Übergangsmetall—methylen-komplexe

摘要: Abstract The α-diazoketones 2a–h,k,l react with the dinuclear organorhodium complex 1 elimination of dinitrogen and concomitant addition their carbonyl-flanked carbene moieties upon metal—metal double bond. μ-alkylidene complexes 3f–h thus accessible, represent final products; trimethylsilyl derivative 3i was synthesized for comparison. By contrast, derivatives 3a–e,l behave rather as IR-spectroscopically identified intermediates that, at room temperature, undergo rapid consecutive intramolecular cycloaddition reactions yielding novel compounds 4a–e 5l, respectively. Formation results from nucleophilic attack keto groups bridging ligands one metal carbonyl units. This type cyclization process comprises construction a new oxygen—carbon metallacyclic structures obtained have been elucidated in cases 4c 4e by means single crystal X-ray diffraction techniques no longer obey structural criteria type-3 complexes. An internal experiment concurrently carried out use diazoalkane 2e furnished proof that occurred regiospecifically: only more keto-oxygen atom is subject to ring closure, whereas oxygen ester group does not participate this reaction. bis(acyl)methylene resist retain even elevated temperatures (cf. boiling tetrahydrofuran). carbocyclic diazo precursor 2k (diazodimedone) requires drastic conditions (boiling benzene) reaction compound occur; here, cycloadduct 5k formed following nitrogen elimination. According study, ketocarbene fragment derived has added across metalcarbonyl core, finally acting unit. In contrast cycloadducts 4a–e, carbon—carbon bond during synthesis 5k. dimetallacycle 5l two-step cyclo-elimination between bisdiazoalkane 2l 1.