Reactions of Low-Coordinate Cobalt(0)-N-Heterocyclic Carbene Complexes with Primary Aryl Phosphines

Dongyang Wang; Qi Chen; Xuebing Leng; Liang Deng

doi:10.1021/acs.inorgchem.8b02937

Reactions of Low-Coordinate Cobalt(0)-N-Heterocyclic Carbene Complexes with Primary Aryl Phosphines

Inorg Chem. 2018 Dec 17;57(24):15600-15609. doi: 10.1021/acs.inorgchem.8b02937. Epub 2018 Dec 3.

Authors

Dongyang Wang¹, Qi Chen¹, Xuebing Leng¹, Liang Deng¹

Affiliation

¹ State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry , University of Chinese Academy of Sciences, Chinese Academy of Sciences , 345 Lingling Road , Shanghai 200032 , P. R. China.

PMID: 30507168
DOI: 10.1021/acs.inorgchem.8b02937

Abstract

Aiming to get knowledge on the reactivity of low-coordinate cobalt(0) species toward primary phosphines, the reactions of [(IPr)Co(vtms)₂] and [(ICy)₂Co(vtms)] (IPr = 1,3-bis(2',6'-diisopropylphenyl)imidazol-2-ylidene, ICy = 1,3-dicyclohexylimidazol-2-ylidene, and vtms = vinyltrimethylsilane) with several primary aryl phosphines have been examined. The reactions of [(IPr)Co(vtms)₂] and [(ICy)₂Co(vtms)] with H₂PDmp (Dmp = 2,6-dimesitylphenyl) at 80 °C furnish the diamagnetic cobalt(I) phosphido complexes [(NHC)Co(PHDmp)] (NHC = IPr, 1; ICy, 2) that feature the Co-(η⁶-mesityl) interaction. Complex 1 can coordinate CO to generate the terminal phosphido complex [(IPr)Co(CO)₃(PHDmp)] (3) and can be oxidized by [Cp₂Fe][BAr^F₄] to yield the cobalt(II) phosphido complex [(IPr)Co(PHDmp)][BAr^F₄] (4, BAr^F₄ = tetrakis(3,5-di(trifluoromethyl)phenyl)borate). For the reactions with sterically less-hindered primary phosphines, [(IPr)Co(vtms)₂] is inert toward H₂PC₆H₂-2,4,6-Me₃ (H₂PMes) at room temperature, whereas [(ICy)₂Co(vtms)] can react with H₂PMes at room temperature to produce the cobalt(II) phosphido alkyl complex trans-[(ICy)₂Co(CH₂CH₂SiMe₃)(PHMes)] (5). At 80 °C, the cobalt(0) alkene complexes [(IPr)Co(vtms)₂] and [(ICy)₂Co(vtms)] and also the cobalt phosphido complexes, 1, 2, and 5 can serve as precatalysts for the dehydrocoupling reaction of H₂PMes to afford MesHPPHMes. NHC-Co(I)-phosphido species are proposed as the in-cycle intermediates for these cobalt-catalyzed dehydrocoupling reactions.