SUBSTITUTED CYCLOPENTADIENIDES OF MAGNESIUM FROM THE REACTION OF DIALKYL MAGNESIUM WITH FULVENES

The reaction of n/sec-dibutyl magnesium with 6-methyl-6-phenyl- and 6, 6-dicyclopropylfulvene gives the beta-hydride transfer products 1,1'-b is(1-phenylethyl)- and 1,1'-bis(dicyclopropylmethyl)magnesocene, respe ctively. The latter crystallizes in the eclipsed conformation, whereas the first one shows an anti conformation in the solid state. Dimethyl magnesium deprotonates 6-methyl-6-phenylfulvene with formation of 1,1' -bis(1-phenylethen-1-yl)magnesocene, which decomposes upon isolation. The deprotonation of 6,6-dicyclopropylfulvene with MgMe2 in thf soluti on yields )-cyclopentadienyl-1',3',3'-tricyclopropyl-1',2',3 tetrahydr openalene)}-3a'-6'-eta(2)-enyl]magnesium. In the absence of beta-hydro gen atoms at the organometallic reagent as well as at the fulvene the addition reaction is the only possible reaction pathway. Thus, one Mg- C bond of MgMe2 adds to tetramethylfulvene to give quantitatively dime ric methylmagnesium ethyltetramethylcyclopentadienide. The bridging me thyl groups are sterically shielded against further attack of the fulv ene.