Di-μ-acetato-κ4 O:O′-bis[(1,10-phenanthroline-κ2 N,N′)(trifluoromethanesulfonato-κO)copper(II)]

The complete molecule of the title compound, [Cu2(C2H3O2)2(CF3O3S)2(C12H8N2)2], is completed by the application of a twofold rotation and comprises two CuII ions, each of which is pentacoordinated by two N atoms from a bidentate 1,10-phenanthroline (phen) ligand, two O atoms from acetate ligands and an O atom from a trifluoromethanesulfonate anion, forming a (4 + 1) distorted square-pyramidal coordination geometry. The CuII ions are connected by two acetate bridges in a syn–syn configuration. The F atoms of the trifluoromethanesulfonate ligands are disordered, with site-occupation factors of 70 and 30. The molecular structure is stabilized by intramolecular face-to-face π–π interactions with centroid–centroid distances in the range 3.5654 (12)–3.8775(12) Å. The crystal structure is stabilized by C—H⋯O interactions, leading to a three-dimensional lattice structure.

Furthermore, this type of dinuclear unit was used as the secondary building block in functionalized polyoxometalate (POMs) materials (Wang et al., 2006;Reinoso et al., 2007;Calvo et al., 2011) to extend the dimensionality of structures leading to new hybrid materials and more selective applications, for example catalytic properties in organic oxidations (Hill & Brown, 1986;Mansuy et al., 1991;Hill, & Zhang, 1995).
A new doubly acetato-bridged dinuclear Cu II compound containing additional trifluoromethanesulfonate anions has been synthesized and its structural features are reported here. Compound I, bis((µ-acetato)(trifluoromethanesulfonato) (1,10-phenanthroline))dicopper(II) crystallized in the space group C2/c with an asymmetric unit containing one half of the dinuclear unit ( Fig.1). This dinuclear unit has C 2 symmetry around the b axis with Cu···Cu distance of 3.0309 (4) Å.  (2)], leading to the (4 + 1) square-pyramidal geometry. The square base of Cu II chromophore is not perfectly planar, with the tetrahedral twist of 16.52 (7)° and Cu II is situated above the basal plane by 0.14 (1) Å pointing towards the O atom of the trifluoromethanesulfonate anion. The distortion of a square pyramid can be best described by the structural parameter τ (τ = 0 for a square pyramid and τ =1 for a trigonal bipyramid (Addison et al., 1984)), with τ = 0.23 for the title compound. The molecular structure of I reveals intramolecular face-to-face π-π interaction between aromatic rings of phen ligands (  Table 1), generating two-dimensional layers parallel to the ab plane ( Fig. 2). Moreover, these two-dimensional sheets are interconnected by hydrogen bond interactions between C-H of phen ligands and oxygen atoms of trifluoromethanesulfonate anions [C1-H1···O5 i ; symetry code (i) = -x+1, -y+2, -z+1] (see Table 2) in direction of crystallographic c axis, leading to three-dimensional lattice structure (Fig. 3). Although containing the same [(phen)Cu(µ-OOCCH 3 ) 2 Cu(phen)] 2+ unit, the structural topology of I is distinct from that of the et al., 1990) in which the apical position is occupied by water molecule. The dinuclear unit of this related compound also crystallized in C2/c space group and has C 2 symmetry around the b axis with Cu···Cu distance of 3.063 Å, but its crystal lattice is mainly stabilized by intra-and intermolecular π-π interactions, generating a one-dimensional chain-like sructure. It is clear that the difference of the structural topology between compound I and the related compound caused by the effect of coordinated trifluoromethanesulfonate anions whereas nitrate anions are not coordinated to Cu in the other structure.
The diffuse reflectance spectrum of I displays a broad band at 15400 cm -1 and a lower energy shoulder at 14300 cm -1 .
This feature corresponds to a dominantly distorted square pyramidal geometry of Cu II ions and is consistent with the observed structural parameters. The transitions may be assigned as d xy , d yz , d xz → d x2-y2 and d z2 → d x2-y2 . The IR spectrum of I, in addition to the phen vibrations shows the broad and intense bands of the stretching of the ionic CF 3 SO 3at 1276 ν as (S-O), 1158 ν as (C-F) and 1031 ν s (S-O) cm -1 (Castro et al., 1992). The IR spectrum also shows two broad and intense bands at 1567 and 1385 cm -1 , corresponding to the ν as (COO -) and ν s (COO -) vibrations of acetate bridging ligands. The latter spectral properties completely disappear for related mononuclear compounds as [Cu (phen)

Refinement
All H atoms were constrained to ideal positions, with C-H = 0.93 Å and U iso (H) =1.2U eq (C) for H atoms at phen and C -H = 0.96 Å and U iso (H) =1.2U eq (C) for H atoms of acetate groups. Fluorine atoms of the trifluoromethanesulfonato ligands are disordered with site occupation factors of 70:30%.  The crystal packing. View of two-dimensional layer constructed by intermolecular hydrogen bonding and view of the intramolecular face-to-face π-π interactions between aromatic rings of phen ligands.