fac-Bis(acetonitrile-κN)tricarbonyl(trifluoroacetato-κO)rhenium(I)

In the title compound, [Re(CF3COO)(CH3CN)2(CO)3], the Re atom has a distorted octahedral configuration. The two acetonitrile molecules and two of the three carbonyl groups occupy the equatorial plane of the complex, with the third carbonyl ligand and the trifluoroacetato ligand in the axial positions. The three carbonyl ligands are arranged in a fac configuration around the Re atom. The CF3 segment of the trifluoroacetato ligand shows rotational disorder and the refined site-occupancy factors of the disordered parts are ca 0.5/0.5. The crystal structure is stabilized by C—H⋯O and C—H⋯F hydrogen bonds.

In the title compound, [Re(CF 3 COO)(CH 3 CN) 2 (CO) 3 ], the Re atom has a distorted octahedral configuration. The two acetonitrile molecules and two of the three carbonyl groups occupy the equatorial plane of the complex, with the third carbonyl ligand and the trifluoroacetato ligand in the axial positions. The three carbonyl ligands are arranged in a fac configuration around the Re atom. The CF 3 segment of the trifluoroacetato ligand shows rotational disorder and the refined site-occupancy factors of the disordered parts are ca 0.5/0.5. The crystal structure is stabilized by C-HÁ Á ÁO and C-HÁ Á ÁF hydrogen bonds.

S1. Comment
The synthesis of solvent-coordinated complexes is a matter of considerable interest since they are useful sources for synthesis of new species resulting from the substitution of the coordinated solvent by a more basic ligand (Davies & Hartely, 1981). The lability of the solvent ligand easily gives rise to a highly reactive 16eelectrophilic fragment able to activate small molecules thus providing an important step in many chemical processes. On the other hand, Rhenium tricarbonyl complexes have been the subject of much attention, mainly because of their photophysical (Meyer 1989) and photochemical properties (Collin & Sauvage 1989) and in supramolecular chemistry (Balzani et al., 1996).
In the title compound (I) (Fig. 1), the Re atom adopts a distorted octahedral geometry. The bond lengths (Allen et al., 1987) and angles are within the normal ranges and are comparable to the related structures (Chan et al., 1977;Lazarova et al., 2004). The two acetonitriles and two carbonyl groups occupy the equatorial plane of the complex, with the third carbonyl ligands and the trifluoroacetate in the axial positions. The three carbonyl ligands at Re atom are arranged in a fac configuration. The cis-equatorial angle of N1-Re1-N2 is 81.88 (13) °. The deviation of the Re atom from the The crystal structure is stabilized by C-H···O and C-H···F hydrogen bonds (Table 1, Fig. 2).

S2. Experimental
The synthetic method has been described earlier (Chan et al., 1977). Single crystals suitable for X-ray diffraction were obtained by evaporation of an acetonitrile solution at room temperature.

S3. Refinement
The hydrogen atoms of the methyl groups were first located from the difference Fourier map and then constrained to refine using a rotating-group model. The CF 3 segment of the trifluoroacete ligand has rotational disorder and the refined site-occupancy factores of the disorder parts are 0.501 (2)/0.499 (2). The highest peak (2.80 eÅ -3 ) is located 0.61 Å from Re1 and the deepest hole (-1.27 eÅ -3 ) is located 1.01 Å from Re1.   The crystal packing of the major component of (I), viewed down the c-axis. Intermolecular interactions are shown as dashed lines.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 2.80 e Å −3 Δρ min = −1.27 e Å −3 Special details Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. 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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (