Tricoordinate Nontrigonal Pnictogen‐Centered Radical Anions: Isolation,Characterization, and Reactivity

The search for main‐group element‐based radicals is one of the main research topics in contemporary chemistry because of their fascinating chemical and physical properties. The Group 15 element‐centered radicals mainly feature a V‐shaped two coordinate structure, with a couple of radical cations featuring trigonal tricoordinated geometry. Now, nontrigonal compounds R₃E (E=P, As, Sb) were successfully synthesized by introducing a new rigid tris‐amide ligand. The selective one‐electron reduction of R₃E afforded the first stable tricoordinate pnictogen‐centered radical anion salts; the pnictogen atoms retain planar T‐shaped structures. EPR spectroscopy and calculations reveal that the spin density mainly resides at the p orbitals of the pnictogen atoms, which is perpendicular to the N₃E planes.     

A Boryl‐Substituted Diphosphene: Synthesis,Structure, and Reaction with n‐Butyllithium To Form a Stabilized Adduct by pπ‐pπ Interaction

A boryl‐substituted diphosphene was synthesized through the nucleophilic borylation of PCl₃ with a borylzinc reagent, followed by a reduction with Mg. A combined analysis of the resulting diboryldiphosphene by single‐crystal X‐ray diffraction, DFT calculations, and UV/Vis spectroscopy revealed a σ‐electron‐donating effect for the boryl substituent that was slightly weaker than that of the 2,4,6‐tri‐tert‐butylphenyl (Mes*) ligand. The reaction of this diboryldiphosphene with ⁿBuLi afforded a boryl‐substituted phosphinophosphide that was, in comparison with the thermally unstable Mes*‐substituted diaryldiphosphene, stabilized by a π‐electron‐accepting effect of the boryl substituent.     

Elusive Antimony‐Centered Radical Cations: Isolation,Characterization, Crystal Structures,and Reactivity Studies

One‐electron oxidation of the stibines Aryl₃Sb ( 1 , Aryl=2,6‐ⁱ Pr₂‐4‐OMe‐C₆H₂; 2 , Aryl=2,4,6‐ⁱ Pr₃‐C₆H₂) with AgSbF₆ and NaBAryl^F₄ (Aryl^F=3,5‐(CF₃)₂C₆H₃) afforded the first structurally characterized examples of antimony‐centered radical cations 1 ^.+[BAryl^F₄]⁻ and 2 ^.+[BAryl^F₄]⁻. Their molecular and electronic structures were investigated by single‐crystal X‐ray diffraction, electron paramagnetic resonance spectroscopy (EPR) and UV/Vis absorption spectroscopy, in conjunction with theoretical calculations. Moreover, their reactivity was investigated. The reaction of 2 ^.+[BAryl^F₄]⁻ and p ‐benzoquinone afforded a dinuclear antimony dication salt 3 ²⁺[BAryl^F₄]₂⁻, which was characterized by NMR spectroscopy and X‐ray diffraction analysis. The formation of the dication 3 ²⁺ further confirms that the isolated stibine radical cations are antimony‐centered.     

Isolation and Reactivity of Homoleptic Diphosphene Lead Complexes

Due to their limited capacity for π-backdonation, isolation of π-complexes of main-group elements remains a great challenge. We report herein the synthesis of a homoleptic diphosphene lead complex ( 2 ) from the degradation of P₄ with a bis(germylene)-stabilized Pb(0) complex. Structural and computational studies showed that 2 possesses significant π bonding interactions between Pb atom and diphosphene ligands, which is reminiscent of transition-metal diphosphene complexes. Consistent with its unique electronic structure, complex 2 can deliver Pb(0) atoms to perform redox reaction with an iminoquinone to produce a cyclic plumbylene ( 4 ) and perform 2,5-dimethyl-3,4-dimethylimidazol-1-ylidene (IMe₂Me₂) induced phosphorus cation abstraction to give an anionic PbP₃ complex ( 6 ).     

Synthesis of γ‐Boryl‐Substituted Homoallylic Alcohols with anti Stereochemistry Based on a Double‐Bond Transposition

The stereoselective synthesis of anti isomers of γ‐boryl‐substituted homoallylic alcohols is disclosed. (E)‐1,2‐Di(boryl)alk‐1‐enes undergo Ru‐catalyzed double‐bond transposition with control of the geometry. The in situ generated (E)‐1,2‐di(boryl)alk‐2‐enes add to aldehydes in a stereospecific manner. The alkenylboron group within the product is amenable to a variety of synthetic derivatizations.     

Tricoordinate Nontrigonal Pnictogen‐Centered Radical Anions: Isolation,Characterization, and Reactivity

The search for main‐group element‐based radicals is one of the main research topics in contemporary chemistry because of their fascinating chemical and physical properties. The Group 15 element‐centered radicals mainly feature a V‐shaped two coordinate structure, with a couple of radical cations featuring trigonal tricoordinated geometry. Now, nontrigonal compounds R₃E (E=P, As, Sb) were successfully synthesized by introducing a new rigid tris‐amide ligand. The selective one‐electron reduction of R₃E afforded the first stable tricoordinate pnictogen‐centered radical anion salts; the pnictogen atoms retain planar T‐shaped structures. EPR spectroscopy and calculations reveal that the spin density mainly resides at the p orbitals of the pnictogen atoms, which is perpendicular to the N₃E planes.     

A Boryl‐Substituted Diphosphene: Synthesis,Structure, and Reaction with n‐Butyllithium To Form a Stabilized Adduct by pπ‐pπ Interaction

A boryl‐substituted diphosphene was synthesized through the nucleophilic borylation of PCl₃ with a borylzinc reagent, followed by a reduction with Mg. A combined analysis of the resulting diboryldiphosphene by single‐crystal X‐ray diffraction, DFT calculations, and UV/Vis spectroscopy revealed a σ‐electron‐donating effect for the boryl substituent that was slightly weaker than that of the 2,4,6‐tri‐tert‐butylphenyl (Mes*) ligand. The reaction of this diboryldiphosphene with ⁿBuLi afforded a boryl‐substituted phosphinophosphide that was, in comparison with the thermally unstable Mes*‐substituted diaryldiphosphene, stabilized by a π‐electron‐accepting effect of the boryl substituent.     

Radical Anions from Urea‐type Carbonyls: Radical Cyclizations and Cyclization Cascades

Radical anions generated from urea carbonyls by reductive electron transfer are exploited in carbon–carbon bond formation. New radical cyclizations of urea radical anions deliver complex nitrogen heterocycles and, depending upon the proton source used in the reactions, a chemoselective switch between reaction pathways can deliver two heterobicyclic scaffolds. A computational study has been used to investigate the selectivity of the urea radical processes. Furthermore, radical cyclization cascades involving urea radical anions deliver unusual spirocyclic aminal architectures.