Copper (II) complexes of a macrocyclic binucleating ligand which exhibit two-electron oxidation and two-electron reduction. Structure of [Cu2(C24H34N4O2)(CH3OH)2](ClO4)2, a macrocyclic dicopper(II) complex involving coordinated methanol
Abstract:Chem. 65, 2815 (1987).The saturated ligand H2L1, derived by template condensation of 4-methyl-2,6-diformylphenol and 1,3-diaminopropane, followed by borohydride reduction, generates binuclear, antiferromagnetically coupled, copper(I1) complexes which exhibit cyclic voltammetry involving two one-electron oxidation steps (Ell, = 1.1 to 1.2 V, 1.3 to 1.4 V; Pt/CH3CN/SCE) and two one-electron reduction steps (Eli2 = -0. [Traduit par la revue]
“…The variable-temperature magnetic susceptibility data for these complexes were fitted to the modified Bleaney−Bowers equation (eq 2) using the isotropic exchange Hamiltonian ( H = −2 JS 1 · S 2 ) for the two interacting S = 1 / 2 centers: ρ and tip are the fraction of metal possibly present as a paramagnetic impurity and the temperature-independent paramagnetism per metal ion, respectively, the tip for Cu 2+ being taken to be 6 × 10 -5 cm 3 g atom -1 , Figure shows the temperature dependence of χ m T for [Cu 2 (Damfb)] ( 4 ). 5 Variable-temperature magnetic data for [Cu 2 (Damfb)] ( 4 ).…”
With nickel(II) or copper(II) acetate,
2,6-bis(acetoximato)-4-methylphenol (H2Damox) and
2,6-bis(acetoximato)-4-tert-butylphenol (H2Dabox) afford
molecular dinuclear complexes
[Cu2(Damox)2] (1),
[Ni2(Damox)2(MeOH)2]·
MeOH (2), [Cu2(Dabox)2]
(5) and
[Ni2(Dabox)2(H2O)2]
(6). Salts of the macrocyclic tetraimine copper
chelates
from diacetylcresol with 1,3-diaminopropane and 1,4-diaminobutane,
[Cu2(Dampn)]2+ and
[Cu2(Dambn)]2+, were
also examined. Pyridine solutions of 2 yielded pink
crystals of
[Ni2(Damox)2(Py)4]·(Py)2
(3a), which effloresce
pyridine to form
[Ni2(Damox)2(Py)2]·Py
(3). The pseudomacrocyclic complexes 1,
5, and 6 react with
BF3·Et2O
to form BF2-bridged macrocyclic complexes
[Cu2(Damfb)] (4),
[Cu2(Dabfb)]·H2O (7), and
[Ni2(Dabfb)] (8).
Crystals of
[Ni2(Damox)2(Py)4]·(Py)2
(3a) are monoclinic (space group
P21/n), with a =
13.297(5) Å, b = 11.240(5) Å, c = 17.396(6) Å, β = 109.03°,
V = 2458(3) Å3, Z = 2,
R = 0.050, and R
w = 0.052.
The [Ni2(Dabfb] (8)
crystals are orthorhombic (space group Pnma), with
a = 11.558(6) Å, b = 17.200(5) Å,
c = 16.058(2) Å, V =
3192(3) Å3, Z = 4, R =
0.057, and R
w = 0.057. The saddle-shaped
molecules of 8 contain low-spin Ni(II).
The
copper(II) centers in 1, 5, 6,
etc., are strongly antiferromagnetically coupled with −2J
values in the range 550−800 cm-1. The nickel(II) centers in
2 and 3 are weakly (−2J = 3.2
cm-1) or moderately (−2J =
19.5 cm-1)
antiferromagnetically coupled, whereas 6 shows a moderate
ferromagnetic interaction with −2J = −5.1
cm-1.
All the complexes are electrochemically reducible in two
1-electron steps. In CH3CN, the mixed-valence
complexes
[Cu2(Dampn)]+ and
[Cu2(Dambn)]+ are valence-localized.
The nature of the carbon monoxide interactions with
the M(I) centers is clearest for
[Cu2(Dambn)]+/0, which in
dimethylformamide solution binds two molecules of
CO in a cooperative fashion.
“…The variable-temperature magnetic susceptibility data for these complexes were fitted to the modified Bleaney−Bowers equation (eq 2) using the isotropic exchange Hamiltonian ( H = −2 JS 1 · S 2 ) for the two interacting S = 1 / 2 centers: ρ and tip are the fraction of metal possibly present as a paramagnetic impurity and the temperature-independent paramagnetism per metal ion, respectively, the tip for Cu 2+ being taken to be 6 × 10 -5 cm 3 g atom -1 , Figure shows the temperature dependence of χ m T for [Cu 2 (Damfb)] ( 4 ). 5 Variable-temperature magnetic data for [Cu 2 (Damfb)] ( 4 ).…”
With nickel(II) or copper(II) acetate,
2,6-bis(acetoximato)-4-methylphenol (H2Damox) and
2,6-bis(acetoximato)-4-tert-butylphenol (H2Dabox) afford
molecular dinuclear complexes
[Cu2(Damox)2] (1),
[Ni2(Damox)2(MeOH)2]·
MeOH (2), [Cu2(Dabox)2]
(5) and
[Ni2(Dabox)2(H2O)2]
(6). Salts of the macrocyclic tetraimine copper
chelates
from diacetylcresol with 1,3-diaminopropane and 1,4-diaminobutane,
[Cu2(Dampn)]2+ and
[Cu2(Dambn)]2+, were
also examined. Pyridine solutions of 2 yielded pink
crystals of
[Ni2(Damox)2(Py)4]·(Py)2
(3a), which effloresce
pyridine to form
[Ni2(Damox)2(Py)2]·Py
(3). The pseudomacrocyclic complexes 1,
5, and 6 react with
BF3·Et2O
to form BF2-bridged macrocyclic complexes
[Cu2(Damfb)] (4),
[Cu2(Dabfb)]·H2O (7), and
[Ni2(Dabfb)] (8).
Crystals of
[Ni2(Damox)2(Py)4]·(Py)2
(3a) are monoclinic (space group
P21/n), with a =
13.297(5) Å, b = 11.240(5) Å, c = 17.396(6) Å, β = 109.03°,
V = 2458(3) Å3, Z = 2,
R = 0.050, and R
w = 0.052.
The [Ni2(Dabfb] (8)
crystals are orthorhombic (space group Pnma), with
a = 11.558(6) Å, b = 17.200(5) Å,
c = 16.058(2) Å, V =
3192(3) Å3, Z = 4, R =
0.057, and R
w = 0.057. The saddle-shaped
molecules of 8 contain low-spin Ni(II).
The
copper(II) centers in 1, 5, 6,
etc., are strongly antiferromagnetically coupled with −2J
values in the range 550−800 cm-1. The nickel(II) centers in
2 and 3 are weakly (−2J = 3.2
cm-1) or moderately (−2J =
19.5 cm-1)
antiferromagnetically coupled, whereas 6 shows a moderate
ferromagnetic interaction with −2J = −5.1
cm-1.
All the complexes are electrochemically reducible in two
1-electron steps. In CH3CN, the mixed-valence
complexes
[Cu2(Dampn)]+ and
[Cu2(Dambn)]+ are valence-localized.
The nature of the carbon monoxide interactions with
the M(I) centers is clearest for
[Cu2(Dambn)]+/0, which in
dimethylformamide solution binds two molecules of
CO in a cooperative fashion.
“…It may be mentioned that substantial antiferromagnetic exchange coupling (d xy ↔ d xy ) occurs in the related dioxovanadium(IV) complex {(VO) 2 L1(μ-SO 4 )]·MeOH·3H 2 O,21d for which J = −128 cm -1 . For the sake of completion we note that the dicopper(II) complex [Cu 2 L1(ClO 4 ) 2 ] exhibits very strong antiferromagnetic exchange with the singlet−triplet energy gap of 824 cm -1 …”
A series of heterobimetallic complexes
[(VIVO)L1CuII(μ-OAC)(MeOH)](ClO4)
(1) and
[(VIVO)L1MII(μ-OAc)(H2O)](ClO4)·H2O (M = Ni
(2), Co (3), Fe (4), Mn
(5)) derived from a symmetric tetraaminodiphenol
macrocyclic
ligand H2L1 have been synthesized and characterized.
The crystal structure of 1 has been determined.
The
complex
(C27H41N4O10ClCuV)
crystallizes in the monoclinic space group
P21/c with a =
13.227(3) Å, b = 14.932(3) Å, c = 17.019(3) Å, β = 112.29(1)°,
and Z = 4. Both the metal centers in 1 are
six-coordinated and are
triply bridged by the two phenolate and the acetate oxygens; the sixth
coordination site of the copper atom is
occupied by a distantly placed methanol oxygen (Cu−O =
2.452(5) Å), while that of the vanadium by the oxo
oxygen (V−O = 1.627(4) Å). The metal centers are
separated by 3.066(1) Å, and the dihedral angle (Δ)
between
the metal planes is 32.0°. Variable-temperature (4−300 K)
magnetic susceptibility measurements of
1
−
5 and of
[(VIVO)L2CuII(μ-OAc)(H2O)](ClO4)
(6) (where H2L2 is an asymmetric
tetraaminodiphenol macrocyclic ligand)
have been made and treated with the spin-Hamiltonian H =
−2J
S
1·S
2.
All the complexes, except 5, exhibit
ferromagnetic exchange interaction with the following values of
J (in cm-1): 42.5
(1), 12.0 (2), 4.4 (3), 4.4
(4),
and 46.0 (6); complex 5 behaves
antiferromagnetically with J = −14.2
cm-1. A linear correlation between
J and
Δ has been proposed for CuIIVIVO
complexes.
“…7) it is evident that even major changes in the ligand itself, e.g. unsaturated versus saturated nitrogen donors and variable chelate ring sizes, do not have major effects on spin exchange (36,37). Also for the butylene bridged complex [ C U~L ( C~O~)~] (Fig.…”
. J. Chem. 67,662 (1989).Binuclear, antiferromagnetically coupled, macrocyclic copper(I1) complexes, [ C U~( C~~H~~N~O~) ] . H~O (11) and [Cu2-(C36H32N404)] .CH3CN.H20 (111), involving asymmetric ligands with two deprotonated amide, two azomethine nitrogen, and two phenoxide donors at the binuclear centre, have been synthesized and characterized by single-crystal X-ray diffraction and variable temperature magnetic studies. Complex I1 crystallizes in the monoclinic system, space group P2'/n, with a = 16.4854(9)& b = 7.6005(13) A, c = 2 1.1617(11) A, P = 104.090(5)", Z = 4, Rf = 0.068 for 2062 significant reflections.The two copper(I1) centres have square planar N202 donor sets with two phenoxide oxygen atoms brid ing the copper centres with a copper-copper separation of 2.898(2) A. A long copper-oxygen (amge) contact (2.808(10) f ) forms a weak dimer association. Com lex I11 crystallizes in the triclinic system, space group P1, with a = 8.7771 (9)
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