Synthesis and characterization of novel Group VI metal (Mo, W) nitride and oxide compounds

dc.contributor.advisor Robert E. McCarley
dc.contributor.author Zhang, Zhihong
dc.contributor.department Chemistry
dc.date 2018-08-23T05:08:39.000
dc.date.accessioned 2020-06-30T07:14:03Z
dc.date.available 2020-06-30T07:14:03Z
dc.date.copyright Wed Jan 01 00:00:00 UTC 1997
dc.date.issued 1997
dc.description.abstract <p>Binary Group VI metal nitrides are characterized by thermodynamic instability towards dissociation to N2 and the N-saturated elements at high temperature. Our investigations into the preparation of tungsten nitrides have involved the synthesis of molecular precursors, and their conversion to tungsten nitrides at relatively low temperatures. Two interesting molecular precursors, (WNCl3·NCCH3] 4 and WN(N3)3· xNCCH3, have been prepared and characterized. The molecular structure of (WNCl3·NCCH3] 4 consists of a W4N4 tetrameric core with multiple and single W-N bonds arranged in an alternating fashion. Three new solid state phases, amorphous W3N5, cubic WN, and W2N2(C2N2), have been discovered by solid state and chemical vapor transport reactions. Cubic WN has a rock salt structure. W2N2(C2N2) has a novel three-dimensional network structure consisting of W2 dimers, hydrazido ligands N24-, and 1,4-diazabutenido ligands represented by three resonance structures, (N-C=C-N) 6-, (N=C-C-N) 6- and (N-C-C=N) 6-;Ternary reduced molybdenum oxides have caused great interest, since the discovery of NaMo4O6 containing trans-edge-shared Mo6 octahedra. Recent investigations have yielded a new family of LnMO8O14 compounds containing cis- and trans-Mo8 bicapped octahedra. A systematic study in the Ln2O3-MoO3-MO (Ln = La, Ce, Pr, Nd, Sm) system has been explored to better understand LnMO8O14. The study has shown that the sizes of the rare-earth cations affect the formation of these phases. Larger cations (La, Ce, and Pr) aid in the formation of trans-Mo8 bicapped octahedra, and the smaller cations (Nd, Sm) only stabilize the cis-Mo8 bicapped octahedra. Magnetic susceptibility measurements have indicated that no effective moment contribution arises from the Mo8 metal clusters, even though the cis-Mo8 cluster in LnMo8O14, containing all cis-Mo8 octahedra, apparently contains an odd number of electrons (23). Electrical resistivity measurements and electronic structure calculations have shown that the LnMo8O14 compounds containing cis-Mo8 clusters are metallic, and the LnMo8O14 compounds containing a 1:1 ratio of cis- to trans-Mo8 clusters are semiconducting.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/rtd/11580/
dc.identifier.articleid 12579
dc.identifier.contextkey 6455537
dc.identifier.doi https://doi.org/10.31274/rtd-180813-4944
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath rtd/11580
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/64853
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/rtd/11580/r_9814717.pdf|||Fri Jan 14 18:53:21 UTC 2022
dc.subject.disciplines Inorganic Chemistry
dc.subject.keywords Chemistry
dc.subject.keywords Inorganic chemistry
dc.title Synthesis and characterization of novel Group VI metal (Mo, W) nitride and oxide compounds
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication 42864f6e-7a3d-4be3-8b5a-0ae3c3830a11
thesis.degree.level dissertation
thesis.degree.name Doctor of Philosophy
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