Previous low resolution gas-phase IR spectra of OP-X and related derivatives generated by pyrolysis are critically examined. Density functional calculations at the B3LYP/aug-cc-pVTZ level have been performed for these and similar benchmark molecules where reliable experimental data exist. These theoretical results, comparison with published high-resolution data, and the reassignment of observed bands to well-known chemical species lead to revisions for OCNCN and total rejection of earlier vibrational assignments for OPCl, OPBr, OPI, OPI3, OSbF3, OSbCl3, OPCN, OPSCN, NSCN, and NSSCN.