Metal-metal bonded compounds of lower-valent niobium and tantalum /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy Link to ProQuest copy |
| Abstract: | A series of reductions of the niobium and tantalum pentachlorides in poorly coordinating solvents followed by the addition of coordinating ligands are described. All the synthesized compounds are characterized by X-ray crystallography. The reduction of TaCl5 with two equivalents of Na/Hg in aromatic solvents followed by addition of THF results information of Ta3Cl9(THF)4*C6H6*THF,1 or Na[Ta3Cl10(THF)3], 2, depending on the ration of the aromatic solvents to THF. The preparation of Na[Nb3Cl10(THF)]*3THF, 3, was accomplished by the reduction of slurry of NbCl4(THF)2 in THF with on equivalent of Na/Hg. Compound 1-3 contain an equilateral triangle of metal atoms capped by one and bridged by three chlorine atoms. The metal-metal separations are approximately 2.85 Å indicating a single bond between the metal atoms. The reduction of TaCl5 with one equivalent of Bu[^n]3 SnH in benzene affords a green solution from which crystals of Sn[Ta2Cl9]2*C6H6, 4, are isolated. The precipitate from this reaction dissolves in THF resulting in compound 1. In the solid state the Sn[^2+] cation of compound 4 interacts with eight terminal chlorine atoms of four [Ta2Cl9]- anions (average Sn-Cl distance of 2.918[9]Å) and the geometry about it may be considered as a square antiprism. Due to the Sn-Cl interactions the Ta2Cl9, a face sharing bioctahedron dimer possessing a single metal-metal bond, is severely distorted. The reduction of NbCl5 with Na/Hg in toluene followed by addition of PhSSPh, THF, and PMe2Ph results in brick - orange solution from which crystals of Nb4S2(SPh)8(PMe2Ph)4*C6H8, 5, are isolated. In this cluster the four niobium and two sulfur atoms form a tetragonal bipyramid with sulfur atoms at the apices. The mean Nb-Nb and Nb-S distances are 2.816[8]Å and 2.491[3]Å respectively. The Nb atoms are bridged by two PhS- groups and one PMe2Ph ligand is coordinated to each metal atom. Identical reagents to prepare 5, but in different stoichiometry, were used to study the reduction of TaCl5. From this reaction only the dinuclear Ta2S2Cl4(PMe2Ph)4, 6, was isolated... |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemistry." |
| Physical Description: | xiii, 141 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |