Journal article
Ligand-Centered Borenium Reactivity in Triaminoborane-Bridged Diphosphine Complexes
Inorganic chemistry, Vol.57(21), pp.13188-13200
11/05/2018
DOI: 10.1021/acs.inorgchem.8b01601
PMID: 30351072
Abstract
Borenium ions (i.e., three-coordinate boron cations) are known to promote a wide variety of stoichiometric and catalytic reactions because of their high Lewis acidity. As demonstrated by the growing number of chemically reactive borane ligands, there is considerable interest in developing ligands with highly electrophilic boron sites that promote multisite reactivity in metal complexes. However, there are currently few examples of ligand-centered borenium ions, especially with ligands that form coordination complexes with a wide range of metals. Here we report borenium-like reactivity on a highly versatile diphosphine ligand. Treating (
TBDPhos)NiCl
(1) with strong Bronsted acids such as HBF
·Et
O, HOTf, or HNTf
resulted in fluoride or chloride abstraction from BF
or NiCl
, respectively, to form trans N-H and B-X bonds on the ligand backbone. HCl addition to the bridgehead N-B bond is reversible, and the reactivity depends on the identity of the supporting counteranions, as observed when treating [(
TBDPhos)NiCl]
X
, where X = NTf
(3), OTf
(4), or BAr
(5), with HCl. The reaction of 4 with HNTf
instead of HCl yielded NMR evidence of the latent borenium cation in solution and showed how poor nucleophiles such as triflate bind to the borenium ion in the solid state. Remarkably, replacing the chloride ligands in 1 with chelating and less-labile thiolates or catecholates, or changing the phosphorus substituents (phenyl to isopropyl), attenuates the reactivity on the ligand backbone. Density functional theory was used to quantify the reaction free energies, and the theoretical results corroborate the experimental observations. Given the broad utility of diphosphines in homogeneous catalysis and the known benefits of strong Lewis acid promotors in many catalytic reactions, we anticipate that the results will provide new opportunities for dual-site reactivity involving boron ligands and metals.
Details
- Title: Subtitle
- Ligand-Centered Borenium Reactivity in Triaminoborane-Bridged Diphosphine Complexes
- Creators
- Kyounghoon Lee - Department of Chemistry , The University of Iowa , E331 Chemistry Building , Iowa City , Iowa 52242 , United StatesClara Kirkvold - Churchill-Haines Laboratories, Department of Chemistry , The University of South Dakota , Vermillion , South Dakota 57069 , United StatesBess Vlaisavljevich - Churchill-Haines Laboratories, Department of Chemistry , The University of South Dakota , Vermillion , South Dakota 57069 , United StatesScott R Daly - Department of Chemistry , The University of Iowa , E331 Chemistry Building , Iowa City , Iowa 52242 , United States
- Resource Type
- Journal article
- Publication Details
- Inorganic chemistry, Vol.57(21), pp.13188-13200
- DOI
- 10.1021/acs.inorgchem.8b01601
- PMID
- 30351072
- ISSN
- 0020-1669
- eISSN
- 1520-510X
- Grant note
- DOI: 10.13039/100006770, name: American Chemical Society Petroleum Research Fund, award: 55989-DNI3; name: Center for Health Effects of Environmental Contamination, University of Iowa
- Language
- English
- Date published
- 11/05/2018
- Academic Unit
- Chemistry
- Record Identifier
- 9984216597102771
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