Lambda nomenclature

In the older literature, derivatives of iodine(III) were known under the general name of iodinanes, while compounds of pentavalent iodine were called periodinanes. According to the 1983 lUPAC recommendations Treatment of variable valence in organic nomenclature (lambda convention) [126], these old names were replaced by -iodanes for iodine(III) and -iodanes for iodine(V) compounds. In the lambda nomenclature. 

According to the 1983 lUPAC recommendations (1984PAC769), the position and the valency of a hypervalent atom in a molecule is indicated by using the Greek letter X. In the lambda nomenclature, the symbol X" is used to indicate any heteroatom in a nonstandard valence state (n) in a formally neutral compound. The lambda terminology is broadly used in the modem literature to indicate the general type of a hypervalent compound and to specify the number of primary bonds at the hypervalent atom. 

Thiatriazines arc not naturally occurring compounds. The nomenclature of 1,2,4,6-thia-triazines is based on the IUPAC rules and Chemical Abstracts.1 2 The valence state of the sulfur atom is assigned with the Greek letter lambda (/.). In this section, the chemistry of the ring system of 124,2,4,6-thiatriazines with three-coordinated sulfur and of the l/4,2,4,6-thiatriazine 1-oxides or 1-imides with four-coordinated sulfur with maximum unsaturation is described. A review of the literature until 1990 is available3 and also a more recent review.82... 

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