ALPHA-H TRANSFER-REACTIONS ON VINYL METAL -COMPOUNDS - PREPARATION OF(ETA(5)-CYCLOPENTADIENYL)(ETA(5) LCYCLOPENTADIENYL)-(2-METHYLIDENE)TITANCYCLOBUTANE

The reaction of CpCpTiCl*(2) (Cp*: C-5(CH3)(5); Cp: C5H5) with two eq uivalents of vinyllithium enables the first isolation of a titanium(IV )-divinyl complex CpCpTi(CH=CH2)(2) (11). In a molar ratio of 1:1 Cp* CpTi(CH=CH2)Cl (15) can be obtained and converted into CpCpTi(CH=CH2) CH3 (16) through further alkylation at a temperature above 0 degrees C a quantitative isomerisation of 11 to the methylidenemetallacyclobuta ne CpCpTiC(=CH2)CH2CH2 (12) occurs as a consequence of characteristic alpha-H-transfer. The influence on the stability of 11 and 16 through Cp/Cp exchance will be discussed in comparison to Cp*Ti-2 derivative s on the basis of NMR data.