Selective Azide Oxidation of 1,2-Bis(diphenylphosphino)benzene and Related Ethylenebis(phosphines) to Asymmetric Multifunctional Phosphorus Ligands and Formation of Rhodium(I) Complexes of These Ligands. Structural Characterization of the Prototypical Ligand 1-(((Trimethylsilyl)imino)diphenylphosphorano)-2-(diphenylphosphino)benzene and Its Rhodium(I) Complex: 1-Ph(2)P=N(SiMe(3))C(6)H(4)-2-(Ph(2)P)Rh(CO)Cl.
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-Ph(2)P=N(SiMe(3))-2-(Ph(2)P)C(6)H(4), 2, has been structurally characterized. Crystal data for 2: crystal dimensions, 0.38 x 0.38 x 0.57 mm; space group, monoclinic, P2(1)/c, (No. 14); a = 11.093(5) Å, b = 14.898(5) Å, c = 18.811(2) Å, beta = 102.76(2) degrees, V = 3031 Å(3), Z = 4. Final R, R(w) and GOF values were 0.068, 0.074, and 1.92 respectively. The P=N-SiMe(3) angle was wide, 152.7(3) degrees, and the P=N 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-Ph(2)P=N(SiMe(3))-C(6)H(4)-2-(Ph(2)P)Rh(CO)Cl, 15 was structurally characterized. Crystal data for 15: crystal dimensions, 0.32 x 0.44 x 0.66 mm; space group, monoclinic, P2(1)/c (No. 14); a = 13.793(3) Å, b = 12.622(11) Å, c = 20.436(6) Å, beta = 105.93(2) degrees, V = 3421.2 Å(3), Z = 4. Final R, R(w), 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.
Reed
Robert W.
RW
Department of Chemistry, University of Alberta, Edmonton, AB, Canada T6G 2G2.
Santarsiero
Bernard
B
Cavell
Ronald G.
RG