Synthesis and reactions of new diphosphenes bearing extremely bulky substituents

Abstract

In this paper, we present the synthesis of new diphosphenes TbtPPTbt and BbtPPBbt having extremely bulky substituents, 2,4,6‐tris[bis(trimethylsilyl)methyl]phenyl (Tbt) and 2,6‐bis[bis(trimethylsilyl)methyl]‐4‐[tris(trimethylsilyl)methyl]phenyl groups (Bbt). Their x‐ray crystallographic analysis revealed their unique structures in the solid state. Furthermore, the configurations of these extremely overcrowded diphosphenes, TbtPPTbt and BbtPPBbt, are twisted in different ways in spite of the close structural similarity between Tbt and Bbt groups. DFT calculations were performed to estimate the energy difference between the two configurations of diphosphenes. In addition, their structures and physical properties were compared with those of their heavier congeners, distibenes (ArSbSbAr, Ar = Tbt and Bbt) and dibismuthenes (ArBiBiAr, Ar = Tbt and Bbt) having the same substituents. Although the reactivities of the extremely hindered diphosphenes might be considerably suppressed owing to the severe steric congestion, it was found that they can react with elemental sulfur and selenium to give the corresponding thia‐ and selenadiphosphirane derivatives, respectively, in addition to the previously reported diphosphenes. Copyright © 2003 John Wiley & Sons, Ltd.