Two new tetranuclear µ4-carbonato copper(II) complexes. Syntheses, crystal structure and magnetic behaviour of [(µ4-CO3)(µ-Br)2 {Cu4(bapa)4}]Br4 and [(µ4-CO3)(µ-Cl)2 {Cu4(bapma)4}]Cl4 ·12H2O [bapa = bis(aminopropyl)amine and bapma = bis(aminopropyl)methylamine]
Abstract
The syntheses, by fixation of atmospheric CO
2
, and the
crystal structures of the new tetranuclear
µ
4
-CO
3
2-
compounds
[(µ
4
-CO
3
)(µ-Br)
2
{Cu
4
(bapa)
4
}]Br
4
1 and
[(µ
4
-CO
3
)(µ-Cl)
2
{Cu
4
(bapma)
4
}]Cl
4
·12H
2
O
2, [bapa and bapma are bis(3-aminopropyl)amine and
bis(3-aminopropyl)methylamine respectively] are reported.
Crystallographic data for 1 space group C2/c,
a = 14.928(5),
b = 19.010(3),
c = 17.337(4) Å,
β = 92.75(4)°, U = 4914(2)
Å
3
and Z = 4, for 2 space group
P2
1
/n,
a = 14.947(6),
b = 13.047(4),
c = 16.084(5) Å,
β = 104.75(5)°,
U = 3033(2) Å
3
and
Z = 2. The analogous compound
[(µ-CO
3
)(µ
4
-Cl)
2
{Cu
4
(bapa)
4
}]Cl
4
3 has been also prepared
for comparative purposes; 1–3 show very strong antiferromagnetic
coupling. According to the molecular structures, the experimental data
were fitted to the expression derived from the Hamiltonian
H = -2J
12
S
1
·S
2
- 2
J
13
(S
1
·S
3
+
S
2
S
4
) - 2
J
14
(S
1
·S
4
+
S
2
·S
3
) -
2J
34
S
3
·S
4
, which corresponds
to a rectangular array of spins. The best fit parameters were for
1–3 respectively:
2J
12
= -275(14), -390(12),
-212(8); 2J
34
= -31(4),
-26(7), -26(3);
2J
14
= -57(10), -10(12),
-72(9); 2J
13
= -8(8),
22(10), -20(7) cm
-1
;
g = 2.03(1), 2.09(1) and 2.12(1).
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