title: Removing the sting from the tail: reversible protonation of scorpionate ligands in cobalt(II) tris(carbene)borate complexes.
abstract: Low-temperature deprotonation of the phenylborane dications, PhB(RIm)3OTf2 (R = tBu, Mes), followed by in situ reaction with CoCl2(thf)1.5, results in the formation of the four-coordinate complexes, kappa3-PhB(RIm)3CoCl, in which the metal is supported by tripodal N-heterocyclic carbene-based ligands. The chloride complexes are exceptionally sensitive to acid and can be reversibly protonated to form the zwitterions kappa2-{PhB(RIm)2(RIm.H)}CoCl2. This unexpected reactivity is attributed to the highly basic nature of the tris(carbene)borate ligands. Reaction of the chloride complexes with methylating reagents results in products that depend on the N-heterocyclic carbene substituent. For R = tBu, the four-coordinate high-spin complex, kappa3-PhB(tBuIm)3CoMe, is formed, while for R = Mes, reduction to a multitude of complexes occurs.
authors.affiliation: Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, USA.
authors.forename: Ryan E
authors.initials: RE
authors.lastname: Cowley
authors.forename: Ranko P
authors.initials: RP
authors.lastname: Bontchev
authors.forename: Eileen N
authors.initials: EN
authors.lastname: Duesler
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Smith
mesh_terms: D001897:Boronic Acids / Q000737:chemistry; D015392:Chemistry, Inorganic / Q000379:methods*; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006838:Hydrocarbons / Q000737:chemistry; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000031:analogs & derivatives / Q000737:chemistry; D008745:Methylation; D015394:Molecular Structure; D011522:Protons
chemical_list: D001897:Boronic Acids; D006838:Hydrocarbons; D008024:Ligands; D011522:Protons; C030011:carbene; D003035:Cobalt; C018021:cobaltous chloride; C010686:benzeneboronic acid; D008697:Methane