An object of the present invention is to provide a novel complex having at least one carbon-carbon double bond and/or carbon-carbon triple bond. The present invention provides a complex represented by formula (1): ((RCOO)8M5(OH)2)n   (1) wherein in the formula (1), M is a metal atom, R is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms or an alkynyl group having 2 to 18 carbon atoms, a plurality of R may be identical to or different from each other, at least one of R is the alkenyl group having 2 to 18 carbon atoms or the alkynyl group having 2 to 18 carbon atoms, and n is an integer of 1 or more.