ample, undergo a complicated redox reaction to give dichlorotriphenylphosphorane and (triphenylphosphoranediylchloro- methy1)triphenylphosphonium chloride [']. In contrast, the reaction of phosphanes with the tetrachlorides of silicon, germanium, tin, or titanium has hitherto only been found to yield 1 : 1 or 2: 1 adducts.
We have disovered that tri-tert-butylphosphane (I), of which complexes with transition metals in low oxidation states are known, does not form stable addition compounds with element(1v) tetrahalides. Instead, (I) is oxidized by the tetrahalides of germanium and tin in benzene solution to give tri-tert-butylhalophosphonium salts (2) ['].
Compounds of type (2) have also been formulated for the reaction of phosphanes with tetrahalomethanes (E = C) as ionpair intermediate but have so far defied detection. The halophosphonium salts (2a)-( ) however, are stable compounds open to identification by analysis and spectroscopy. Nevertheless, on variation of the stoichiometry formation of (2) may be followed by secondary reactions. Thus the anions SnCl; and SnCli-are formed from SnCl, and (2c). In the presence of an excess of ( I ) the halophosphonium salts are accompanied by tri-tert-butylphosphane-dichloro-and -dibromogermanediyls and stannanediyls which are poorly soluble in benzeneL3] : [(CHS)~C]QPX+X-+ [ ( C H ~) ~C I ~P E X Z (3a). X = C1 (3b). X = B r ( 4 a ) , E = G e , X = C 1 (4b), E = G e , X = B r ( 4 c ) , E = Sn, X = C1