S. Ogoshi et al., Carbon-carbon bond formation by electrophilic addition at the central carbon of the mu-eta(3)-allenyl/propargyl ligand on the Pd-Pd bond, J AM CHEM S, 123(14), 2001, pp. 3223-3228
The mu-eta (3)-allenyl/propargyldipalladium complexes were synthesized by t
he reaction of the corresponding eta (1)-allenyl- or eta (1)-propargylpalla
dium complexes with Pd-2(dba)(3) The X-ray diffraction analysis indicates t
hat the dinuclear complex has a unique structure, in which two palladium, t
hree carbon, two phosphorus, and one halogen atoms are in the same plane. T
hese dinuclear complexes react with electrophiles, such as HCl or AcCl, at
the central carbon of the mu-eta (3)-allenyl/propargyl ligand to give the m
u-eta (3)-vinylcarbenedipalladium complexes. Intramolecular reaction procee
ded smoothly to give cyclization products quantitatively. Addition of a cat
alytic amount of a palladium(0) complex dramatically accelerated the carbon
-carbon bond formation. The MO calculations on the mu-eta (3)-allenyl/propa
rgyl complexes indicated that the reaction proceeds via orbital control.