The fir
st coordination compound
s of 1,2,3,4-butanetetracarboxylate anion (butca
4-) of the formula [M
2(butca)(H
2O)
5]
n·2
nH
2O [M = Mn(II) (
1), Co(II) (
2), and Ni(II) (
3)] were prepared and their X-ray cry
stal
structure
s andmagnetic propertie
s inve
stigated. The three complexe
s have a very
similar two-dimen
sional
structure which con
si
st
sof (4,4) network
s,
1 and
2 being i
so
structural. The tetracarboxylate ligand act
s a
s a 4-fold connector leading totwo-dimen
sional (4,4) network
s of metal atom
s, thi
s topology being po
ssible becau
se of it
s planar conformation.The node
s of the
se network
s are formed by dinuclear motif
s which exhibit the unu
sual (
![](/image<font color=)
s/entitie
s/mgr.gif">-aqua)bi
s(
![](/image<font color=)
s/entitie
s/mgr.gif">-carboxylate)bridging unit which i
s analogou
s to that ob
served in
some molecule
s of biological intere
st. The variable-temperaturemagnetic
su
sceptibility mea
surement
s of
1-
3 show that
1 and
2 are antiferromagnetically coupled
sy
stem
s wherea
s3 exhibit
s a ferromagnetic behavior. The analy
si
s of the magnetic data of
1-
3 through a
simple dinuclear modelallowed the determination of the value
s of the magnetic coupling (
J) -3.6 (
1), -1.2 (
2), and +1.47 cm
-1 (
3) withthe Hamiltonian being defined a
s H = -
JSA·
SB. The countercomplementarity between the two bridge
s (aqua and
syn-
syn carboxylate) account
s for the trend exhibited by the value
s of the magnetic coupling in thi
s family.