The present invention provides an initiator system including an infrared-absorbing compound that exhibits an electronic transition band in the near-infrared region, an initiator, and a metallocene compound. Upon exposure to infrared radiation, the initiator system is capable of producing radicals sufficient to initiate a photopolymerization reaction. Suitable infrared-absorbing compounds include indocyanine dyes, for example. Trihalomethyl triazine compounds and onium compounds are suitable initiators. Suitable metallocene compounds include ferrocenes and titanocenes. The present invention also provides an infrared-sensitive composition including an ethylenically unsaturated polymerizable component, an infrared-absorbing compound that exhibits an electronic transition band in the near-infrared region, an initiator, and a metallocene compound. The infrared-sensitive composition provides improved photospeed and sensitivity in some embodiments. A printing plate precursor including an infrared-sensitive coating is also provided. The printing plate precursor exhibits enhanced shelf life in some embodiments. A method of making a printing plate precursor and a method for making a printable lithographic printing plate are further provided by the invention.