Isolation and Characterization of Radical Anions Derived from a Boryl‐Substituted Diphosphene

Abstract

Radical anions of a diphosphene with two boryl substituents were isolated and characterized by single‐crystal X‐ray diffraction, electron spin resonance (ESR), and UV/Vis absorption spectroscopy as well as DFT calculations. Structural analysis of the radical anions revealed an elongation of the P=P bond and a contraction of the B−P bonds relative to the neutral diphosphene. The UV/Vis spectra of these radical anions showed a strong absorption in the visible region, which was assigned to SOMO‐related transitions on the basis of DFT calculations. The ESR spectra revealed that the hyperfine coupling constant with the phosphorus nuclei is the smallest that has been reported thus far. The results of the DFT calculations furthermore suggest that this should be attributed to a soaking of electron spin to the vacant p orbitals of the boryl substituents.

Synthesis of a Ga-Stabilized As-Centered Radical and a Gallastibene by Tailoring Group 15 Element–Carbon Bond Strengths

“…boron, silicon, and nitrogen, [5] have also been studied to some extent, whereas the number of persistent or stable radicals of heavier main group elements is still limited, [6,7] even though new strategies to stabilize these highly reactive species including coordination of σ-donating carbenes have been developed in the last decade. [8][9][10][11][12] Pnictogen-based radicals are well known in case of phosphinyl radicals and their structures and electronic properties were studied, [5,[13][14][15][16][17][18] whereas stable radicals of the heavier group 15 elements are still rare. A few stable arsenicbased radicals have been reported (Scheme 1), which are typically stabilized by coordination of strong σ-donors (A, B), by use of sterically-demanding organic substituents (C), and/or by incorporation the radical center into a heterocyclic system (D, E, F).…”

Redox Potentials of Group 13 Metal-Substituted Dipnictenes: A Comparative Cyclic Voltammetry Study

“…•− (bbt = 2,6-[CH-(SiMe 3 ) 2 ]-4-[C(SiMe 3 ) 3 ]-C 6 H 2 ]). 34,35 In addition, the redox behavior of some heavier dipnictenes was studied by CV. 20,36−38 We prepared several L(X)M-coordinated dipnictenes [L-(X)MPn] 2 by reactions of the gallanediyl LGa with PnX 3 (Pn = As, Sb, Bi) in recent years.…”

An Isolable Diphosphene Radical Cation Stabilized by Three‐Center Three‐Electron π‐Bonding with Chromium: End‐On versus Side‐On Coordination

“…[10] Forc omparison, we also obtained crystals of precursor 1 and determined the structure at low temperature ( Figure S2). 4 ]crystallizes in the orthogonal space group Pbca, and cations 2 are separated by anions of [Al(OR F ) 4 ] À .The P À Pbond (2.069(2) )isslightly longer than those (2.034(2) ) in the free diphosphene Mes*P = PMes* [5a] and the parent molecule 1.T he Cr1 À P2 bond (2.299(1) )i ss horter than that in the previously reported radical cation [7] [(arene)Cr-(CO) 2 PPh 3 ] + .T he P1ÀC1 bond is longer while the P2ÀC7 bond is shorter than in parent molecule 1.Strikingly,the C1-P1-P2 angle (83.9(1)8 8)isthe smallest among the C-P-P angles observed in diphosphenes [5] and complexes thereof (89.4-121.48 8), [11] forming astrained planar four-membered ring. 4 ]crystallizes in the orthogonal space group Pbca, and cations 2 are separated by anions of [Al(OR F ) 4 ] À .The P À Pbond (2.069(2) )isslightly longer than those (2.034(2) ) in the free diphosphene Mes*P = PMes* [5a] and the parent molecule 1.T he Cr1 À P2 bond (2.299(1) )i ss horter than that in the previously reported radical cation [7] [(arene)Cr-(CO) 2 PPh 3 ] + .T he P1ÀC1 bond is longer while the P2ÀC7 bond is shorter than in parent molecule 1.Strikingly,the C1-P1-P2 angle (83.9(1)8 8)isthe smallest among the C-P-P angles observed in diphosphenes [5] and complexes thereof (89.4-121.48 8), [11] forming astrained planar four-membered ring.…”

“…The presence of phosphorus in DNA, RNA, ATP, and lipids makes it ak ey element of the circle of life.T he isolation of phosphorus-centered radicals [1][2][3][4] is an area of high current interest because of their importance for understanding chemical bonding,life on the early Earth, biological processes,o rganic synthesis,a nd functional materials.T riarylphosphines (Ar 3 P), tetraaryldiphosphines (Ar 2 PÀPA r 2 ), and biaryldiphosphenes (ArP = PA r) are three well-known types of organophosphorus compounds with different oxidation states on P( III, II, and I). Removal of one electron from these compounds could lead to the formation of the corresponding radical cations.I nf act, radical cations Ar 3 PC + (Ar = 2,4,6i Pr 3 C 6 H 3 or 2,4,6-Me 3 C 6 H 3 ) [3d,e] and (Ar 2 PÀPA r 2 )C + (Ar = 2,4,6-i Pr 3 C 6 H 3 ) [3f] were isolated and structurally characterized in 2013.…”