Abstract
Selective azide mono-oxidation of o-bis(phosphines) such as o-bis(diphenylphosphino)benzene and other bis(phosphines) with cis-substituents on a rigid backbone such as an ethylene structure occurs as the result of the steric control exerted during the azide oxidation (Staudinger) reaction process. The azides used were the trimethylsilyl, 4-cyanotetrafluorophenyl, benzyl, and diphenoxyphosphonyl azides. The prototypical ligand 1-Ph2PN(SiMe3)-2-(Ph2P)C6H4, 2, has been structurally characterized. Crystal data for 2: crystal dimensions, 0.38 × 0.38 × 0.57 mm; space group, monoclinic, P21/c, (No. 14); a = 11.093(5) Å, b = 14.898(5) Å, c = 18.811(2) Å, β = 102.76(2)°, V = 3031 Å3, Z = 4. Final R, Rw and GOF values were 0.068, 0.074, and 1.92 respectively. The PNSiMe3 angle was wide, 152.7(3)°, and the PN bond length short (1.529(5) Å) relative to arylated iminophosphoranes but in keeping with the trends for silylated analogs. The iminophosphorane center can be selectively transformed with other agents in a Wittig type reaction converting the azides to the monooxide, monosulfide, etc. The iminophosphoranophosphines are also good complexing agents and the Rh(I) complex derived from 2, 1-Ph2PN(SiMe3)-C6H4-2-(Ph2P)Rh(CO)Cl, 15 was structurally characterized. Crystal data for 15: crystal dimensions, 0.32 × 0.44 × 0.66 mm; space group, monoclinic, P21/c (No. 14); a = 13.793(3) Å, b = 12.622(11) Å, c = 20.436(6) Å, β = 105.93(2)°, V = 3421.2 Å3, Z = 4. Final R, Rw, and GOF values were 0.064, 0.061, and 1.45 respectively. The complex shows typical square planar geometry about Rh, a cis phosphine−CO relationship, and no exceptional steric crowding of the coordination site.

This publication has 36 references indexed in Scilit: