Metal cluster topology 19. Beyond the auride ion: triangulated gold networks and ethane-like structural units in binary and ternary alkali metal gold intermetallics

摘要

The range of known structurally characterized alkali metal gold intermetallics now extends Ear beyond the simple 'auride' derivatives CsAu and RbAu containing the discrete auride ion, Au-, isoelectronic with Hg-O. The structurally characterized binary alkali metal gold intermetallics M(2)AU(3) (M = K, Rb), Rb3Au7 and MAu5 (M = K, Rb) contain infinite triangulated anionic gold subnetworks which can be constructed from linear sp-hybridized gold atoms linked to each other through multicenter bonding within Au, tetrahedra (for Rb3Au7), Au-4 butterflies (for M2Au3) or Au-5 trigonal bipyramids (for MAu5). The infinite anionic gold subnetworks in other alkali metal gold intermetallics provide examples of two-coordinate gold in Na2Au; four-coordinate gold in AeAu(2) (Ae = Ca, Sr). Na2LiAu3 and NaAuGe; and six-coordinate gold in MAu2 (M = Na, K) and NaAuIn2. More complicated gold structures are found in other sodium-gold-indium ternary intermetallics including In-centered Au-12 and empty Au-6 octahedra in Na2Au6In5 as well as squashed Au6In pentagonal bipyramids in Na8Au11In6. Many ternary gold intermetallics (E = Ge, In) also contain ethane-like E2Au6 units with unbridged E-E bonds (e.g., K4Au7Ge2, NaAuGe, and NaAuIn2) or diborane-like E2Au6 units with E-E bonds bridged by two gold atoms (e.g., Na2Au6In5). (C) 1998 Elsevier Science S.A. All rights reserved. [References: 44]