A method of utilizing a catalytic complex having a transition metal (e.g. nickel, cobalt) ion coordinated to a calixarene ligand in upgrading hydrocarbon feedstocks containing C20 through C50 hydrocarbons (e.g. vacuum gas oil) to produce light petroleum products (e.g. medium distillate, naphtha) is specified. A method of using the catalytic complex with a supported co-catalyst to synergistically hydrocrack the feedstocks is also provided.