell of dimensions a
) 29.958(9) Å, b ) 11.342(3) Å, c ) 21.196(7) Å, â ) 107.94(1)°, and V ) 6852.2(4) Å3, with Z ) 8. 3
crystallizes in space group P1h, in a cell of dimensions a ) 8.7419(8) Å, b ) 12.512(1) Å, c ) 14.598(1) Å, R
) 110.737(1)°, â ) 95.742(2)°, γ ) 103.286(2)°, V ) 1424.1(2) Å3, with Z ) 2.
Introduction
form complexes which have been shown to have diverse
stereochemistries.15-21
Many binuclear Cu(II) carboxylato compounds have been
isolated and their magnetostructural correlations studied.1-3 In
most cases, the formula of the complexes is Cu2(OOCR)4L2 [L
) H2O, dmf (dimethylformamide), dmso (dimethyl sulfoxide),
Py (pyridine)]. The presence of binuclear copper(II) carboxylates
under catalytic reaction conditions has enhanced the interest in
the coordination modes of this class of compounds. In general,
binuclear copper(II) carboxylates exhibit a paddle-wheel cage
structure, but due to the various coordination modes of the
carboxylato ligand, additional interesting structures have been
confirmed by X-ray crystallography (vide infra). The isolation
of mononuclear carboxylato compounds has also confirmed the
existence of unidentate and bidentate coordination modes of the
ligands.4-7 The electrochemical behavior of binuclear complexes
as one means of determining reactivity differences between
binuclear and mononuclear complexes has also attracted much
interest.8-14 Phenoxyalkanoic acids interact with Cu(II) ions to
We have initiated studies on the coordination of herbicide
and/or antiinflammatory carboxylate agents with Cu(II) and d10
ions in an attempt to examine their mode of binding and possible
synergetic effects.22-29 In this paper, we report the solid and
solution behavior of mononuclear and binuclear Cu(II) com-
(9) Lintvedt, R. L.; Schoenfelner, B. A.; Rupp, K. A. Inorg. Chem. 1986,
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† Aristotle University of Thessaloniki.
‡ NCSR “Demokritos”.
§ Michigan State University.
(1) Doedens, R. J. Prog. Inorg. Chem. 1975, 19, 173.
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3326.
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Murray-Rust, P.; Rossotti, F. J. C. J. Chem. Soc. A 1968, 2791.
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10.1021/ic991476q CCC: $19.00 © 2000 American Chemical Society
Published on Web 06/13/2000

Copper(II)-Carboxylato Complexes
Inorganic Chemistry, Vol. 39, No. 14, 2000 3043
Preparation of the Ligands. The sodium salts of the ligands were
prepared by the reaction of the protonated ligand with NaOH or CH3-
ONa in methanol. The white solids were recrystallized from methanol
and dried in the air.
Chart 1
Synthesis of Tetrakis[(2,4-dichlorophenoxy)acetato]bis(2,2′-bi-
pyridylamine)dicopper(II), 1. 2,4-D (2.21 g, 10 mmol) was dissolved
in CH3OH (50 cm3), and CH3ONa (0.54 g, 10 mmol) was added. After
30 min of stirring, CuCl2‚2H2O (0.85 g, 5 mmol) and bipyam (1.71 g,
10 mmol) in CH3OH (25 cm3) were added dropwise. The reaction
mixture was refluxed for 1 h. The blue solution was reduced in volume
and left for slow evaporation. Crystals of Cu2(C6H3Cl2-OCH2COO)4-
(bipyam)2, 1, suitable for X-ray structure determination deposited over
1 week. Yield: 70%. Anal. Calcd for C52H38Cl8N6O12Cu2 (fw )
1349.62): C, 46.28; H, 2.84; N, 6.23; Cu, 9.42. Found: C, 46.50; H,
3.00; N, 6.10; Cu, 9.50. IR, (KBr pellet), νmax/cm-1; ν(N-H) 3275
(m), 3230 (m); νas(CO2) 1635, 1585 (vs); ν(CdN) 1470 (vs), 1435
(vs); νsym(CO2) 1395 (vs). UV-vis (dmf solution), λ/nm (ꢀ/dm3 mol-1
cm-1); 735 (111), 400 (162), 314 (16 600).
plexes with the commercial auxin herbicides MCPA, 2,4-D, and
2,4,5-T (Chart 1) in the presence of phen or bipyam. A
biological study of a series of copper complexes with herbicide
ligands will be presented in a following paper.29b
Synthesis of Bis(1,10-phenanthroline)[(2,4,5-trichlorophenoxy)-
acetato]copper(II) Chloride, 2. 2,4,5-T (2.555 g, 10 mmol) was
dissolved in CH3OH (50 cm3), and CH3ONa (0.54 g, 10 mmol) was
added. After 30 min of stirring, CuCl2‚2H2O (0.85 g, 5 mmol) and
phen (1.80 g, 10 mmol) in CH3OH (25 cm3) were added dropwise.
The reaction mixture was refluxed for 1 h. The blue solution was
reduced in volume and left for slow evaporation. Crystals of [Cu(C6H2-
Cl3OCH2COO)(phen)2]Cl, 2, suitable for X-ray structure determination
were deposited over 1 week. Yield: 65%. Anal. Calcd for C31H37-
Cl4N4O8Cu (fw ) 799.01): C, 46.60; H, 4.67; N, 7.01; Cu, 7.95).
We also report the molecular and the crystal structures of
tetrakis[(2,4-dichlorophenoxy)acetato]bis(2,2′-bipyridylamine)-
dicopper(II), 1 the first example of a binuclear structure with
two bridging and two unidentate carboxylato ligands, [bis(1,10-
phenanthroline)[(2,4,5-trichlorophenoxy)acetato]copper(II) chlo-
ride, 2, and aqua(1,10-phenanthroline)bis[(2-methyl-4-chloro-
phenoxy)acetato]copper(II), 3.
Experimental Section
Found: C, 46.90; H, 4.25; N, 7.35; Cu, 8.10. IR (KBr, pellet), νmax
/
cm-1: νas(CO2) 1620, 1585 (vs); ν(CdN) 1465(vs), 1430(vs); νsym
-
Materials. The chemicals for the syntheses of the compounds were
used as purchased. Acetonitrile (CH3CN) was distilled from calcium
hydride (CaH2) and CH3OH from magnesium (Mg), and both were
stored over 3 Å molecular sieves. Diethyl ether, anhydrous grade, and
absolute ethanol were used without any further purification. 2,4-D,
2,4,5-T, MCPA, phen, bipyam, and CuCl2‚2H2O were purchased from
Aldrich. All chemicals and solvents were of reagent grade.
(CO2) 1395 (vs). UV-vis (dmf solution), λ/nm (ꢀ/dm3 mol-1 cm-1):
957 (63), 723 (100), 328 (2450), 293 (20 240).
Synthesis of Aqua(1,10-phenanthroline)bis[(2-methyl-4-chloro-
phenoxy)acetato]copper(II), 3. MCPA (2.00 g, 10 mmol) was
dissolved in CH3OH (50 cm3) and CH3ONa (0.54 g, 10 mmol) was
added. After 30 min of stirring, CuCl2‚2H2O (0.85 g, 5 mmol) in CH3-
OH (25 cm3) was added dropwise. The reaction mixture was stirred
for 1 h and reduced in volume under vacuum. Microcrystalline Cu-
[C6H3(CH3)ClOCH2COO]2(H2O)2 deposited and was collected by
filtration. Cu[C6H3(CH3)ClOCH2COO]2(H2O)2 (3 mmol) was dissolved
in CH3CN (50 cm3), phen (0.54 g, 3 mmol) in CH3CN (25 cm3) was
added, and the mixture was stirred for 1 h and left for slow evaporation.
Crystals of Cu[C6H3(CH3)ClOCH2COO]2(phen)(H2O), 3, suitable for
X-ray structure determination deposited over 1 week. Yield: 60%. Anal.
Calcd for C30H26Cl2N2O7Cu (fw ) 660.97): C, 54.51; H, 3.97; N, 4.24;
Cu, 9.61. Found: C, 54.40; H, 3.90; N, 4.45; Cu, 9.50. IR (KBr pellet),
Physical Measurements. Infrared spectra (200-4000 cm-1) were
recorded on a Perkin-Elmer FT-IR 1650 spectrometer with samples
prepared as KBr pellets, and UV-vis spectra were recorded on a
Shimadzu 160A dual-beam spectrophotometer. Room-temperature
magnetic measurements were carried out by Faraday’s method using
mercury tetrathiocyanatocobaltate(II) as a calibrant. Variable-temper-
ature magnetic susceptibility measurements were carried out on
powdered samples in the 3-300 K temperature range using a Quantum
Design SQUID susceptometer in a 6.0 kG applied magnetic field.
Magnetization measurements were performed at 4 K and in the field
range 0-5 T. EPR spectra were recorded on a Bruker ER 200D-SRC
X-band spectrometer equipped with an Oxford ESR 9 cryostat. C, H,
and N elemental analyses were performed on a Perkin-Elmer 240B
elemental analyzer; Cu was determined by atomic absorption spec-
troscopy on a Perkin-Elmer 1100B spectrophotometer. Electric con-
ductance measurements were carried out with a WTW model LF 530
conductivity outfit and a type C cell, which had a cell constant of 0.996.
This represents a mean value calibrated at 25 °C with potassium
chloride. All temperatures were controlled with an accuracy of (0.1
°C using a Haake thermoelectric circulating system.
ν
max/cm-1: νas(CO2) 1630 (vs), 1605 (vs); ν(CdN) 1490 (vs), 1430
(vs); νsym(CO2) 1408 (vs). UV-vis (dmf solution), λ/nm (ꢀ/dm3 mol-1
cm-1): 675 (94).
X-ray Crystal Structure Determinations. A green prismatic crystal
of tetrakis[(2,4-dichlorophenoxy)acetato]bis(2,2′-bipyridylamine)di-
copper(II), 1, with approximate dimensions 0.15 × 0.30 × 0.60 mm,
and a blue crystal of bis(1,10-phenanthroline)[(2,4,5-trichlorophenoxy)-
acetato]copper(II) chloride, 2, with approximate dimensions 0.10 ×
0.25 × 0.55 mm, were mounted in air. Diffraction measurements were
made on a Nicolet P21 diffractometer upgraded by Crystal Logic using
Ni-filtered Cu radiation for 1 and on a Crystal Logic dual-goniometer
diffractometer using graphite-monochromated Mo radiation for 2. A
pale blue prismatic crystal of aqua(1,10-phenanthroline)bis[2-methyl-
4-chlorophenoxy)acetato]copper(II), 3 with dimensions 0.77 × 0.16
× 0.16 mm, was mounted on the top of a glass fiber, and data were
collected at room temperature with a Bruker SMART Platform CCD
diffractometer. A full sphere of data (2082 frames) were collected. Final
cell constants were calculated from a set of 6770 strong reflections (I
> 10σ(I)) obtained from the data collection. Crystal data and parameters
for the data collections of 1-3 are reported in Table 1. Unit cell
dimensions were determined and refined by using the angular settings
of 25 automatically centered reflections in the ranges 24° < 2 θ < 54°
for 1 and 11° < 2 θ < 23° for 2. Intensity data were recorded using
θ-2θ scans. Three standard reflections, monitored every 97 reflections,
showed <3.0% intensity fluctuation and no decay. Lorentz, polarization,
(24) Kessissoglou, D. P.; Manoussakis, G. E.; Hatzidimitriou, A. G.;
Kanatzidis, M. G. Inorg. Chem. 1987, 26, 1395.
(25) Hatzidimitriou, A. G.; Kessissoglou, D. P.; Manoussakis, G. E.;
Kourounakis, P. N.; Economidis, G. J. Inorg. Biochem. 1990, 39, 263.
(26) Hatzidimitriou, A. G.; Kessissoglou, D. P.; Manoussakis, G. E. J. Inorg.
Biochem. 1993, 47, 157.
(27) Dendrinou-Samara, C.; Psomas, G.; Christophorou, K.; Tangoulis, V.;
Raptopoulou, C. P.; Terzis, A.; Kessissoglou, D. P. J. Chem. Soc.,
Dalton Trans. 1996, 3737.
(28) Psomas, G.; Dendrinou-Samara, C.; Philippakopoulos, P.; Tangoulis,
V.; Raptopoulou, C. P.; Samaras, H.; Kessissoglou, D. P. Inorg. Chim.
Acta 1998, 272, 24.
(29) (a) Dendrinou-Samara, C.; Tsotsou, G.; Raptopoulou, C. P.; Kortsaris,
A.; Kyriakidis, D.; Kessissoglou, D. P. J. Inorg. Biochem. 1998, 71,
171. (b) Dendrinou-Samara, C.; Psomas, G.; Raptopoulou, C. P.;
Kessissoglou, D. P. J. Inorg. Biochem. to be submitted for publication.

3044 Inorganic Chemistry, Vol. 39, No. 14, 2000
Psomas et al.
Table 1. Crystallographic Data for Complexes 1-3
1
2
3
formula
space group
crystal system
fw
a/Å
b/Å
C52H38Cl8Cu2N6O12
P1h
triclinic
C31H37Cl4CuN4O8
I2/a
triclinic
C30H26Cl2CuN2O7
P1h
triclinic
1349.62
799.01
660.97
10.813(1)
12.138(1)
11.909(1)
86.448(3)
80.127(3)
63.982(3)
1383.7(2)
1
1.620, 1.59
5.077
0.0406, 1.0929
0.0369, 0.0976
0.0405, 0.1016
29.958(9)
11.342(3)
21.196(7)
8.7419(8)
12.512(1)
14.598(1)
110.737(1)
95.742(2)
103.286(2)
1424.1(2)
2
c/Å
R/deg
â/deg
γ/deg
V/Å3
107.94(1)
6852.2(4)
8
1.508, 1.48
9.97
0.0375, 19.0622
0.0542, 0.1513
0.0769, 0.1818
Z
D
calcd, Dmeasd/g cm-3
1.541, 1.51
10.06
µ/cm-1
a, b for wa
R1, wR2b
0.0464, 0.0839
0.0878, 0.0971
R1, wR2b (all data)
2
2
2
2
a w ) 1/[σ2(Fo ) + (aP)2 + bP]; P [max(Po 0) - 2Fc2]/3. b R1 ) ∑(|Fo| - |Fc|)/∑(|Fo|); wR2 ) [∑w(|Fo - Fc2)2/∑w(Fo )2]1/2
.
and ψ-scan absorption corrections were applied using Crystal Logic
software. Scattering factors were taken from ref 30. The structures of
1 and 2 were solved by direct methods using the program SHELXS-
8631 and refined by full-matrix least-squares techniques on F2 with
SHELXL-93.32 For the structure of 3 four different sets of frames were
collected using 0.30° steps in ω. The exposure time was 15 s per frame,
and the detector-to-crystal distance was ∼5 cm. The resolution of the
data set was 0.78 Å. SMART33 software was used for data acquisition
and SAINT34 for data extraction. The absorption correction was applied
using SADABS35 and all refinements were done using the SHELXTL36
or SHELX9737 package of crystallographic programs. The structure
was solved with direct methods. Initially attempts to solve the structure
in P1h were unsuccessful, so the symmetry was dropped and the structure
introduced at calculated positions as riding on bonded atoms) were
located by difference maps and refined isotropically. All non-hydrogen
atoms were refined anisotropically.
Results and Discussion
The synthesis of the binuclear complex was achieved via the
reaction of CuCl2‚2H2O with the sodium salt of the ligand in
the presence of bipyam. The reaction involves deprotonation
of the ligand using NaOH or CH3ONa as the base, e.g.
C6H3Cl2OCH2COOH + CH3ONa f
C6H3Cl2-OCH2COONa
was solved in P1. Later, using a missing-center utility in teXsan,38
a
4C6H3Cl2OCH2COONa + 2CuCl2 + 2bipyam f
Cu2(C6H3Cl2-OCH2COO)4(bipyam)2
center of symmetry was found, and the space group was changed to
P1h. All nonhydrogen atoms were refined anisotropically. The water
hydrogen atoms were found from a difference map and were refined
using a riding model. The rest of hydrogen atoms were placed in
idealized positions and also refined using a riding model. The final
R1, wR2, and GOF values for all data were 0.0878, 0.0971, and 0.552,
the maximum and minimum residual peaks in the final difference map
were 0.353 and -0.532 e/Å3, and the largest shift/esd on the final cycle
was 0.012. Further crystallographic details for 1: 2θ ) 130°; scan speed
4.5°/min; scan range 2.45° + R1-R2 separation; numbers of collected/
unique/used reflections ) 4943/4675 (Rint ) 0.0093)/4675; 437
parameters refined; R1/wR2 (for all data) ) 0.0405/0.1016; (∆F)max
and (∆F)min ) 0.392 and -0.652 e/Å3: (∆/σ)max ) 0.003. All hydrogen
atoms were located by difference maps and refined isotropically. All
non-hydrogen atoms were refined anisotropically. Further crystal-
lographic details for 2: 2θ ) 50°; scan speed 3.0°/min; scan range
2.15 + R1-R2 separation; numbers of collected/unique/used reflections
) 6154/6018 (Rint ) 0.0164)/6018; 521 parameters refined; R1/wR2
(for all data) ) 0.0899/0.1427; (∆F)max/(∆F)min ) 0.569 and -0.580
e/Å3; (∆/σ)max ) 2.507 for the torsion parameter of HCM2. All
hydrogen atoms (except those of the methanol solvents which were
The complex is a green crystalline solid soluble in dmf, dmso,
and Py.
The synthesis of the mononuclear complexes was achieved
in two ways:
(i) A one-step reaction of CuCl2‚2H2O, NaOH, phen, and
2,4,5-T resulted in the formation of the cationic complex:
C6H2Cl3OCH2COOH + NaOH + 2CuCl2 + 2phen f
{Cu[C6H2Cl3OCH2COO](phen)2}Cl
The compound is a 1:1 electrolyte in dmf and dmso solutions.
(ii) The synthesis of the mononuclear neutral complex was
carried out via the addition of phen to the copper complex
without any nitrogen donor heterocyclic ligands, e.g.
C6H3(CH3)ClOCH2COOH + NaOCH3 f
C6H3(CH3)ClOCH2COONa
(30) International Tables for X-ray Crystallography; Kynoch, Press:
Birmingham, U.K., 1974; Vol. IV.
(31) Sheldrick, G. M. SHELX-86; University of Go¨ttingen: Go¨ttingen,
Germany, 1986.
(32) Sheldrick, G. M. SHELXL-93: Crystal Structure Refinement; Uni-
versity of Go¨ttingen: Go¨ttingen, Germany, 1993.
(33) SMART, v5.049; Bruker Analytical X-ray Systems Inc.: Madison, WI,
1998.
(34) SAINT, v5.0; Bruker Analytical X-ray Systems Inc.: Madison, WI,
1998.
(35) Sheldrick, G. M. SADABS; University of Go¨ttingen, Germany.
Manuscript to be published.
(36) SHELXTL, v5.1; 1999 Bruker Analytical Xray Systems Inc. Madison,
WI, 1999.
(37) Sheldrick, G. M. SHELX-97; University of Go¨ttingen, Germany.
(38) teXsan, v1.8; Molecular Structure Corp.: The Woodlands, TX, 1996.
2C6H3(CH3)ClOCH2COONa + CuCl2 f
{Cu[C6H3(CH3)ClOCH2COO]2}2(H2O)2
Cu[C6H3(CH3)ClOCH2COO]2(H2O)2 + phen f
Cu[C6H3(CH3)ClOCH2COO]2(phen)(H2O)
The complex is blue crystalline solid and nonelectrolyte in
dmf and dmso solution.
Description of the Structure Cu2(C6H3Cl2OCH2COO)4-
(bipyam)2 (1). The crystal structure of 1 is composed of
centrosymmetric dimers. An ORTEP diagram of the complex

Copper(II)-Carboxylato Complexes
Inorganic Chemistry, Vol. 39, No. 14, 2000 3045
Table 2. Coordination Modes, Cu‚‚‚Cu Separations, and J Values for Carboxylato-Bridged Complexes
a [Cu(idae)Cl(H2O)]n idae ) O-ethyliminodiacetato.39 b CuII4[(2-Py)2CO(OH)2](O2CCH3)6(H2O)2.40 c [{Cu(tzq)2(HCO2)}(µ-HCOO)2]‚4H2O,
tzq ) [1,2,3]triazolo[1,5-a]quinoline.41 d catena-Poly((bis(µ-Diphenylacetato-O,O′)dicopper)(µ3-Diphenylacetato-1-O,2-O′,1′-O′)(µ3-diphenyl-
acetato-1-O,2-O′,2′-O′)).42 e [{Cu4(bdmap)2(O2CCH3)6(H2O)6}n], Hbdmap ) 1,3-bis(dimethylamino)propan-2-ol.43 f [Cu2(µ-OH)(µ-CH3COO)(phen)2]-
(NO3)2‚2H2O, phen ) 1,10-phenanthroline.44 g [Cu2L(µ-OH)(µ-CH3COO)](ClO4)2‚2H2O, L ) a hexaimidazole dinucleating ligand.45
h [Cu2(SalDpl)(Phenac)(4-ethylphenol)], PhenacH ) phenylacetic acid, SalDpl ) a dinucleating ligand formed by the condensation of a substituted
salicylaldehyde and 1,3-diamino-2-propanol.46 i [Cu2(µ2-OH)(µ2-CH3COO)(tacd)2](ClO4)2, tacd ) 1,4,7-triazacyclododecane.47 j {[Cu2(BMDP)(OAc)2]N3}-
(ClO4)2‚8.5H2O, HBMDP ) N,N,N′-tris[(N-methyl-2-benzimidazolyl)methyl]-N′-methyl-1,3-diamino-2-propanol.48 [Cu2(L-1)(CH3COO)](ClO4)‚
H2O‚0.5NaClO4, H2L-1 ) racemic 1-[bis(2-pyridylmethyl)amino]-3-(salicylideneamino)propan-2-ol.49 [Cu2L2(µ-OH)(µ-C6H5COO)](ClO4)2, L )
1,4,7-trimethyl-1,4,7-triazacyclononane.50 [{Cu4(bdmap)2(O2CCH3)6(H2O)6}n], Hbdmap ) 1,3-bis(dimethylamino)propan-2-ol.43 k [Cu2(BMDP)-
(OAc)](ClO4)2‚2H2O, HBMDP ) N,N,N′-tris[(N-methyl-2-benzimidazolyl)methyl-N′-methyl-1,3-diamino-2-propanol.48 l Present work. m [Cu2(µ-
OH)(µ-H2O)(µ-CH3COO)(bipy)](ClO4)2, bipy ) 2,2′-bipyridine.51 n [Cu3(OH)2(H2O)2(Me3NCH2COO)4](ClO4)4‚2H2O.52 o [Cu2(µ-H2O)2(µ-L-AlaH+)]n
) [Cu2(alanine)2(H2O)4](SO4)2‚2H2O.53 p [Cu5(PIBA)10(H2O)4] ) [Cu(H2O)4]2+{[Cu2(PIBA)5]-}2, HPIBA ) 2-methyl-2-phenoxypropanoic acid.54
q [Cu5(PIBA)10(H2O)9] ) [Cu(H2O)5]2+{[Cu2(PIBA)5]-}2‚4H2O, HPIBA ) 2-methyl-2-phenoxypropanoic acid.54 r [Cu2(O2CMe)3(bipy)2](ClO4).51
s [Cu2L(OAc)2]+.55 t More than 200 examples are available in the literature. Some representative compounds are given here: catena-tetrakis[µ-
(2-chlorophenoxy)ethanoato-O,O′]dicopper(II), [{Cu2(O2CCH2OC6H4Cl-2)4}n];56 [Cu2(O2CCPh3)4(H2O)2]‚2H2O;57 [Cu2(O2CCPh2Me)4(H2O)4]‚H2O.57
u Tetrakis(µ-1-phenylcyclopropane-1-carboxylato-O,O′)bis(ethanol-O)dicopper(II);42 [Cu2(PCIBA)4(2-aminopyrimidine)2]2, HPCIBA ) 2-methyl-
2-(4-chlorophenoxy)propanoic acid.54 V catena-(2-Aminopyrimidine-N,N′)-tetrakis[µ-(2-chlorophenoxy)ethanoato-O,O′]dicopper(II);56 Cu2(CF3COO)4‚
2CH3CN.58
appears in Figure 1. Selected bond distances and angles are
given in Table 3. Two bidentate carboxylato ligands form syn-
syn bridges between isolated pairs of copper atoms separated
by 4.50 Å. The other two carboxylato ligands are bound to the
Cu(II) atoms in a unidentate mode, while the two bipyam neutral
ligands are coordinated to the copper atoms in a bidentate
fashion. The present mode of coordination is unique (Table
2),39-58 and the Cu‚‚‚Cu distance of 4.50 Å falls in the range
between 4.0 and 5.0 Å, for which no other examples have been
reported. Thus, the present compound provides an opportunity
to study the magnetic behavior and the EPR spectra of a Cu‚‚‚
Cu system separated by 4.50 Å and having only carboxylato
(43) Wang, S.; Pang, Z.; Smith, K. D. L.; Wagner, M. J. J. Chem. Soc.
Dalton Trans. 1994, 955.
(44) Tokii, T.; Hamamura, N.; Nakashima, M.; Muto, Y. Bull. Chem. Soc.
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3046 Inorganic Chemistry, Vol. 39, No. 14, 2000
Psomas et al.
in Table 2) for about 10 examples, and that of two bridging
ligands falling in the range 3.01-4.50 Å (coordination modes
2, 3, 4, in Table 2) for more than 15 examples but only one
example, the present compound, with a Cu‚‚‚Cu separation
above 4.0 Å. For one bridging ligand, only one example has
been reported, with a distance of 5.25 Å.
The bridging ligands are bound to two Cu(II) metal ions in
an asymmetric fashion [Cu-O(1) ) 1.963(2) Å, Cu-O(2) )
2.209(2) Å]. Each unidentate carboxylato ligand is bound to a
Cu(II) ion through O(4) at a distance of 1.951(2) Å, while the
uncoordinated carboxylato oxygen O(5) is H-bonded to the
bipyam ligand of a neighboring molecule, through the NH group,
[N(2)H′‚‚‚O(5) ) 2.045 Å and N(2)′‚‚‚O(5) ) 2.797 Å] giving
a polymeric arrangement with interdimer Cu‚‚‚Cu separations
of 6.46 Å.
Each copper atom is five-coordinate with the two nitrogen
atoms N(1) and N(3) (1.984(2) and 2.027(2) Å) of the bipyam
molecule occupying the remaining two positions. The polyhe-
dron cannot be described as having a regular square pyramidal
or trigonal bipyramidal geometry. The tetragonality60a T5 )
0.897 based on the changes in bond lengths, along with the
trigonality index60b (τ ) (F1 - F2)/60°, where F1 and F2 are the
largest angles in the coordination sphere; τ ) 0 for a perfect
square pyramid, and τ ) 1 for a perfect trigonal bipyramid), τ
) (177.54 - 148.61)/60 ) 0.48, show a distortion from the
regular square-based pyramidal geometry.61-64
Figure 1. ORTEP view of complex 1 with 50% thermal ellipsoids
Description of the Structure of [Cu(C6H2Cl3OCH2COO)2-
(phen)2]Cl‚2CH3OH, (2). In 2 the carboxylate group of 2,4,5-T
behaves as a unidentate ligand. An ORTEP diagram of 2 is
shown in Figure 2, and selected bond distances and angles are
listed in Table 4. In this complex, the copper atom is five-
coordinate and could be described as having a distorted square
pyramidal geometry. The tetragonality60a T5 ) 0.914, based on
the changes in bond lengths, along with the trigonality index,60b
τ ) (175.7 - 160.01)/60 ) 0.2615, show distortion from the
regular square-based pyramidal geometry. N(1) and N(2) [2.006-
(4) and 2.059(4) Å] of one phen molecule, N(4) [2.010(4) Å]
of the second phen molecule, and the carboxylate oxygen atom
O(1) [1.987(4) Å] occupy the four positions in the basal plane,
while N(3) of the second phen molecule is 2.205(4) Å away in
the apical position. An arrangement similar to that of the two
phen ligands has been observed in a series of [Cu(bipy)2X]+
complexes.61-64 The uncoordinated carboxylato oxygen atom
O(2) [Cu‚‚‚O(2) ) 2.728(4) Å] lies below the basal plane of
the pyramid. The trans atom system of the basal plane gives
angles of O(1)-Cu-N(2) ) 160.0(1)° and N(1)-Cu-N(4) )
175.7(2)°. The ionic unit [Cu(C6H3Cl3OCH2COO)(phen)2]+ is
neutralized by a chloride ion 5.038 Å away from the metal atom.
Description of the Structure Cu[C6H3(CH3)(Cl)OCH2-
COO]2(phen)(H2O) (3). In 3, the carboxylate group of MCPA
behaves as a unidentate ligand. An ORTEP diagram of 3 is
shown in Figure 3, and selected bond distances and angles are
given in Table 5. In this complex, the copper atom is
five-coordinate and could be described as having a distorted
square pyramidal geometry. The tetragonality60a T5 ) 0.872,
based on the changes in bond lengths, along with the trigonality
index,60b τ ) (174.1 - 161.4)/60 ) 0.2117, show a small
showing the atom-labeling scheme around the Cu atoms.
Table 3. Selected Bond Distances (Å) and Angles (deg) for
Complex 1
Distances
Cu-O(4)
Cu-N(1)′
Cu-O(2)
Cu-O(1)′
1.951(2)
1.984(2)
2.209(2)
1.963(2)
Cu-N(3)′
2.027(2)
Cu‚‚‚Cu′
Cu‚‚‚O(5)
4.502(2)
3.100(2)
Angles
O(4)-Cu-O(1)
O(1)-Cu-N(1)
O(1)-Cu-N(3)
O(4)-Cu-O(2)
N(1)′-Cu-O(2)
89.19(8)
89.60(8)
148.61(8)
87.13(7)
91.38(8)
O(4)-Cu-N(1)′
O(4)-Cu-N(3)′
N(1)′-Cu-N(3)′
O(1)′-Cu-O(2)
N(3)′-Cu-O(2)
177.54(8)
93.55(8)
88.60(8)
113.23(7)
98.14(7)
bridges. An analogous distance of 4.96 Å has been observed
for the helix-like-chain copper(II) complex [CuL(H2O)]n (H3L
) 1,3-dimethyl-5-[(2-carboxyphenyl)azo]barbituric acid).59 In
binuclear structures, the Cu‚‚‚Cu distance generally increases
as the number of bridging ligands decreases, with that of four
bridging ligands falling in the range 2.58-2.76 Å for more than
200 paddle-wheel structures, that of three bridging ligands
falling in the range 2.85-3.39 Å (coordination modes 5, 6, 7
(52) Chen, X. M.; Feng, X. L.; Yu, X. L.; Mak, T. C. W. Inorg. Chim.
Acta 1997, 266, 121.
(53) Davies, H. O.; Gillard, R. D.; Hursthouse, M. B.; Lehmann, A. J.
Chem. Soc., Chem. Commun. 1993, 1137.
(54) Mak, T. C. W.; Fulwood, J. C.; Kennard, C. H. L.; O’Reilly, E. J.;
Sagatys, D. S.; Smith, G. Polyhedron 1987, 6, 855.
(55) Lubben, M.; Hage, R.; Meetsma, A.; Bøma, K.; Feringa, B. L. Inorg.
Chem. 1995, 34, 2217.
(56) Smith, G.; O’Reilly, E. J.; Kennard, C. H. L.; White, A. H. J. Chem.
Soc. Dalton Trans. 1985, 243.
(57) Steward, O. W.; Johnston, B. S.; Chang, S. C.; Harada, A.; Ohba, S.;
Tokii, T.; Kato, M. Bull. Chem. Soc. Jpn. 1996, 69, 3123.
(58) Karpova, E. V.; Boltalin, A. I.; Zakharov, M. A.; Sorokina, N. I.;
Korenev, Y. M.; Troyanov, S. I. Z. Anorg. Allg. Chem. 1998, 624,
741.
(60) (a) Hathaway, B. J. Struct. Bonding (Berlin) 1973, 14, 49. (b) Addison,
A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verchoor, G. C. J. Chem.
Soc., Dalton Trans. 1984, 1349.
(61) Bertini, I.; Gatteschi, D.; Scozzafava, A. Coord. Chem. ReV. 1979,
29, 67.
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Laurent, J.-P.; Ruiz, J.; Sundberg, M. Inorg. Chem. 1992, 31, 774.

Copper(II)-Carboxylato Complexes
Inorganic Chemistry, Vol. 39, No. 14, 2000 3047
Table 5. Selected Bond Distances (Å) and Angles (deg) for
Complex 3
Distances
Cu(1)-O(5)
Cu(1)-N(1)
Cu(1)-O(7)
1.937(2)
2.012(3)
2.269(2)
Cu(1)-O(2)
Cu(1)-N(2)
1.944(2)
2.023(3)
Angles
O(5)-Cu(1)-O(2)
O(2)-Cu(1)-N(1)
O(2)-Cu(1)-N(2)
O(5)-Cu(1)-O(7)
N(1)-Cu(1)-O(7)
93.3(1)
174.2(1)
93.3(1)
99.5(1)
89.3(1)
O(5)-Cu(1)-N(1)
O(5)-Cu(1)-N(2)
N(1)-Cu(1)-N(2)
O(2)-Cu(1)-O(7)
N(2)-Cu(1)-O(7)
90.8(1)
161.5(1)
81.6(1)
94.1(1)
97.4(1)
Chart 2
Figure 2. ORTEP view of complex 2 with 50% thermal ellipsoids
showing the atom-labeling scheme around the Cu atom.
Table 4. Selected Bond Distances (Å) and Angles (deg) for
Complex 2
Distances
Cu-O(1)
Cu-N(4)
Cu-N(3)
1.987(3)
2.010(4)
2.205(4)
Cu-N(1)
Cu-N(2)
Cu‚‚‚O(2)
2.006(4)
2.059(4)
2.727(3)
Cu‚‚‚O(6) ) 4.059(3) Å] lie below and above the basal plane
of the pyramid, respectively. The ligand atoms that form this
basal plane of the pyramid are not strictly coplanar. The Cu-
O(W) distance of 2.269(2) Å is comparable to those observed
for the methoxyacetato (2.24 Å)7 and maleato (2.26 Å)
analogues.53
Angles
92.4(2)
175.7(2)
81.4(2)
98.8(1)
79.5(2)
O(1)-Cu-N(1)
N(1)-Cu-N(4)
N(1)-Cu-N(2)
O(1)-Cu-N(3)
N(4)-Cu-N(3)
O(1)-Cu-N(4)
O(1)-Cu-N(2)
N(4)-Cu-N(2)
N(1)-Cu-N(3)
N(2)-Cu-N(3)
91.8(1)
160.0(1)
94.3(2)
100.5(1)
101.0(1)
There are intra- and intermolecular hydrogen-bonded interac-
tions. The intramolecular interaction is between the water
molecule and the uncoordinated O(3) atom at a distance H(W)‚
‚‚O(3) ) 2.02 Å, while the intermolecular interaction is between
the water molecule and the uncoordinated carboxylato oxygen
atom, O(6), of a neighboring molecule at a distance H(W)‚‚‚
O(6)′ ) 1.93 Å, giving a polymer chain. The oxygen atom O(W)
lies 2.670 and 2.738 Å away from O(3) and O(6)′, respectively
(Chart 2). The copper atom is displaced 0.23 Å toward the water
ligand. The trans N-Cu-O system of the basal plane gives
angles of O(5)-Cu-N(2) ) 161.4(1)° and O(2)-Cu-N(1) )
174.1(1)°.
Magnetic Susceptibility and EPR Studies of Complex 1.
Variable-temperature solid-state magnetic susceptibility data
were collected on powdered samples of complex 1 in a 6.0 kG
applied magnetic field and in the temperature range 3.0-300
K. Magnetization measurements were carried out at 4 K and in
a field range from 0 to 5 T.
Figure 3. ORTEP view of complex 3 with 50% thermal ellipsoids
showing the atom-labeling scheme around the Cu atom.
The temperature dependence of the øMT for the 1 reveals a
plateau from room temperature to 50 K having a value of 0.82
distortion from the regular square-based pyramidal geometry.
N(1) and N(2) (2.012(3) and 2.023(3) Å) of the phen molecule
and the carboxylate oxygen atoms O(2) and O(5) (1.937(2) and
1.944(2) Å) occupy cis positions in the basal plane, while the
water oxygen is 2.269(2) Å away. The uncoordinated carboxy-
lato oxygen atoms O(3) and O(6) [Cu‚‚‚O(3) ) 3.127(3) Å,
1
cm3 mol-1 K, which is expected for two uncoupled S ) /2
spins (g ) 2.09), and then decreases with decreasing temperature
to the value of 0.67 cm3 mol-1 K at 3 K. This behavior is
consistent with a small antiferromagnetic interaction between
the two metal ions.

3048 Inorganic Chemistry, Vol. 39, No. 14, 2000
Psomas et al.
Figure 4. Magnetic susceptibility of 1 plotted as øMT versus T (left
axis) and øM versus T (right axis) with the fit to eq 1 (solid line).
Figure 5. Magnetization measurements, at 4 K, along with the Brillouin
(dotted line, g ) 2.0; solid line, g ) 2.09) function for a system with
1
two S ) /2 magnetic ions.
The øMT vs T and the øM vs T plots for complex 1 are shown
in Figure 4. The data were fit to the Bleaney-Bowers equation65
based on the zero-field spin Hamiltonian H ) -2JS1S2,
2
2Ng2µB
1
øM )
(1)
[
]
kT
3 + exp(2x)
where x ) -J/kT, N is Avogadro’s number, and the other
symbols have their usual meanings. Data were satisfactorily fit
into eq 1 with J ) -0.8 cm-1, g ) 2.098(2), and R ) 5.4 ×
10-6 for
2
[(øT)exp - (øT)calc
]
∑
R )
2
(øT)
∑
exp
The magnetization measurements, at 4 K, along with the
Brillouin (dotted line, g ) 2.0; solid line g ) 2.09) function
for a system with two S ) 1/2 magnetic ions, are shown in
Figure 5. The discrepancy between the solid curve and the
magnetization data is due to the small antiferromagnetic
interaction between the metal ions in accordance with the fitting
results.
Figure 6. X-Band powder ESR spectrum of 1 at 4 K.
However, it seems that the copper chemistry can be extended
even more. In this paper, for the first time, a novel motif of a
binuclear tetracarboxylato copper(II) complex with two bridging
and two unidentate ligands is reported. This structure shows a
Cu(II)‚‚‚Cu(II) distance of 4.5 Å, which is also unique and
provides an opportunity to study the interaction of two copper
atoms separated by this length. These results are quite surprising,
considering the strong Cu‚‚‚Cu interactions of the dinuclear
tetracarboxylate compounds with a paddle-wheel motif. The
structure of this compound can be considered as an intermediate
in the transition from the paddle-wheel structure to mononuclear
structure achieved adding N-donor ligands.
The EPR spectrum of 1 at 4 K in the solid state exhibits an
axial signal (gx,y ) 2.067, gz ) 2.24) which corresponds to
1
almost isolated S ) /2 magnetic ions (Figure 6). The value of
g ) (gx,y + gz)/3 ) 2.12 is close to the value obtained from the
susceptibility data. The EPR spectra of 2 and 3 are given as
Supporting Information. The ESR spectrum of 2 in frozen
solution is a typical axial spectrum with gx,y ) 2.042, gz ) 2.252,
and A ) 165 G, while the polycrystalline ESR spectrum of 3 is
rhombic with gx ) 2.017, gy ) 2.103 and gz ) 2.243.
Acknowledgment. The X-ray laboratory of NCSR “Demokri-
tos” thanks Mr. John Boutaris and the Agricultural Bank of
Greece for financial support.
Conclusions. The coordination chemistry of copper(II) has
been extensively studied and well understood. Especially for
binuclear complexes with carboxylate ligands, the coordination
modes show a rich variety of structure motifs, giving the
opportunity for a better understanding of Cu(II) behavior.
Supporting Information Available: EPR spectra of 2 and 3 and
X-ray crystallographic files, in CIF format, for 1-3. This material is
available free of charge via the Internet at http://pubs.acs.org.
(65) Bleaney, B.; Bowers, K. D. Proc. R. Soc. London, Ser. A 1952, 214,
451.
IC991476Q