Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005 is the 2005 version of Nomenclature of Inorganic Chemistry (which is informally called the Red Book). It is a collection of rules for naming inorganic compounds, as recommended by the International Union of Pure and Applied Chemistry (IUPAC).
Summary The 2005 edition replaces their previous recommendations Nomenclature The Red Book of Inorganic Chemistry, IUPAC Recommendations 1990 (Red Book I), and "where appropriate" (sic) Nomenclature of Inorganic Chemistry II, IUPAC Recommendations 2000 (Red Book II).
The recommendations take up over 300 pagesNomenclature of Inorganic Chemistry IUPAC Recommendations 2005 ed. N. G. Connelly et al. RSC Publishing https://iupac.org/what-we-do/books/redbook/ and the full text can be downloaded from IUPAC.Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005 - Full text (PDF) Corrections have been issued.Corrections to Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005
Apart from a reorganisation of the content, there is a new section on organometallics and a formal element list to be used in place of electronegativity lists in sequencing elements in formulae and names. The concept of a preferred IUPAC name (PIN), a part of the revised blue book for organic compound naming, has not yet been adopted for inorganic compounds. There are however guidelines as to which naming method should be adopted.
Naming methods The recommendations describe a number of different ways in which compounds can be named. These are: compositional naming (e.g. sodium chloride) substitutive naming based on parent hydrides (GeCl2Me2 dichlorodimethylgermane) additive naming ([MnFO3] fluoridotrioxidomanganese) Additionally there are recommendations for the following: naming of cluster compounds allowed names for inorganic acids and derivatives naming of solid phases e.g. non-stoichiometric phases For a simple compound such as AlCl3 the different naming conventions yield the following: compositional: aluminium trichloride (stoichiometrically) or dialuminium hexachloride (dimer) substitutional: trichloralumane additive: trichloridoaluminium; hexachloridodialuminium (dimer without structural information); di-μ-chlorido-tetrachlorido-1κ2Cl,2κ2Cl-dialuminium (dimer with structural information)
Sequencing elements—the "electronegativity" list Throughout the recommendations, the use of the electronegativity of elements for sequencing has been replaced by a formal list which is loosely based on electronegativity. The recommendations still use the terms electropositive and electronegative to refer to an element's relative position in this list.
A simple rule of thumb, ignoring lanthanides and actinides, is: for two elements in different groups, the element in the higher numbered group has higher "electronegativity" for two elements within the same group, the element with the lower atomic number has higher "electronegativity" Hydrogen is fitted in to be less electronegative than any chalcogen and more electronegative than any pnictogen. Hence the formulae of water and ammonia can be written H2O and NH3 respectively.
The full list, from highest to lowest "electronegativity" (with the addition of elements 112 through 118, that had not yet been named in 2005, to their respective groups): Group 17 in atomic number sequence i.e. F–Ts followed by Group 16 in atomic number sequence i.e. O–Lv followed by H, hydrogen, followed by Group 15 in atomic number sequence i.e. N–Mc followed by Group 14 in atomic number sequence i.e. C–Fl followed by Group 13 in atomic number sequence i.e. B–Nh followed by Group 12 in atomic number sequence i.e. Zn–Cn followed by Group 11 in atomic number sequence i.e. Cu–Rg followed by Group 10 in atomic number sequence i.e. Ni–Ds followed by Group 9 in atomic number sequence i.e. Co–Mt followed by Group 8 in atomic number sequence i.e. Fe–Hs followed by Group 7 in atomic number sequence i.e. Mn–Bh followed by Group 6 in atomic number sequence i.e. Cr–Sg followed by Group 5 in atomic number sequence i.e. V–Db followed by Group 4 in atomic number sequence i.e. Ti–Rf followed by Group 3 in atomic number sequence i.e. Sc–Y followed by the lanthanoids in atomic number sequence i.e. La–Lu followed by the actinoids in atomic number sequence i.e. Ac–Lr followed by Group 2 in atomic number sequence i.e. Be–Ra followed by Group 1 (excluding H) in atomic number sequence i.e. Li–Fr followed by Group 18 in atomic number sequence i.e. He–Og
Determining the nomenclature to use + Decision table based on IUPAC flowchart Action Additioncompound?Definitestoichiometry?mono-atomic?molecular?metal present?Bond to carbon?transition metalgroup 3–12?main group metalgroups 1, 2, 3–6? Treat each component separatelyuse compositional Use solids naming Element or monatomic cation/anion/radical naming Divide components into "electropositive"/"electronegative"Treat each component separatelyUse generalised stoichiometric naming Use Blue book(Organic compound)' Use additive naming forgroup 3- 12 organometallics Use substitutive naming forgroup 3–6 organometallicsUse compositionalfor groups 1–2 organometallics Use additive naming for coordination complexes Choose either substitutive or additive Note "treat separately" means to use the decision table on each component
Element names Sample of indeterminate structure An indeterminate sample simply takes the element name. For example a sample of carbon (which could be diamond, graphite etc or a mixture) would be named carbon.
Specific allotrope Molecular O2 dioxygen (acceptable name oxygen) O3 trioxygen (acceptable name ozone) P4 tetraphosphorus (acceptable name white phosphorus) S6 hexasulfur (acceptable name ε-sulfur) S8 cyclo-octasulfur (acceptable names for the polymorphic forms are α-sulfur, β-sulfur, γ-sulfur)
Crystalline form This is specified by the element symbol followed by the Pearson symbol for the crystal form. (Note that the recommendations specifically italicize the second character.) Cn carbon(cF8) (acceptable name diamond) Snn tin(tI4) (acceptable name β- or white tin) Mnn manganese(cI58) (acceptable name α-manganese)
Amorphous recognised allotropes Examples include Pn,. red phosphorus ; Asn, amorphous arsenic.
Compounds Compositional names impart little structural information and are recommended for use when structural information is not available or does not need to be conveyed. Stoichiometric names are the simplest and reflect either the empirical formula or the molecular formula. The ordering of the elements follows the formal electronegativity list for binary compounds and electronegativity list to group the elements into two classes which are then alphabetically sequenced. The proportions are specified by di-, tri-, etc. (See IUPAC numerical multiplier.) Where there are known to be complex cations or anions these are named in their own right and then these names used as part of the compound name.
Binary compounds In binary compounds the more electropositive element is placed first in the formula. The formal list is used. The name of the most electronegative element is modified to end in -ide and the more electropositive elements name is left unchanged.
Taking the binary compound of sodium and chlorine: chlorine is found first in the list so therefore comes last in the name. Other examples are PCl5 phosphorus pentachloride Ca2P3 dicalcium triphosphide NiSn nickel stannide Cr23C6 tricosachromium hexacarbide
Ternary compounds and beyond The following illustrate the principles.
The 1:1:1:1 quaternary compound between bromine, chlorine, iodine and phosphorus: phosphorus bromide chloride iodide (phosphorus is the most electropositive, the others are all designated as electronegative and are sequenced alphabetically)
The ternary 2:1:5 compound of antimony, copper and potassium can be named in two ways depending on which are designated as electronegative. CuK5Sb2 copper pentapotassium diantimonide, (both copper and potassium are designated as electropositive and are sequenced alphabetically) K5CuSb2 pentapotassium diantimonide cupride (only potassium is designated as electropositive and the two electronegative elements are sequenced alphabetically) (Note the red book shows this example incorrectly)
Naming of ions and radicals Cations Monatomic cations are named by taking the element name and following it with the charge in brackets e.g sodium(1+) chromium(3+)
Sometimes an abbreviated form of the element name has to be taken, e.g. germide for germanium as germanide refers to .
Polyatomic cations of the same element are named as the element name preceded by di-, tri-, etc., e.g.: dimercury(2+) Polyatomic cations made up of different elements are named either substitutively or additively, e.g.: phosphanium tetrafluorostibanium (substitutive) or tetrafluoridoantimony(1+) Note that ammonium and oxonium are acceptable names for and respectively. (Hydronium is not an acceptable name for )
Anions Monatomic anions are named as the element modified with an -ide ending. The charge follows in brackets, (optional for 1−) e.g.: Cl− chloride(1−) or chloride S2− sulfide(2−) Some elements take their Latin name as the root e.g silver, Ag, argentide copper, Cu, cupride iron, Fe, ferride tin, Sn, stannide
Polyatomic anions of the same element are named as the element name preceded by di-, tri-, etc., e.g.: O22− dioxide(2−) (or peroxide as an acceptable name) C22− dicarbide(2−) (or acetylide as an acceptable name) S22− disulfide(2−)
or sometimes as an alternative derived from a substitutive name e.g.
S22− disulfanediide
Polyatomic anions made up of different elements are named either substitutively or additively, the name endings are -ide and -ate respectively e.g. : GeH3− germanide (substitutive), or trihydridogermanate(1−) (additive) TeH3− tellanuide substitutive where -uide specifies anion composed of additional hydride attached to parent hydride [PF6]− hexafluoro-λ5-phosphanuide (substitutive), or hexafluoridophosphate(1−) (additive) SO32− trioxidosulfate(2−) (additive), or sulfite (acceptable non-systematic name)
A full list of the alternative acceptable non-systematic names for cations and anions is in the recommendations. Many anions have names derived from inorganic acids and these are dealt with later.
Radicals The presence of unpaired electrons can be indicated by a "·". For example: He·+ helium(·+) N2(2·)2+ dinitrogen(2·2+)
Naming of hydrates and similar lattice compounds The use of the term hydrate is still acceptable e.g. Na2SO4·10H2O, sodium sulfate decahydrate. The recommended method would be to name it sodium sulfate—water(1/10). Similarly other examples of lattice compounds are: CaCl2·8NH3, calcium chloride— ammonia (1/8) 2Na2CO3·3H2O2, sodium carbonate—hydrogen peroxide (2/3) AlCl3·4EtOH, aluminium chloride—ethanol (1/4)
Specifying proportions using charge or oxidation state As an alternative to di-, tri- prefixes either charge or oxidation state can be used. Charge is recommended as oxidation state may be ambiguous and open to debate.
Substitutive nomenclature This naming method generally follows established IUPAC organic nomenclature. Hydrides of the main group elements (groups 13–17) are given -ane base names, e.g. borane, BH3. Acceptable alternative names for some of the parent hydrides are water rather than oxidane and ammonia rather than azane. In these cases the base name is intended to be used for substituted derivatives.
This section of the recommendations covers the naming of compounds containing rings and chains.
Base hydrides