Chemical and Electrochemical Oxidation of Tris(3,5‐di‐tert‐butylphenyl)phosphine – High Z′ Crystal Structures and Conformational Effects Associated with Bulky meta Substituents

Abstract

Synthesis and single-crystal X-ray diffraction structures of (3,5-tBu 2 -C 6 H 3 ) 3 P, (3,5-tBu 2 -C 6 H 3 ) 3 PO·H 2 O, (3,5-tBu 2 -C 6 H 3 ) 3 PS and (3,5-tBu 2 -C 6 H 3 ) 3 PSe are reported. The structure of (3,5-tBu 2 -C 6 H 3 ) 3 P has Z′ = 4, with both M and P enantiomers of a helical conformation and a conformation with one flat ring in the same lattice. The pyramidality index, Σ{∠CPC}, is smaller for the helical compared to the flat conformers. All four have structures that are more pyramidal than the corresponding Ph 3 P(E) derivatives, which is attributed to stronger intramolecular dispersion forces. The oxide crystallizes with Z′ = 2 as a water-bridged dimer that is the most separated such dimer [a]

Sterically Crowded Tris(2‐(trimethylsilyl)phenyl)phosphine – Is it Still a Ligand?

“…However, the oxidation potential is also sensitive to the electronic influence of the substituents [55] . Electron donating substituents will also raise the HOMO energy and basicity of the phosphine and lower the oxidation potential [56] . This matches the electron donating effect of the TMS groups which lowers the potential slightly with respect to PPh 3 [57,58] …”

On the Edge of the Known: Extremely Electron‐Rich (Di)Carboranyl Phosphines

“…Based on previous studies of bulky phosphines, showing that electrogenerated phosphoniumyl radical cations can be stabilized by sterically demanding substituents, the redox properties of the B9-Phos ligands were investigated. [28,29] Cyclic voltammograms of the oxidation of B9-Phos ligands 1-4 and PPh 3 in CH 2 Cl 2 (0.1 M [N(nBu) 4 ]PF 6 ) at scan rates of 100 mV s À 1 are shown in Figure 3 all referenced against the E 1/2 of [CcH]/[CcH] + (CcH = [Cp 2 Co])). [28,30,31] B9-Phos ligands 2 and 4 show a moderate chemical reversibility with i r /i f = 0.64 (2) and 0.81 (4) compared to PDipp 3 (Dipp = 2,6-diisopropylphenyl) i r /i f = 0.97.…”

Am Rande des Bekannten: Extrem elektronenreiche (Di)carboranylphosphane

“…Auf der Grundlage früherer Studien über sperrige Phosphane, die zeigten, dass elektrochemisch generierte Phosphoniumylradikalkationen durch sterisch anspruchsvolle Substituenten stabilisiert werden können, wurden die Redox‐Eigenschaften der B9‐Phos‐Liganden untersucht [28, 29] . Cyclovoltammogramme der Oxidation der B9‐Phos‐Liganden 1 – 4 und PPh 3 in CH 2 Cl 2 (0.1 M [N( n Bu) 4 ]PF 6 ) bei einer Scanrate von 100 mV s −1 sind in Abbildung 3 dargestellt, alle bezogen auf das Halbstufenpotential E 1/2 von [CcH]/[CcH] + (CcH=[Cp 2 Co])) [28, 30, 31] .…”

“…Substituenten stabilisiert werden können, wurden die Redox-Eigenschaften der B9-Phos-Liganden untersucht. [28,29] Cyclovoltammogramme der Oxidation der B9-Phos-Liganden 1-4 und PPh ). [28,30,31] Die B9-Phos-Liganden 2 und 4 zeigen eine mäßige chemische Reversibilität mit i r /i f = 0.64 (2) und 0.81 (4) im Vergleich zu PDipp 3 (Dipp = 2,6-Diisopropylphenyl) i r /i f = 0.97.…”