33654_31a - Previous Page 31.3 Compounds of the actinides Table 31.4 Oxidation states and stereochemistries of compounds of the actinides An is

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§31.3 Compounds of the actinides 1267 Table 31.4 Oxidation states and stereochemistries of compounds of the actinides “An” is used as a general symbol for the actinide elements Oxidation Coordination state number Stereochemistry Examples 0 16 See Figs. 19.31 and 31.10 [An(q8-C8H8)2] (An = Th + Pu), [u(v8-c8&ph4)z1 3 6 Octahedral [AIIC~~]~- (An = Np, Am, Bk) 8 Bicapped trigonal prismatic 9 Tricapped trigonal prismatic AnC13 (An = U -+ Cm) AnC13 (X = Br, An = Pu + Bk; X = I, An = Pa + Pu) 15 Seep. 1278 [ThIo5-C5H3(SiMe3)z131 4 4 Complex U(NPW4 5 Trigonal bipyramidal U2(NEtz)8 6 Octahedral 7 Pentagonal bipyramidal UBr4 8 Cubic [An(NCS)814- (An = Th [An&]’- (An = U, Np, Pu; X = C1, Br) Dodecahedral Square antiprismatic Capped square antiprismatic Complex [Th(N03 )4(0PPh )21‘”) [Th(C2O4hl4-, [An(SzCNEthI (An = Th, U, Np, h) [An(acac)4] (An = Th, U, Np, Pu) [Th( tropolonate)4 (H2 O)] 9 Tricapped trigonal prismatic (NH4)3[ThF71 10 Bicapped square antiprismatic &[Th(C204)4].4H20 11 See Fig. 3 1 .Sa [TWO3 )4(H20)3 1.2Hz0 14 Bicapped hexagonal antiprismatic [U(BH4)4] 20 See Fig. 31.9 [An(v5GH5)41 (An = Th, U) 12 Icosahedral [Th(N03)6]2-(a) 5 6 Octahedral Cs[AnF6] (An = U, Np, 7 Pentagonal bipyramidal PaCl5 8 Cubic Na3[AnFs] (An = Pa, U, Np) 9 Tricapped trigonal prismatic M2[PaF7] (M = Nb, K, Rb, CS) 6 6 Octahedral An& (An = U, Np, Pu), UCl6, CS~[UO~&](~) (X = I Pentagonal bipyramidal [UO2(S2CNEt2)2(0NMe3)lfb) 8 Hexagonal bipyramidal [UOP(N~~)~(H~~)ZI(~) 7 6 Octahedral Lis[An06] (An = Np, ‘a)These compounds are isostmctural with the corresponding compounds of Ce (see Fig. 30.5, p. 1245) and can be visualized as octahedral if each NO3- is considered to occupy a single coordination site. ‘b”I’he polyhedra of these complexes are actually flattened because the two trans U-0 bonds of the U0z2+ group are shorter than the bonds to the remaining groups which form an equatorial plane. now to be found in the +4 oxidation state rather than +3 as in the lanthanides. Compounds with many non-metals are prepared, in principle simply, by heating the elements. 22 G. MEYER and L. R. MORS (eds.) Synthesis of Lanfha- mide and Actinide Compounds, Kluwer, Dordrecht, 1991, 367 pp. 23 K. W. BAGNALL, Chap. 40, pp. 1129-228, in Compre- hensive Coordination Chemistty, Vol. 3, Pergamon Press, Oxford, 1987. 241. SANTOS, A. P. de MATOS and A. G. MADDOCK, Adv. Inorg. Chem. 34, 65-144 (1989). Hydrides of the types AnH2 (An = Th, Np, PU, Am, Cm) and AnH3 (Pa + Am), as well as Th4H15 (i.e. ThH3.75) have been so obtained but are not very stable thermally and are decidedly unstable with respect to air and moisture. Borides, carbides, silicides and nitrides (4.v.) are mostly less sensitive chemically and, being refractory materials, those of Th, U and in particular have been studied extensively as possible nuclear f~els.(’~,~~) Their stoichiometries are very varied but the more important ones are the semi-metallic monocarbides, AnC, and mononitrides, AnN, all of which have the rock-salt structure: they are predominantly ionic 25 K. NAITO and N. KAGEGASHIRA, Adv. Nucl. Sei. Tech.
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33654_31a - Previous Page 31.3 Compounds of the actinides Table 31.4 Oxidation states and stereochemistries of compounds of the actinides An is

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