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Unexpected Vulnerability of DPEphos to C−O Activation in the Presence of Nucleophilic Metal Hydrides
Author(s) -
Cybulski Mateusz K.,
Beattie Nicholas A.,
Macgregor Stuart A.,
Mahon Mary F.,
Whittlesey Michael K.
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202001685
Subject(s) - carbene , nucleophile , chemistry , ligand (biochemistry) , steric effects , hydride , medicinal chemistry , catalysis , aryl , photochemistry , stereochemistry , metal , organic chemistry , biochemistry , receptor , alkyl
C−O bond activation of DPEphos occurs upon mild heating in the presence of [Ru(NHC) 2 (PPh 3 ) 2 H 2 ] (NHC=N‐heterocyclic carbene) to form phosphinophenolate products. When NHC=IEt 2 Me 2 , C−O activation is accompanied by C−N activation of an NHC ligand to yield a coordinated N ‐phosphino‐functionalised carbene. DFT calculations define a nucleophilic mechanism in which a hydride ligand attacks the aryl carbon of the DPEphos C−O bond. This is promoted by the strongly donating NHC ligands which render a trans dihydride intermediate featuring highly nucleophilic hydride ligands accessible. C−O bond activation also occurs upon heating cis ‐[Ru(DPEphos) 2 H 2 ]. DFT calculations suggest this reaction is promoted by the steric encumbrance associated with two bulky DPEphos ligands. Our observations that facile degradation of the DPEphos ligand via C−O bond activation is possible under relatively mild reaction conditions has potential ramifications for the use of this ligand in high‐temperature catalysis.