a metal catalyst for hydrogenating unsaturated carbon - carbon bonds of copolymer is provided . the metal catalyst is a bimetallic complex comprising iridium and ruthenium . the metal catalyst has a formula comprising m 1 a m 2 b x m n , wherein the m 1 is iridium , m 2 is ruthenium ; x is hydrogen , chlorine , bromine , iodine or pseudo halide ; l 1 is phosphine , bisphosphine , arsane or organic with nitrogen , sulfur and oxygen .