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American Chemical Society, Organometallics, 8(33), p. 2019-2026, 2014

DOI: 10.1021/om500173j

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Synthesis and Characterization of Dimethylbis(2-pyridyl)borate Nickel(II) Complexes: Unimolecular Square-Planar to Square-Planar Rotation around Nickel(II)

Journal article published in 2014 by Jeff A. Celaje, Megan K. Pennington Boggio, Robinson W. Flaig, Michael G. Richmond, Travis J. Williams ORCID
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

The syntheses of novel dimethylbis(2-pyridyl)borate nickel(II) complexes 4 and 6 are reported. These complexes were unambiguously characterized by X-ray analysis. In dichloromethane solvent, complex 4 undergoes a unique square-planar to square-planar rotation around the nickel(II) center, for which activation parameters of ΔH (⧧) = 12.2(1) kcal mol(-1) and ΔS (⧧) = 0.8(5) eu were measured via NMR inversion recovery experiments. Complex 4 was 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)).