title: A Cobalt(I) Pincer Complex with an η(2) -C(aryl)-H Agostic Bond: Facile C-H Bond Cleavage through Deprotonation, Radical Abstraction, and Oxidative Addition.
abstract: The synthesis and reactivity of a Co(I) pincer complex [Co(ϰ(3) P,CH,P-P(CH)P(NMe) -iPr)(CO)2](+) featuring an η(2)-C(aryl)-H agostic bond is described. This complex was obtained by protonation of the Co(I) complex [Co(PCP(NMe) -iPr)(CO)2]. The Co(III) hydride complex [Co(PCP(NMe) -iPr)(CNtBu)2(H)](+) was obtained upon protonation of [Co(PCP(NMe) -iPr)(CNtBu)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(PCP(NMe) -iPr)(CO)2]. Second, C-H bond cleavage is achieved upon exposure of [Co(ϰ(3)P,CH,P-P(CH)P(NMe) -iPr)(CO)2](+) to oxygen or TEMPO to yield the paramagnetic Co(II) PCP complex [Co(PCP(NMe) -iPr)(CO)2](+). Finally, replacement of one CO ligand in [Co(ϰ(3) P,CH,P-P(CH)P(NMe) -iPr)(CO)2](+) by CNtBu promotes the rapid oxidative addition of the agostic η(2) -C(aryl)-H bond to give two isomeric hydride complexes of the type [Co(PCP(NMe) -iPr)(CNtBu)(CO)(H)](+).
authors.affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060, Wien, Austria.
authors.forename: Sathiyamoorthy
authors.initials: S
authors.lastname: Murugesan
authors.affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, 1060, Wien, Austria.
authors.forename: Berthold
authors.initials: B
authors.lastname: Stöger
authors.affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, 1060, Wien, Austria.
authors.forename: Ernst
authors.initials: E
authors.lastname: Pittenauer
authors.affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, 1060, Wien, Austria.
authors.forename: Günter
authors.initials: G
authors.lastname: Allmaier
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais No. 1, 1049-001, Lisboa, Portugal.
authors.forename: Luis F
authors.identifier: http://orcid.org/0000-0001-5841-3519
authors.initials: LF
authors.lastname: Veiros
authors.affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060, Wien, Austria. kkirch@mail.tuwien.ac.at.
authors.forename: Karl
authors.initials: K
authors.lastname: Kirchner
keywords: C−H activation; agostic interactions; cobalt; pincer complexes; protonation