Page 49 - 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-10.2

Substituents on the equivalent cyclopentadienyl rings of the metallocene entity a re given the
lowest possible numerical locants in the usual manner. The first ring i s n umbered 1 –5 and
0
the second r ing 1 –5 (see Examples 9 and 10).
0
Examples:
9.
COMe

Os

COMe
0
0
0
1,1 -diacetylosmocene, or 1,1 -(osmocene-1,1 -diyl)bis(ethan-1-one)
10.

Fe

CH CO H
2
2
0
1,1 -(4-carboxybutane-1,3-diyl)ferrocene, or
0
3,5-(ferrocene-1,1 -diyl)pentanoic a cid
5
11. [Ru(Z -C 5 Me 5 ) 2 ]
decamethylruthenocene, or
5
bis(pentamethyl-Z -cyclopentadienyl)ruthenium
5
12. [Cr(Z -C 5 Me 4 Et) 2 ]
0
1,1 -diethyloctamethylchromocene, or
5
bis(1-ethyl-2,3,4,5-tetramethyl-Z -cyclopentadienyl)chromium
5
13. [Co(Z -C 5 H 4 PPh 2 ) 2 ]
1,1 -bis(diphenylphosphanyl)cobaltocene, or
0
0
(cobaltocene-1,1 -diyl)bis(diphenylphosphane)
Metallocene nomenclature does not, however, apply t o a ll transition elements. For example,
there are at least two isomers w ith the empirical formula C 10 H 10 Ti but neither has
the regular sandwich structure analogous to that of ferrocene, and so neither should b e n amed
5
‘titanocene’. Similarly, ‘manganocene’ i s a misnomer for [Mn(Z -C 5 H 5 ) 2 ] s ince it has a
chain structure in the solid state, with no individual sandwich entities. However,
5
decamethylmanganocene, [Mn(Z -C 5 Me 5 ) 2 ], has a n ormal sandwich structure, a s d oes
5
decamethylrhenocene, [Re(Z -C 5 Me 5 ) 2 ]. With increasing atomic n umber, the occurrence of
5
the classic f errocene-type bis(Z -cyclopentadienyl) sandwich structure becomes rare.
The name-ending ‘ocene’ should t herefore be confined to discrete molecules of
5
the form bis(Z -cyclopentadienyl)metal (and ring-substituted analogues), where the
cyclopentadienyl rings are essentially parallel, a nd the metal is in the d-block [i.e. t he
terminology does not apply t o c ompounds of the s- or p-block elements such as Ba(C 5 H 5 ) 2
or Sn(C 5 H 5 ) 2 ].
The oxidized s pecies have been referred to as metallocenium(nþ) s alts, although it
should be noted that in this case the ending ‘ium’ does not c arry the usual meaning it has
in substitutive nomenclature, i.e. the addition of a h ydron to a n eutral parent compound.

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