Pericyclic organometallic reactions. The reactions of (cht)Fe(CO)(2)L (L =CO, P(OPh)(3), PPh3) and (carbomethoxy)maleic anhydride revisited

Kinetic studies of the reaction of(cht)Fe(CO)(2)L (L = CO, P(OPh)(3), PPh3) and (carbomethoxy)maleic anhydride reveal, contrary to our previous report , that the reactions proceed by a tandem 3 + 2-cycloaddition-[2,2]-sigmahap totropic rearrangement, to give the corresponding eta(2),eta(2)-Diels-Alder adducts as main products, in equilibrium with the primary eta(1),eta(3)-si gma,pi-allylic kinetic isomers. The labile primary isomers were characteriz ed by H-1-, C-13- and P-31-NMR spectra. Substitution of carbonyl by phospho rus ligands increased the rates of both cycloadditions and rearrangements i n the order PPh3 > P(OPh)(3) > CO. (C) 1999 Elsevier Science S.A. All right s reserved.