Plumbylenes heteroleptic

Note also the reactivity of the heteroleptic plumbylene 174 toward carbon disulfide. Treatment of 174 with excess amount of carbon disulfide resulted in a formation of unexpected product, lead(II) bis(aryl trithiocarbonate) (192), as a yellow, air- and moisture-stable solid (Scheme 14.85). The reaction must involve not only the insertion of carbon disulfide into the Pb—S bond, but also the formal insertion of a sulfur atom into the Pb C(Tbt) bond and subsequent insertion of another... 

Surprisingly, in compound 31 two relatively short Pb Si contacts to adjacent Me3Si groups are observed49 which are only about 20% longer than the covalent Pb(II)—Si bonds in heteroleptic aryl(silyl)plumbylenes. 

FIGURE 8. Molecular structure of the heteroleptic plumbylene 43a in the crystal... 

Apart from the heteroleptic plumbylenes 43a,b, one homoleptic species is known to form intramolecular N — Pb contacts bis-l-[2-(A,A/-dimethylaminoethyl)ferrocenyl] plumbylene (50)53, the Pb—N distances in 50 with 266.1 and 270.8 pm being again much longer than covalent Pb11—N bonds (ca 220 pm) or the Pb—N bonds in the plumbylene 43a (234.4 232.2 pm). 

In 1974 the first stable diaminoplumbylene (76) was synthesized by Lappert and coworkers68 and since then many other stable plumbylenes with heteroatom substituents have been reported. Recently, the synthesis and characterization of a stable aryl(arylthio)-plumbylene (77), which is one of the rare examples of heteroleptic plumbylenes, have also been reported (Scheme 29)69. 

Heteroleptic diplumbenes even shorter Pb-Pb bond lengths from 2.903-2.9899(5) A can be obtained by the substituent exchange between two homoleptic plumbylenes, equation (6), Sisyl = (MesSifsSi, presumably formed by initial formation of the symmetrical diplumbene. 

---