New pathways to tungsten and molybdenum oxides, nitrides and azides

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6973748

Close, M R

This research effort focused on the use of both inorganic solution synthesis of molecular precursors and solid state reactions involving molecular compounds to yield desired condensed materials. Two types of molecular compounds have been investigated. First, trichloronitridotungsten(VI) ([WNCl[sub 3]][sub 4]) has been prepared using an improved synthetic approach and characterized structurally by single crystal X-ray diffraction techniques. [WNCl[sub 3]][sub 4] crystallizes in the space group P1 as planar 8- membered W-N rings interconnected through chloride bridges. The inter-tetramer linkage is weak and broken easily to accommodate basic ligands in the site trans to the W-N triple bond. The reactivity of WNCl[sub 3], with nitriding agents, such as ammonia, ytrimethylsilylazide and lithium nitride, has been investigated, which resulted in the preparation and spectroscopic identification of new tungsten azido and nitrido compounds. Second, the reactivity of the metal dimers Mo[sub 2] (O[sub 2]CCH[sub 3])[sub 4] and Mo[sub 2]Cl[sub 4]py[sub 4] with trimethylsilylazide has been explored, and the reactions in pyridine were found to yield a material corresponding to the formulation MoN (N[sub 3])py. Thermolytic decomposition of this azide at 280[degrees]C was performed under argon, dynamic vacuum or ammonia. The thermal decomposition in ammonia was found to produce a molybdenum nitride relatively free of carbon (5%, compared to 24% in materials decomposed in inert environments) with a Mo:N ratio of 1:1.8. Through the use of solid state reactions, WNCl[sub 3] was converted into a hexagonal ammonium tungsten bronze, (NH[sub 4])[sub 0.28]WO[sub 3[minus]y] (NH)[sub y]. Relative to conventional preparations, this new ammonium bronze synthesis increased the probability of isoelectronic imido substitution for oxide in the bronze framework.

• Research Organization: Iowa State Univ. of Science and Technology, Ames, IA (United States)
• OSTI ID: 6973748
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201 -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AZIDES
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
KINETICS
MATERIALS
MOLYBDENUM COMPOUNDS
MOLYBDENUM NITRIDES
MOLYBDENUM OXIDES
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
SEMICONDUCTOR MATERIALS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN COMPOUNDS
TUNGSTEN NITRIDES
TUNGSTEN OXIDES