Hexaorganodilead Compounds

The hexeorganodilead compounds in Table 505 are prepared by methods from the following scheme. 

Individual Hexaorganodilead Compounds may be found following Table 50.  

By rxn. of PbClg with MegCCHeMgCl at 0° as by-prod. (1955), in EtaO at -10% in 30% crude yield (2187). 

170 (dec.) (2865), UV spectrum (203, 9 7), electrochemical study, redox couple (2560), polarography (963, 965-7, 969), thermodynamic data (305). Rxn. with °Co irradiation - investigation by ESR spectroscopy (693). Y-irradiation at -192° - evidence of radical formation by IR, visible and ESR spectra (2685). 

Activity as fungicide against Aspergillus niger, Botrytis allii, Penicillium niger, Rhizopus nigricans (221). 

---

Hexaorganodilead compounds tend to be yellow in color, especially in solution. Because of their color, it was originally postulated that these compounds were capable of dissociating into triorganolead free radicals, RgPb- (see Section 2). The hexaalkyl compounds tend to be yellow oils, although the hexaneopentyldilead is a pale yellow solid 298,338). Hexaaryl derivatives are crystalline solids, generally soluble in the same types of solvents as are the tetraaryllead compounds. Similarly, the hexaalkyl compounds tend to be soluble in the same types of solvents as are the tetraalkyl derivatives. 

The cleavage of hexaorganodilead compounds with metals was first reported in 1939, when triphenylleadsodium was prepared by the action of... 

The Pb-Pb derivatives are by far the least numerous of the Group 14 singly bonded compounds due to the inherent wetikness of the metal-metal bonding. Chain compounds are limited to up to four linked lead units. The hexaorganodilead compounds represent the most studied class. Synthetic routes to access RjPb-PbRj include Wurtz coupling of triorganolead halides as well as reaction of lead(II) chloride with Grignards (Eq. (14.15)) [54]. 

II Oxidation of hexaorganodilead compounds with ozone in presence of carboxylic acid. 

In the first class are found the tetraorganolead, the hexaorganodilead, and the diorganolead compounds, as well as the newly discovered polylead compounds, such as tetrakis (triphenylplumbyl) lead, [(CgHs) 3-Pb]4Pb. 

What appears to be anomalously low thermal stability is often observed with alkyl-substituted ditins and dileads. The case of hexamethylditin 204, 206) is noted in the section on physical properties of tin compounds. The series of relative stabilities of hexaorganodileads 296) might also be viewed critically. The relatively high stability of hexacyclohexyldilead (in compari-... 

---