Nickel complexes of phosphine-appended benzannulated boron heterocycles

Essex, Laura A.; Taylor, Jordan W.; Harman, W. Dean

doi:10.1016/j.tet.2019.02.047

Cited by 11 publications

(9 citation statements)

References 37 publications

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“…In contrast to 1 in which the BC 4 rings are puckered, the rings within the dinickel complex are planar, perhaps attributable to the change from amino to alkoxy substitution on boron (maximum deviations from planarity of 0.070 and 0.097 Å) . Half-sandwich complex 2 may be best compared to a 9-borafluorene complex recently reported by Harman, which features a 0.251 Å shorter Ni–B bond and longer Ni–C bonds [range of 2.212(2)–2.238(2) Å], likely as a consequence of the rigidity imposed by the pendent phosphine on the 9-borafluorene-phosphine ligand …”

Section: Results and Discussionmentioning

confidence: 94%

“…19b Half-sandwich complex 2 may be best compared to a 9-borafluorene complex recently reported by Harman, which features a 0.251 Å shorter Ni−B bond and longer Ni−C bonds [range of 2.212(2)−2.238(2) Å], likely as a consequence of the rigidity imposed by the pendent phosphine on the 9-borafluorene-phosphine ligand. 25 The redox properties of 1 and 2 (1 mM) were investigated by means of cyclic voltammetry in CH 2 Cl 2 (0.1 M NBu 4 PF 6 ) under an Ar atmosphere. The cyclic voltammogram (CV) of 2 (Figure S28) displays one oxidation event centered at −0.34 V versus Fc 0/+ closely followed by a second oxidation event at −0.18 V versus Fc 0/+ that features a significantly smaller current density.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Nickel–Borolide Complexes and Their Complex Electronic Structure

et al. 2021

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Borolides (BC 4 2− ) can be considered as dianionic heterocyclic analogues of monoanionic cyclopentadienides. Although both are formally six-π-electron donors, we herein demonstrate that the electronic structure of their corresponding transition metal complexes differs significantly, leading to altered properties. Specifically, the 18-electron sandwich complex Ni(iPr 2 NBC 4 Ph 2 ) 2 (1) features an ∼90°angle between the Ni−B−N planes and is best described as a combination of three limiting resonance structures with the major contribution stemming from a formally Ni 2+ species bound to two monoanionic radical (BC 4•− ) ligands. Compound 1 displays two sequential one-electron oxidation events over a small potential range of <0.2 V, which strikingly contrasts the large potential separations between redox partners in the family of metallocenes, and the potential reasons for this unusual observation are discussed.

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Section: Results and Discussionmentioning

confidence: 94%

Section: ■ Results and Discussionmentioning

confidence: 99%

Nickel–Borolide Complexes and Their Complex Electronic Structure

et al. 2021

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“…For adducts with a carbon–boron bond and a chelated base, aryllithium reagents are generated in situ from the halogenated aromatics and n BuLi and react with 9-halo-9-borafluorenes ( 2 and 45 ) to give rise to 9-borafluorenes 84 and 161 – 167 (Table , entry 19–26). ,− Shimizu and Kawachi synthesized a series of tetracoordinate 9-borafluorenes ( 173 – 175 ) starting from the lithium halogen exchange of o -(dimethylsilyl)bromobenzene ( 168 ) with t BuLi (Figure ). The resulting o -silyl(lithio)benzene reacts with 9-isopropoxy-9-borafluorene ( 58 ) or 9- tert -butoxy-9-borafluorene ( 72 ) to form the borate intermediate ( 169 or 170 ), which undergoes hydride-alkoxy exchange to form the hydroborate ( 171 or 172 ).…”

Section: Synthesismentioning

confidence: 99%

9-Borafluorenes: Synthesis, Properties, and Reactivity

Bartholome

Tidwell

et al. 2021

Chem. Rev.

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This review covers all aspects of 9-borafluorene chemistry, from the first attempted synthesis in 1960 to the present. This class of molecules consists of a tricyclic system featuring a central antiaromatic BC 4 ring with two fused arene groups. The synthetic routes to all 9-borafluorenes and their adducts are presented. The Lewis acidity and photophysical properties outlined demonstrate potential utility as sensors and in electronic materials. The reactivity of borafluorenes reveals their prospects as reagents for the synthesis of other boron-containing molecules. The appealing traits of 9-borafluorenes have stimulated investigations into analogues that bear different aromatic groups fused to the central BC 4 ring. Finally, we offer our views on the challenges and future of borafluorene chemistry.

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“…OH this work significant interest as a particularly robust reaction platform that is capable of accommodating multiple electron equivalents and subsequently performing multi-electron bond activations with a rapidly growing host of molecules such as CO2, O2, C2H4 and H2. 15 Recently we developed a DBA based disphosphine ligand (B2P2) and reported its Ni, 16 Cu, Ag 17 and Au complexes. 18 The reduced form of the Au complex exhibits diverse twoelectron reductive chemistry with H + , CO2 19 and organic carbonyls.…”

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confidence: 99%