A closer look at the phosphorus-phosphorus double bond lengths in meta-terphenyl substituted diphosphenes

摘要

The single crystal X-ray structure of DmpPPDmp (1, Dmp = 2,6-Mes _2C_6H_3), which was previously reported to have a relatively short PP bond distance of 1.985(2) at room temperature, has been reexamined at variable temperatures. Crystallographic analyses of 1 at 100 K allow for resolution of disorder of the two phosphorus atoms (which is unresolvable from room temperature diffraction data), and for determination of a more conventional PP bond length of 2.029(1). Single crystals of the closely related diphosphene DxpPPDxp (2, Dxp = 2,6-(2,6-Me_2C _6H_3)_2C_6H_3) show similar disorder in one of two crystallographically independent molecules in the unit cell. A value of 2.0276(4) is found for the non-disordered PP bonds at 100 K for 2. A new diphosphene Ar′PPAr′ (3, Ar′ = 2,6-Mes _2-4-OMe-C_6H_3) has been prepared and its structure has also been examined. The PP bond length for 3 was determined to be 2.0326(9) and relatively free of the effects of disorder.