Tetra-μ3-hydroxido-tetrakis[tricarbonylrhenium(I)] pyridine tetrasolvate

The title compound, [Re4(μ3-OH)4(CO)12]·4C5H5N, crystallizes with one tetranuclear rhenium(I) cubane-like molecule and four pyridine molecules in the asymmetric unit. The coordination environment of each ReI atom is distorted octahedral. Four intramolecular O—H⋯N and four intermolecular C—H⋯O hydrogen-bond interactions are observed. Relatively strong hydrogen bonds are found between the hydrogen-bond donor (μ3-OH) and acceptor (basic N atom of pyridine), with N⋯O distances between 2.586 (10) and 2.628 (10) Å. Intercube distances of 9.873 (2) and 12.376 (3) Å are observed.

The University of the Free State, the the Department of Chemistry at the University of the Free State, the NRF and Sasol Ltd. are gratefully acknowledged for funding and Theunis Muller for assistance with the refinement of the data.
the rhenium cluster as well as DMF and OPPh 3 reported by Egli et al. (1997). Four intermolecular hydrogen interactions are reported between an aromatic carbon of the pyridine molecule to a carbonyl oxygen atom of the next rhenium cluster.

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 pyridine. The mixture was stirred at room temperature for 3 h and left to stand. The colourless cuboidal crystals formed by evaporation after a few days.

Refinement
Aromatic and hydroxyl H atoms were positioned geometrically and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (parent) and U iso (H) = 1.5U eq (parent) of the parent atom with a C-H and O-H distance of 0.93 Å and 0.85 (2) Å respectively.

Figure 2
Packing of the title compound in the unit cell.