Dimethyldiphenylphosphonium Iodide and Its Diethyl Derivative.

Abstract

Li-PPh_2 reacts with R-I (R : CH_3,C_2H_5) in the mole ratio 1 : 2 to give phosphonium iodide [PR_2Ph_2] I directly. The phosphonium salts of the type [PRR'_3]X, [PR"_4]X (R : CH_3 ; R' : C_6H_5 ; R" : CH_3,C_6H_5 , X Cl^-, Br^-, I^-) have been widely known to act as counter ions^1 In them, [Pme_4]Br is particurally known to lead to a chelating phosphonium ylide (CH_3)_3P=CH_2^2 for the metal complexes . Yet, di-ethyldiarylphosphonium salt has been elusive. The direct reactions of Li-PPh_2,which has been previously prepared by dealing PPh_3 with Li, with twice molar quantities of R-I (R : Me, Et) give [PR_2Ph_2] I*, possibly via PRPh_2^3 as shown in Scheme 1. ^1H-nmr evidencies for the compounds are as following : [Pme_2Ph_2] I^4 : δ_Me 2.89 PPM doublet (3), Jp-_H 14 Hz, δc-_H (Ph) 7.66 PPM multiplet (5) ; [Pet_2Ph_2] I : δMe (C_2H_5) 1.20 PPM doublet of triplet (3), Jp-_H 19 Hz, δ_C_H_2 (C_2H_5) 3.06 PPM doublet of quartet (2), Jp-_H' 14 Hz, J_H-_H' 8 Hz, δc-_H (C_6H_5) 7.70 PPM multiplet (5). [chemical formula][chemical formula][chemical formula][PR_2Ph_2]I Scheme 1 The metathesis of [PR_2Ph_2] I with AgClO_4 or NaBF_4 easily proceed stoichiometrically, but no reaction with NaBH_4 or LiAIH_4 even in boiling methanol can occur.