An improved hydroconversion process for carbonaceous materials wherein an ammonium or hydrocarbyl substituted ammonium salt of a metal-sulfur analog of cubane having an anion with a core structure of M.sub.4 S.sub.4 is used as a catalyst precursor. In the general formula, M may be the same or a different metal having hydrogenation catalytic activity when used as a sulfide and capable of occupying one or more vertices in a cubane structure. The metal may also have the capability of bridging one or more such structures. The improved process is effective for both normally solid and normally liquid carbonaceous materials and for carbonaceous materials which are either solid or liquid at the conversion conditions. The hydroconversion will be accomplished at a temperature within the range from about 500.degree. to about 900.degree. F., at a total pressure within the range from about 500 to about 7000 psig and at a hydrogen partial pressure within the range from about 400 to about 5000 psig.