Crystal structure of fac-tricarbonylchloridobis(4-hydroxypyridine)rhenium(I)–pyridin-4(1H)-one (1/1)

Molecules of the complex fac-[ReCl(4-pyOH)2(CO)3] (4-pyOH is 4-hydroxypyridine) and 4-pyridone are associated in ladder chains by hydrogen and coordination bonds.


Chemical context
The structural stability of the fac-{Re I (CO) 3 } fragment and its trend to form sixfold coordinated octahedral complexes make it a suitable candidate for the construction of self-assambled metallomacrocycles, with some of them showing interesting properties (Slone et al., 1998;. Bipyridine (and pyrazine) based ligands are usually chosen to obtain square or rectangular metallocycles, [Re 4 (L) 4 (CO) 12 ] (L is the bridging ligand) with internal diameters of 5-9 nm. In the present work, we present the structure of a rhenium complex, where the square architecture is achieved by a coordinative Re-L link (where L is 4-hydroxypyridine) and by hydrogenbonding interactions involving a 4-pyridone molecule (a tautomer of 4-hydroxypyridine L).
The molecular structure of fac-[ReCl(4-pyOH) 2 (CO) 3 ] is similar to other tricarbonylrhenium(I) complexes with two pyridine-based ligands (Abel & Wilkinson, 1959;Farrell et al., 2016). The coordination polyhedron around the Re atom can be described as slightly distorted octahedral (all angles are close to 90 or 180 ), formed by coordination of the two N atoms of the two 4-pyOH ligands (N1 and N2), by the three carbonyl C atoms, in a facial configuration, and the chloride ligand. Both Re-N bond lengths [2.208 (4) and 2.210 (4) Å ] are statistically equivalent. Neverthless, the Re-Cl bond in the present compound [2.4986 (10) Å ] is longer that those found in pyridine derivatives described recently by Farrell et al. (2016), with an average value of 2.4649 (4) Å . This fact is likely due to the hydrogen-bonding interaction involving the chloride and the N-H group of a neighbouring 4-pyridone since this interaction is absent in those structures.

Supramolecular features
The molecular association in the crystal is strongly directed by hydrogen bonding (Table 1). Two 4-pyridone molecules bridge between two fac-[ReCl(4-pyOH) 2 (CO) 3 ] using the ketone O C group as the hydrogen-bonding acceptor to two different HO-groups, forming R 2 4 (28) rings centred at the g Wyckoff site (Fig. 2). The N-H group of the pyridone unit also establishes hydrogen-bond interactions, with the chloride group, yielding a new centrosymmetric ring R 4 4 (28) (at the f Wickoff site). Although the centroid-to-centroid distance between the pyridone and hydroxypyridone is rather long (3.791 Å ), some distances between the atoms and centroids of the rings [C4Á Á ÁN3 vi = 3.231 Å , C4Á Á ÁC14 vi = 3.470 Å , C5Á Á ÁC14 vi = 3.478 Å and C5Á Á ÁCi vi = 3.365 Å ; symmetry code: (vi) 1 À x, 2 À y, 1 À z; see Fig. 2] suggest a (slipped)stacking interaction. Both intermolecular interactions work to form infinite chains, as represented in Fig. 2, which are further supported by weak C-HÁ Á ÁO and C-HÁ Á ÁCl interactions (the most representative ones are included in Table 1). The formation of the R 2 4 (28) rings yields a small channel-like void of ca 103 Å 3 per unit cell, as shown in Fig. 3. No substantial electron density is found in the channels (ca 4 electrons per void based on a PLATON/SQUEEZE analysis (Spek, 2009(Spek, , 2015. The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms on O and N atoms were located via difference Fourier analyses and refined with U iso (H) = 1.5U eq (O) and 1.2U eq (N). Other H atoms were included at calculated sites and allowed to ride on their carrier atoms, with U iso (H) = 1.2U eq (C).

Figure 3
Association of the chains and formation of the empty channels in the crystal structure.

Crystal data
[ Extinction correction: SHELXL2013 (Sheldrick, 2015b), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0119 (9) Special details 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.