Free Metallophosphines: Extremely Electron‐Rich Phosphorus Superbases That Are Electronically and Sterically Tunable**

Abstract

We report herein a facile and highly modular access to an intriguing class of free Au-substituted phosphines (AuPhos), namely (LAu) n PR 3À n (L = singlet carbene ligand; R = H, aryl, alkyl, silyl) (n = 1-3). The Tolman electronic parameter (TEP) values coupled with theoretical investigations showcase that Au-substitution can boost the electron-releasing ability of AuPhos, thus leading to an electronically and sterically tunable, extremely electron-rich phosphorus center. The high basicity of AuPhos is attributed to the d-p lone pair πrepulsion arising from interaction between Au substituents and the lone pair at P. A series of multi-nuclear transition metal complexes (i.e. Rh, Ir, Pd, Au, W, Mn) ligated by AuPhos are readily prepared via a straightforward process. Preliminary catalytic results reveal the facilitation of Pd-catalyzed CÀ N coupling reactions and Ir-catalyzed decarbonylation reactions via AuPhos. This work provides insights for future development of electron-rich ligands.

Cleavage of the Au−P Bond in Au‐Substituted Phosphines

“…Indeed, even in the presence of protic substrates (e. g. EtOH, H 2 O), this AuÀ P bond is robust. [8] It is noteworthy that the intermediacy of [Pd]À PR 2 was proposed in Pd-catalyzed hydrophosphination reactions, which was postulated to add to unsaturated bonds as a key step. [16] However, considering the high electronegative nature of Pd (χ = 2.2) as well, [Pd]À PR 2 is very unlikely to engage in such insertion reactions.…”

“…Compounds 1 and 4 were synthesized according to our recent work. [8] Deposition numbers 2234817-2234820 contain the supplementary crystallographic data for this paper. These data are provided free of charge by the joint Cambridge Crystallographic Data Centre and Fachinformationszentrum Karlsruhe Access Structures service.…”

“…The NMR of 6 fitted well with the reported values. [8] Synthesis of 7 a: Selenium powder (3.2 mg, 0.04 mmol) was added into a THF solution (1 mL) of 1 a (15 mg, 0.02 mmol) at room temperature. After stirring for 5 min, the solvent was removed under vacuum.…”

“…In 2022, we systematically investigated a series of AuPhos. [8] Such compounds have proved one of the extremely electron-rich phosphorus superbases owing to the dp lone pair repulsion. [1a,c,9] Unlike the ionic MÀ P bonds in TM phosphido complexes, [3] AuPhos contain a highly covalent AuÀ P bond and are not sensitive to alcohol, amine and water.…”

Am Rande des Bekannten: Extrem elektronenreiche (Di)carboranylphosphane

“…Die Donorstärke wird noch weiter erhöht, wenn eine zweite 9‐ m Cb‐Gruppe an das Phosphoratom gebunden wird. Verbindung 3 weist den niedrigsten experimentell gemessenen TEP‐Wert (2047 cm −1 ) der B9‐Phos‐Liganden auf und liegt im Bereich anderer extrem elektronenreicher Phosphane wie YPhos ( III ) [7] und Mono‐AuPhos ( VIII ), [13] erreicht aber nicht die Werte von Phosphazenylphosphan VII [12] . Das Gleiche gilt für den B9‐Phos‐Liganden 4 , für den mit Hilfe einer linearen Regression aus der Korrelation zwischen dem TEP und der P−Se‐Kopplungskonstante (siehe Hintergrundinformationen für Fit‐Parameter) ein TEP von 2044 cm −1 , und damit sogar ein niedriger TEP als 3 , ermittelt wurde [44] …”