Tetra-μ-acetato-κ8 O:O′-bis[(3,5-dimethyl-1H-pyrazole-κN 2)copper(II)]

The dinuclear centrosymmetric title compound, [Cu2(CH3CO2)4(C5H8N2)2], has a distorted square-pyramidal coordination geometry around each CuII atom in which four O atoms from the bridging acetate ligands form the basal plane while two N atoms from the pyrazole ligands occupy the apical positions. The crystal has two half molecules in the asymmetric unit with a Cu⋯Cu distance of 2.6762 (4) Å. Disorder was found for two O atoms and two C atoms of one acetate ligand and refined with occupancies of 0.265 (7) and 0.735 (7). The crystal also features molecules linked through two N—H⋯O hydrogen bonds resulting in one-dimensional chains extending along the crystallographic b axis.

The dinuclear centrosymmetric title compound, [Cu 2 (CH 3 -CO 2 ) 4 (C 5 H 8 N 2 ) 2 ], has a distorted square-pyramidal coordination geometry around each Cu II atom in which four O atoms from the bridging acetate ligands form the basal plane while two N atoms from the pyrazole ligands occupy the apical positions. The crystal has two half molecules in the asymmetric unit with a CuÁ Á ÁCu distance of 2.6762 (4) Å . Disorder was found for two O atoms and two C atoms of one acetate ligand and refined with occupancies of 0.265 (7) and 0.735 (7). The crystal also features molecules linked through two N-HÁ Á ÁO hydrogen bonds resulting in one-dimensional chains extending along the crystallographic b axis.

S1. Comment
Pyrazolyl ligands containing a carbonyl linker has been utilized to prepare a number of coordination compounds with palladium salts (Guzei et al., 2003;Mohlala et al., 2005, Ojwach et al., 2005. In these compounds the pyrazolyl carbonyl moiety appear to be robust enough to avoid hydrolysis. However in a few instances the presence of metal ions like Cu(II) (Deka et al., 2006) and Pd(II) (Nelana et al., 2008) appear to catalyze the hydrolysis of the benzoyl fragments. We have observed similar hydrolysis when reacting copper(II) acetate with (3,5-dimethyl-pyrazol-1-yl)-o-benzoyl-methane. The title compound formed from this reaction is the subject of this report. The half "solvent" molecule excluded from the structure had a total number of 30.7 electrons which is approximately half the total number of electrons that acetophenone has.
Compound (I) crystallizes with two half molecules in the assymetric unit. The compound is dinuclear with each of the Cu atoms coordinated to four O atoms and a N atom from the pyrazole ligand. The O atoms are from acetate ions, all in the equatorial positions of a slightly distorted octahedral geometry around the Cu atoms. The N atom is bound trans to the Cu-Cu vector completing a the distorted octahedral geometry as axial ligands.
The crystal structure of (I) is composed of two N-H···O hydrogen bonded chains ( Table 1) that extend in the crystallographic b axis (Fig. 2).

S3. Refinement
The methyl, methine and aromatic H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H = 0.95 Å and U iso (H) = 1.2U eq (C) for aromatic, C-H = 0.98 Å and U iso (H) = 1.2U eq (C) for CH 3 and N-H = 0.88 Å and U iso (H) = 1.2U eq (C) for NH. Half a molecule of acetophenone that resided on an inversion center was grossly disordered and was was excluded using the SQUEEZE subroutine in PLATON (Spek (2009  View of (I) (50% probability displacement ellipsoids) with H atoms presented as small spheres of arbitrary radii.

Figure 2
N-H···O hydrogen bond interactions in the crystal structure of (I). [Symmetry operators:

Tetra-µ-acetato-κ 8 O:O′-bis[(3,5dimethyl-1H-pyrazole-κN 2 )copper(II)
Crystal data [Cu 2 (C 2 H 3 O 2 ) 4 (C 5 H 8 N 2 ) 2 ] M r = 555.52 Triclinic, P1 Hall symbol: -P 1 a = 8.1125 (4) Å b = 13.6429 (7) Å c = 13.7755 (7) Special details Experimental. Diorder: Disorder was found for two O atoms and two C atoms of one acetate ligand in which is not an uncommon situation. The disorder was modelled for two O-, two C-and H-atoms using distance restraints and PART instructions and the total occupancy at each atom site was kept as 1 during the refinement. DELU and SIMU constraints and restraints were used on the disordered atoms. All carbon atoms involved in disorder were modelled with anisotropic thermal parameters and refined with occupancies of 0.265 (7) and 0.735 (7). The "solvent" molecule resided in a special position and looked disordered as well. Modelling the disorder only distabillized the refinement. As a result, the moleculed was removed using the SQUEEZE subroutine in PLATON giving an R factor of 3.0%. H-atom Placement: All H-atoms were placed in idealized locations and refined as riding with appropriate thermal displacement coefficients U iso (H) = 1.2 or 1.5 times U eq (bearing atom). Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

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Acta Cryst. (2011). E67, m1299 Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.