Patent ID: 7420064

Claim:
A process for preparing lactones which comprises catalytic carbonylating an oxirane with a catalyst system comprising a) at least one cobalt compound as component A and b) at least one metal compound of the formula (I) as component B, MX X R n-X (I) where M Al, Mg or Zn, R hydrogen or C 1-32 -alkyl, C 2-20 -alkenyl, C 3-20 -cycloalkyl, C 6-18 -aryl, C 7-20 -aralkyl or C 7-20 -alkaryl, where substituents may be present on the carbon atoms other than the carbon atom bound to M, X Cl, Br, I, sulfonate, oxide, C 1-32 -alkoxide or amide, n is a number corresponding to the valence of M and x is in the range from 0 to n, with n and x being selected so that the compound is uncharged, and wherein said oxirane is ethylene oxide, propylene oxide, butylene oxide, cyclopentene oxide or cyclohexene oxide.