Structure description
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Oxalato-bridged coordination compounds have played a key role in the theoretical
and experimental development of areas such as molecular magnetism (Verdaguer,
2001) and crystal engineering (Marinescu et al., 2002). It has been
established that two crystal hydrates are formed in this system
MnC2O4.2H2O and MnC2O4.3H2O. Both crystal hydrates differ in color
and structure. The white α-MnC2O4.2H2O is monoclinic, space group
C2/c (Deyrieux et al., 1973), while the pink-colored
MnC2O4.3H2O is orthorhombic, space group Pcca (Huizing et
al., 1977, Fu et al., 2005; Wu et al., 2005). However, the
paper published by Deyrieux et al. does not include atomic coordinates.
A neutron diffraction study for MnC2O4.two-dimensional2O, using powdered
samples, has been published recently (Sledzinska et al., 1987). It is
noticeable that an orthorhombic polymorphs for the title polymer is also known
(Huizing et al., 1977; Lethbridge et al.., 2003;). In this way,
our X-ray study deals with the monoclinic polymorph. It is expected that the
difference in the crystal lattice of the compounds and the different way of
bonding of water molecules would affect some properties, such as a thermal
stability, oxidation, and magnetic behavior. The wide variety of coordination
modes of the oxalate anion with different metals allows the use of
metal-oxalato units as excellent building blocks to construct a great
diversity of homo- and heterometallic structural frameworks ranging from
discrete polymeric entities (Chiozzone et al., 2003) to one-, two- and
three-dimensional networks (Castillo et al. 2001).
Figure 1 shows that the O3 and O3d atoms of the two coordinated water molecules
occupy the axial positions, while O1, O1d, O2a and O2c atoms of bridging
oxalate ligands form the equatorial plane. The O3—Mn—O3d angle is almost
linear, 179.05 (4)°. Therefore, coordination sphere around the MnII center,
placed on a twofold symmetry axis, is almost octahedral. The torsion angles
show that the oxalate ligand is planar. Also, the result shows that
one-dimensional linear chains are formed in the crystal structure through
bridging bis-bidentate oxalate ligands. The bond angles show that the two
coordinated water molecules are arranged trans. A remarkable feature in
the crystal structure of (I) is the presence of strong O—H···O hydrogen
bonds, connecting one-dimensional chains in the crystal structure (Fig. 2).
The title complex is isomorphous to the corresponding CoII-based polymer
(Bacsa et al., 2005).
A preliminary report on the monoclinic polymorph of the title polymer was
published by Deyrieux et al. (1973). For a neutron study of
[Mn(µ-ox)(D2O)2]n, see Sledzinska et al. (1987). The
reported structure is isostructural with that based on CoII (Bacsa et
al., 2005). For further details of the related chemistry, see: Chiozzone
et al. (2003); Aghabozorg et al. (2006); Verdaguer (2001);
Marinescu et al. (2002); Castillo et al. (2001); Fu et
al. (2005); Wu et al. (2005). [From the Section Editors: Please
revise the scheme. The C?C bond should be single and the C—O bonds should be
single/double or delocalized.]
Oxalato-bridged coordination compounds have played a key role in the theoretical and experimental development of areas such as molecular magnetism (Verdaguer, 2001) and crystal engineering (Marinescu et al., 2002). It has been established that two crystal hydrates are formed in this system MnC2O4.2H2O and MnC2O4.3H2O. Both crystal hydrates differ in color and structure. The white α-MnC2O4.2H2O is monoclinic, space group C2/c (Deyrieux et al., 1973), while the pink-colored MnC2O4.3H2O is orthorhombic, space group Pcca (Huizing et al., 1977, Fu et al., 2005; Wu et al., 2005). However, the paper published by Deyrieux et al. does not include atomic coordinates. A neutron diffraction study for MnC2O4.two-dimensional2O, using powdered samples, has been published recently (Sledzinska et al., 1987). It is noticeable that an orthorhombic polymorphs for the title polymer is also known (Huizing et al., 1977; Lethbridge et al.., 2003;). In this way, our X-ray study deals with the monoclinic polymorph. It is expected that the difference in the crystal lattice of the compounds and the different way of bonding of water molecules would affect some properties, such as a thermal stability, oxidation, and magnetic behavior. The wide variety of coordination modes of the oxalate anion with different metals allows the use of metal-oxalato units as excellent building blocks to construct a great diversity of homo- and heterometallic structural frameworks ranging from discrete polymeric entities (Chiozzone et al., 2003) to one-, two- and three-dimensional networks (Castillo et al. 2001).
Figure 1 shows that the O3 and O3d atoms of the two coordinated water molecules occupy the axial positions, while O1, O1d, O2a and O2c atoms of bridging oxalate ligands form the equatorial plane. The O3—Mn—O3d angle is almost linear, 179.05 (4)°. Therefore, coordination sphere around the MnII center, placed on a twofold symmetry axis, is almost octahedral. The torsion angles show that the oxalate ligand is planar. Also, the result shows that one-dimensional linear chains are formed in the crystal structure through bridging bis-bidentate oxalate ligands. The bond angles show that the two coordinated water molecules are arranged trans. A remarkable feature in the crystal structure of (I) is the presence of strong O—H···O hydrogen bonds, connecting one-dimensional chains in the crystal structure (Fig. 2). The title complex is isomorphous to the corresponding CoII-based polymer (Bacsa et al., 2005).