The delta lambda notation, usually abbreviated to δλ notation, is a specific notation in the coordination chemistry. In chemistry, the way in which compounds are compounded is more complex than at first sight. In coordination links, the number of ligands is important in addition to the electrovalence. To be able to name this unambiguously, the δλ notation is used. Hereby δ indicates the number of ligands and λ the valency of the central coordinating atom. The numbers are expressed in Arabic with superscript δ and λ. Examples
Of phosphorus, both phosphorus (V) and phosphorus (III) as well as valence are known. In this system, a phosphine (R3P) is referred to as an δλ compound: phosphorus has valence 3 and has 3 ligands.
The iron complex potassium hexacyanoferrate (II) is an δλ-iron compound. Iron has valence 3 and has 6 cyanide ligands.
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