Gasphasen- und Kristall-Struktur sowie Reaktionen von Hexahydrido(η⁵-pentamethylcyclopentadienyl)rhenium(VII), (η⁵-C₅Me₅)ReH₆: Elektronen- und Röntgenbeugung

The hexahydrido rhenium complex (η⁵-C₅Me₅)ReH₆ (1) has been studied by use of gas-phase electron diffraction (Oslo), while the derivative (η⁵-C₅Me₄Et)ReH₆ (1′) has structurally been defined by a single-crystal X-ray diffraction study at 23°C (Munich). The data confirm an earlier proposal based on NMR data, that both compounds have the rare pentagonal-bipyramidal geometry, with the five hydrido ligands adopting equatorial positions. The hydrogen-to-rhenium distances are 140-166 pm (X-ray) and 166.5(14) pm (electron diffraction), respectively. The umbrella-type configuration of the H′ReH₅ structural unit (angle H′ReH 66-70°; X-ray data) is probably due to the relatively large steric bulk of the (centrically π-bonded) ring ligand. Hydridic rather than protic H-ligands are chemically and structurally in evidence. The structural data obtained independently for the gas-phase and for the crystalline state are consistent with NMR data obtained for solution; the found T,₁ values indicates that η¹-H- rather than η²-H₂ ligands are present.