Synthesis and structural studies of reduced ternary tantalum oxides and intercalation studies of group VB metal oxides

High temperature methods were utilized to synthesize a variety of reduced ternary tantalum oxides. Two basic classes of compounds were studied, those in the tetragonal tungsten bronze (TTB) structure and those containing isolated {dollar}rm Tasb6Osb{lcub}12{rcub}{dollar} clusters. Single crystal x-ray diffraction determined that {dollar}rm Basb3Tasb5Osb{lcub}15{rcub}{dollar} crystallizes in the TTB structure (space group P4/mbm) with a = 12.590(1) A and c = 3.967(2) A. Powder diffraction studies of {dollar}rm Basb{lcub}3-x{rcub}Tasb5Osb{lcub}15{rcub}{dollar} and the observation of physical properties showed that this material can be classified as a metal oxide bronze. The europium and strontium analogs were also prepared.; The isolated {dollar}rm Tasb6Osb{lcub}12{rcub}{dollar} cluster compounds were synthesized in two structure types, {dollar}rm Msb2Tasb{lcub}15{rcub}Osb{lcub}32{rcub}{dollar} and {dollar}rm Ybsb3Tasb{lcub}14{rcub}Osb{lcub}32{rcub}Cl.{dollar} {dollar}rm Msb2Tasb{lcub}15{rcub}Osb{lcub}32{rcub}{dollar} (M = K, Sr, Ba, Eu) compounds crystallize in the space group R3 and are isostructural with {dollar}rm Basb2Nbsb{lcub}15{rcub}Osb{lcub}32{rcub}.{dollar} Three compounds were studied by single crystal x-ray diffraction, {dollar}rm Ksb2Tasb{lcub}15{rcub}Osb{lcub}32{rcub}{dollar} (a = 7.814(1) A, c = 35.733(6) A), {dollar}rm Basb2Tasb{lcub}15{rcub}Osb{lcub}32{rcub}{dollar} (a = 7.792(1) A, c = 35.494(4) A), and {dollar}rm Eusb2Tasb{lcub}15{rcub}Osb{lcub}32{rcub}{dollar} (a = 7.773(2) A, c = 35.165(4) A). Structurally, {dollar}rm Msb2Tasb{lcub}15{rcub}Osb{lcub}32{rcub}{dollar} is characterized by four types of tantalum environments; {dollar}rm Tasb6Osb{lcub}12{rcub}{dollar} clusters, {dollar}rm Tasb3Osb{lcub}13{rcub}{dollar} units, isolated Ta atoms, and cluster-linking Ta atoms. The linking Ta atoms are situated on 3-fold axes between clusters and are {dollar}sim{dollar}3.1 A from the nearest cluster tantalums. No Ta-Ta bonding occurs in the {dollar}rm Tasb3Osb{lcub}13{rcub}{dollar} units. Magnetic susceptibility measurements, valence bond sums, and a molecular orbital calculation are used to help understand these materials.; {dollar}rm Ybsb3Tasb{lcub}14{rcub}Osb{lcub}32{rcub}Cl{dollar} crystallizes in the hexagonal space group P6{dollar}sb3{dollar}/m with cell parameters of a = 7.792(1) A and c = 24.592(2) A. This structure is similar to that of {dollar}rm Msb2Tasb{lcub}15{rcub}Osb{lcub}32{rcub},{dollar} but the layer of isolated Ta atoms has been replaced by a layer of {dollar}rm Ybsb3Cl{dollar} units. Magnetic susceptibility measurements and valence bond sums established that the ytterbium cations are trivalent.; Intercalation studies were performed on both {dollar}rm LaNbsb3Osb9{dollar} and {dollar}rm LaTasb3Osb9.{dollar} Lithium and magnesium were used as guest materials in {dollar}rm LaNbsb3Osb9.{dollar} The magnesium occupancy (x = 1.5) was established by thermogravimetric analysis. Li intercalation into {dollar}rm LaTasb3Osb9{dollar} proceeded up to x = 0.8 using butyl lithium in hexane. Attempts to intercalate {dollar}rm Basb3Tasb5Osb{lcub}15{rcub}{dollar} with lithium were unsuccessful.