Pakistan Research Repository


Siddiqui, M.S. (1978) MOLECULAR ADDITION COMPOUNDS OF PHOSPHINES. PhD thesis, University of Karachi, Karachi.



Addition compounds of tertiary phosphines with arbon disulphide, p-quinones and nitroatromatics have been reported. It has beep found that the first two ets of compounds are zwitterionic in nature while the set set is of the charge transfer type. Addition and eplacement reactions of the adducts with mineral Acids, icric acid, metal salts and phos1) 1ine complexes have been carried out and the mechanism of these reactions has been discussed. Phosphoniodithioformates obtained from alkylphosphines and carbon disulphide are basic in n2ture and form salts it11 hydrochloric and picric acids. Reaction of the .hydrochloride with picric acid eliminates hydrochloric acid and forms the corresponding phosphoniumdithioformate picrate he dithioformate moiety is eliminated on reacting the ompounds wit p-quinones of high oxidation potential or ith Cobalt chloride forming respectively phosphobetaines and his (phosphine) dichlorocobalt. Mechanism of these eaction has been proposed. Stability of these compounds has been discussed in terms of molecular effective electronegativity, Xeff. Their constitution has been elucidated by using infra red pectrn. The shift of Vas(P-C) to higher frequencies and or' those related to carbon disulphide to lower frequencies on compound formation suggests quaternization of the phosphine 'which supports the phosphoniodithioformate formulation H3P+CSS-. Phosphobetaine formation has been found to depend on the donor property of phosphines as well as on the accepting ability of quinones given by their oxidation potential. The reaction of phosphobetaines with acids alkyl halides metallic salts and displacement reactions of the hydrochloride with picric acid etc. have been carried out. The reactions of quinones with phosphonium salts like R3 PHX also yields the corresponding phosphonium halide. Infrared spectra of phosphobetaines in the 1400 - 1500, 1220 - 1250 and 600 - 800 cm-1 region indicate that substitution occurs in the quinone ring with P-C bond formation and that they are resonance hybrids of the phosphinemethylene and zwitterionic structure Ultraviolet spectra of the phosphobetaines recorded at pH 2,6 and 8 shows that the position, and intensity of bands is susceptible to changes in pH. There is a decrease in the intensity of the N-Л in the acid medium which characterizes ionized carboxyl’s. A red shift with an enhancement in intensity is noted in the basic medium and this characterizes phenols. The pattern therefore suggests that a zwitterionic structure is favoured in the acid while the phosphinemethylene structure is dominant in the basic medium With picric acid they form phosphonium picrates such as 2,5 dihydroxyaryl (trialkyl/aryl) phosphonium picrates.The infrared and ultraviolet studies ,of phosphobetaine picrates at pH 2,6 and 8 and ,also other characteristic properties support n proton transfer reaction mechanism whereby the proton is transferred from picric acid to phosphobetaine. Spectroscopic studies suggest that phosphine nitroaryls are charge transfer complexes since their I.R. spectra do not have the characteristic proton transfer bands for example, V (P-H) or V(C-O) while a charge transfer band, similar to that of amine-nitroaryls is found in the ultraviolet spectra of these complexes.

Item Type:Thesis (PhD)
Uncontrolled Keywords:phosphines, phosphoniodithioformates, carbon disulphide, phosphobetaine tetrachlorocobaltates, phosphine-nitroaryl
Subjects:Physical Sciences (f) > Chemistry(f2)
ID Code:701
Deposited By:Mr. Muhammad Asif
Deposited On:27 Sep 2006
Last Modified:04 Oct 2007 21:02

Repository Staff Only: item control page