Compounds that resemble the halogen elements, X2, in their chemistry, e.g. (CN)2 cyanogen, (SCN)2 thiocyanogen, ICN iodine cyanide. Certain ions that have sufficient resemblance to halide ions are sometimes referred to as pseudohalide ions, e.g. N3, SCN, CN.
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1361 [Terms] [Paper]