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Unformatted text preview: very high nuclearity have been obtained, often
by thermolysis. These are especially numerous
for Rh and in certain Rh13, Rhl4 and Rh15 anions
have structures conveniently visualized either as
polyhedra encapsulating further metal atoms, or
alternatively as arrays of metal atoms forming
portions of hexagonal close packed or body centred cubic lattices stabilized by CO ligands.
[Rhl3H3(C0)24I2- (Fig 26.9a) is typical.
The anionic cluster [Ir,j(CO)1,]2- is octahedral
and an increasing number of Ir clusters have been
reported recently though their preparations are
more difficult and yields usually smaller than for
rhodium. [1rl4(CO)27]- has the highest nuclearity
so far and is obtained as black crystals by
oxidizing [Ir6(C0)15l2- with ferricinium ion(40)
The incorporation of interstitial or encapsulated
heteroatoms is a common and stabilizing feature.
Carbon is the most common and, as is the case in
40 R. D. PERGOLA, L. GARLASCHELLI, M. MANASSERO,
N. MASCIOCCHI P. ZANELLO, ngew. Chem. Int. Edn.
Engl. 32, 1347-9 (1993). 1142 Cobalt, Rhodium and Iridium Ch. 26 Figure 26.9 Schematic representations of the metal cores of some clusters of group 9 metals.
(a) [Rh13H3(C0)24]2-;the H atoms migrate within the cluster. (b) [Iri4(CO)27]-.( c) [Rh&(CO),s]*-.
(d) [Rh8C(C0)19]; a trigonal prism of 6 Rh atoms has one face capped by a seventh Rh atom
and one edge bridged by the eighth Rh atom. (e) [co8c(co)~8]2-;the 8 C o atoms define a
distorted bicapped trigonal prism which, alternatively, can be viewed as a distorted square antiprism.
( f) [Rhi 2(C2)(CO)25I. group 8 (p. 1107), ma...
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