Compositions comprising at least one copper salt, and an aromatic nitroso compound precursor are provided. The copper salt may oxidize the aromatic nitroso compound precursor to provide an aromatic nitroso compound. The compositions may find utility in polymer to metal, in particular, rubber to metal bonding. The aromatic nitroso compound precursor may be a nitrosobenzene/dinitrosobenzene precursor. The nitrosobenzene or dinitrosobenzene precursor may be at least one of a quinone oxime or a quinone dioxime.