Structural and Electrochemical Comparison of Copper(II) Complexes with Tripodal Ligands

Article abstract of DOI:10.1021/ic960303n

A series of copper(II) complexes with tripodal polypyridylmethylamine ligands, such as tris(2-pyridylmethyl)-amine (tpa), ((6-methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Me₁tpa), bis((6-methyl-2-pyridyl)methyl)-(2-pyridylmethyl)amine (Me₂tpa), and tris((6-methyl-2-pyridyl)methyl)amine (Me₃tpa), have been synthesized and characterized by X-ray crystallography. [Cu(H₂O)(tpa)](ClO₄)₂ (1) crystallized in the monoclinic system, space group P2₁/a, with a = 15.029(7) ?, b = 9.268(2) ?, c = 17.948(5) ?, β = 113.80(3)°, and Z = 4 (R = 0.061, R_w = 0.059). [CuCl(Me₁tpa)]ClO₄ (2) crystallized in the triclinic system, space group P1?, with a = 13.617(4) ?, b = 14.532(4) ?, c = 12.357(4) ?, α = 106.01(3)°, β= 111.96(2)°, γ = 71.61(2)°, and Z = 4 (R = 0.054, R_w = 0.037). [CuCl(Me₂tpa)]ClO₄ (3) crystallized in the monoclinic system, space group P2₁/n, with a = 19.650(4) ?, b = 13.528(4) ?, c = 8.55(1) ?, β= 101.51(5)°, and Z = 4 (R = 0.071, R_w = 0.050). [CuCl(Me₃tpa)]-[CuCl₂(Me₃tpa)]ClO₄ (4) crystallized in the monoclinic system, space group P2₁/a, with a = 15.698(6) ? b = 14.687(7) ?, c = 19.475(4) ?, β= 97.13(2), and Z = 4 (R = 0.054, R_w = 0.038). All the Cu atoms of 1-4 have pentacoordinate geometries with three pyridyl and one tertiary amino nitrogen atoms, and a chloride or aqua oxygen atom. Nitrite ion coordinated to the Cu(II) center of Me₁tpa, Me₂tpa, and Me₃tpa complexes with only oxygen atom to form nitrito adducts. The cyclic voltammograms of [Cu(H₂O)(Me_ntpa)]²⁺ (n = 0, 1,2, and 3) in the presence of NO₂^- in H₂O (pH 7.0) revealed that the catalytic activity for the reduction of NO₂^- increases in the order Me₃tpa ? Me₂tpa ? Me₁tpa < tpa complexes.

Full text of DOI:10.1021/ic960303n

Inorg. Chem. 1996, 35, 6809-6815
6809
Structural and Electrochemical Comparison of Copper(II) Complexes with Tripodal
Ligands
Hirotaka Nagao,† Nobutoshi Komeda,§ Masao Mukaida,† Masatatsu Suzuki,‡ and
Koji Tanaka*,§
Department of Chemistry, Faculty of Science and Technology, Sophia University, Kioi-cho, Chiyoda-ku,
Tokyo 102, Japan, Department of Chemistry, Faculty of Science, Kanazawa University, Kakumamachi,
Kanazawa 920-11, Japan, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
ReceiVed March 20, 1996X
A series of copper(II) complexes with tripodal polypyridylmethylamine ligands, such as tris(2-pyridylmethyl)-
amine (tpa), ((6-methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Me1tpa), bis((6-methyl-2-pyridyl)methyl)-
(2-pyridylmethyl)amine (Me2tpa), and tris((6-methyl-2-pyridyl)methyl)amine (Me3tpa), have been synthesized
and characterized by X-ray crystallography. [Cu(H2O)(tpa)](ClO4)2 (1) crystallized in the monoclinic system,
space group P21/a, with a ) 15.029(7) Å, b ) 9.268(2) Å, c ) 17.948(5) Å, â ) 113.80(3)°, and Z ) 4 (R )
0.061, Rw ) 0.059). [CuCl(Me1tpa)]ClO4 (2) crystallized in the triclinic system, space group P1h, with a ) 13.617(4)
Å, b ) 14.532(4) Å, c ) 12.357(4) Å, R ) 106.01(3)°, â ) 111.96(2)°, γ ) 71.61(2)°, and Z ) 4 (R ) 0.054,
Rw ) 0.037). [CuCl(Me2tpa)]ClO4 (3) crystallized in the monoclinic system, space group P21/n, with a ) 19.650(4)
Å, b ) 13.528(4) Å, c ) 8.55(1) Å, â ) 101.51(5)°, and Z ) 4 (R ) 0.071, Rw ) 0.050). [CuCl(Me3tpa)]-
[CuCl2(Me3tpa)]ClO4 (4) crystallized in the monoclinic system, space group P21/a, with a ) 15.698(6) Å, b )
14.687(7) Å, c ) 19.475(4) Å, â ) 97.13(2)°, and Z ) 4 (R ) 0.054, Rw ) 0.038). All the Cu atoms of 1-4
have pentacoordinate geometries with three pyridyl and one tertiary amino nitrogen atoms, and a chloride or aqua
oxygen atom. Nitrite ion coordinated to the Cu(II) center of Me1tpa, Me2tpa, and Me3tpa complexes with only
oxygen atom to form nitrito adducts. The cyclic voltammograms of [Cu(H2O)(Mentpa)]2+ (n ) 0, 1, 2, and 3)
in the presence of NO2- in H2O (pH 7.0) revealed that the catalytic activity for the reduction of NO2- increases
in the order Me3tpa , Me2tpa , Me1tpa < tpa complexes.
Introduction
imidazole,9-14 pyrazole,12,13,18,19 benzothiazole,22 thioester,23
histidine,24 and azomethine25,26) and PL′3 type (L′ ) imida-
zolyl27) have been synthesized. The redox behavior of Cu(II)/
Coordination chemistry of copper complexes is a subject of
continuing importance in connection with the structures and the
reactivities of the active site in copper-containing metallo-
proteins. Along this line, a variety of mono- and dinuclear
copper complexes with tripodal ligands such as NL3 type (L )
pyridine,1-15 phenolate,5,7 benzimidazole,5,13,16,17 quinoline,6,8
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* Author to whom correspondence should be addressed.
† Sophia University.
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J. J. Coord. Chem. 1992, 25, 171. (b) Driessen, W. L.; Wiesmeijer,
W. G. R.; Schipper-Zablotskaja, M.; De Graaff, R. A. G.; Reedijk, J.
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‡ Kanazawa University.
§ Institute for Molecular Science.
X Abstract published in AdVance ACS Abstracts, October 1, 1996.
(1) (a) Sanyal, I.; Ghosh, P.; Karlin, K. D. Inorg. Chem. 1995, 34, 3050.
(b) Harata, M.; Jitsukawa, K.; Masuda, H.; Einaga, H. Chem. Lett.
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S0020-1669(96)00303-5 CCC: $12.00 © 1996 American Chemical Society

6810 Inorganic Chemistry, Vol. 35, No. 23, 1996
Nagao et al.
Cu(I) couples of those complexes2,5,6,8,12,13,17,19,21,22,28 and the
interaction with O2, NO, and NO2- have been studied from the
standpoint of structural models of Cu-proteins. On the other
hand, catalytic activity toward reduction of NO2- as functional
models of copper-containing NO2- reductases have hardly been
discussed so far.
This work undertakes to elucidate the relationship between
the structural changes and the redox potential of [CuX-
(Mentpa)]m+; X ) Cl, H2O; m ) 1, 2; n ) 0, 1, 2, 3) caused by
successive introduction of three methyl groups into the 6-posi-
tion of pyridine moieties of the tpa ligand and the catalytic
ability of these four Cu(II) complexes toward the reduction of
NO2- in H2O (pH 7.0). A part of this work has been reported
elsewhere.3
with stirring. The resulting solution was stirred at room temperature
for 12 h and then acidified by addition of concentrated hydrochloric
acid to quench excess hydride. The solution was evaporated almost
to dryness under reduced pressure. The residue was dissolved into
water, and the resulting solution was made alkaline by addition of
Na2CO3. The dark brown oil that separated was extracted with
chloroform. The extract was dried over Na2SO4 and concentrated under
reduced pressure. The residue was distilled and the distillate was
purified as described in the literature.29 Yield: 12.5 g (55%). 1H NMR
(CDCl3, 400 MHz): δ ) 2.54 (6H, s, CH3), 3.94 (4H, s, CH2), 7.01
(2H, d, pyH), 7.17 (2H, d, pyH), 7.52 (2H, t, pyH). 13C NMR (CDCl3,
100 MHz): δ ) 24.5 (CH3), 55.0 (CH2), 119.1 (py), 121.4 (py), 136.6
(py), 157.9 (py), 159.1 (py). MS: m/z 227 [M]+.
Bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine (Me2tpa).
Sodium cyanoborohydride (1.63 g, 0.026 mol) was added dropwise to
a cold mixture of 2-pyridinecarboxaldehyde (3.53 g, 0.033 mol), L-2
(6.82 g, 0.030 mol), and acetic acid (4.2 g, 0.07 mol) in 100 mL of
methanol with stirring. The resulting solution was stirred at room
temperature for 3 days, then acidified by addition of concentrated
hydrochloric acid to quench excess hydride, and evaporated almost to
dryness under reduced pressure. The residue was dissolved into water
and the resulting solution was made alkaline by addition of Na2CO3.
A dark brown oil separated and was extracted with chloroform. The
extract was dried over Na2SO4 and the solvent was evaporated under
reduced pressure to afford a brownish solid product. It was recrystal-
lized from ligroin (bp 80-100 °C). Yield: 7.1 g (74%). 1H NMR
(CDCl3, 400 MHz): δ ) 2.56 (6H, s, CH3), 3.90 (4H, s, CH2), 3.93
(2H, s, CH2), 7.03 (2H, d, pyH), 7.18 (1H, t, pyH), 7.47 (2H, d, pyH),
7.59 (2H, t, pyH), 7.66 (1H, d, pyH), 7.69 (1H, t, pyH), 8.56 (1H, d,
pyH). 13C NMR (CDCl3, 100 MHz): δ ) 24.4 (CH3), 60.2 (CH2),
60.3 (CH2), 119.5 (py), 121.4 (py), 121.9 (py), 122.8 (py), 136.3 (py),
136.6 (py), 149.1 (py), 157.6 (py), 159.0 (py), 159.7 (py). MS: m/z
318 [M]+.
Experimental Section
Materials. [Cu(H2O)(tpa)](ClO4)2,10 [CuCl(tpa)]ClO4,14 [Cu(NO2)-
(tpa)]PF6, and [Cu(ONO)(tpa)]PF6 3 were prepared by the modification
of methods in the literature. Acetonitrile was purified by distillation
over CaH2. All other chemicals were commercially available and used
without further purification.
Physical Measurements. IR spectra were obtained as KBr pellets
and CD3CN solutions using a Shimadzu FTIR-8100 spectrophotometer.
Elemental analyses were performed at the Chemical Materials Center
of the Institute for Molecular Science and the Sophia University
Analytical Facility. 1H and 13C NMR spectra were measured on a JEOL
GX400 spectrophotometer. Mass and FAB-mass spectra were obtained
on a JEOL JMS-SX102A and a Shimadzu/Kratos Concept 1S.
Electrochemical measurements were performed in a cell equipped with
a glassy-carbon working electrode (φ ) 3 mm), a Pt-wire auxiliary
electrode, an Ag|AgCl reference electrode, and a nozzle for bubbling
of N2. Cyclic voltammograms were obtained by use of a Hokuto Denko
HAB-151 potentiostat/galvanostat with a function generator and a Riken
Denshi F-35 X-Y recorder.
((6-Methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Me1tpa).
This was prepared by a method similar to that for Me2tpa using
6-methyl-2-pyridinecarboxaldehyde (13.3 g, 0.11 mol) and bis(2-
pyridylmethyl)amine (19.9 g, 0.10 mol) instead of 2-pyridinecarbox-
aldehyde and bis(6-methyl-2-pyridylmethyl)amine, respectively. So-
dium cyanoborohydride (5.02 g, 0.08 mol) was used. The crude product
was recrystallized from ligroin (bp 80-100 °C) to give pale yellow
crystals. Yield: 13.5 g (44%). 1H NMR (CDCl3, 400 MHz): δ )
2.52 (3H, s, CH3), 3.86 (2H, s, CH2), 3.88 (4H, s, CH2), 6.99 (1H, d,
pyH), 7.14 (2H, t, pyH), 7.42 (1H, d, pyH), 7.55 (1H, t, pyH), 7.59
(2H, d, pyH), 7.65 (2H, t, pyH), 8.52 (2H, d, pyH). 13C NMR (CDCl3,
100 MHz): δ ) 24.4 (CH3), 60.2 (CH2), 60.3 (CH2), 119.6 (py), 121.4
(py), 121.9 (py), 122.9 (py), 136.3 (py), 136.6 (py), 149.1 (py), 157.7
(py), 158.8 (py), 159.6 (py). MS: m/z 304 [M]+.
Synthesis of Ligands. Although the preparations of Me1tpa, Me2tpa,
and Me3tpa were reported by Mota et al.,29 we prepared them by
different methods, described below.
((6-Methyl-2-pyridyl)methyl)amine (L-1). Hydroxylamine hydro-
chloride (7.6 g, 0.11 mol) was dissolved in a minimum amount of water,
to which was added 6-methyl-2-pyridinecarboxaldehyde (12.1 g, 0.1
mol) in 40 mL of methanol. Oxime formed was deposited as a white
powder. To this suspension was added 1 g of 5% Pd-C and the oxime
was hydrogenated at 45 °C under an atmospheric pressure of H2 with
vigorous stirring. After hydrogenated, 5% Pd-C was removed by
filtration and the filtrate was evaporated almost to dryness under reduced
pressure and the residue was dissolved into water. The aqueous solution
was made strongly alkaline by addition of NaOH, giving a brown oil,
which was extracted with chloroform. The extract was dried over
Na2SO4, and the solvent was removed under reduced pressure. The
residue was fractionally distilled to afford L-1 as a colorless oil: bp
62 °C (20 mmHg). Yield: 8.8 g (72%). 1H NMR (CDCl3, 400
MHz): δ (ppm) ) 2.54 (3H, s, CH3), 3.93 (2H, s, CH2), 7.01 (1H, d,
pyH), 7.08 (1H, d, pyH), 7.52 (1H, t, pyH). 13C NMR (CDCl3, 100
MHz): δ ) 24.4 (CH3), 47.9 (CH2), 118.0 (py), 121.2 (py), 136.7 (py),
157.9 (py), 161.3 (py). MS: m/z 122 [M]+.
Tris((6-methyl-2-pyridyl)methyl)amine (Me3tpa). This was pre-
pared by a method similar to that for Me2tpa using bis(6-methyl-2-
pyridylmethyl)amine (6.82 g, 0.030) and 6-methyl-2-pyridinecarbox-
aldehyde (4.0 g, 0.033 mol) instead of 2-pyridinecarboxaldehyde.
Sodium cyanoborohydride (1.51 g, 0.024 mol) was used. The crude
product was recrystallized from ligroin (bp 80-100 °C) to give pale
yellow crystals. Yield: 6.8 g (68%). 1H NMR (CDCl3, 400 MHz):
δ ) 2.56 (9H, s, CH3), 3.85 (6H, s, CH2), 6.98 (3H, d, pyH), 7.42 (3H,
d, pyH), 7.53 (3H, t, pyH). 13C NMR (CDCl3, 100 MHz): δ ) 24.4
(CH3), 60.3 (CH2), 119.5 (py), 121.3 (py), 136.6 (py), 157.6 (py), 159.1
(py). MS: m/z 332 [M]+.
Bis((6-methyl-2-pyridyl)methyl)amine (L-2). 6-Methyl-2-pyridine-
carboxaldehyde (12.1 g, 0.1 mol) was added to L-1 in 100 mL of
methanol, to which sodium borohydride (5.0 g, 0.08 mol) was added
Synthesis of Complexes. Caution! Although the complexes as
perchlorate salts described below are stable, they are potentially
explosiVe and should be handled with care.
(23) (a) Nishida, Y.; Takahashi, K. Inorg. Chem. 1988, 27, 1406. (b) Suzuki,
M.; Kanatomi, H.; Koyama, H.; Murase, I. Inorg. Chim. Acta 1980,
44, L41.
(24) Goldfarb, D.; Fauth, J.-M.; Tor, Y.; Shanzer, A. J. Am. Chem. Soc.
1991, 113, 1941.
(25) McLachlan, G. A.; Fallon, G. D.; Martin, R. L.; Spiccia, L. Inorg.
Chem. 1995, 34, 254.
(26) Fenton, D. E.; Westwood, G. P.; Bashall, A.; McPartlin, M.; Scowen,
I. J. J. Chem. Soc., Dalton Trans. 1994, 2213.
(27) Sorrell, T. N.; Allen, W. E.; White, P. S. Inorg. Chem. 1995, 34, 952.
(28) Addison, A. W. Inorg. Chim. Acta 1989, 162, 217.
(29) Da Mota, M. M.; Rogers, J.; Nelson, S. M. J. Chem. Soc. A 1969,
2036.
[Cu(H2O)(L)](ClO4)2 (L ) Me1tpa, Me2tpa, and Me3tpa).
A
series of aqua Cu(II) complexes were synthesized by a modified method
of [Cu(H2O)(tpa)](ClO4)2.10 An addition of L (1.0 mmol) to a stirred
C2H5OH (20 cm3) solution containing Cu(ClO4)2‚5H2O (1.0 mmol)
afforded
a greenish blue precipitate of [Cu(H2O)(L)](ClO4)2.
[Cu(H2O)(Me2tpa](ClO4)2 and [Cu(H2O)(Me3tpa](ClO4)2 were recrystal-
lized from CH2Cl2/ether. Yield: ca. 70%. Anal. Calcd for [Cu(H2O)-
(Me1tpa)](ClO4)2‚1.5H2O: C, 37.30; H, 4.12; N, 9.16. Found: C,
37.40; H, 4.07; N, 9.01. Calcd for [Cu(H2O)(Me2tpa)](ClO4)2‚0.5CH2-
Cl2: C, 38.39; H, 3.93; N, 8.74. Found: C, 38.49; H, 3.69; N, 8.87.

Cu(II) Complexes with Tripodal Ligands
Inorganic Chemistry, Vol. 35, No. 23, 1996 6811
Table 1. Crystallographic Data
1
2
3
4
formula
fw
space group (No.)
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
C18H20N4O9Cl2Cu
C19H20N4O4Cl2Cu
502.84
P1h (2)
C20H22N4O4Cl2Cu
516.87
P21/n (14)
19.650(4)
13.528(4)
8.55(1)
90
101.51(5)
90
2227(2)
1.54
C42H48N8O4Cl4Cu2
997.80
P21/a (14)
15.698(6)
14.687(7)
19.475(4)
90
97.13(2)
90
4455(2)
1.49
570.83
P21/n (14)
15.029(7)
9.268(2)
17.948(5)
90
113.80(3)
90
2287(1)
1.66
13.617(4)
14.532(4)
12.357(4)
106.01(3)
111.96(2)
71.61(2)
2117(1)
1.58
F
calc/g cm-3
Z
4
4
4
4
µ/cm-1
radiation
T, °C
12.46
13.18
12.54
12.45
graphite-monochromated Mo KR (λ ) 0.710 69 Å)
23
0.054/0.037
23
23
23
a
R/Rw
0.061/0.059
0.071/0.050
0.054/0.038
2
a R ) ∑||Fo| - |Fc||/∑|Fo|, Rw ) (∑w(|Fo| - |Fc|)2/∑w|Fo| )1/2, w ) 1/σ2(Fo).
equilibrium mixture in solutions.3 On the other hand, the
reaction of NO2- with Cu(II) complexes with Me1tpa, Me2tpa,
and Me3tpa ligands selectively produced the nitrito isomers,
[Cu(ONO)(Mentpa)]+ (n ) 1, 2, 3), since only the ν(NdO) and
ν(NsO) bands of the nitrito isomers were observed in the IR
spectra of the crude and purified products (1428 and 1076 cm-1
for the Me1tap complex, 1410 and 1098 cm-1 for the Me2tap
complex, and the 1400 and 1094 cm-1 for Me3tap complex).
The IR spectra of these complexes in CD3CN also displayed
only the ν(NdO) band at almost same wavenumber as those in
the solid state,32 and neither νasym(NO2) nor νsym(NO2) band of
a nitrito isomer was detected in the regions of 1470-1370 and
1340-1320 cm-1, respectively.33
Calcd for [Cu(H2O)(Me3tpa)](ClO4)2: C, 41.15; H, 4.28; N, 9.14.
Found: C, 41.13; H, 4.25; N, 9.13.
[CuCl(L)]ClO4 (L ) Me1tpa, Me2tpa, and Me3tpa). Addition of
KCl (2.0 mmol) to a stirred H2O/C2H5OH (2:5 v/v, 35 cm3) solution
containing Cu(ClO4)2‚5H2O (1.0 mmol) and L (1.0 mmol) afforded a
blue precipitate of [CuCl(L)]ClO4. Yield: ca. 80%. Anal. Calcd for
[CuCl(Me1tpa)]ClO4: C, 45.38; H, 4.01; N, 11.14. Found: C, 45.30;
H, 4.12; N, 11.10. Calcd for [CuCl(Me2tpa)]ClO4: C, 46.48; H, 4.29;
N, 10.84. Found: C, 46.13; H, 4.22; N, 10.71. Calcd for [CuCl-
(Me3tpa)][CuCl2(Me3tpa)]ClO4: C, 50.56; H, 4.85; N, 11.23. Found:
C, 50.59; H, 4.84; N, 11.17.
[Cu(ONO)(L)]PF6 (L ) Me1tpa, Me2tpa, and Me3tpa). Addition
of NH4PF6 (2.0 mmol) to a stirred H2O/C2H5OH (2:5 v/v, 35 cm3)
solution containing (CH3COO)2Cu.H2O (1.0 mmol), L (1.0 mmol), and
NaNO2 (2.0 mmol) afforded a green precipitate of [Cu(ONO)(L)]PF6.
Yield: ca. 60%. Anal. Calcd for [Cu(ONO)(Me1tpa)]PF6: C, 40.83;
H, 3.61; N, 12.53. Found: C, 40.71; H, 3.52; N, 12.16. Calcd for
[Cu(ONO)(Me3tpa)]PF6: C, 42.97; H, 4.12; N, 11.93. Found: C, 42.99;
H, 4.11; N, 11.86. FAB-Mass Spectrum for [Cu(ONO)(Me2tpa)]PF6:
427[M-PF6]+. IR spectral data (KBr): [Cu(ONO)(Me1tpa)]PF6, ν(NdO)
1428 cm-1 and ν(NsO) 1076 cm-1; [Cu(ONO)(Me2tpa)]PF6, ν(NdO)
1410 cm-1 and ν(NsO) 1098 cm-1; [Cu(ONO)(Me3tpa)]PF6, ν(NdO)
Electrochemical Behavior of Copper(II) Complexes. Con-
trolled-potential electrolysis of [Cu(H2O)(tpa)]2+ in the presence
-
of NO2 at -0.40 V in H2O (pH 7.0) catalytically produces
NO and N2O, in which both [Cu(ONO)(tpa)]+ and [Cu(NO2)-
(tpa)]+ play the active species in the reduction.3 Stoichiometri-
cal NO evolution from LCuNO2 (L ) 1,4,7-triisopropyl-1,4,7-
triazacyclononane) is also demonstrated by treatment of the
complex with 2 equiv of glacial acetic acid in CH2Cl2.34 The
redox behavior of [Cu(H2O)(Mentpa)]2+ (n ) 0, 1, 2, 3) was
examined in the absence and the presence of NO2- to evaluate
1400 cm-1 and ν(NsO) 1094 cm-1
.
X-ray Crystallographic Data Collection and Refinement of the
Structures. A single crystal was mounted on a glass fiber. The
diffraction intensities were collected with graphite-monochromated Mo
KR radiation on Enraf-Nonius FR-590, Rigaku AFC5S, or Rigaku
AFC5R diffractometer at 23 °C and the ω-2θ scan technique to a
2θmax value of 50.0° or 55.0°. Crystallographic data for 1-4 are given
in Table 1. All of the calculations were carried out on an IRIS Indigo
computer of the Silicon Graphics corporation, using the TEXSAN
crystallographic software package of the Molecular Structure Corp. The
structures were solved by direct methods and expanded using Fourier
techniques. Empirical absorption corrections using DIFABS30 were
applied after a full isotropic refinement of non-hydrogen atoms. The
non-hydrogen atoms were refined anisotropically and hydrogen atoms
were included by no refined. Atomic scattering factors were taken
from tables.31 Complete information on collected data and refinement
and atomic coordinates, are included as Supporting Information.
the catalytic activity of these complexes for the reduction of
-
NO2
.
The cyclic voltammograms (CVs) of [Cu(H2O)-
(Mentpa)]2+ in aqueous solution (pH 7) are depicted as solid
lines in Figure 1. The electrochemical parameters in H2O and
CH3CN are summarized in Table 2.35 As depicted in Figure 1,
the cathodic and anodic waves of the Cu(I)/Cu(II) redox couples
unexpectedly shift to positive potentials in the order, tpa <
Me1tpa < Me2tpa < Me3tpa complexes. The peak separation
(∆E ) Epa - Epc) of the redox couples increases in the same
order. The E1/2 and ∆E values of the [CuCl(Mentpa)]+/0 and
the [Cu(H2O)(Mentpa)]2+/+ couples in CH3CN also showed the
same tendency. Thus, the electron density of the copper center
and the reversibility of the Cu(II)/Cu(I) redox couple of these
complexes decrease with an increase in the number of methyl
group in the Mentpa ligand. The CVs of [Cu(H2O)(Mentpa)]2+
Results and Discussion
Synthesis of Copper(II) Complexes Containing Nitrite
Ligand. A series of [CuCl(Mentpa)]+ ions (n ) 1, 2, 3) were
prepared in a manner similar to [CuCl(tpa)]+. The reaction of
(32) The ν(N-O) bands were obscured by the strong absorption band of
CD3CN.
(33) Nakamoto, K., Infrared and Raman Spectra of Inorganic and
Coordination Compounds; 4th ed.; Wiley-Interscience: New York,
1986; p 221.
-
[Cu(H2O)(tpa)]2+ with NO2 produced [Cu(ONO)(tpa)]+ and
[Cu(NO2)(tpa)]+, and these nitrito and nitro isomers exist as an
(34) Halfen, J. A.; Mahapatra S.; Wilkinson, E. C.; Gengenbach, A. J.;
Young, V. G., Jr.; Que, L., Jr.; Tolman, W. B. J. Am. Chem. Soc.
1996, 118, 763.
(30) DIFABS: Walker, N; Stuart, D. Acta Crystallogr, Sect. A 1983, A39,
158.
(31) International Tables for X-ray Crystallography; Kynoch Press: Bir-
mingham, U.K., 1974; Vol. IV.
(35) The CVs of [Cu(H2O)(Mentpa)]2+ and [CuCl(Mentpa)]+ were com-
pletely consistent with each other in H2O (pH 7). Thus, [CuCl(Men-
tpa)]+ is converted to [Cu(H2O)(Mentpa)]2+ in H2O.

6812 Inorganic Chemistry, Vol. 35, No. 23, 1996
Nagao et al.
1
less than /40 compared with that by [Cu(H2O)(tpa)]2+. The
catalytic activity of [Cu(H2O)(Me2tpa)]2+ and [Cu(H2O)-
(Me3tpa)]2+ for the reduction of NO2- further decreased, because
the increases in cathodic currents at more negative potentials
than the cathodic waves of the [Cu(H2O)(Me2tpa)]2+/+ and
[Cu(H2O)(Me3tpa)]2+/+ couples are quite small even in the
-
presence of 5.0 × 102 and 1.5 × 103 molar excesses of NO2
(Figure 1c,d). Thus, the catalytic activity for the reduction of
-
NO2 by [Cu(H2O)(Mentpa)]2+ (n ) 0, 1, 2, 3) decreases in
the order tpa > Me1tpa . Me2tpa . Me3tpa complexes. In
fact, the controlled-potential electrolysis of [Cu(H2O)(Me1tpa)]-
(ClO4)2 in the presence of a 75 molar excess of NO2- at -0.40
V in H2O (pH 7.0) catalytically produced N2O and a small
amount of NO, similar to that with [Ru(H2O)(tpa)]2+,3 while
[Cu(H2O)(Me2tpa)](ClO4)2 hardly catalyzed the reduction of
-
NO2 under the similar electrolysis conditions. It should be
noticed that the order of the catalytic activity does not result
from the steric hindrance of methyl groups of the Mentpa ligand
-
for the attack of NO2 to the Cu2+ center, since [Cu(ONO)-
(Mentpa)]+ ions (n ) 0, 1, 2, 3) are smoothly formed in the
- 36
reaction of [Cu(H2O)(Mentpa)]+ with NO2
.
Structures of Copper(II) Complexes. Single crystals of
[Cu(H2O)(tpa)](ClO4)2 (1), [CuCl(Me1tpa)]ClO4 (2), [CuCl(Me2-
tpa)]ClO4 (3), and [CuCl(Me3tpa)][CuCl2(Me3tpa)]ClO4 (4) were
obtained by recrystallization of the crude complexes from
CH2Cl2/Et2O or slow evaporation of the synthesized solution.
Except for the neutral [CuCl2(Me3tpa)] unit in 4, all the Cu(II)
atoms of 1-4 are pentacoordinated structures with three pyridyl
nitrogens, one amino nitrogen, and a chloride or oxygen atom
of H2O. Selected bond distances and angles of all complexes
are summarized in Table 3. The molecular structures of copper
complexes are shown in Figure 2-6. The structures of the
present pentacoordinated Cu(II) complexes are trigonal bipyra-
mid, square pyramid, and the intermediate between them. The
changes in the bond distances in the series [CuCl(Mentpa)]+ (n
) 0, 1, 2, 3) are depicted in Figure 7.
Furthermore, a structural index parameter τ ()(â - R)/60)
introduced by Reedijk,37 where R and â represent two basal
angles (â g R), was also adopted to systematize the change in
the geometries of the complexes. A perfect trigonal-bipyramid
is associated with R ) 120° and â ) 180° (τ ) 1), and idealized
square pyramidal geometries are defined as R ) â ) 180° (τ
) 0). In the real square pyramidal structures, metal atoms
usually are located out of the equatorial plane toward the axial
bond. The C4v geometries still can be characterized by τ ≈ 0
(R ≈ â < 180°). The structural parameters R, â, and τ are
summarized in Table 4.
The geometry of 1 is expressed by an almost idealized trigonal
bipyramid with τ ) 0.97. Three pyridyl nitrogen atoms
equivalently coordinate to Cu2+ in the equatorial plane (2.054(6),
2.038(7), and 2.069(6) Å for the Cu-N2, -N3, and -N4 bonds,
and 119.9(2), 118.2(3), and 116.8(2)° for three N-Cu-N
angles), and amino nitrogen and aqua oxygen atoms are in the
axial positions (Figure 2). A series of [CuX(tpa)]+ ions (X )
Cl, F, ONO, NO2) also have the trigonal bipyramidal structure,
and the Cu-N bond distances in the basal plane of those
complexes are also close to those of 1. On the other hand, the
Cu-N1 (amino nitrogen) bond distance (1.941(6) Å) is sig-
nificantly shorter than that of [CuX(tpa)]+ (2.050(6), 2.069(10),
2.031(2), and 2.023(5) Å for X ) Cl,14 F,10 ONO, and NO2,3
respectively). A relatively strong coordination of amino nitrogen
Figure 1. Cyclic voltammograms of [Cu(H2O)(tpa)](ClO4)2 (a),
[Cu(H2O)(Me1tpa)](ClO4)2 (b), [Cu(H2O)(Me2tpa)](ClO4)2 (c), and
[Cu(H2O)(Me3tpa)](ClO4)2 (d) in the absence (solid lines) and the
presence of NaNO2 (dotted lines) in H2O at pH 7.0. [NO2-]/[complex]
) 1.5 for (a), 50 for (b), 500 for (c), and 1500 for (d).
Table 2. Redox Potentials (Vs Ag|AgCl) of [Cu(H2O)L](ClO4)2 in
H2O (pH 7.0) and CH3CNa
L
Epa/V
Epc/V
E1/2b/V
∆E/V
tpa
-0.37
(0.07)
-0.27
(0.13)
-0.08
(0.26)
0.16
-0.47
(-0.02)
-0.38
(0.04)
-0.31
(0.12)
-0.23
(0.27)
-0.42
(0.03)
-0.33
(0.09)
-0.20
(0.19)
-0.04
(0.44)
0.10
(0.09)
0.11
(0.09)
0.23
(0.14)
0.39
(0.33)
Me1tpa
Me2tpa
Me3tpa
(0.60)
b
a The value in parentheses is in CH3CN. E1/2 ) (Epa + Epc)/2.
in the presence of NaNO2 in H2O (pH 7) are also depicted by
dotted lines in Figure 1. An addition of 1.5 equiv of NaNO2 to
the aqueous solution of [Cu(H2O)(tpa)]2+ causes a strong
cathodic current due to the reduction of NO2- at more negative
potentials than the threshold potential of the cathodic waves of
the Cu(II)/Cu(I) couples (Figure 1a). Complete disappearance
of the anodic wave in the reverse potential sweep also shows
the high catalytic activity of the complex toward NO2- reduction
producing N2O through NO (eqs 1 and 2). Similarly,
NO2- + 2H+ + e- f NO + H2O
(1)
(2)
2NO2- + 6H+ + 4e- f N2O + 3H2O
[Cu(H2O)(Me1tpa)]2+ in the presence of 50 equiv of NaNO2
displays a catalytic current due to the reduction of NO2- (Figure
1b). On the basis of the current density depending on the mole
ratios of [NO2-]/[Cu2+], the catalytic activity of [Cu(H2O)-
(36) The reaction of [Cu(H2O)(Mentpa)]2+ (n ) 0, 1, 2, 3) with NO2 is
-
rapid, because greenish blue color of [Cu(H2O)(Mentpa)]2+ rapidly
changed to green by the addition of NaNO2.
(37) Addison, A. W.; Rao, T. N.; Reedijk, J.; Rijn, J.; Verschoor, G. C. J.
Chem. Soc., Dalton Trans. 1984, 1349.
-
(Me1tpa)]2+ toward the reduction of NO2 is estimated to be

Cu(II) Complexes with Tripodal Ligands
Inorganic Chemistry, Vol. 35, No. 23, 1996 6813
Table 3. Selected Bond Distances (Å) and Bond Angles (deg)
[Cu(H2O)(tpa)](ClO4)2 (1)
Cu-O1
Cu-N2
Cu-N4
1.980(5)
2.054(6)
2.069(6)
Cu-N1
Cu-N3
1.941(6)
2.038(7)
O1-Cu-N1
O1-Cu-N3
N1-Cu-N2
N1-Cu-N4
N2-Cu-N4
177.8(2)
98.9(2)
83.4(2)
82.1(2)
118.2(3)
O1-Cu-N2
O1-Cu-N4
N1-Cu-N3
N2-Cu-N3
N3-Cu-N4
94.5(2)
99.4(2)
81.7(3)
119.9(2)
116.8(2)
[CuCl(Me1tpa)]ClO4 (2)
Cu1-Cl1
Cu1-N2
Cu1-N4
Cu2-N5
Cu2-N7
2.251(3)
1.988(8)
2.337(8)
2.038(8)
1.975(8)
Cu1-N1
Cu1-N3
Cu2-Cl2
Cu2-N6
Cu2-N8
2.057(8)
1.990(8)
2.247(3)
1.966(9)
2.581(8)
Figure 2. Molecular structure of [Cu(H2O)(tpa)]2+ (1) with atom
labeling. Carbon atoms are not labeled and hydrogen atoms are omitted
for clarity.
Cl1-Cu1-N1
Cl1-Cu1-N3
N1-Cu1-N2
N1-Cu1-N4
N2-Cu1-N4
Cl2-Cu2-N5
Cl2-Cu2-N7
N5-Cu2-N6
N5-Cu2-N8
N6-Cu2-N8
169.3(2)
95.6(3)
83.5(3)
80.1(3)
86.5(3)
177.9(3)
97.7(3)
84.0(4)
78.6(3)
83.5(3)
Cl1-Cu1-N2
Cl1-Cu1-N4
N1-Cu1-N3
N2-Cu1-N3
N3-Cu1-N4
Cl2-Cu2-N6
Cl2-Cu2-N8
N5-Cu2-N7
N6-Cu2-N7
N7-Cu2-N8
97.0(3)
110.6(2)
81.2(3)
159.8(3)
103.7(3)
97.1(3)
103.3(2)
81.0(3)
163.6(4)
99.8(3)
[CuCl(Me2tpa)]ClO4 (3)
Cu-Cl
Cu-N2
Cu-N4
2.253(4)
1.98(1)
2.27(1)
Cu-N1
Cu-N3
2.064(9)
2.02(1)
Cl-Cu-N1
Cl-Cu-N3
N1-Cu-N2
N1-Cu-N4
N2-Cu-N4
163.5(3)
99.6(3)
83.4(4)
80.8(4)
89.6(4)
Cl-Cu-N2
Cl-Cu-N4
N1-Cu-N3
N2-Cu-N3
N3-Cu-N4
93.4(3)
115.4(3)
79.5(4)
159.3(4)
99.1(4)
Figure 3. Molecular structure of [CuCl(Me1tpa)]+ (2) with atom
labeling. Carbon atoms are not labeled and hydrogen atoms are omitted
for clarity.
[CuCl(Me3tpa)][CuCl2(Me3tpa)]ClO4 (5)
Cu1-Cl1
Cu1-N2
Cu1-N4
Cu2-Cl2
Cu2-N5
Cu2-N7
2.240(2)
2.047(7)
2.161(6)
2.292(2)
2.145(6)
2.017(6)
Cu1-N1
2.092(6)
2.035(7)
Cu1-N3
Cu2-Cl3
Cu2-N6
2.373(2)
2.014(6)
Cl1-Cu1-N1
Cl1-Cu1-N3
N1-Cu1-N2
N1-Cu1-N4
N2-Cu1-N4
Cl2-Cu2-Cl3
Cl2-Cu2-N6
Cl3-Cu2-N5
Cl3-Cu2-N7
N5-Cu2-N7
135.3(2)
96.0(2)
80.6(3)
83.9(2)
92.4(3)
131.4(1)
95.9(2)
105.1(2)
93.4(2)
82.2(2)
Cl1-Cu1-N2
Cl1-Cu1-N4
N1-Cu1-N3
N2-Cu1-N3
N3-Cu1-N4
Cl2-Cu2-N5
Cl2-Cu2-N7
Cl3-Cu2-N6
N5-Cu2-N6
N6-Cu2-N7
94.3(2)
140.8(2)
80.9(3)
161.0(3)
89.6(3)
123.3(2)
90.6(2)
93.9(2)
81.2(2)
163.1(2)
to Cu2+ of 1 may be associated with an elongation of the trans
Cu-OH2 bond distance (1.980(5) Å) compared with the Cu-
ONO distance of [Cu(ONO)(tpa)]+ (1.938(2) Å).
Figure 4. Molecular structure of [CuCl(Me2tpa)]+ (3) with atom
labeling. Carbon atoms are not labeled and hydrogen atoms are omitted
for clarity.
Blue [CuCl(Me1tpa)]ClO4 (2) crystallized in the triclinic
system, P1h, and Z ) 4. In the unit cell, therefore, two
independent molecules (Cu1 and Cu2) exist and showed slightly
different geometries with each other. The geometries of the
cationic units of 2 were distorted square pyramid (τ ) 0.16
and 0.24), in which two pyridyl nitrogen atoms, one amino
nitrogen, and chloride atom form the basal plane, and the
6-methylpyridyl ligand is located in the axial position (Figure
3). The Cu-Npy bond distances in the basal plane (1.988(8)
and 1.990(8) Å for the Cu1 unit and 1.966(9) and 1.975(8) Å
for the Cu2 unit) are shortened compared with those of 1
(2.054(6), 2.038(7) Å), while the Cu-Npy bond distances at the
axial position (2.337(8) and 2.581(8) Å) of 2 are substantially
elongated compared with the Cu-Npy bond distances in the
basal plane (Figure 6). Shortening of the bond distances in the
basal plane (Cu-Namino, Cu-Npy, and Cu-Cl) and lengthening
of the axial bond length (Cu-Npy) are commonly observed in
square pyramidal copper(II) complexes.
The geometry of 3 is slightly distorted square pyramid as
similar to 2, and Cl, N1, N2, and N3 atoms form a basal plane
with an axial Cu-N4 bond (τ ) 0.07) (Figure 4). Despite the
ligation of the 6-methylpyridyl nitrogen (N3) to Cu2+ in the
basal plane, the Cu-N and Cu-Cl bond distances in the
equatorial plane of 3 are close to those of 2. The Cu-N bond
distances of 3 are in the following order: Cu-N2 (pyridyl in
the basal plane) < Cu-N3 (6-methylpyridyl in the basal plane)
< Cu-N1 (amino nitrogen in the basal plane) < Cu-N4 (6-

6814 Inorganic Chemistry, Vol. 35, No. 23, 1996
Nagao et al.
Figure 5. Molecular structure of [CuCl(Me3tpa)]+ with atom labeling.
Carbon atoms are not labeled and hydrogen atoms are omitted for
clarity.
Figure 7. The relevant bond lengths of [CuCl(Mentpa)]+ (n ) 0, 1, 2,
3); Cl (0), N1 (O), N2 (b), N3 (4), and N4 (]).
Table 4. Summary of Coordination Geometry Parameters
formula
no. â/deg R/deg
τ
type
[Cu(H2O)(tpa)]2+
[CuCl(Me1tpa)]+ a
1
2
177.8 119.9 0.97 trigonal bipyramidal
169.3 159.8 0.16 square pyramidal
177.9 163.6 0.24 square pyramidal
163.5 159.3 0.07 square pyramidal
161.0 135.3 0.43 intermediate
[CuCl(Me2tpa)]+
[CuCl(Me3tpa)]+ b
[CuCl2(Me3tpa)]
3
4
163.1 131.4 0.53 intermediate
a There are two independent molecules in the unit cell. b The formula
of complex 4 is [CuCl(Me3tpa)][CuCl2(Me3tpa)]ClO4.
distances in [CuCl2(Me3tpa)] are longer than the Cu1-Cl1 one
(2.239(2) Å) in [CuCl(Me3tpa)]+. The two axial bonds between
6-methylpyridyl nitrogen atoms (N6 and N7) and Cu2 are
2.014(6) and 2.017(6) Å, which are substantially shrunken
compared with the axial Cu1-N4 bond length (2.161(6) Å).
Relationship between Structures and Electrochemical
Behavior. The Cu-Cl and the Cu-N1 (amino nitrogen) bond
distances of [CuCl(Mentpa)]+ (n ) 0, 1, 2, 3) are almost
constant, while the Cu-Npy bond distances are largely dependent
on the Mentpa ligands (Figure 7). The bond distances between
Cu2+ and 6-methylpyridyl nitrogen atoms in [CuCl(Me1tpa)]+
and [CuCl(Me2tpa)]+ are longer than the remaining Cu-Npy
bonds (Figure 7). The Cu-N4 bond distances of [CuCl-
(Mentpa)]+ (n ) 1, 2, 3), however, have shrunk with an increase
in the number of methyl groups (Figure 7), suggesting that
[CuCl(Me3tpa)]2+ is not necessarily a sterically hindered
complex compared with [CuCl(Me2tpa)]+ and [CuCl(Metpa)]+.
The redox potentials of Cu(II)/Cu(I) couples have been discussed
in terms of the thermal stability of the Cu(I) state and
hydrophobicity of the ligands.2,4,6,8,13,17,19,21,25 The E1/2 values
of the Cu(II)/Cu(I) redox couples shift to positive potentials in
the order tpa < Me1tpa < Me2tpa < Me3tpa complexes. These
Cu(II) complexes have various structures such as trigonal
bipyramidal, square pyramidal, and an intermediate between
them. The redox potentials of the Cu(II)/Cu(I) couples in the
present study, therefore, may be primarily controlled by the
molecular structures rather than hydrophobicity of the com-
plexes. Furthermore, redox reactions of the present Cu(II)
complexes are likely to be accompanied by configurational
changes, since copper(I) complexes with tripodal ligands such
as [Cu(CH3CN)(tpa)]+,9 [Cu(tepa)]+,15 [Cu(CH3CN)(tppa)]+,
Figure 6. Molecular structure of [CuCl2(Me3tpa)] with atom labeling.
Carbon atoms are not labeled and hydrogen atoms are omitted for
clarity.
methylpyridyl in the axial bond). The fact that the Cu-N3 (6-
methylpyridyl) bond distance (2.02(1) Å) is close to the Cu-
N2 (pyridyl) one (1.98(1) Å) suggests that 6-methylpyridyl
nitrogen in the equatorial plane is linked to Cu2+ in the square
pyramid geometry without a serious steric hindrance.
For [CuCl(Me3tpa)][CuCl2(Me3tpa)]+ (4), two different Cu(II)
complexes (cationic Cu1 and neutral Cu2) exist in the unit cell;
one is [CuCl(Me3tpa)]+ and the other is [CuCl2(Me3tpa)]. The
geometries of these complexes were intermediate between
trigonal bipyramid and square pyramid (τ ) 0.43 and 0.53 for
the Cu1 and Cu2 complexes). In [CuCl(Me3tpa)]+, a basal plane
is formed by a chloride atom (Cl1), an amino nitrogen atom
(N1), and two pyridyl nitrogen atoms (N2 and N3) (Figure 5).
Although the Cu-N bond distances in the basal plane (Cu1-
N1, Cu1-N2, and Cu1-N3) are slightly longer than those of
2 and 3, not only the Cu1-Cl1 but also the Cu1-N2 and Cu1-
N3 bond distances in [CuCl(Me3tpa)]+ are almost same as those
in [CuCl(tpa)]+ (Figure 7). For [CuCl2(Me3tpa)], the Cl2-
Cu2-Cl3 (131.4(1)°), Cl2-Cu2-N5 (123.3(2)°), and Cl3-
Cu2-N5 (105.1(2)°) bond angles revealed that these atoms form
an almost regular triangle plane in the equatorial plane (Figure
6). The Cu2-Cl2 (2.292(2) Å) and Cu2-Cl3 (2.373(2) Å) bond
8
[Cu(tppa)]+,2 and [Cu(tmqa)] are trigonal bipyramidal or
tetrahedral structures. The pentagonal trigonal bipyramid
structures of [Cu(H2O)(tpa)]2+ and [CuX(tpa)]+ (X ) F, Cl,
ONO, NO2) probably are retained in their Cu(I) states from the
analogy to the trigonal bipyramidal [Cu(CH3CN)(tpa)]+.9 En-

Cu(II) Complexes with Tripodal Ligands
Inorganic Chemistry, Vol. 35, No. 23, 1996 6815
and 0.60 Å for n ) 3, respectively. The degree of the deviation
of Cu(II) out of the equatorial plane has a similar tendency to
decrease with the reversibility of the Cu(II)/Cu(I) couple.
Taking into account that the adduct formation between
[Cu(H2O)(Mentpa)]2+ (n ) 0, 1, 2, 3) and NO2- smoothly took
place, the catalytic activity of these complexes for the reduction
of NO2- may be correlated with the rate of the electron transfer
to the adducts and the redox potentials of the Cu(II)/Cu(I)
couples. The present study indicates that Cu-ONO (or Cu-
NO2) adducts which undergo redox reactions without serious
structural changes are suitable for functunal models of copper-
containing nitrite reductases.
Figure 8. Structural change between square pyramid and trigonal
bipyramid.
ergy barriers for configurational changes of metal complexes
with tripodal ligands would be higher than those with mono-
dentate ligands. The quasi-reversible [Cu(H2O)(Mentpa)]2+/+
(n ) 1, 2, 3) redox couples, therefore, presumably result from
the configurational changes between square pyramidal or
distorted square pyramidal Cu(II) complexes and trigonal
bipyramidal or tetrahedral Cu(I) ones. Figure 8 shows the most
reasonable path for the configurational changes between square
pyramid and trigonal bipyramid.25 Such a process may be
largely influenced by the N1-Cu-Cl and N2-Cu-N3 bond
angles and the position of Cu. The N1-Cu-Cl and N2-Cu-
N3 bond angles and the distances of Cu2+ from the least-square
plane formed by the Cl, N1, N2, and N3 atoms of [CuCl(Men-
tpa)]+ (n ) 1, 2, 3) are 169.3 and 159.8° and 0.22 Å for n )
1; 163.5 and 159.3° and 0.28 Å for n ) 2; and 135.3 and 161.0°
Acknowledgment. This research was supported by a Grant-
in-Aid for Scientific Research on Priority Areas (No. 07740532)
from the Ministry of Education, Science and Culture.
Supporting Information Available: Tables of complete informa-
tion on collected data and refinement, atomic coordinates, thermal
parameters, bond lengths and angles, torsion or conformation angles,
and least-squares planes and ORTEP drawings with atom labeling for
complexes 1-4 (66 pages). Ordering information is given on any
current masthead page.
IC960303N