Effect of pyrazole-substitution on the structure and nuclearity of Cu(II)-pyrazolato complexes

Article abstract of DOI:10.1016/j.ica.2004.03.016

Trinuclear Cu(II)-pyrazolates of the general formula (Bu₄N) ₂[Cu₃(μ₃-Cl)₂(μ-4-R-pz) ₃Cl₃] (pz=pyrazolato anion, R=Cl, Br, I, Me), 1-4, have been prepared and characterized by X-r

Full text of DOI:10.1016/j.ica.2004.03.016

Inorganica Chimica Acta 357 (2004) 3279–3288
www.elsevier.com/locate/ica
Effect of pyrazole-substitution on the structure and nuclearity of
Cu(II)-pyrazolato complexes
*
Gellert Mezei, Raphael G. Raptis
Department of Chemistry, University of Puerto Rico, P.O. Box 23346, San Juan PR 009313346, USA
Received 25 February 2004; accepted 13 March 2004
Available online 8 May 2004
Abstract
Trinuclear Cu(II)-pyrazolates of the general formula (Bu4N)2[Cu3(l3-Cl)2(l-4-R-pz)3Cl3] (pz ¼ pyrazolato anion, R ¼ Cl, Br, I,
1
Me), 1–4, have been prepared and characterized by X-ray diffraction and/or H NMR, IR, UV–Vis spectroscopy and elemental
analysis. Their structure and spectroscopic properties match the ones of the parent unsubstituted complex (Bu4N)2[Cu3(l3-Cl)2(l-
pz)3Cl3], indicating that 4-substitution of the pyrazole ligands with halogen or methyl groups does not induce structural variation. In
contrast, dinuclear complexes (Bu4N)4[Cu2(l-3-Me-pz)2Cl4]Cl2 Æ 4H2O, Cu2(l-Cl)(l-3,5-Me2-pz)(3,5-Me2-pzH)4Cl2, Cu2(l-Cl)(l-
OH)(3-Me-5-Ph-pzH)4Cl2 Æ 3-Me-5-Ph-pzH and Cu2(l-Cl)2(3,5-Ph2-pzH)4Cl2, 5–8, have been prepared with 3- and 3,5-substituted
pyrazoles by the same or similar synthetic protocols.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Copper; Pyrazole; Dinuclear complexes; Trinuclear complexes
1. Introduction
the peripheral substitution of the pyrazolate ligands has
been undertaken. The outcome was expected to provide
insight into the molecular and crystal structure, as well
as physico-chemical properties of new trinuclear Cu(II)-
pyrazolate complexes.
Triangular trinuclear copper(II)-complexes have been
generating great interest due to their unusual magnetic
and spectral properties [1], interesting redox chemistry
[2] and the potential to model the active sites of several
multicopper enzymes (e.g., ascorbate oxidase [3], laccase
[3], ceruloplasmin [3], particulate methane monooxy-
genase [4]) [5]. Recently, we have shown that the nine-
membered (Cu–N–N)3 framework formed by three
pyrazolato anions (pz) and three Cu(II)-centers can ac-
commodate different l3-bridging anions (O2ꢀ, HOꢀ,
Clꢀ, Brꢀ) [6]. The controlled interchange of these anions
brings about an orderly transition from antiferromag-
netic to ferromagnetic exchange among the copper
centers [7]. Ferromagnetically coupled Cu3-complexes
are especially important as they are closely related to the
also ferromagnetic active centers of particulate methane
monooxygenase [8]. In order to further explore the
possibilities of chemical diversification of trinuclear
Cu(II)-pyrazolates, a synthetic and structural study on
2. Experimental
2.1. Materials and methods
All commercially available reagents were used as re-
ceived. Pyrazole, 4-methyl-pyrazole, 3-methyl-pyrazole
and 3,5-dimethyl-pyrazole were purchased from Al-
drich Chemical Company. 4-Chloro-pyrazole [9], 4-
bromo-pyrazole [9], 3,5-diphenyl-pyrazole [10] and
Cu(CH3CN)4PF6 [11] were prepared according to the
literature procedures. Elemental analyses were per-
formed by Galbraith Laboratories, Inc., Knoxville, TN.
Infrared, NMR and UV–Vis spectra were recorded on a
Nicolet FT-IR 6000, Bruker Advance DRX-500 and
Varian Cary 500 Scan, respectively, at room tempera-
ture. Melting points were measured on an Electrothermal
IA9100 apparatus and are reported without correction.
* Corresponding author. Tel.: +7877640000x2598; fax: +7877568242.
E-mail address: raphael@adam.uprr.pr (R.G. Raptis).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.03.016

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G. Mezei, R.G. Raptis / Inorganica Chimica Acta 357 (2004) 3279–3288
X-ray diffraction data, collected at room temperature
795w, 832w, 876w, 910w, 964m, 1032w, 1060w, 1077m,
1103w, 1153w, 1178w, 1204m, 1275w, 1294w, 1313w,
1329w, 1375w, 1409w, 1462m, 1515m, 1574m, 1580m,
1590s, 2756m, 2826m, 2855m, 2899m, 2952m, 2975m,
3012m, 3086s, 3128m, 3184m.
from a single crystal mounted atop a glass fiber with a
Bruker AXS SMART 1K CCD diffractometer, graphite-
monochromated Mo Ka radiation [12a], were corrected
for Lorentz and polarization effects [12b]. The structures
were solved employing the SHELXTL-direct methods
program and refined by full-matrix least-squares meth-
ods on F 2 [12c]. Crystallographic details are summarized
in Table 1.
2.4. Synthesis of Cu3(3,5-Ph2-pz)3
Cu(CH3CN)4PF6 (3.579 g, 9.60 mmol) and 3,5-di-
phenyl-pyrazole (2.115 g, 9.60 mmol) are dissolved in 25
ml acetone with stirring to give a clear, slightly green
solution. Dropwise addition of Et3N (1.6 ml, 1.162 g,
11.48 mmol) induces the formation of a white pre-
cipitate, which is stirred for 30 min, then filtered,
washed with three 5 ml portions of acetone and vacuum-
2.2. Synthesis of 4-iodo-pyrazole
Pyrazole (5.00 g, 73 mmol) and anhydrous Na2CO3
(4.10 g, 39 mmol) are dissolved in 60 ml hot H2O. A
solution of I2 (18.64 g, 73 mmol) and KI (26.00 g, 157
mmol) in 70 ml H2O is added dropwise. The reaction
mixture is kept at 100 ꢁC for 30 min, 70 ml H2O is ad-
ded, it is brought to reflux and filtered hot. Slightly
yellowish needles separate from the light red solution
upon cooling to 0 ꢁC, which are filtered out, washed
with ice-cold water and air-dried. Yield: 11.26 g (79%).
M.p. 105–107 ꢁC. Recrystallization from water gives
shiny, colorless needles of 4-iodo-pyrazole. 1H NMR
(CDCl3, ppm): 7.64 (s, 2H, H-3 and H-5), 11.95 (s, br,
1H, NH). 13C NMR (CDCl3, ppm): 56.4 (C-3 and C-5),
138.6 (broad, C-4). IR (KBr pellet, cmꢀ1): 610s, 648w,
653w, 812s, 872s, 938s, 954m, 1033m, 1142m, 1178w,
1268w, 1321m, 1328m, 1365s, 1456w, 1475w, 1537m,
2788s, 2844s, 2909s, 2957s, 3040s, 3114s, 3123s.
1
dried. Yield: 2.701 g (99%). H NMR (CDCl3, ppm):
6.77 (s, 1H, H-4pz), 7.08 (t, 4H, H-metaPh), 7.21 (t,
2H, H-paraPh), 7.71 (d, 4H, H-orthoPh). 13C NMR
(CDCl3, ppm): 102.2 (C-4pz), 126.6 (C-orthoPh),
128.0(C-paraPh), 128.6 (C-metaPh), 132.6 (C-ipsoPh),
155.1 (C-3(5)pz).
2.5. (Bu4N)2[Cu3(l3-Cl)2(l-4-Cl-pz)3Cl3] (1)
CuCl2 Æ 2H2O (128 mg, 0.75 mmol), 4-chloro-pyrazole
(77 mg, 0.75 mmol), NaOH (30 mg, 0.75 mmol) and
Bu4NCl (139 mg, 0.5 mmol) are stirred in 10 ml CH2Cl2
for 12 h, at ambient temperature, and NaCl is filtered
out. Treatment of the green filtrate with 50 ml Et2O
crushes out complex 1 as a green solid, which is filtered,
washed with Et2O and recrystallized from CH2Cl2/Et2O.
Yield: 235 mg (81%). M.p. 175 ꢁC. Anal. for
C41H78Cl8Cu3N8, calculated/found: C, 42.55/42.67; H,
6.81/6.79; N, 9.68/9.70%. 1H NMR (CD3CN, ppm):
38.99 (w1=2 ¼ 95:4 Hz). IR (KBr pellet, cmꢀ1): 618s,
738m, 748m, 757m, 797m, 857s, 876m, 890m, 968vs,
996m, 1028w, 1052vs, 1105w, 1160m, 1201m, 1234w,
1305s, 1328w, 1347w, 1379s, 1400m, 1459s, 1487s,
2876s, 2943s, 2962vs, 3133m, 3141m. UV–Vis (CH2Cl2,
cmꢀ1): ꢁ12 600 (sh), 14 608, ꢁ27 000 (sh), 35 718.
Crystals suitable for X-ray diffraction are obtained by
vapor diffusion of Et2O into a CH2Cl2 solution of 1.
2.3. Synthesis of 3(5)-methyl-5(3)-phenyl-pyrazole
The procedure for the preparation of 3,5-diphenyl-
pyrazole is adopted for use here [10]. Benzoylacetone
(19.26 g, 0.12 mol) is suspended in 40 ml EtOH 95% and
hydrazine monohydrate (7.5 ml, 7.74 g, 0.15 mol) is
added dropwise, under stirring. The solid quickly dis-
solves and a clear, yellowish solution is obtained.
CAUTION! The reaction is highly exothermic and might
cause vigorous boiling. The reaction mixture is refluxed
for 30 min, then cooled to room temperature. A snow-
white, voluminous, cotton-like solid forms, which is
taken up as a suspension into 150 ml distilled water,
filtered, washed thoroughly with water and dried in an
oven. This material is sufficiently pure (as indicated by
its clean 1H NMR spectrum) and has been used without
further purification. Yield: 17.98 g (96%). M.p. 128–129
2.6. (Bu4N)2[Cu3(l3-Cl)2(l-4-Br-pz)3Cl3] (2)
A similar procedure using CuCl2 Æ 2H2O (980 mg, 5.75
mmol), 4-bromo-pyrazole (845 mg, 5.75 mmol), NaOH
(230 mg, 5.75 mmol) and Bu4NCl (1.065 g, 3.83 mmol)
in 30 ml CH2Cl2 yields 2.390 g (97%) of 2. M.p. 176 ꢁC.
Anal. for C41H78Br3Cl5Cu3N8, calculated/found: C,
38.15/38.31; H, 6.10/6.20; N, 8.68/8.56%. 1H NMR
(CD3CN, ppm): 38.23 (w1=2 ¼ 85:5 Hz). IR (KBr pellet,
cmꢀ1): 452m, 615s, 737m, 748m, 756m, 797w, 858s,
876m, 888m, 952vs, 996m, 1027w, 1052vs, 1109w, 1162s,
1192m, 1232w, 1298s, 1332w, 1351w, 1379s, 1394m,
1459m, 1487s, 2875s, 2942s, 2960vs, 3132m. UV–Vis
1
ꢁC. H NMR (CDCl3, ppm): 2.24 (s, 3H, CH3), 6.33 (s,
1H, H-4pz), 7.29 (t, 1H, H-paraPh), 7.35 (t, 2H, H-
metaPh), 7.72 (d, 2H, H-orthoPh), 11.78 (s, br, 1H,
w1=2 ¼ , NH). 13C NMR (CDCl3, ppm): 11.4 (CH3),
101.9 (C-4pz), 125.7 (C-orthoPh), 127.6 (C-paraPh), 128.5
(C-metaPh), 132.6 (C-ipsoPh), 142.93 (Cpz–CH3), 149.9
(Cpz–Ph). The 13C NMR assignments have been made
according to previous results in different solvents [13].
IR (KBr pellet, cmꢀ1): 510w, 644w, 690s, 716w, 764s,

Table 1
Crystallographic data
1
2
4
5
6
7
8
Formula
Formula weight
T (K)
k (A)
Crystal system
C
41H78Cl8Cu3N8
C41H78Br3Cl5Cu3N8 C44H87Cl5Cu3N8
1290.71
298(2)
C72H162Cl6Cu2N8O4 C25H39Cl3Cu2N10
1543.88
293(2)
C50H51Cl3Cu2N10
1041.44
298(2)
O
C60H48Cl4Cu2N8
1149.94
293(2)
1157.33
298(2)
1096.09
293(2)
713.09
298(2)
ꢀ
0.71073
monoclinic
C2=c (No. 15)
18.704(3)
18.674(3)
16.412(3)
90
0.71073
monoclinic
C2=c (No. 15)
18.880(4)
18.897(4)
16.545(3)
90
0.71073
monoclinic
C2=c (No. 15)
18.716(2)
18.559(2)
16.639(2)
90
0.71073
triclinic
0.71073
monoclinic
P21=c (No. 14)
18.110(2)
15.348(2)
12.034(1)
90
0.71073
monoclinic
P21=c (No. 14)
11.548(2)
22.220(3)
19.744(2)
90
0.71073
monoclinic
P21=n (No. 14)
13.404(2)
15.162(2)
13.647(2)
90
ꢁ
Space group
ꢀ
P1 (No. 2)
a (A)
10.389(3)
14.226(4)
16.488(5)
95.823(5)
101.868(5)
98.706(5)
2335(1)
1
ꢀ
b (A)
ꢀ
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
106.086(3)
90
106.588(4)
90
106.349(1)
90
94.357(2)
90
103.095(2)
90
109.491(2)
90
3
ꢀ
V (A )
5507.9(15)
4
1.396
5657(2)
4
1.516
5546.0(8)
4
1.313
3335.1(6)
4
1.420
4934(1)
4
1.402
2614.7(5)
2
1.461
Z
Dcalc (g cmꢀ3
)
1.098
0.670
2316
l (mmꢀ1
F ð000Þ
)
1.572
2412
3.508
2628
1.417
842
1.547
1472
1.072
2152
1.067
1180
Crystal size (mm)
Reflections collected
Unique reflections
Observed reflections
(I > 2rðIÞ)
0.20 · 0.14 · 0.03
12 002
3969
0.12 · 0.10 · 0.06
12 326
4083
0.30 · 0.26 · 0.18
12 043
4001
0.38 · 0.10 · 0.09
10 287
6709
0.18 · 0.16 · 0.12
14 304
4808
0.18 · 0.12 · 0.06
21 681
7106
0.12 · 0.10 · 0.06
11 305
3756
3019
2857
3378
5284
3826
4543
2800
h range (ꢁ)
1.57–23.28
3969/0/277
0.0335; 0.0697
1.045
1.56–23.32
4083/0/277
0.0362; 0.0767
0.962
1.58–23.27
4001/0/280
0.0252; 0.0710
1.077
1.46–23.29
6709/0/442
0.0577; 0.1802
1.047
1.13–23.28
4808/0/371
0.0272; 0.0682
1.033
1.40–23.30
7106/0/602
0.0383; 0.0789
0.986
2.08–23.26
3756/0/334
0.0292; 0.0639
0.949
Data/restraints/parameter
RðF Þ; RwðF Þ (I > 2rðIÞ)
Goodness-of-fit
ꢀ3
ꢀ
Largest peak/hole (e A
)
0.363/)0.359
0.695/)0.606
0.231/)0.312
0.562/)0.296
0.228/)0.256
0.297/)0.246
0.205/)0.309

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(CH2Cl2, cmꢀ1): ꢁ12 600 (sh), 14 598, ꢁ27 000 (sh),
2.10. Cu2(l-Cl)(l-3,5-Me2-pzH)(3,5-Me2-pzH)4Cl2 (6)
36 048.
CuCl2 Æ 2H2O (352 mg, 2.06 mmol), 3,5-dimethyl-
pyrazole (198 mg, 2.06 mmol) and NaOH (110 mg, 2.75
mmol) are stirred in 10 ml THF for 15 h, at ambient
temperature. The green solution is filtered and an equal
volume of hexanes is added. A green solid is filtered out,
washed with hexanes and dried at 90 ꢁC. Crystals are
obtained by layering an Et2O solution with hexanes.
Yield: 147 mg. M.p. 168 ꢁC. IR (KBr pellet, cmꢀ1):
434m, 605m, 660m, 680m, 744w, 759m, 789s, 810s,
981w, 1027s, 1042s, 1117w, 1153m, 1174s, 1278s, 1345m,
1380m, 1417s, 1472s, 1528m, 1572vs, 1622w, 2860m,
2925s, 2958s, 3035m, 3111s, 3141s, 3265vs. UV–Vis
(CH2Cl2, cmꢀ1): 13 508, ꢁ24 300 (sh), ꢁ28 500 (sh),
37 388.
2.7. (Bu4N)2[Cu3(l3-Cl)2(l-4-I-pz)3Cl3] (3)
A similar procedure using CuCl2 Æ 2H2O (298 mg, 1.75
mmol), 4-iodo-pyrazole (845 mg, 1.75 mmol), NaOH (70
mg, 1.75 mmol) and Bu4NCl (324 mg, 1.17 mmol) in 25
ml CH2Cl2 yields 2.390 g (98%) of 3. M.p. 180 ꢁC. Anal.
for C41H78Cl5Cu3I3N8, calculated/found: C, 34.39/
1
34.34; H, 5.50/5.50; N, 7.83/7.86%. H NMR (CD3CN,
ppm): 37.62. IR (KBr pellet, cmꢀ1): 419s, 616s, 737m,
799w, 858s, 882s, 914vs, 995w, 1025w, 1055vs, 1106w,
1166s, 1183w, 1289s, 1322w, 1351w, 1378s, 1419w,
1462s, 1483s, 2873s, 2933s, 2961vs, 3129m. UV–Vis
(CH2Cl2, cmꢀ1): ꢁ12 600 (sh), 14568, ꢁ27 000 (sh),
35578.
2.11. Cu2(l-Cl)(l-OH)(3-Me-5-Ph-pzH)4Cl2 ꢂ 3-Me-5-
Ph-pzH (7)
2.8. (Bu4N)2[Cu3(l3-Cl)2(l-4-Me-pz)3Cl3] (4)
A similar procedure using CuCl2 Æ 2H2O (336 mg, 1.97
mmol), 3-methyl-5-phenyl-pyrazole (311 mg, 1.97
mmol) and NaOH (105 mg, 2.63 mmol) yields crystals of
7 (178 mg) by slow evaporation of the filtered mother
liquor. M.p. ꢁ190 ꢁC (decomp.). IR (KBr pellet, cmꢀ1):
449w, 487w, 503w, 534w, 614m, 628m, 664m, 692s,
717m, 762vs, 794s, 802s, 913w, 962m, 1002m, 1029s,
1041s, 1073w, 1169m, 1205s, 1267s, 1294s, 1413m,
1473s, 1500s, 1565s, 1587w, 2871m, 2925m, 2965m,
3031m, 3057m, 3132s, 3241vs, 3445m. UV–Vis (CH2Cl2,
cmꢀ1): ꢁ11 400 (br), ꢁ12 600 (br), ꢁ24 600 (sh), ꢁ28 500
(sh), 39 368.
A similar procedure using CuCl2 Æ 2H2O (469 mg, 2.75
mmol), 4-methyl-pyrazole (226 mg, 2.75 mmol), NaOH
(110 mg, 2.75 mmol) and Bu4NCl (510 mg, 1.84 mmol)
in 10 ml CH2Cl2 yields 990 mg (99%) of 4. M.p. 191 ꢁC.
Anal. for C44H87Cl5Cu3N8, calculated/found: C, 48.20/
48.14; H, 8.01/8.40; N, 10.22/10.26%. 1H NMR
(CD3CN, ppm): 35.04. IR (KBr pellet, cmꢀ1): 405w,
630m, 678w, 748w, 799w, 851m, 860m, 876m, 887w,
990w, 1016s, 1030w, 1069vs, 1106w, 1156w, 1175m,
1318m, 1349w, 1378m, 1459m, 1486s, 2875s, 2941s,
2961vs, 2997m, 3093w, 3116w, 3136w. UV–Vis
(CH2Cl2, cmꢀ1): ꢁ9759 (sh), ꢁ12 600 (sh), 14 608,
ꢁ27 000 (sh), 30 488, ꢁ36 000 (sh).
2.12. Cu2(l-Cl)2(3,5-Ph2-pzH)4Cl2 (8)
2.9. (Bu4N)4[Cu2(l-3-Me-pz)2Cl4]Cl2 ꢂ 4H2O (5)
A similar procedure using CuCl2 Æ 2H2O (374 mg, 2.19
mmol), 3,5-diphenyl-pyrazole (483 mg, 2.19 mmol) and
NaOH (117 mg, 2.93 mmol) yields crystals of 8 (280 mg)
by layering a THF solution with hexanes. M.p. 207 ꢁC.
IR (KBr pellet, cmꢀ1): 549m, 628w, 659w, 668w, 692s,
760vs, 808w, 815w, 919w, 980m, 1001w, 1028w, 1060m,
1081m, 1103m, 1190s, 1257m, 1295w, 1321w, 1395w,
1414w, 1446m, 1458s, 1472s, 1486s, 1566s, 1611w,
3035m, 3048m, 3065m, 3137m, 3209s, 3431m. UV–Vis
(CH2Cl2, cmꢀ1): 11 635, 23 158, 28 958, ꢁ40 000 (br).
CuCl2 Æ 2H2O (456 mg, 2.68 mmol), 3-methyl-pyraz-
ole (220 mg, 2.68 mmol), NaOH (107 mg, 2.68 mmol)
and Bu4NCl (721 mg, 2.59 mmol) are stirred in 10 ml
CH2Cl2 for 12 h, at ambient temperature, and the so-
lution is filtered. Treatment of the green filtrate with 30
ml Et2O crushes out a green oily material; the super-
natant liquid is decanted, the oil washed with Et2O and
let in air. After several weeks the green oil transforms
into a soft, orange crystalline mass. After a suitable
crystal for X-ray diffraction is isolated, the solid is taken
up into Et2O, filtered and air-dried. Yield: 543 mg. M.p.
69 ꢁC (the color of the melt is green). IR (KBr pellet,
cmꢀ1): 405m, 516w, 641w, 661w, 673w, 739m, 759s,
794w, 886m, 924w, 955m, 1006w, 1030m, 1082m,
1125m, 1151w, 1168w, 1205w, 1284w, 1316w, 1346s,
1383s, 1469s, 1485s, 1496m, 1626w, 2874s, 2938s, 2961s,
3105w, 3122w, 3361m, 3444m. UV–Vis (CH2Cl2, cmꢀ1):
ꢁ9100 (sh), 14 078, ꢁ26 500 (sh), ꢁ29 000 (sh), ꢁ36 000
(br), ꢁ39 500 (br).
3. Results and discussion
3.1. Synthesis
The trinuclear complexes 1–4 are prepared similarly
as the parent compound, (Bu4N)2[Cu3(l3-Cl)2(l-
pz)3Cl3] (9) [6]. In a typical synthesis, equimolar
amounts of CuCl2 Æ 2H2O, 4-substituted pyrazole (4-R-
pzH; R ¼ H, Cl, Br, I, Me, NO2), NaOH and Bu4NCl

G. Mezei, R.G. Raptis / Inorganica Chimica Acta 357 (2004) 3279–3288
3283
are stirred together in dichloromethane, to give the
corresponding trinuclear complex in nearly quantitative
yield. Under the same experimental conditions, how-
ever, 3- and 3,5-substituted pyrazoles fail to provide
similar complexes. The product of the reaction em-
ploying 3-methyl-pyrazole has been crystallized and
shown by X-ray crystallography to be a dinuclear
complex. Since trinuclear Cu(II)-pyrazolates with un-
substituted pyrazole can easily be obtained under several
different conditions and in various solvents [6], two al-
ternative procedures have also been tried using 3,5-di-
substituted pyrazoles. In one procedure, CuCl2 Æ 2H2O is
reacted with the corresponding 3,5-disubstituted pyraz-
ole (3,5-Me2-pzH, 3-Me-5-Ph-pzH or 3,5-Ph2-pzH) and
NaOH in a 3:3:4 molar ratio in tetrahydrofuran. In each
case, the product of the reaction has been identified to
be a dinuclear complex. In the other procedure, the
copper(I)-trimer Cu3(3,5-Ph-pz)3 is oxidized with aque-
ous H2O2 in the presence of Bu4NCl. Again, the isolated
product of the reaction is the dinuclear complex 8.
A possible explanation for this observation is that
there is a steric hindrance between the 3- or 3,5-sub-
stituents of the pyrazole ligands and the terminal chlo-
rine atoms attached to the copper centers. The
deformation of the copper-pyrazolate framework, in
order to avoid that repulsion, seems unfavorable over
the formation of dinuclear structures. A fact that sup-
ports this presumption is that several two-coordinate
Cu(I)3- [14], as well as Ag(I)3- [14e,15] and Au(I)3-pyr-
azolates [15a,16] with various 3,5-substituted pyrazoles
(no terminal halogen ligands) are known (Scheme 1(a)).
[M(l-3,5-R2-pz)]3 frameworks of four-coordinate M-
centers are known only with the two additional ligands
perpendicular to the (M–N–N)3-plane (Scheme 1(b)): in
Cu3[l-3,5-(F3C)2-pz]5, the four-coordination around the
two Cu(II) centers is completed by two extra bridging
3,5-(F3C)2-pz ligands, one on either side of the planar
methyl-pyrazole; in this case the Au-Cl bonds are ori-
ented above and below, not in the plane of the Au3-
trimer, thus allowing sufficient space for the pyrazolate
ligands’ methyl substituents [18]. In the recently re-
ported [Cu3(l3-OMe)(l-3-R-pz)3X(3-R-pzH)2]X (R ¼
mesityl, X ¼ Cl, Br), only one copper atom bears a
halogen ligand; the two adjacent pyrazole groups orient
their mesityl substituents away from it, in order to avoid
steric crowding (Scheme 1(c)). This trinuclear structure
does not persist in solution, however [19].
Compounds 1–4, 9 and the NO2-substituted analogue
(Bu4N)2[Cu3(l3-Cl)2(l-4-NO2-pz)3Cl3] (10) [7], are in-
soluble in cold or boiling diethyl ether, hexane, benzene,
toluene and ethyl acetate (exception is 10 which is sol-
uble in ethyl acetate). They are sparingly soluble in cold
THF, chloroform and ethanol, fairly soluble in cold
methanol, dichloromethane and acetone and very solu-
ble in cold acetonitrile, nitromethane, dimethylsulfoxide
and N,N-dimethylformamide. The solubilities increase
in the order: 1 < 2 < 3 < 9 < 4 < 10. Only 9 is soluble
in water. 5–8 are soluble in polar organic solvents and 6
is also very soluble in diethyl ether.
3.2. Description of the crystal structures
Compounds 1, 2 and 4 are isostructural. They crys-
tallize in the same space group, C2=c, as the parent
compound 9, but are not isostructural with it. Their
structures consist of a nine-membered (Cu–N–N)3 me-
tallacycle, with a C2-axis running through a terminal Cl–
Cu bond and bisecting the pyrazolate ring on the
opposite side of the metallacycle (Fig. 1). The three Cu-
atoms, three terminal chlorides and one pyrazolate ring
form a planar unit; the remaining two pyrazolate rings
are bent one above and one below this plane (Fig. 2).
Two unsymmetrically capping chlorine atoms, one on
ꢀ
either side of the metallacycle (at 1.666–1.681 A
from the Cu3-plane), complete the distorted trigonal
bipyramidal coordination of the copper atoms. The
2þ
Cu(II)2Cu(I)[(F3C)2pz]3 framework [17]. Moreover, a
Au(III)3-pyrazolate has also been obtained with 3,5-di-
Scheme 1.

3284
G. Mezei, R.G. Raptis / Inorganica Chimica Acta 357 (2004) 3279–3288
Table 2
ꢀ
Selected bond lengths (A) and angles (ꢁ) for 1, 2 and 4
1
2
4
Cu(1)ꢂ ꢂ ꢂCu(2)
Cu(1)ꢂ ꢂ ꢂCu(10)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(2)–N(3)
Cu(1)–Cl(1)
Cu(1)–Cl(3)
Cu(2)–Cl(2)
Cu(2)–Cl(3)
Cu(10)–Cl(3)
3.3962(8)
3.453(1)
1.942(3)
1.941(3)
1.946(3)
2.281(1)
2.359(1)
2.286(1)
2.545(1)
2.923(1)
3.4052(9)
3.473(1)
1.944(3)
1.940(3)
1.947(3)
2.280(1)
2.361(1)
2.283(1)
2.549(1)
2.931(1)
3.4045(5)
3.4864(6)
1.942(2)
1.938(2)
1.941(2)
2.3021(7)
2.3539(7)
2.301(1)
2.5602(7)
2.9773(7)
N(2)–Cu(1)–N(1)
N(2)–Cu(1)–Cl(1)
N(1)–Cu(1)–Cl(1)
N(2)–Cu(1)–Cl(3)
N(1)–Cu(1)–Cl(3)
Cl(1)–Cu(1)–Cl(3)
Cl(3)–Cu(1)–Cl(30)
N(30)–Cu(2)–N(3)
N(3)–Cu(2)–Cl(2)
N(30)–Cu(2)–Cl(3)
N(3)–Cu(2)–Cl(3)
Cl(2)–Cu(2)–Cl(3)
Cl(3)–Cu(2)–Cl(30)
Cu(1)–Cl(3)–Cu(2)
Cu(1)–Cl(3)–Cu(10)
162.8(1)
92.99(9)
93.82(8)
92.81(9)
94.49(9)
131.36(4)
80.67(4)
175.5(2)
92.25(9)
86.87(9)
89.82(9)
137.40(2)
85.20(5)
87.58(3)
80.88(3)
162.3(2)
93.4(1)
161.37(9)
93.58(6)
94.06(6)
92.72(6)
94.67(6)
132.22(3)
81.02(2)
174.9(1)
92.55(5)
86.92(6)
89.35(6)
136.95(2)
86.10(3)
87.60(2)
80.76(2)
93.84(9)
92.4(1)
94.6(1)
132.32(5)
80.41(4)
175.1(2)
92.43(9)
86.7(1)
Fig. 1. ORTEP drawing for compound 1, viewed perpendicular to the
C2-axis. Thermal ellipsoids are shown at the 50% probability level.
89.8(1)
137.50(3)
85.00(6)
87.73(4)
81.26(4)
While the few known stable triangular Cu(II)-pyraz-
olates all involve unsubstituted pyrazoles [6,20] 1–4 and
10 are the first examples of such complexes with 4-
substituted pyrazoles.
Fig. 2. Ball-and-stick representation for compound 2, viewed along the
C2-axis.
intramolecular Cu–Cu distances range from 3.3962(8) to
ꢀ
3.4864(6) A. There are no significant intermolecular in-
teractions between the trinuclear units.
Bond lengths and angles for 1, 2 and 4 (Table 2) do
not vary significantly with substitution of the pyrazole
4-position with Cl, Br or Me groups, as compared with
the unsubstituted 9 [6]. Although similar bond lengths
are also observed in the case of 10 [7], there are two
notable differences between the structure of the latter
and 1, 2, 4, 9. First, the [Cu(4-NO2-pz)]3 framework of
10 is almost planar, with a slight bowl-shaped defor-
mation. Second, both capping chlorine atoms are
Fig. 3. ORTEP drawing for compound 5, showing the atom labeling
scheme. Thermal ellipsoids at the 30% probability level. Hydrogen
atoms omitted for clarity.
Table 3
ꢀ
symmetrically placed at 2.501(1)–2.628(1) A from the
three copper centers.
ꢀ
Selected bond lengths (A) and angles (ꢁ) for 5
Cu(1)ꢂ ꢂ ꢂCu(10)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–Cl(1)
Cu(1)–Cl(2)
3.810(1)
1.946(3)
1.947(3)
2.260(1)
2.256(1)
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–Cl(2)
N(2)–Cu(1)–Cl(2)
N(1)–Cu(1)–Cl(1)
N(2)–Cu(1)–Cl(1)
Cl(2)–Cu(1)–Cl(1)
101.3(1)
100.3(1)
128.2(1)
127.5(1)
101.2(1)
101.76(5)
A crystal structure analysis is not yet available for 3,
but its trinuclear nature, similar to those of other
members of this series, is clearly established based
on elemental analysis, IR, 1H NMR and UV–Vis
spectroscopy.

G. Mezei, R.G. Raptis / Inorganica Chimica Acta 357 (2004) 3279–3288
3285
The structure of 5 (Fig. 3) lies on an inversion center
ꢀ
and consists of two Cu atoms held at 3.810(1) A by two
bridging 3-methyl-pyrazolate ligands (crystallographi-
cally imposed dihedral angle between pyrazole planes:
180ꢁ). Each copper atom bears two terminal chlorine
atoms and has a distorted tetrahedral coordination ge-
ometry, with angles of 100.3(1)–128.2(1)ꢁ (Table 3). The
structure of this complex should be different in solution
Fig. 4. ORTEP drawing for compound 6, showing the atom labeling scheme. Thermal ellipsoids at the 50% probability level. C–H hydrogen atoms
omitted for clarity.
Fig. 5. ORTEP drawing for compound 7, showing the atom labeling scheme. Thermal ellipsoids at the 50% probability level. C–H hydrogen atoms
omitted for clarity.

3286
G. Mezei, R.G. Raptis / Inorganica Chimica Acta 357 (2004) 3279–3288
Fig. 6. ORTEP drawing for compound 8, showing the atom labeling scheme. Thermal ellipsoids at the 30% probability level. C–H hydrogen atoms
omitted for clarity.
Table 4
and molten state, since the latter are green but the
crystals are orange.
ꢀ
Selected bond lengths (A) and angles (ꢁ) for 6
In the structures of 6–8 (Figs. 4–6), each Cu atom has
two terminal, protonated pyrazole ligands and a ter-
Cu(1)ꢂ ꢂ ꢂCu(2) 3.7543(6)
N(10)–Cu(1)–N(1)
N(10)–Cu(1)–N(3)
N(1)–Cu(1)–N(3)
N(10)–Cu(1)–Cl(1)
N(1)–Cu(1)–Cl(1)
N(3)–Cu(1)–Cl(1)
N(10)–Cu(1)–Cl(3)
N(1)–Cu(1)–Cl(3)
N(3)–Cu(1)–Cl(3)
Cl(1)–Cu(1)–Cl(3)
N(9)–Cu(2)–N(5)
N(9)–Cu(2)–N(7)
N(5)–Cu(2)–N(7)
N(9)–Cu(2)–Cl(2)
N(5)–Cu(2)–Cl(2)
N(7)–Cu(2)–Cl(2)
N(9)–Cu(2)–Cl(3)
N(5)–Cu(2)–Cl(3)
N(7)–Cu(2)–Cl(3)
Cl(2)–Cu(2)–Cl(3)
Cu(1)–Cl(3)–Cu(2)
166.6(1)
86.74(9)
89.37(9)
89.76(9)
89.18(7)
158.46(7)
92.91(7)
100.39(7)
101.24(7)
100.15(3)
167.07(9)
87.00(9)
88.93(9)
90.42(7)
88.98(7)
158.95(7)
93.21(7)
99.67(7)
102.92(7)
98.08(3)
99.31(3)
Cu(1)–N(1)
Cu(1)–N(3)
Cu(1)–N(10)
Cu(1)–Cl(1)
Cu(1)–Cl(3)
Cu(2)–N(5)
Cu(2)–N(7)
Cu(2)–N(9)
Cu(2)–Cl(2)
Cu(2)–Cl(3)
2.009(2)
2.057(2)
1.974(2)
2.3809(8)
2.4593(8)
2.006(2)
2.083(2)
1.971(2)
2.3661(8)
2.4665(8)
1
minal Cl atom coordinated. The two ligands bridging
the two copper centers are in each case different: a 3,5-
dimethyl-pyrazolate and a chloride for 6, a hydroxide
and a chloride for 7 and two chlorides for 8. This is
reflected in different Cu–Cu separations, from 3.1963(7)
ꢀ
ꢀ
ꢀ
A in 7, through 3.5253(7) A in 8, to 3.7543(6) A in 6
(Tables 4–6). The coordination geometries of the copper
atoms are in between ideal square-pyramidal and tri-
gonal-bipyramidal, closer to the former in 6 and 8, but
closer to the latter in 7. A particularity of structure 7 is
the inclusion of a free 3-methyl-5-phenyl-pyrazole li-
gand molecule, which is integrated in the crystal lattice
by N–Hꢂ ꢂ ꢂCl and O–Hꢂ ꢂ ꢂN hydrogen bonds, p ꢂ ꢂ ꢂ p and
C–H ꢂ ꢂ ꢂ p interactions. Intra- and/or intermolecular N–
Hꢂ ꢂ ꢂCl hydrogen bonds are also observed in the struc-
tures of 6 and 8.
While structural analogues of 8 with other pyrazoles
(3,5-Me2-pzH [22], 3,5-Et2-4-Me-pzH [23], 3,4-Me2-5-
Ph-pzH [24]) have been reported, 5–7 are unique ex-
amples of dinuclear Cu(II)-pyrazole complexes. Other
similar complexes with two bridging fluoride [25] or
bromide [26] ligands are also known.
3.3. Spectroscopic results
1
The structure of 8, refined as a disordered model, has been
1H NMR shows that the trinuclear structures of 1–4
are maintained in solution, as indicated by the presence
of a single downfield shifted pyrazole signal, at 38.99,
previously reported [21]. Our use of Mo Ka radiation and CCD area
detector improved the refinement and structural parameters, leading to
a non-disordered model with better R values and lower esd’s.

G. Mezei, R.G. Raptis / Inorganica Chimica Acta 357 (2004) 3279–3288
3287
CH3), 2942 cmꢀ1 (mas CH2), 1379 cmꢀ1 (ds CH3) and
1459 cmꢀ1 (das CH3 and ds CH2-scissoring) [27].
Table 5
Selected bond lengths (A) and angles (ꢁ) for 7
ꢀ
Cu(1)ꢂ ꢂ ꢂCu(2) 3.1963(7)
O(1)–Cu(1)–N(1)
O(1)–Cu(1)–N(3)
N(1)–Cu(1)–N(3)
O(1)–Cu(1)–Cl(3)
N(1)–Cu(1)–Cl(3)
N(3)–Cu(1)–Cl(3)
O(1)–Cu(1)–Cl(1)
N(1)–Cu(1)–Cl(1)
N(3)–Cu(1)–Cl(1)
Cl(3)–Cu(1)–Cl(1)
O(1)–Cu(2)–N(7)
O(1)–Cu(2)–N(5)
N(7)–Cu(2)–N(5)
O(1)–Cu(2)–Cl(2)
N(7)–Cu(2)–Cl(2)
N(5)–Cu(2)–Cl(2)
O(1)–Cu(2)–Cl(3)
N(7)–Cu(2)–Cl(3)
N(5)–Cu(2)–Cl(3)
Cl(2)–Cu(2)–Cl(3)
Cu(1)–Cl(3)–Cu(2)
Cu(1)–O(1)–Cu(2)
173.8(1)
90.8(1)
95.1(1)
In the spectra of dinuclear complexes 6–8, a very
strong, broad band with several maxima between 3100
and 3300 cmꢀ1 is indicative of N–H groups involved in
hydrogen bonding. The absence of this band in the
spectrum of 5 confirms the deprotonated nature of the 3-
methyl-pyrazole ligands. For 5–7, the presence of the
pyrazole ligands’ methyl-substituent is indicated by
bands at ꢃ2870, 2925 and 2958 cmꢀ1. In the case of 5,
these bands are overlapped by the very strong Bu4N-
bands. For the latter compound, the presence of lattice
H2O-molecules is indicated by broad bands with max-
ima at 3361 and 3444 cmꢀ1 (ms and mas OH), and at 1626
cmꢀ1 (HOH bending). Absorptions between 3030 and
3065 cmꢀ1 for 6–8 and 3105 and 3122 cmꢀ1 for 5 are due
to pyrazole and phenyl C–H stretching vibrations.
Cu(1)–O(1)
Cu(1)–N(1)
Cu(1)–N(3)
Cu(1)–Cl(1)
Cu(1)–Cl(3)
Cu(2)–O(1)
Cu(2)–N(5)
Cu(2)–N(7)
Cu(2)–Cl(2)
Cu(2)–Cl(3)
1.903(3)
1.987(3)
2.059(3)
2.445(1)
2.409(1)
1.905(3)
2.074(3)
1.980(3)
2.384(1)
2.450(1)
82.33(9)
93.8(1)
111.3(1)
87.64(8)
90.5(1)
125.0(1)
122.86(5)
169.1(1)
88.7(1)
94.1(1)
95.4(1)
92.6(1)
118.2(1)
81.21(9)
88.7(1)
126.8(1)
114.69(5)
82.27(4)
114.2(2)
4. Conclusions
Here, we have demonstrated that the established
procedure for the preparation of the parent compound,
(Bu4N)2[Cu3(l3-Cl)2(l-pz)3Cl3], can also be applied for
the preparation of other trinuclear Cu(II)-pyrazolates
with 4-substituted pyrazoles. This peripheral substitu-
tion with different electron-withdrawing or-releasing
groups (Cl, Br, I, Me, NO2) does not induce any sig-
nificant change on the bond lengths of the trinuclear
Cu(II)-pyrazolates studied. As for their three-dimen-
sional molecular structure, the Cl-, Br- and Me-deriva-
tives are identical to the parent compound, with a
distorted [Cu(4-R-pz)]3 framework, while the NO2-an-
alogue is approximately planar.
Table 6
ꢀ
Selected bond lengths (A) and angles (ꢁ) for 8
Cu(1)ꢂ ꢂ ꢂCu(10)
Cu(1)–N(1)
Cu(1)–N(3)
Cu(1)–Cl(1)
Cu(1)–Cl(2)
Cu(1)–Cl(20)
3.5253(7) N(3)–Cu(1)–N(1)
2.055(2)
2.009(2)
90.37(8)
87.85(6)
178.16(6)
150.96(7)
92.24(6)
89.54(3)
114.87(7)
92.31(6)
88.03(2)
93.92(3)
91.97(2)
N(3)–Cu(1)–Cl(2)
N(1)–Cu(1)–Cl(2)
2.3296(8) N(3)–Cu(1)–Cl(1)
2.3009(8) N(1)–Cu(1)–Cl(1)
2.5930(8) Cl(2)–Cu(1)–Cl(1)
N(3)–Cu(1)–Cl(20)
N(1)–Cu(1)–Cl(20)
Cl(2)–Cu(1)–Cl(20)
Cl(1)–Cu(1)–Cl(20)
Cu(1)–Cl(2)–Cu(10)
All attempts to extend this synthetic protocol for the
preparation of similar trinuclear complexes with 3- or
3,5-substituted pyrazoles failed; dinuclear complexes
were obtained instead. The reason for these results is
assumed to be related to a steric repulsion between the
pyrazole ligands’ 3- or 3,5-substituents and the terminal
chlorine atoms attached to the copper(II)-pyrazolate
framework. The dinuclear complexes obtained provide,
however, several new motifs in Cu(II) pyrazole- and
pyrazolate-chemistry.
38.23, 37.62 and 35.04 ppm for 1, 2, 3 and 4, respec-
tively. The observed trend is in agreement with the de-
creasing electronegativity of the substituent attached to
the pyrazole ligand. Signals for the tetrabutylammo-
nium counterion appear in the normal region for satu-
rated hydrocarbons. Due to the presence of
paramagnetic copper centers, pyrazole C-atoms could
not be detected by 13C NMR spectroscopy.
In the IR spectra of 1–3, the C–Cl, C–Br and C–I
stretching vibrations produce strong absorption bands
at 968, 952 and 941 cmꢀ1, respectively. For 1–4, the
strongest absorption peaks attributed to the pyrazole
ligands have been assigned as follows: 615–618 (630 for
4) cmꢀ1, out-of-plane ring bending; 851–858 cmꢀ1, out-
of-plane C–H bending; 1052–1055 (1069 for 4) cmꢀ1, in-
5. Supplementary material
CCDC 232032–232038 contain the supplementary
crystallographic data for 1, 2, 4–8, respectively. These
data can be obtained free of charge via www.ccdc.ca-
m.ac.uk/data_request/cif,
by
emailing
data_re-
plane C–H bending; 1289–1300 and 1483–1487 cmꢀ1
,
quest@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Center, 12, Union Road, Cam-
bridge CB2 1EZ, UK; fax: +44-1223-336033. Tables
of atomic coordinates and equivalent isotropic
ring stretching; 3093–3140 cmꢀ1, C–H stretching. The
presence of tetrabutylammonium groups is indicated by
strong absorptions at 2875 and 2962 cmꢀ1 (ms and mas

3288
G. Mezei, R.G. Raptis / Inorganica Chimica Acta 357 (2004) 3279–3288
[13] M. Begtrup, G. Boyer, P. Cabildo, C. Cativiela, R.M. Claramunt,
displacement parameters, bond lengths and angles, an-
isotropic displacement parameters, ORTEP drawings
for 2 and 4 are available from the authors by request.
ꢃ
J. Elguero, J.I. Garcıa, C. Toiron, P. Vedsø, Magn. Reson. Chem.
31 (1993) 107.
[14] (a) M.K. Ehlert, S.J. Rettig, A. Storr, R.C. Thompson, J. Trotter,
Can. J. Chem. 68 (1990) 1444;
(b) M.K. Ehlert, S.J. Rettig, S13, R.C. Thompson, J. Trotter,
Can. J. Chem. 70 (1992) 2161;
Acknowledgements
(c) G.A. Ardizzoia, S. Cenini, G. La Monica, N. Masciocchi, A.
Maspero, M. Moret, Inorg. Chem. 37 (1998) 4284;
(d) R.G. Raptis, J.P. Fackler Jr., Inorg. Chem. 27 (1988) 4179;
(e) H.V.R. Dias, S.A. Polach, Z. Wang, J. Fluorine Chem. 103
(2000) 163;
G.M. acknowledges a doctoral fellowship from NSF-
EPSCoR (Grant No. EPS-9874782).
(f) K. Fujisawa, Y. Ishikawa, Y. Miyashita, K. Okamoto, Chem.
Lett. 33 (2004) 66.
References
[15] (a) H.H. Murray, R.G. Raptis, J.P. Fackler Jr., Inorg. Chem. 27
(1988) 26;
[1] (a) B. Cage, F.A. Cotton, N.S. Dalal, E.A. Hillard, B. Rakvin,
C.M. Ramsey, J. Am. Chem. Soc. 125 (2003) 5270;
(b) M.I. Belinsky, Inorg. Chem. 43 (2004) 739;
(c) J. Padilla, D. Gatteschi, P. Chaudhuri, Inorg. Chim. Acta 260
(1997) 217.
(b) F. Meyer, A. Jacobi, L. Zsolnai, Chem. Ber./Recl. 130 (1997)
1441.
[16] (a) B. Bovio, F. Bonati, G. Banditelli, Inorg. Chim. Acta 87 (1984)
25;
(b) S.J. Kim, S.H. Kang, K.-M. Park, H. Kim, W.-C. Zin, M.-G.
Choi, K. Kim, Chem. Mater. 10 (1998) 1889;
[2] (a) D. Datta, A. Chakravorty, Inorg. Chem. 22 (1983) 1611;
(b) D. Datta, A. Chakravorty, Inorg. Chem. 21 (1982) 363;
(c) D. Datta, P.K. Mascharak, A. Chakravorty, Inorg. Chem. 20
(1981) 1673;
(c) J. Barbera, A. Elduque, R. Gimenez, F.J. Lahoz, J.A. Lopez,
L.A. Oro, J.L. Serrano, Inorg. Chem. 37 (1998) 2960.
[17] M.K. Ehlert, A. Storr, D.A. Summers, R.C. Thompson, Can. J.
Chem. 75 (1997) 491.
(d) Y. Agnus, R. Louis, B. Metz, C. Boudon, J.P. Gisselbrecht, M.
Gross, Inorg. Chem. 30 (1991) 3155.
[18] G. Yang, R.G. Raptis, Dalton Trans. (2002) 3936.
[19] X. Liu, M.P. de Miranda, E.J.L. McInnes, C.A. Kilner, M.A.
Halcrow, Dalton Trans. (2004) 59.
[3] (a)K.D. Karlin, Z. Tyeklar (Eds.), Bioinorganic Chemistry of
Copper, Chapman & Hall, New York, 1993;
(b) E.I. Solomon, U.M. Sundaram, T.E. Machonkin, Chem. Rev.
96 (1996) 2563;
[20] (a) F.B. Hulsbergen, R.W.M. ten Hoedt, G.C. Verschoor, J.
Reedijk, A.L. Spek, Dalton Trans. (1983) 539;
(b) M. Angaroni, G.A. Ardizzoia, T. Beringhelli, G. La Monica,
D. Gatteschi, N. Masciocchi, M. Moret, Dalton Trans. (1990)
3305;
(c) A. Messerschmidt, Struct. Bond. 90 (1998) 37.
[4] (a) H.-H.T. Nguyen, S.J. Elliott, J.H.-K. Yip, S.I. Chan, J. Biol.
Chem. 273 (1998) 7957;
(b) S.S. Lemos, H. Yuan, M.L.P. Collins, W.E. Antholine, Curr.
Top. Biophys. 26 (2002) 43.
(c) K. Sakai, Y. Yamada, T. Tsumobura, M. Yabuki, M.
Yamaguchi, Inorg. Chem. 35 (1996) 542.
[5] (a) A.P. Cole, D.E. Root, P. Mukherjee, E.I. Solomon, T.D.P.
Stack, Science 273 (1996) 1848;
[21] M. Malecka, M.J. Grabowski, T.A. Olszak, K. Kostka, M.
Strawiak, Acta Crystallogr., Sect. C 54 (1998) 1770.
[22] V. Chandrasekhar, S. Kingsley, A. Vij, K.C. Lam, A.L. Rhein-
gold, Inorg. Chem. 39 (2000) 3238.
(b) D.E. Root, M.J. Henson, T. Machonkin, P. Mukherjee,
T.D.P. Stack, E.I. Solomon, J. Am. Chem. Soc. 120 (1998) 4982;
(c) L. Spiccia, B. Graham, M.T.W. Hearn, G. Lasarev, B.
Moubaraki, K.S. Murray, E.R.T. Tiekink, Dalton Trans. (1997)
4089;
[23] (a) V.M. Agre, I.A. Krol, V.K. Trunov, Dokl. Akad. Nauk. SSSR
235 (1977) 341;
(b) V.M. Agre, I.A. Krol, V.K. Trunov, V.M. Dziomko, O.V.
Ivanov, Koord. Khim. 5 (1979) 1413.
(d) P. Chaudhuri, I. Karpenstein, M. Winter, C. Butzlaff, E. Bill,
€
A.X. Trautwein, U. Florke, H.-J. Haupt, Chem. Commun. (1992)
[24] F.S. Keij, J.G. Haasnoot, A.J. Oosterling, J. Reedijk, C.J. O’Con-
nor, J.H. Zhang, A.L. Spek, Inorg. Chim. Acta 181 (1991) 185.
[25] (a) W.C. Velthuizen, J.G. Haasnoot, A.J. Kinneging, F.J. Riet-
meijer, J. Reedijk, Chem. Commun. (1983) 1366;
(b) F.J. Rietmeijer, R.A.G. de Graaff, J. Reedijk, Inorg. Chem. 23
(1984) 151;
321.
[6] P.A. Angaridis, P. Baran, R. Boea, F. Cervantes-Lee, W. Haase,
ꢂ
G. Mezei, R.G. Raptis, R. Werner, Inorg. Chem. 41 (2002) 2219.
ꢂ
ꢃꢄ
ꢃ
[7] R. Boca, L. Dlhan, G. Mezei, T. Ortiz-Perez, R.G. Raptis, J.
Telser, Inorg. Chem. 42 (2003) 5801.
[8] H.-H.T. Nguyen, A.K. Shiemke, S.J. Jacobs, B.J. Hales, M.E.
Lidstrom, S.I. Chan, J. Biol. Chem. 269 (1994) 14995.
[9] M.K. Ehlert, S.J. Rettig, A. Storr, R.C. Thompson, J. Trotter,
Can. J. Chem. 69 (1991) 432.
(c) R.W.M. ten Hoedt, J. Reedijk, G.C. Verschoor, Recl. Trav.
Chim. Pays-Bas 100 (1981) 400;
(d) F.S. Keij, J.G. Haasnoot, A.J. Oosterling, J. Reedijk, C.J.
O’Connor, J.H. Zhang, A.L. Spek, Inorg. Chim. Acta 181 (1991)
185;
[10] N. Kitajima, K. Fujisawa, C. Fujimoto, Y. Morooka, S.
Hashimoto, T. Kitagawa, K. Toriumi, K. Tatsumi, A. Nakamura,
J. Am. Chem. Soc. 114 (1992) 1277.
(e) E. van der Voort, P. van der Sluis, A.L. Spek, J.L. de Boer, Acta
Crystallogr., Sect. C 43 (1987) 887.
[11] G.J. Kubas, Inorg. Synth. 19 (1979) 90.
[26] K.M. Szecsenyi, V.M. Leovac, V.I. Cesljevic, A. Kovacs, G.
Pokol, Gy. Argay, A. Kalman, G.A. Bogdanovic, Z.K. Jacimovic,
A. Spasojevic-de-Bire, Inorg. Chim. Acta 353 (2003) 253.
[27] (a) R.M. Silverstein, G.C. Bassler, T.C. Morrill, Spectrometric
Identification of Organic Compounds, Wiley, New York, 1981;
(b) K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, Wiley, New York, 1997.
[12] (a) Data Collection: SMART-NT Software Reference Manual,
version 5.0, 1998, Bruker AXS, Inc., Madison, WI 53719-1173;
(b) Data Reduction: SAINT-NT Software Reference Manual,
verion 4.0,12Inc., Madison, WI 53719-1173
(c) G.M. Sheldrick, SHELXTL-NT, version 5.1, Bruker AXS, Inc.,
Madison, WI 53719-1173, 1999.