Binor-S is prepared by the dimerization of norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) at an excellent conversion and an excellent selectivity using an effective amount of a two component catalytic system of tris(triphenylphosphine)rhodium chloride and diethylaluminum chloride or ethylaluminum dichloride or aluminum ethylsesquichloride. The range of mole ratio of norbornadiene to tris(triphenylphosphine)rhodium chloride is between from about 100 to about 1000 and the range of mole ratio of one of the aluminum chlorides to the rhodium chloride is between from about 0.5 to about 100. The reaction rate is rapid. Binor-S can be used as precursor for hydrocarbons having utility for either jet or rocket propulsion.