A Multidimensional Approach to Carbodiphosphorane–Bismuth Coordination Chemistry: Cationization, Redox-Flexibility, and Stabilization of a Crystalline Bismuth Hydridoborate

Abstract

Bismuth complexes stabilized by carbon-based donor ligands are underserved by their instability, often due to facile ligand dissociation and deleterious protonolysis. Herein, we show that the ortho-bismuthination of hexaphenylcarbodiphosphorane enables a robust framework with geometrically constrained carbone–bismuth bonding interactions, which are highly tunable by cationization. The carbodiphosphorane bismuth halides (1 and 2) are remarkably air-stable and feature unprecedented trans carboneC–Bi–X ligation, resulting in highly elongated Bi–X bonds. In contrast to known carbone–bismuth complexes, hydrolytic activation of the carbone yields well-defined organobismuth complexes, and subsequent dehydrohalogenation is feasible using potassium bis(trimethylsilyl)amide or N-heterocyclic carbenes. The redox-flexibility of this framework was evaluated in the high catalytic activity of 1 and 2 for silylation of 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) under mild conditions (50 °C, 24–96 h) and low catalyst loadings (5–10 mol %), which suggests the accessibility of short-lived hydridic and radical bismuth species. The reaction of 1, PhSiH3, and tris(pentafluorophenyl)borane (BCF) yields the first crystallographically characterized bismuth hydridoborate complex as an ionic species (9), presumably by BCF-mediated hydride abstraction from an unobserved [Bi]–H intermediate. All isolated compounds have been characterized by heteronuclear NMR spectroscopy and X-ray crystallography, and the bonding situation in representative complexes (1, 2, 5, and 9) were further evaluated using density functional theory.

Metallomimetic Chemistry of a Cationic, Geometrically Constrained Phosphine in the Catalytic Hydrodefluorination and Amination of Ar–F Bonds

“…1 + was prepared using a similar methodology recently reported by Sundermeyer, which showed that hexaphenyl-carbodiphosphorane can be doubly deprotonated by n BuLi, producing a dilithiated hexaphenyl-carbodiphosphorane ligand, which can be used as a dianionic tridentate CCC pincer-type ligand. , Thus, hexaphenyl-carbodiphosphorane ( 2 ) was treated with 2 equiv of n BuLi followed by addition of PCl 3 , which resulted in precipitation of the desired [ 1 + ]­[Cl] (Scheme ). The 31 P NMR of [ 1 + ]­[Cl] in CDCl 3 was measured, showing two broad singlets with chemical shifts of δ = 29.80 and 54.24 ppm with the integration ratio of 2:1, respectively.…”

Charge Makes a Difference: Molecular Ionic Bismuth Compounds

“…These challenges have been met by the use of chelating ligands, bulky ligands with π‐donating abilities, and weakly coordinating anions [36–38, 51] . Very recently, the reversible protonation of a dianionic ligand at its carbodiphosphorane functional group has been reported as a new access to cationic bismuth compounds [64] …”

Charge Makes a Difference: Molecular Ionic Bismuth Compounds

“…These challenges have been met by the use of chelating ligands, bulky ligands with π‐donating abilities, and weakly coordinating anions [36–38, 51] . Very recently, the reversible protonation of a dianionic ligand at its carbodiphosphorane functional group has been reported as a new access to cationic bismuth compounds [64] …”