Cyclic Bis(phosphanyl)carbenium Ion by Protonation of a 1,3‐Diphosphacyclobutane‐2,4‐diyl

Abstract

Strong interactions with the lone pairs of the neighboring, pyramidalized phosphorus atoms stabilize the cyclic carbenium ion 2. The 1,3‐bis(phosphanyl)carbenium unit was obtained by protonation of a 1,3‐diphosphacyclobutane‐2,4‐diyl 1 (R=2,4,6‐tBu3C6H2, HX=trifluoromethanesulfonic acid).

Theoretical Study of Substituted PBPB Dimers: Structural Analysis, Tetraradical Character, and Excited States

“…However, recently, a few stable diradicals based on main-group elements have been isolated. [26][27][28][29][30][31][32][33][34][35] Among them, 1,3-diborata-2,4-diphosphoniocyclobutane-1,3-diyls (1A in Figure 1) yield a "localized singlet diradical that is indefinitely stable at room temperature" upon † University of California and Lawrence Berkeley National Laboratory. ‡ adequate choice of substituents.…”

Diverse reactions of sterically-protected 1,3-diphosphacyclobutane-2,4-diyls with hydride

“…4, 5 Nonetheless, in 1995, Niecke and co-workers reported a room temperature stable compound containing the 1,3diphosphacyclobutane-2,4-diyl skeleton I for the first time. 6 Subsequent studies on systems modelled on this biradical 6 have provided much new fundamental information on these uniquely stable biradicals, pioneered by Niecke et al [7][8][9][10][11][12][13] and ourselves. [14][15][16][17][18] Besides P,C-based 4-membered heterocyclic biradicals, other structurallyrelated cyclic biradicals have also attracted interest.…”

Phosphorus-substituted carbene complexes: Chelates, pincers and spirocycles

“…This ligand, unlike its silyl progenitor, has been shown to coordinate to Rh thus dispelling the notion that these systems were ineffective donors and also illustrating the dramatic effect of substitution on the character of the ligand [10]. Other remarkable examples are the bis(phosphanyl)carbenium ion isolated from protonation of 1,3-diphosphanylcyclobutane-2,4-diyl [11] and the heterocyclic four membered P-N-C-P ring carbene reported in early 2005 also by Bertrand and co-workers [12]. Four-coordinate phosphonium centres have also recently been linked to the carbene, as [13] and [R 3 P-C-N i Pr 2 ][CF 3 SO 3 ] (R = Cy, Ph), again by the Bertrand group [14].…”