Übergangsmetall-methylen-komplexe. IXL. Über metallzentrierte umlagerungsreaktionen von diazoalkanen und die einfache synthese von alkylidenamido- sowie isocyanato-komplexen

The dinuclear 2-diazopropane complex 1 undergoes a novel type of fragmentation upon heating in boiling toluene: irreversible nitrogennitrogen bond cleavage of the metal-coordinated heterocumulene with subsequent rearrangement of the intermediate nitrido(carbonyl)metal species yields a terminal isocyanato ligand while the remaining 2-propylidene amido fragment symmetrically bridges the metalmetal double bond (d(MoMo) 274.5(2) pm) of the reaction product 2. This unexpected rearrangement reaction is to be considered as a further variant of the "Hieber base reaction". A chemical test of the multiple bond character of the molybdenummolybdenum bond present in compound 2 was provided by the reversible addition of carbon monoxide which reaction yields compound 3. Insertion of a nitrido metal moiety into a methylene bridge was observed, for the first time, in the case of the methodologically related rearrangement process of the diazomethane derivative 4; the resulting dinuclear bis(methylene amido) derivative 5 was again characterized by means of X-ray diffraction techniques.