Iridium reactions with other substrate complexes

Tilley and coworkers reported a more direct procedure for the synthesis of late transition metal silylenoid complexes by reaction with silanes [equation (7.1)].36,37 Exposing iridium complex 14 to dimesitylsilane afforded iridium silylenoid 15.36 In addition to dimesitylsilane, other silanes could be used, including diphenyl-, diethyl-, or dimethylsilane. Primary silanes such as mesitylsilane and 2,4,6-triisopropylphe-nylsilane were also tolerated as substrates.37... 

In many other cases, oxidative additions of alkanes occur readily to transition-metal-alkyl complexes to generate hydride dialkyl intermediates that subsequently eliminate alkane and form a new metal-alkyl complex. For example, cations related to the alkyl hydrides of iridium formed by oxidative addition undergo reaction with alkanes at or below room temperature to generate new alkyl complexes (Equation 6.34). Cationic platinum complexes undergo similar reactions with substrates containing aromatic and aliphatic C-H bonds (Equation 6.35). " The C-H activation of the platinum complexes has been studied, in part, to understand and to develop systems related to the ones reported by Shilov that lead to H/D exchange, and oxidation and halogenation of alkanes. 

However, others have shown that oxidative additions of much less acidic substrates, such as water, ° alcohols, unactivated anilines and azole heterocycles, " occur to low-valent transition metal complexes. For example, iridium(I) complexes containing tri-ethylphosphine as ligand undergo oxidative addition of water rapidly at room temperature (Equation 7.17). Both [Ir(PEtj)J and [Ir(PEt3)jCl] also add aniline rapidly at room temperature (Equation 7.17). The latter reaction is a step in the catalytic hydroamination of norbornene. These substrates react readily with early metal complexes, but tliese reactions do not occur by oxidative addition. ... 

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