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Title: Dimolybdenum(III) complexes of -OSi(OtBu)3, -O2P(OtBu)2 and-OB[OSi(OtBu)3]2 as single-source molecular precursors tomolybdenum-containing, multicomponent oxide materials

Abstract

The following dimolybdenum complexes containing -OSi(O{sup t}Bu){sub 3}, -O{sub 2}P(O{sup t}Bu){sub 2}, and -OB[OSi(O{sup t}Bu){sub 3}]{sub 2} ligands have been synthesized and structurally characterized: Mo{sub 2}(NMe{sub 2}){sub 4}[OSi(O{sup t}Bu){sub 3}]{sub 2} (1), Mo{sub 2}(O{sup t}Bu)4[OSi(O{sup t}Bu){sub 3}]{sub 2} (2), Mo{sub 2}(NMe){sub 4}(OB[OSi(O{sup t}Bu){sub 3}]{sub 2}){sub 2} (3), Mo{sub 2}(NMe{sub 2}){sub 2}[-O{sub 2}P(O{sup t}Bu){sub 2}]{sub 2}[O{sub 2}P(O{sup t}Bu){sub 2}]{sub 2} (4), Mo{sub 2}(NMe{sub 2}){sub 2}[OSi(O{sup t}Bu){sub 3}]{sub 2}[-O{sub 2}P(O{sup t}Bu){sub 2}]{sub 2} (5), and Mo{sub 2}(NMe{sub 2}){sub 2}[-O{sub 2}P(O{sup t}Bu){sub 2}]{sub 2}OB[OSi(O{sup t}Bu){sub 3}]{sub 2} (6). The isolation and structural characterization of trans- and cis-isomers of complexes 4 and 5 (4a and 4b, 5a and 5b, respectively) are also reported. Studies of the thermal decompositions of the complexes (by thermogravimetric analysis and solution 1H NMR spectroscopy) were performed. Xerogels with approximate compositions of 2MoO{sub 1.5}{center_dot}2P{sub 2}O{sub 5} and 2MoO{sub 1.5}{center_dot}2P{sub 2}O{sub 5}{center_dot}2SiO{sub 2} were derived from 4a and 5a or 5b, respectively, via solution thermolyses (toluene). The as-synthesized (and dried) xerogels contain one equiv of HNMe{sub 2} per molybdenum center (by combustion analysis, IR spectroscopy, and thermogravimetric analysis), and these materials have high surface areas (up to 270 m{sup 2} g{sup -1}). Upon calcination at 300 C, the coordinated amines aremore » lost and the surface areas are significantly reduced (to 40 m{sup 2} g{sup -1} and <5 m{sup 2} g{sup -1} for the materials derived from 4 and 5a or 5b, respectively). Solid-state {sup 31}P MAS NMR spectroscopy suggests that the as-synthesized xerogels retain structural features of the starting molecular precursors, as indicated by the presence of resonances that correspond to both bridging and terminal -O{sub 2}P(O{sup t}Bu){sub 2} ligands. Upon calcination at 300 C, the resonances for bridging -O{sub 2}P(O{sup t}Bu){sub 2} groups are replaced by those for PO{sub 4}{sup 3-}. The material derived from 4 exhibits low activity and poor selectivity for the oxidative dehydrogenation (ODH) of propane to propylene. Cothermolyses of 4 and Bi[OSi(O{sup t}Bu){sub 3}]{sub 3} resulted in formation of Bi/Mo/P/Si/O materials with improved performance for the ODH of propane.« less

Authors:
;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director. Office of Science. Basic EnergySciences
OSTI Identifier:
917046
Report Number(s):
LBNL-54417
Journal ID: ISSN 0897-4756; CMATEX; R&D Project: 401701; BnR: KC0302010; TRN: US200816%%249
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 16; Related Information: Journal Publication Date: 2004; Journal ID: ISSN 0897-4756
Country of Publication:
United States
Language:
English
Subject:
37; AMINES; CALCINATION; COMBUSTION; DEHYDROGENATION; MOLYBDENUM; OXIDES; PERFORMANCE; PROPANE; PROPYLENE; PYROLYSIS; SPECTROSCOPY; SURFACE AREA; THERMAL GRAVIMETRIC ANALYSIS; TOLUENE

Citation Formats

Fujdala, Kyle L, and Tilley, T Don. Dimolybdenum(III) complexes of -OSi(OtBu)3, -O2P(OtBu)2 and-OB[OSi(OtBu)3]2 as single-source molecular precursors tomolybdenum-containing, multicomponent oxide materials. United States: N. p., 2004. Web. doi:10.1021/cm030563k.
Fujdala, Kyle L, & Tilley, T Don. Dimolybdenum(III) complexes of -OSi(OtBu)3, -O2P(OtBu)2 and-OB[OSi(OtBu)3]2 as single-source molecular precursors tomolybdenum-containing, multicomponent oxide materials. United States. doi:10.1021/cm030563k.
Fujdala, Kyle L, and Tilley, T Don. Thu . "Dimolybdenum(III) complexes of -OSi(OtBu)3, -O2P(OtBu)2 and-OB[OSi(OtBu)3]2 as single-source molecular precursors tomolybdenum-containing, multicomponent oxide materials". United States. doi:10.1021/cm030563k.
@article{osti_917046,
title = {Dimolybdenum(III) complexes of -OSi(OtBu)3, -O2P(OtBu)2 and-OB[OSi(OtBu)3]2 as single-source molecular precursors tomolybdenum-containing, multicomponent oxide materials},
author = {Fujdala, Kyle L and Tilley, T Don},
abstractNote = {The following dimolybdenum complexes containing -OSi(O{sup t}Bu){sub 3}, -O{sub 2}P(O{sup t}Bu){sub 2}, and -OB[OSi(O{sup t}Bu){sub 3}]{sub 2} ligands have been synthesized and structurally characterized: Mo{sub 2}(NMe{sub 2}){sub 4}[OSi(O{sup t}Bu){sub 3}]{sub 2} (1), Mo{sub 2}(O{sup t}Bu)4[OSi(O{sup t}Bu){sub 3}]{sub 2} (2), Mo{sub 2}(NMe){sub 4}(OB[OSi(O{sup t}Bu){sub 3}]{sub 2}){sub 2} (3), Mo{sub 2}(NMe{sub 2}){sub 2}[-O{sub 2}P(O{sup t}Bu){sub 2}]{sub 2}[O{sub 2}P(O{sup t}Bu){sub 2}]{sub 2} (4), Mo{sub 2}(NMe{sub 2}){sub 2}[OSi(O{sup t}Bu){sub 3}]{sub 2}[-O{sub 2}P(O{sup t}Bu){sub 2}]{sub 2} (5), and Mo{sub 2}(NMe{sub 2}){sub 2}[-O{sub 2}P(O{sup t}Bu){sub 2}]{sub 2}OB[OSi(O{sup t}Bu){sub 3}]{sub 2} (6). The isolation and structural characterization of trans- and cis-isomers of complexes 4 and 5 (4a and 4b, 5a and 5b, respectively) are also reported. Studies of the thermal decompositions of the complexes (by thermogravimetric analysis and solution 1H NMR spectroscopy) were performed. Xerogels with approximate compositions of 2MoO{sub 1.5}{center_dot}2P{sub 2}O{sub 5} and 2MoO{sub 1.5}{center_dot}2P{sub 2}O{sub 5}{center_dot}2SiO{sub 2} were derived from 4a and 5a or 5b, respectively, via solution thermolyses (toluene). The as-synthesized (and dried) xerogels contain one equiv of HNMe{sub 2} per molybdenum center (by combustion analysis, IR spectroscopy, and thermogravimetric analysis), and these materials have high surface areas (up to 270 m{sup 2} g{sup -1}). Upon calcination at 300 C, the coordinated amines are lost and the surface areas are significantly reduced (to 40 m{sup 2} g{sup -1} and <5 m{sup 2} g{sup -1} for the materials derived from 4 and 5a or 5b, respectively). Solid-state {sup 31}P MAS NMR spectroscopy suggests that the as-synthesized xerogels retain structural features of the starting molecular precursors, as indicated by the presence of resonances that correspond to both bridging and terminal -O{sub 2}P(O{sup t}Bu){sub 2} ligands. Upon calcination at 300 C, the resonances for bridging -O{sub 2}P(O{sup t}Bu){sub 2} groups are replaced by those for PO{sub 4}{sup 3-}. The material derived from 4 exhibits low activity and poor selectivity for the oxidative dehydrogenation (ODH) of propane to propylene. Cothermolyses of 4 and Bi[OSi(O{sup t}Bu){sub 3}]{sub 3} resulted in formation of Bi/Mo/P/Si/O materials with improved performance for the ODH of propane.},
doi = {10.1021/cm030563k},
journal = {Chemistry of Materials},
issn = {0897-4756},
number = ,
volume = 16,
place = {United States},
year = {2004},
month = {1}
}