STEREOSELECTIVE SYNTHESIS OF NEW HETERO(P,SI,GE,SN)CYCLIC DERIVATIVESFROM ZIRCONIUM DIYNE AND DIENE COMPLEXES

The dipropargylic derivatives of Si, Ge, P, la-c, react with the zirco nocene entity 'Cp2Zr' and give the intermediate bicyclocomplexes 2a-c characterized by H-1 and P-31-NMR. The electrophilic addition of H+, B r-2 leads to the corresponding exo dienic metallacyclopentanes 3,4. Th e cyclozirconation reaction with hetero-diallylic compounds 5a-d gives the metallacyclopentanes 7-15, after reaction with different electrop hiles such as H+, PCl3, PhPCl2, Ph2PCl or Ph2PCl(BH3), Br-2. The cyclo zirconation reaction of diynes is stereoselective and leads to the E,E -exocyclic dienes whereas the selectivity of cyclozirconation of diene s depends on the substituents on the heteroatom. (C) 1998 Elsevier Sci ence S.A. All rights reserved.