Mehrfachbindungen zwischen Hauptgruppenelementen und Uebergangsmetallen. LXII. Alkin-Komplexe der Organorheniumoxide: Redox-Chemie und Nucleophilie der Oxo-Funktion von (η5-Pentamethylcyclopentadienyl)(η2-diphenylethin)oxorhenium(III)

Article abstract of DOI:10.1016/0022-328X(89)87255-9

The novell Re^III oxo alkyne complexes (η⁵-C5Me5)Re(=O)(η²-RCCR) (3a-c; R=C6H5, CH3, C2H5) are obtained almost quantitatively by alkaline hydrolysis of the dichloro precursor compounds (η⁵-C5Me5)ReCl2(η²-RCCR) (4a-c).An X-ray diffraction study has revealed that in the phenyl derivative 3a the alkyne group is best described as a two-electron ligand. 17O NMR spectroscopy shows the remarkable electron deficiency of the terminal oxo group.This oxo function however is sufficiently nucleophilic to be converted into the hydroxo species <(η²-diphenylalkyne)hydroxo(η⁵-pentamethylcyclopentadienyl)rhenium(III) tetrafluoroborate (5a) and <(η²-butyne(2))hydroxo(η⁵-pentamethylcyclopentadienyl)rhenium(III)> tetrafluoroborate (5b) by O-protonation with HBF4.One-electron oxidation of 3a leads to the dinuclear Re^IV species <((μ-O)(η⁵-C5Me5)Re(η²-C6H5CCC6H5))2>²⁺ without loss of the alkyne ligand.The Re^V systems (η⁵-C5Me5)Re(=O)2(η⁵-RCCR) (2), generated oxidatively, are not stable as they decompose rapidly by eliminating the alkyne ligand.