718b indium clusters have also recently been

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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, T W J . Chem. SOC., hem. Commun., 460-2 (1989). C S . C. SEVEOV J . D. CORBETT,. anorg. allg. Chem. and Z 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 N. C K. P and H. G. VON S CHNERING, anorg. allg. Chem. 619, Z. 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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This note was uploaded on 10/12/2012 for the course CHEMISTRY CHM1040 taught by Professor Jhon during the Spring '12 term at Florida A&M.

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