Substituent effects on methane activation and elimination by high-valent Zr complexes

✍ Scribed by Thomas R. Cundari; Scot Curtiss

• Book ID: 102654453
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 742 KB
• Volume: 60
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1996)60:3<779::aid-qua6>3.0.co;2-u

✦ Synopsis

A computational study of substituent effects on methane activation and elimination by high-valent zirconium complexes is reported. Substituent ( Z ) effects (in a structural, electronic, and enthalpic sense) are substantially less important for the imido (L,Zr = NZ) and imidolike TS than the amido ( L , M-NHZ). For the microscopic reverse reaction, methane CH activation, it suggests that tailoring imido reactivity through electronic modification of nitrogen substituents will be difficult. Analysis of the earliest part of the reaction coordinate for methane elimination entails structural deformation of the Zr-amido to assume an appropriate geometry for elimination, which, in some cases, is directly reflected in substantially higher elimination barriers. Lower elimination barriers correlate with stronger agostic bonding, providing further support for the crucial importance of agostic bonding in facilitating alpha-elimination processes for high-valent transition-metal complexes. 0 1996 John Wiley & Sons, Inc. cal vapor deposition (CVD) of solid-state oxides, carbides, and nitrides, from organometallic precursors [2]. In the prototypical reaction (11,