1-alkynyllead compounds

Fig. 3. 62.8 MHz solid-state 207Pb CP MAS NMR spectra of 1-alkynyllead compounds as shown.121 The spinning side bands arise from rotation of the samples (upper trace 3.4kHz middle trace 3.1 kHz lower trace 2.4kHz). The isotropic d207Pb NMR data are indicated by arrows [<5207Pb (in C6D6)/(S207Pb (solid) Me3Pb-C=C-PbMe3 -158.6/-169.0 Me2Pb(C=C- Bu)2 -298.5/-295.0 Pb(C=C-Me)4 -687.5/-695.0],...

Alkenyl- or alkynyllead compounds can be prepared by specific methods, some of which can be generalized. 

Besides the early preparation by Gilman173 of alkynyllead compounds using sodium acetylides and triorganolead halides, and the following modification of the method174 ... 

Alkynyllead compounds were also prepared by the decarboxylation of triphenylplumbyl esters of alkyne carboxylic acids176 ... 

Vinyllead and alkynyllead tricarboxylates can only be prepared by metal-metal exchange, such as mercury-lead,ll6 ll7 tin-lead,ll6,ll7 boron-lead i or zinc-lead.l In the case of tin-lead exchange, cleavage of the methyl-tin bond is much slower than cleavage of the vinyl-tin or alkynyl-tin bond. Therefore (trimethyl)vinyltin derivatives are preferred to the corresponding (tributyl)vinyltin analogues for the synthesis of the unstable vinyllead and alkynyllead compounds. 

The 3-borolenes (97) were among the several products obtained by the reaction of dichloro-(diisopropylamino)borane with the corresponding 1,3-dienes (96) in the presence of Na/K alloy (Equation (20)) <90JOM(386)i >. Reaction of alkenylboranes with alkynyllead compounds is another approach <9)ZN1207>. 

A summary of all alkynyllead compounds prepared up to 1965 is given by Davidsohn and Henry (41) therefore, we will deal with them only briefly. Four procedures are known for the preparation of alkynylleads. 

This procedure is very mild and should be the most suitable method to prepare alkynyllead compounds with functional groups such as CN, CONH2, =CO, etc. These still unknown compounds cannot be prepared by the first two procedures mentioned and would certainly be difficult to obtain by the fourth procedure. 

In spite of the synthesis of numerous new alkynyllead compounds, knowledge about their reactivity is very limited. The Pb—C= bond is generally more susceptible to polar reagents such as water, halogen, K2Hgl4, and AgN03 than the vinyllead grouping. 

Alkynyltin and alkynyllead derivatives were extensively studied by PES, together with NMR and pseudopotential calculations88,92,93,97. For the sake of simplicity we will divide the compounds investigated into two classes ... 

Alkynyllead triacetates.1 Pb(OAc)4 reacts with a 1-alkynyltrimethyltin to form trimethyltin acetate and an unstable 1-alkynyllead triacetate (a), which can effect alkynylation of (i-dicarbonyl compounds and nitronates. In general yields are highest with R = QH, and lowest with R = H. 

Davies and Puddephatt recently established 43, 45) that the alkynyllead grouping is cleaved easily in polar reactions, but less readily than alkynyl Grignard compounds. Thus mild syntheses are possible e.g., with acid chlorides. 

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