New extended clusters in ternary molybdenum oxides

Three new compounds representative of different structure types in the family of ternary metal oxides with extended metal-metal bonded arrays are discussed. InMo 4O 6 (isomorphous with NaMo 4O 6) contains infinite anion chains of condensed octahedral cluster units, (Mo 4O 6 −) ∞, crosslinked to form channels where In + cations reside in sites of square pyramidal coordination to oxygen. The linear array of In atoms in the channels, with d(In-In)=2.8628(4) Å, suggests some degree of In-In bonding, and these interactions may contribute to the metallic conductivity determined for this compound over the range 2–300 K. Infinite chains with Mo 2O 4 repeat units condensed as rhomboidal clusters fused on opposite edges are the outstanding structural feature of NaMo 2O 4. The compound also has a doublelayer lattice MoO 2 with Na + ions fractionally occupying octahedral coordination sites between alternate layers. The compound Ca 5.45Mo 18O 32 contains three different kinds of cluster chains with Mo 1, Mo 2, and Mo 4 repeat units. Metal cluster electron counts on the three different repeat units, estimated from Mo-O bond strength-bond distance relations, are reflected in the formula Ca 5.45(MoO 3 2.26−) 2(Mo 2 O 3.5 0.22−) 4(Mo 4O 6 2.65−) 2.