Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen. LXXVIII. Über oxo- und methylimido-komplexe des rheniums mit sauerstoff-, schwefel- und stickstoffchelaten: Synthese, spaltungsreaktionen und strukturchemie

The organorhenium(V) chelates 4-9 (dianion chelates of the O,N-, S,O-, N,N′-type) are derivatives of the oxo- and methylimido complexes (η⁵-C₅Me₅)Re(O)Cl₂ (2) and (η⁵-C₅Me₅)Re(NCH₃)Cl₂ (3b). They are described and compared with each other. The starting compound 3b is readily obtained in 95% yield from (η⁵-C₅Me₅)ReCl₄ (1) and heptamethyldisilazane. The complexes 7-9 of the imido-type are very moisture-sensitive and are hydrolyzed to the corresponding oxo complexes: L_xReNCH₃ → L_xReO. None of the imido compounds in the entire series undergoes clean thermal decomposition with elimination of olefins. Protolytic degradation with HBF₄ gives the free, protonated ligands which are also formed with aqueous H₂O₂ (in addition to formation of the oxidation product (η⁵C₅Me₅)ReO₃). X-ray diffraction studies (23°C) of the O,N- and N,N′-chelate complexes (η⁵-C₅Me₅)Re(O)(OCH₂CH₂NCH₃) (5b) and (η⁵-C₅Me₅)Re(O)(CH₃CNCH₂CH₂NCH₃) (6b), respectively, reveal planar rhenacycles, in contrast to the known envelope-conformation of the O,O′-glycolate complex (η⁵-C₅Me₅)Re(O) (OCH₂CH₂O) (4a).