Page 51 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

O R G A N O M E T A L L I C C O M P O U N D S IR-10.3

referred to as ‘cyclooctatetraenyl’. This name is incorrect as it can only be used for the
(as yet hypothetical) ligand C 8 H 7 .

IR-10.3 N O M E N C L A T U R E O F O R G A N O M E T A L L I C C O M P O U N D S
O F T H E M A I N G R O U P E L E M E N T S

IR-10.3.1 Introduction

The nomenclature of organometallic compounds of the main group elements is an area of
current and ongoing development. This section b riefly describes key aspects of the naming
of such compounds, leaving a f ull treatment of the subject to a f uture IUPAC project.
Detailed i nformation on the nomenclature of organic compounds containing the elements of
groups 13–16 may be found in Sections P-68 and P-69 of Ref. 3.
In principle, all organometallic compounds, whether of the transition or main group
elements, can be given n ames based on the additive system of nomenclature that is applied
to coordination compounds, p rovided the constitution of the compound is known. Examples
of such names were given in Sections IR-7.2 and IR-7.3. I n a ddition, compounds of elements
such as boron, silicon, arsenic and selenium are often considered to be organometallic, a nd
are commonly named by notionally substituting the hydrogen atoms of the parent hydride
with the appropriate substituent g roups.
If a c hoice must be made, it is recommended here that organometallic compounds
derived from the elements of groups 13–16 be named by a s ubstitutive process, while
those derived from the elements of groups 1 a nd 2 b e n amed using t he additive system
of nomenclature or in some c ases j ust compositional nomenclature if less structural
information is to be conveyed. Where an organometallic compound c ontains two or more
central atoms (which may be associated with different nomenclature systems according to
the above recommendation), a choice must again be made to provide the basis of the name.
A g eneral rule is recommended i n S ection IR-10.4.

IR-10.3.2 Organometallic compounds of groups 1 and 2
Organometallic compounds of the elements of groups 1 a nd 2 w ith a d efined coordination
structure are named according to the additive system of nomenclature, the general
definitions and rules of which are given in Chapter IR-7 and Sections IR-9.1 and IR-9.2.
Thus, prefixes denoting the organic groups and any other l igands are placed in alphabetical
order before the name of the metal. These prefixes may adopt either the additive ‘ido’,
‘diido’, etc. e ndings or, in the case of hydrocarbyl groups, the substitutive ‘yl’, ‘diyl’, etc.
endings (see Sections IR-10.2.2 and IR-10.2.3). The l atter practice allows n ames in common
usage for organic groups to be applied unchanged. The presence of a h ydrogen atom
attached to the metal centre must always be indicated (by the prefix ‘hydrido’) and the name
of a c yclic compound with the central atom in the ring m ay be formed using appropriate
locants of a d ivalent ‘ diido’ or ‘diyl’ group to indicate chelate-type bonding to the metal, as
in Example 5 b elow.

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