A Cobalt(I) Pincer Complex with an η2‐Caryl−H Agostic Bond: Facile C−H Bond Cleavage through Deprotonation, Radical Abstraction, and Oxidative Addition
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Abstract
The synthesis and reactivity of a CoI pincer complex [Co(ϰ 3P ,CH ,P ‐P(CH)PNMe‐i Pr)(CO)2]+ featuring an η2‐ Caryl−H agostic bond is described. This complex was obtained by protonation of the CoI complex [Co(PCPNMe‐i Pr)(CO)2]. The CoIII hydride complex [Co(PCPNMe‐i Pr)(CNt Bu)2(H)]+ was obtained upon protonation of [Co(PCPNMe‐i Pr)(CNt Bu)2]. Three ways to cleave the agostic C−H bond are presented. First, owing to the acidity of the agostic proton, treatment with pyridine results in facile deprotonation (C−H bond cleavage) and reformation of [Co(PCPNMe‐i Pr)(CO)2]. Second, C−H bond cleavage is achieved upon exposure of [Co(ϰ 3P ,CH ,P ‐P(CH)PNMe‐i Pr)(CO)2]+ to oxygen or TEMPO to yield the paramagnetic CoII PCP complex [Co(PCPNMe‐i Pr)(CO)2]+. Finally, replacement of one CO ligand in [Co(ϰ 3P ,CH ,P ‐P(CH)PNMe‐i Pr)(CO)2]+ by CNt Bu promotes the rapid oxidative addition of the agostic η2‐Caryl−H bond to give two isomeric hydride complexes of the type [Co(PCPNMe‐i Pr)(CNt Bu)(CO)(H)]+.
