Organoleads disproportionation

It is interesting to mention that PbCl2 is stable whereas PbCLj is thermodynamically unstable and decomposes at room temperature to yield PbCl2 and elemental CI2. On the other hand, organolead(IV) compounds have been prepared (and have been used extensively as fuel additives, such as PbEtq) whereas species like PbEt2 have yet to be prepared and are likely not possible, as they disproportionate to the more thermodynamically stable PbEt4 and solid Pb. This tendency is also reflected in the reaction enthalpies of the methyl... 

Further disproportionation reaction is important in organolead chemistry. As reported in Section m. C, tetraorganylplumbanes were obtained by reacting PbCl2 with organometal-lic compounds via the intermediates PbR2. The processes were accompanied by cleavage and formation of C—Pb and Pb—Pb bonds as described by equations 22 and 23. 

Decay of °Pb(CH3)4 in the gas and in the liquid phase has been studied under different conditions. Bi(CH3)3 [1, 5] and also Po(CH3)2 [1] are assumed as decay products, and evidence of molecular survival, i.e., failure of bond rupture in the primary p- and internal conversion process was obtained [5, 6] see also [7, 10]. [Bi(CH3)4]+ is presumed to be the initial ionic species of the decay process [9,10]. A very detailed study revealed that at low pressures no Bi(CH3)3 is obtained, the primary ion [Bi(CH3)4]+ disproportionates and gives depositions on the wall however, at higher pressures, production of Bi(CH3)3 becomes the dominant process since the primary ion undergoes many collisions before reaching the wall [10]. A volatile organolead compound was produced in a methane atmosphere by Pb recoiling from... 

The former process, when applied to isoprene living ends, has been shown to initiate the block copolymerization of styrene with an efficiency of 0.43 if both radical species initiate, or with an efficiency of 0.86 if the organolead radical disproportionates and the polyisoprenyl radical is the sole initiator. 

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