Abstract: | Studies on the Reactivity of Isomeric Heterodinuclear Fischer-Carbene Complexes exhibiting a Titanaoxetan or Titanaoxolen Substructure – Cycloreversion and Insertion Reactions The reactivity of isomeric four- and five-membered carbene complexes Cp*2 3 and Cp*2 4 [MLn: Cr(CO)5 ( a ); W(CO)5 ( b ); Cp*: C5(CH3)5] has been investigated. A cycloreversion reaction, unusual for common metallaoxetanes, is found to dominate the chemical behaviour of 3 . The generation of vinylidene fragment [Cp*2Ti?C?CH2] 2 as an intermediate is proved either by trapping with ethylene and isocyanate or by protonation of the α-carbon atom. On the other hand no cycloreversion is observed for the titanaoxolene carbene complexes 4 . Ringenlargement is found by the reaction of 3 and 4 with isonitriles under formation of iminoacyl complexes. Accordingly 2,6-dimethylphenylisonitrile reacts with 3 b forming Cp*2 12 [Ar: 2,6-(CH3)2? C6H3]. A reversible insertion of cyclohexylisonitrile in 4a leads to isolation of the six-membered metallacycle Cp*2 16 (Cy: C6H11). |