Page 32 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

IR-10.2 O R G A N O M E T A L L I C C O M P O U N D S

H 2
C
M C H 2
M M
μ-methylene methylidene

Likewise, the ligand HC will have at least three different bonding modes: bridging t hree
metals (m 3 -methanetriyl), b ridging t wo metals ( m-methanylylidene) a nd coordinating to one
metal (methylidyne, see Section IR-10.2.4).
H H
C C
M M M C H
M M M
μ -methanetriyl μ-methanylylidene methylidyne
3

In a b ridging m ode the ligand CH 2 CH 2 should b e c alled m-ethane-1,2-diyl, while the same
2
ligand coordinating through both carbon atoms to a s ingle metal centre should b e c alled Z -
ethene (see Section IR-10.2.5).

H 2 H 2 H C 2 C H 2
C C
M M M
2
μ-ethane-1,2-diy1 η -ethene
A s imilar situation arises with CHCH which, when bridging w ith the carbon atoms
individually bonded to each of two metals, should b e c alled m-ethene-1,2-diyl or, when the
metal-carbon bonds are double, m-ethanediylidene (see Section IR-10.2.4). The same l igand
coordinating through both carbon atoms to both metal centres should b e c alled m-ethyne;
2
when coordinated through both carbons to one metal it is named Z -ethyne (see Section
IR-10.2.5).

H H H H
C C C C
M M M M
μ-ethene-1,2-diyl μ-ethanediylidene

HC
CH HC CH
M M M
2
2
2
μ-η :η -ethyne η -ethyne
IR-10.2.3.2 Chelating ligands
Where a c helating ligand is formed by removing t wo or more h ydrogen atoms from a p arent
compound, t he atoms with free valencies, understood to form the bonds to the central atoms,
are indicated by using the appropriate ligand name (such as propane-1,3-diyl), cf. S ection
IR-10.2.3. This is demonstrated in Examples 1–3 below. Note that an alternative
nomenclature for such metallacycles is currently being developed.

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