[Bis(pyridin-2-ylmethyl)amine-κ3 N,N′,N′′]tricarbonylrhenium(I) bromide hemihydrate

The title compound, fac-[Re(C12H12N3)(CO)3]Br·0.5H2O, crystallizes with a cationic rhenium(I) unit, a bromide ion and half a water molecule, situated on a twofold rotation axis, in the asymmetric unit. The ReI atom is facially surrounded by three carbonyl ligands and a tridentate bis(pyridin-2-ylmethyl)amine ligand in a distorted octahedral environment. N—H⋯Br, O—H⋯Br, C—H⋯O and C—H⋯Br hydrogen bonds are present in the crystal structure and π–π stacking is also observed [centroid–centroid distances = 3.669 (1) Å and 4.054 (1) Å], giving rise to a three-dimentional network. The molecules pack in a head-to-head fashion along the ac plane.

We would like to thank the University of the Free State, the Chemistry Department, the NRF and Sasol Ltd for financial support. observed in the crystal structure. Some weak π-π stacking, with a centroid-to-centroid distance of 3.669 (1) Å and 4.054 (1) Å, is also observed between the different pyridine rings of the ligand system. These interactions complete a three dimensional polymericnetwork formed between the Re I units. Overall, the bond distances and angles compare well with the similar structure reported by Banerjee et al. (2002), N,N-bis(2-pyridylmethyl) 2 aminetricarbonylrhenium(I)bromide, that crystallized in the tetragonal P4 1 spacegroup. The three Rhenium to carbonyl distances ranging  (7) Å. The Re-amine distance of 2.210 (2) Å and the Re-pyridine distances of 2.182 (2) Å and 2.191 (2) Å are slightly longer than the Re-Amine distance of 2.187 (4) Å and the Re-pyridine distances of 2.177 (5) Å and 2.183 (5) Å reported by Banerjee et al. (2002).

Experimental
[NEt 4 ] 2 [Re(CO) 3 Br 3 ] (75 mg, 0.097 mmol), as prepared by Alberto et al. (1996), was dissolved in 20 ml of water, acidified with HNO 3 to pH 2.2. Silver nitrate (50 mg, 0.291 mmol) was added to the solution and stirred for 24 h at room temperature. The grey silver bromide precipitate was filtered off, N,N-bis(2-pyridylmethyl)amine (19.4 mg, 0.100 mmol) was added to the filtrate and stirred overnight at room temperature. The colourless crystals were grown from the filtrate by slow evaporation.

Refinement
Aromatic H atoms were positioned geometrically and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (parent) of the parent atom with a C-H distance of 0.93. The methene H atoms were placed in geometrically idealized positions and constrained to ride on its parent atoms with U iso (H) = 1.2U eq (C) and at a distance of 0.97 Å. The N-bound H atom was placed from the electron density map.

Figure 1
Representation of the title compound, showing the numbering scheme and displacement ellipsoids (50% probability).

Figure 2
Packing of the title compound in the unit cell and the observed π-π stacking in the crystal structure, indicated by dashed lines (hydrogen atoms omitted for clarity). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.004 Δρ max = 1.14 e Å −3 Δρ min = −0.60 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s 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 > 2σ(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.