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Unformatted text preview: eous solution. Other 7-coordinate macrocyclic
In"' complexes of potential relevance in radiopharmaceutical applications have been prepared,
including [InL] where L is the triacetate of the
tetraaza macrocycle shown in Fig. 7.18(a).(70)In
this case the coordination polyhedron is a trigonal
prism with one of its quadrilateral faces capped
by a carboxylate 0 atom as shown schematically
in Fig. 7.18(b).
Indium clusters have also recently been characterized, notably in intermetallic compounds.
Thus, the Zintl phase, Rb2In3, (prepared by direct
reaction between the two metals at 1530°C) has
layers of octahedral closo-In6 clusters joined into
sheets through exo bonds at four coplanar verti~es.(~l)
These four In atoms are therefore each
bonded to five neighbouring In atoms at the
comers of a square-based pyramid, whereas the
remaining two ( trans) In atoms in the In6 cluster
70 A. RIESEN, . A. KADEN, . RITTER and H. A. MACKE,
J . Chem. SOC., hem. Commun., 460-2 (1989).
S . C. SEVEOV J . D. CORBETT,. anorg. allg. Chem.
619, 128-32 (1993). show pyramidal 4-fold bonding only, to contiguous In atoms in the same cluster. Cs2In3
is isostructural. The intermetallic compound
K3Na26In48 (synthesized from the elements in
sealed Nb ampoules at 600°C) has a more complicated structure in which the In forms both
closo icosahedral In12 clusters and hexagonal
antiprismatic In12 clusters.(72)All the various In12
clusters are interconnected by 12 exo bonds forming a covalent 3D network (In-In 291-315 pm)
and the In12 hexagonal antiprisms are additionally
centred by single Na atoms. The phase contains
several other interesting structural features and
the original paper (in English) makes rewarding
reading. 7.3.6 Organometallic compounds
Many organoaluminium compounds are known
which contain 1, 2, 3 or 4 A1-C bonds per A1
atom and, as these have an extensive reaction
chemistry of considerable industrial importance,
they will be considered before the organometallic
compounds of Ga, In and TI are discussed.
72 W. CARRILLO-CABRERA, AROCA-CANALES,ETERS
and H. G. VON S CHNERING, anorg. allg. Chem. 619,
1556-63 (1993). 258 Aluminium, Gallium, Indium and Thallium Organoaluminium Compounds
Aluminium trialkyls and triaryls are highly
reactive, colourless, volatile liquids or lowmelting solids which ignite spontaneously in
air and react violently with water; they should
therefore be handled circumspectly and with Ch. 7 suitable precautions. Unlike the boron trialkyls
and triaryls they are often dimeric, though
with branched-chain alkyls such as Pr', Bu'
and Me3CCH2 this tendency is less marked.
A12Me6 (mp 15", bp 126") has the methylbridged structure shown and the same dimeric
structure is found for &Ph6 (mp 225"). Applications of III-V Semiconductors
The 9 compounds that Al, Ga and In form with P, As and Sb have been extensively studied because of their many
applications in the electronics industry, particularly those centred on the interconversion of electrical and optical (light)
energy. For example, they are produced commercially as light-emitting diodes (LEDs) familiar...
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