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Title: [Metal alkoxides---models for metal oxides: Alkoxide ligands in early transition metal organometallic chemistry]. Progress report

Abstract

An effort was made to compare and contrast the reactivity of trialkylsiloxide vs tert-butoxide supported dinuclear centers, and an initiative aimed at studying the syntheses of polynuclear hydridoalkoxides and their reactions has been implemented.

Publication Date:
Research Org.:
Indiana Univ., Bloomington, IN (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10147710
Report Number(s):
DOE/ER/13570-7
ON: DE93013260
DOE Contract Number:
FG02-86ER13570
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: [1992]
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; TUNGSTEN COMPLEXES; ORGANOMETALLIC COMPOUNDS; PROGRESS REPORT; ALKOXIDES; CHEMICAL REACTIONS; 400201; CHEMICAL AND PHYSICOCHEMICAL PROPERTIES

Citation Formats

Not Available. [Metal alkoxides---models for metal oxides: Alkoxide ligands in early transition metal organometallic chemistry]. Progress report. United States: N. p., 1992. Web. doi:10.2172/10147710.
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Not Available. [Metal alkoxides---models for metal oxides: Alkoxide ligands in early transition metal organometallic chemistry]. Progress report. United States. doi:10.2172/10147710.
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Not Available. Thu . "[Metal alkoxides---models for metal oxides: Alkoxide ligands in early transition metal organometallic chemistry]. Progress report". United States. doi:10.2172/10147710. https://www.osti.gov/servlets/purl/10147710.
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@article{osti_10147710,
title = {[Metal alkoxides---models for metal oxides: Alkoxide ligands in early transition metal organometallic chemistry]. Progress report},
author = {Not Available},
abstractNote = {An effort was made to compare and contrast the reactivity of trialkylsiloxide vs tert-butoxide supported dinuclear centers, and an initiative aimed at studying the syntheses of polynuclear hydridoalkoxides and their reactions has been implemented.},
doi = {10.2172/10147710},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Dec 31 00:00:00 EST 1992},
month = {Thu Dec 31 00:00:00 EST 1992}
}
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Technical Report:
View Technical Report (0.36 MB)
DOI:  10.2172/10147710
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  • Alkoxide clusters of molybdenum and tungsten provide structural models for the oxides of these elements in their lower valencies. The steric bulk of a given alkoxide ligand allows for the molecular design of unsaturated species which may model surface sites. The organometallic chemistry of these alkoxides clusters is being investigated. Activation of alkynes and carbon monoxide by these clusters leads to alkylidyne and carbido species. This 6 electron reduction of the substrate parallels surface chemistry wherein chemisorbed X identical to Y molecules (X, Y = C, N, O) are cleaved leading to surface bound carbido, nitrodo, alkylidyne and oxo ligands.more » Addition of RO-H to certain tungsten clusters leads to hydridoalkoxide clusters which have been found to be catalytically active in olefin isomerization. Current work is aimed at studying the reactivity of these alkoxide clusters as models for heterogeneous catalysts. This work provides a new dimension to organometallic cluster chemistry and is expected to yield mechanistic information of fundamental importance in the understanding of the activation of small molecules.« less

  • An effort was made to compare and contrast the reactivity of trialkylsiloxide vs tert-butoxide supported dinuclear centers, and an initiative aimed at studying the syntheses of polynuclear hydridoalkoxides and their reactions has been implemented.

  • Structural analogies between polynuclear metal alkoxides/metal oxoalkoxides and metal oxides have been noted, with the former providing models for the subunits within the extended networks of the latter. The presence of metal-metal bonds imposes a rigidity to alkoxide clusters in solution and the nuclearity of the cluster is maintained. The ability of alkoxide ligands to act as terminal or bridging ligands (..mu../sub 2/ and ..mu../sub 3/) and to respond to electron-deficient metal centers by ..pi.. donation, together with their ability to interconvert between these various modes of bonding allows for the uptake and release of substrate molecules. An extensive organometallicmore » chemistry supported by alkoxide ligands is emerging. Key findings during the reporting period have been: (1) the reduction of carbon-monoxide by molybdenum and tungsten alkoxides; (2) the coupling, co-coupling and sometimes metathesis-like reactions between C-C, C-N, and M-M triple bonds supported by alkoxide ligands; (3) unusual ..beta..-hydrogen effects in alkyl ligands bonded to M/sub 2/(OR)/sub x/ centers; (4) the isolation of quadruple bonds between Mo atoms supported by RO ligands; (5) the synthesis of new hydrido-tungsten alkoxides of formula NaW/sub 2/(H)(OR)/sub 8/; and (6) the synthesis and characterization of the first examples of carbido, nitrido, imido and alkylidyne clusters of tungsten and molybdenum supported by alkoxide ligands. MO calculations employing Extended Huckel or Fenske-Hall methods have been performed on several of these cluster alkoxides and the results compared with observed spectrochemical and electrochemical data.« less

  • Structural analogies between polynuclear metal alkoxides and metal oxides have been noted, with the former providing models for subunits within the extended networks of the latter. An extensive organometallic chemistry supported by alkoxy ligands is emerging. Their facile interconversion between terminal and bridging positions and between sigma/sup 2/ and (sigma/sup 2/ + ..pi../sup 2/) donors allows for easy uptake and release of substrate molecules. Key reports during the 1984 to 1985 period are: (1) the cleavage of C identical with O to carbido and oxo tungsten alkoxide clusters; (2) the coupling, co-coupling, and sometimes metathesis-like reactions (M = W) betweenmore » C idential with C, C identical with N and M identical with M bonds in M/sub 2/(OR)/sub 6/ compounds; (3) unusual ..beta..-hydrogen effects in dinuclear alkyl-alkoxides of molybdenum; and (4) the isolation of Mo-Mo quadruply bonded compounds supported by alkoxide ligands. Recent developments have led to general synthesis of hydridoditungsten alkoxide anions W/sub 2/(..mu..-H)(OR/sub 8//sup -/ which have been isolated as sodium salts. New nitrido and amido clusters have been discovered, Mo/sub 4/(..mu../sub 3/-N)/sub 2/(OPr/sup i/)/sub 12/ and W/sub 3/(..mu../sub 3/-NH)OPr/sup i/)/sub 10/ which may provide models for the Haber synthesis of NH/sub 3/ from N/sub 2/ and H/sub 2/.« less

  • During the past 12 months work has continued on the cleavage of carbon monoxide by W{sub 4}(OCH{sub 2}R){sub 12} compounds. This reaction occurs under extremely mild conditions in hydrocarbon solvents. We have initiated a study of the reactivity of the hydride ligand in the compounds W{sub 2}({mu}-H)(O-cyclo-pentyl){sub 7}L where L = a substitutionally labile ligand. We know that it reacts with a variety of unsaturated molecules including ethylene, allene, acetylene, nitriles, ketones, carbon monoxide and carbon dioxide. The products and the details of these reactions are under investigation. In a new initiative we have started to look at the chemistrymore » of some siloxide supported Mo and W clusters. The simple dinuclear siloxide W{sub 2}(OSiBu{sup t}Me{sub 2}){sub 6} (M {equivalent to} M) shows a remarkable rich chemistry and one that is surprisingly different from the structurally related W{sub 2}(OR){sub 6} compounds.« less