title: Synthesis and Characterization of Dimethylbis(2-pyridyl)borate Nickel(II) Complexes: Unimolecular Square-Planar to Square-Planar Rotation around Nickel(II).
abstract: The syntheses of novel dimethylbis(2-pyridyl)borate nickel(II) complexes4and6are reported. These complexes were unambiguously characterized by X-ray analysis. In dichloromethane solvent, complex4undergoes a unique square-planar to square-planar rotation around the nickel(II) center, for which activation parameters of ΔH⧧= 12.2(1) kcal mol-1and ΔS⧧= 0.8(5) eu were measured via NMR inversion recovery experiments. Complex4was also observed to isomerize via a relatively slow ring flip: ΔH⧧= 15.0(2) kcal mol-1; and ΔS⧧= -4.2(7) eu. DFT studies support the experimentally measured rotation activation energy (cf. calculated ΔH⧧= 11.1 kcal mol-1) as well as the presence of a high-energy triplet intermediate (ΔH= 8.8 kcal mol-1).
authors.affiliation: Loker Hydrocarbon Institute and Department of Chemistry, University of Southern California , Los Angeles, California, 90089-1661, United States.
authors.forename: Jeff A
authors.initials: JA
authors.lastname: Celaje
authors.affiliation: Loker Hydrocarbon Institute and Department of Chemistry, University of Southern California , Los Angeles, California, 90089-1661, United States.
authors.forename: Megan K
authors.initials: MK
authors.lastname: Pennington-Boggio
authors.affiliation: Loker Hydrocarbon Institute and Department of Chemistry, University of Southern California , Los Angeles, California, 90089-1661, United States.
authors.forename: Robinson W
authors.initials: RW
authors.lastname: Flaig
authors.affiliation: Department of Chemistry, University of North Texas , Denton, Texas, 76203-5017, United States.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Richmond
authors.affiliation: Loker Hydrocarbon Institute and Department of Chemistry, University of Southern California , Los Angeles, California, 90089-1661, United States.
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Williams