One of the most important challenges facing chemists, fundamentally and practically speaking, is the efficient and mild activation and functionalization of the major components of natural gas: methane, ethane, and other alkanes. New lab-scale techniques to this end are needed to supplement the industrial standards in this area, such as steam reforming, cracking, and the Fischer-Tropsch process, which are energy and capital-intensive. The transient titanium alkylidyne, (PNP)Ti≡CtBu (PNP- = N[2-PiPr 2-4-methylphenyl]2-) complex, previously demonstrated to activate C–H bonds of benzene and tetramethylsilane at room temperature by a 1,2-addition across the Ti≡C linkage is now shown to cleave the C–H bonds of the most inert organic molecules, methane, heavier alkanes, under mild conditions. Methane reacts to form a stable titanium-methyl bond, and careful deuterium labeling and kinetics studies show rapid tautomerization processes in this molecules, implicating a terminal, transient titanium methylidene. ≥C 2 alkanes are demonstrated to react by &agr;,β-double-CH activation to ultimately yield terminal olefins with >99% selectivity. Detailed experimental and theoretical studies allow for the elucidation of this unprecedented reaction. Furthermore, two-electron redox reactions of titanium(II)-olefin complexes are presented, as well as the dynamic solution-phase behavior of a titanium-acetylene complex.
|Advisor:||Mindiola, Daniel J.|
|Commitee:||Caulton, Kenneth G.|
|School Location:||United States -- Indiana|
|Source:||MAI 51/01M(E), Masters Abstracts International|
|Subjects:||Inorganic chemistry, Organic chemistry|
|Keywords:||Alkane, Alkylidyne, CH activation, Carbon-hydrogen activation, Dehydrogenation, Organometallics, Titanium|
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