A negative-working, infrared radiation-sensitive lithographic printing plate precursor comprising: a substrate having a hydrophilic surface, and an infrared radiation-sensitive imageable layer that is disposed on the hydrophilic surface of the substrate, and comprises: one or more free radically polymerizable compounds; one or more infrared radiation absorbers; an initiator composition that provides free radicals upon exposure of the infrared radiation-sensitive imageable layer to infrared radiation, the initiator composition comprising compound A represented by the following Structure and, one or more compounds collectively as compound B that are represented by the following Structure or Structure; and a primary polymeric binder, wherein: R 1, R 2, R 3, R 4, R 5 and R 6 are independently substituted or unsubstituted alkyl groups or substituted or unsubstituted alkoxy groups each having 2 to 9 carbon atoms; at least one of R 3 and R 4 is different from R 1 or R 2; the difference between the total number of carbon atoms in R 1 and R 2 and the total number of carbon atoms in R 3 and R 4 is 0 to 4; the difference between the total number of carbon atoms in R 1 and R 2 and the total number of carbon atoms in R 5 and R 6 is 0 to 4; and X 1, X 2 and X 3 are the same or different anions. a substrate having a hydrophilic surface, and an infrared radiation-sensitive imageable layer that is disposed on the hydrophilic surface of the substrate, and comprises: one or more free radically polymerizable compounds; one or more infrared radiation absorbers; an initiator composition that provides free radicals upon exposure of the infrared radiation-sensitive imageable layer to infrared radiation, the initiator composition comprising compound A represented by the following Structure and, one or more compounds collectively as compound B that are represented by the following Structure or Structure; and a primary polymeric binder, wherein: R 1, R 2, R 3, R 4, R 5 and R 6 are independently substituted or unsubstituted alkyl groups or substituted or unsubstituted alkoxy groups each having 2 to 9 carbon atoms; at least one of R 3 and R 4 is different from R 1 or R 2; the difference between the total number of carbon atoms in R 1 and R 2 and the total number of carbon atoms in R 3 and R 4 is 0 to 4; the difference between the total number of carbon atoms in R 1 and R 2 and the total number of carbon atoms in R 5 and R 6 is 0 to 4; and X 1, X 2 and X 3 are the same or different anions. one or more free radically polymerizable compounds; one or more infrared radiation absorbers; an initiator composition that provides free radicals upon exposure of the infrared radiation-sensitive imageable layer to infrared radiation, the initiator composition comprising compound A represented by the following Structure and, one or more compounds collectively as compound B that are represented by the following Structure or Structure; and a primary polymeric binder, wherein: R 1, R 2, R 3, R 4, R 5 and R 6 are independently substituted or unsubstituted alkyl groups or substituted or unsubstituted alkoxy groups each having 2 to 9 carbon atoms; at least one of R 3 and R 4 is different from R 1 or R 2; the difference between the total number of carbon atoms in R 1 and R 2 and the total number of carbon atoms in R 3 and R 4 is 0 to 4; the difference between the total number of carbon atoms in R 1 and R 2 and the total number of carbon atoms in R 5 and R 6 is 0 to 4; and X 1, X 2 and X 3 are the same or different anions. R 1, R 2, R 3, R 4, R 5 and R 6 are independently substituted or unsubstituted alkyl groups or substituted or unsubstituted alkoxy groups each having 2 to 9 carbon atoms; at least one of R 3 and R 4 is different from R 1 or R 2; the difference between the total number of carbon atoms in R 1 and R 2 and the total number of carbon atoms in R 3 and R 4 is 0 to 4; the difference between the total number of carbon atoms in R 1 and R 2 and the total number of carbon atoms in R 5 and R 6 is 0 to 4; and X 1, X 2 and X 3 are the same or different anions.