Chapter 6 Naming Inorganic Compounds（2）

Allotropes

Allotropes are different structural modifications of an element whose atoms are bonded together in a different manner. They should not be confused with isomers, which are chemical compounds that share the same molecular formula but have different structures.

Molecular

• O2dioxygen (acceptable name oxygen)

• O3trioxygen (acceptable name ozone)

• P4tetraphosphorus (acceptable name white phosphorus)

• S6hexasulfur (acceptable name e-sulfur)

• S8cyclo-octasulfur (acceptable names for the polymorphic forms are a-sulfur, fl-sulfur, y-sulfur)

Crystalline form

This is specified by the symbol of the element followed by the Pearson symbol for the crystal form. Note that the recommendations specifically italicise the second character.

• Cncarbon (c F8) (acceptable name diamond)

• Snntin (t I4) (acceptable name β- or white tin)

• Mnnmanganese (c I58) (acceptable name a-manganese)

Amorphous recognized allotropes

• Pnred phosphorus

• Asnamorphous arsenic

Mineral Names

Generally mineral names should not be used to specify chemical composition. However, mineral names can be used to specify the structure types in formulae.

• Al2Si2O5(OH)4kaolinite • Mg3Si4O10(OH)2talc

• Ca SO 4•2H2O gypsum • Ca CO3calcite

• Ca F2fluorite • Ca5(PO4)3(OH,Cl,F) apatite

• KAl Si3O8orthoclase • Si O2 quartz

• Al2Si O4(OH,F)2topaz • A12O3corundum

• Ba Ti O3perovskite type

Variable Composition

It can be written to indicate that there is a continuous range of composition, e.g., K(Br,Cl) for a mixture of KBr and KC1 and (Li2,Mg)Cl2for a mixture of Li Cl and Mg Cl2. The recommendation is to use the following generalized method.

• CuxNi1-xfor (Cu,Ni) • KBrxCl1-xfor K(Br,Cl)

Note that cation vacancies in Co O may be described by Co O1-x

Polymorphism

It is recommended that polymorphs are identified, e.g., for Zn S where the two forms zincblende (cubic) and wurtzite (hexagonal) as Zn S(c) and Zn S(h) respectively. 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. For the ordering of the elements, follow the formal electronegativity list for binary compounds and electronegativity list and group the elements into two classes, then alphabetically sequence them. The proportions are specified by “di-”, “tri-”, etc.

Naming of Ions

Sometimes an abbreviated form of the element name has to be taken, e.g., germide for germanium as germanide refers to Ge H3-. Polyatomic cations of the same element are named using the element name preceded by “di-”, “tri-”, etc.

• Hg22+dimercury(2+)

Polyatomic cations comprising different elements are named either substitutively or additively.

• PH4+phosphanium

•Sb F4+tetrafluorostibanium (substitutive) or tetrafluoridoantimony(l+)

Note that ammonium and oxonium are acceptable names for NH4+and OH3+ respectively.(Hydronium is not an acceptable name for OH3+.)

Polyatomic anions containing different elements are named either substitutively or additively, with a suffix “-ide” or “-ate” respectively.

• Ge H3-germanide (substitutive), or trihydridogermanate( 1 -) (additive)

• Te H3-tellanuide (substitutive) where -uide specifies anion composed of additional hydride attached to parent hydride

• [PF6]-hexafluoro-λ5-phosphanuide (substitutive), or hexafluoridophosphate(l-) (additive)

• SO32-trioxidosulfate(2-) (additive), or sulfite (acceptable non-systematic name) Specifying Proportions Using Charge or Oxidation State An alternative to “di-”, “tri ” prefixes is to use either charge or oxidation state. Charge is preferred as oxidation state may be ambiguous and open to debate.

Substitutive Nomenclature In general, this naming method follows established IUPAC organic nomenclature. Hydrides of the main group elements (groups IIIA-VIIA) are given “-ane” base names e.g., BH3, borane; Si H4, silane. In these cases, use the base name for substituted derivatives. But there are some exceptions, for example, water rather than oxidane, and ammonia rather than azane are used.

Naming of Hydrates and Similar Lattice Compounds

The use of the term, hydrate, is still acceptable (e.g., Na2SO4•10H2O, sodium sulfate decahydrate). It is recommended to name it sodium sulfate-water(l/10). Similarly other examples of lattice compounds are:

• Ca Cl2-8NH3calcium chloride-ammonia (1/8)

• 2Na2CO3-3H2O2sodium carbonate-hydrogen peroxide (2/3)

• Al Cl3•4Et OH aluminium chloride-ethanol (1/4)

Coordination Compounds

Coordination compounds are a large class of compounds discussed in inorganic chemistry textbooks. Examples range from strictly inorganic species, such as [Co(NH3)6]Cl3, to organometallic compounds such as Fe(C5H5)2, and extending to bioinorganic compounds, such as the hydrogenase enzymes.

Naming Mononuclear Coordination Compounds

Naming mononuclear compounds can be summarized very briefly:

1. Identify the central atom.

2. Identify and name the ligands.

3. Specify coordination mode of ligands, i.e. using k (kappa) and/or r\ (eta) conventions.

4. Sequence the ligands.

5. Specify coordination geometry, i.e. polyhedral symbol, configuration index, and absolute configuration for optically active compounds.

Anionic Ligands If the anion name ends in “-ide”, its name is changed to end in“-o” as a ligand. For example the chloride anion, Cl- becomes a chlorido ligand. This is different from organic compound naming and substitutive naming where chlorine is treated as neutral and it is chloro, as in PC13, which can be named either substitutively as trichlorophosphane or additively as trichloridophosphorus.

Similarly if the anion names end in “-ite” or “-ate”, their ligand names are “-ito” or “-ato”.

Neutral Ligands Neutral ligands do not change name except the following:

• Water, “aqua”

• Ammonia, “ammine”

• Carbon monoxide bonded via carbon “, carbonyl”

• Nitrogen monoxide bonded via nitrogen, “nitrosyl”

The following are examples of ligand names:

Sequence and Position of Ligands and Central Atoms Ligands precede the central atom name and are ordered alphabetically by name. The number of ligands coordinating is indicated by the prefixes “di-”, “tri-”, “tetra-”, “penta-”, etc., for simple ligands or “bis-”, “tris-”, “tetrakis-”, etc., for complex ligands.

• [Co Cl(NH3)5]Cl2pentaamminechloridocobalt (2+) chloride where ammine (NH3) precedes chloride

The name of the central atom comes after the ligands. When there is more than one central atom it is preceded by “di-”, “tri-”, “tetra-”, etc.

• Os3(CO)12dodecacarbonyltriosmium

Where there are different central atoms they are sequenced according to the electronegativity list.

• [Re Co(CO)9] nonacarbonylrheniumcobalt