A heterogeneous polynuclear complex for use as a raw material in the chemical deposition of composite metal or composite metal thin films with the below formula. In the formula, M1 and M2 are mutually different transition metals, x is an integer of 0 or more and 2 or less, y is in integer of 1 or more and 2 or less, z is an integer of 1 or more and 10 or less, R1 to R4 are each one of a hydrogen atom and an alkyl group with a carbon number of 1 or more and 5 or less, and R5 is a hydrogen atom, a carbonyl, an alkyl group with a carbon number of 1 or more and 7 or less, an allyl group or an allyl derivative. The heterogeneous polynuclear complex allows a composite metal thin film or a composite metal compound thin film containing a plurality of metals to be formed from a single raw material.