REACTIONS OF A DICARBENIUM FULVALENYL COMPLEX WITH AROMATIC NUCLEOPHILES AND SYNTHESIS OF (MU-ALKYNE)(FULVALENYL)TETRACARBONYLDIMOLYBDENUM COMPOUNDS - A STRUCTURE-REACTIVITY RELATIONSHIP

The compound vMo(2)(CO)(4)(mu-eta(3):eta(3)-CH2C=CCH2)][BF4](2) (3) re acts with weak nucleophiles to give the related carbenium complexes FV Mo2(CO)(4)(mu-eta(2):eta(3)-CH2C=CCH(2)Nu)][BF4] (Nu = -C6H4OH, -C6H4O Me), where attack occurs exclusively on one carbenium center (-CH2+). Subsequent treatment by NaBH4 reduces the second carbenium center (-CH 2+) to yield the disubstituted alkyne fulvalenyl adducts. The differen ce in reactivity between 3 and the analogous dicarbenium Cp system Cp2 Mo2(CO)(4)(mu-eta(3):eta(3)-CH2C=CCH2)][BF4](2) is attributed to the f ulvalene effect.