SYNTHESIS AND CRYSTAL-STRUCTURE OF [CO2(CO)4(PHCCC(O)CH3)3] - ITS ROLE IN THE CYCLOTRIMERIZATION OF 1-PHENYLBUT-1-YN-3-ONE TO 1,3,5-TRIPHENYLTRIS(CARBOXYMETHYL)BENZENE

The reaction Of [Co2(CO)8] with 1-phenylbut-1-yn-3-one in refluxing toluene yields [Co2(CO)6{mu-PhC=CC(O)CH3}], the symmetrical trimer (PhC2C(O)CH3}3, which were characterized by spectroscopic techniques, and the title complex, the structure of which has been elucidated by X-ray analysis. The crystals are monoclinic P2(1)/c with a = 10.640(2), b = 17.741(4), c = 17.845(4) angstrom, beta = 90.50(3)-degrees, Z = 4. The molecule has a Co-Co bond and the (PhC2C(O)CH3)3 chain links the cobalt atoms in a ''flyover'' arrangement. To our knowledge, this is the first example of stepwise formation of a symmetrical benzene from an asymmetrical, internal alkyne via this type of intermediate.