Attempted synthesis of 1,3,5-triphenyl-2,4,9-trithia-1,3,5-triplumbaadamantane. Decomposition of organolead iodides

Article abstract of DOI:10.1021/om00054a069

MNDO calculations suggest that the strength of the bridgehead carbon-hydrogen bond in 2,4,9-trithia-1,3,5-triplumbaadamantane (2a) should be only 54 kcal/mol and the hydride affinity of the corresponding bridgehead cation 2a⁺ should be only 215 kcal/mol. As a donor of hydrogen atoms or hydride, plumbaadamantane 2a should therefore be even more reactive than the analogous stannaadamantane 1a. Unfortunately, substituted derivative 2b could not be prepared from (Ph₃PbCH₂)₃CH by controlled iodinolysis followed by treatment of the intermediate hexaiodide (PhI₂PbCH₂)₃CH with Ph₃SnSSnPh₃. This failure results in part from the tendency of organolead diiodides R₂PbI₂ to undergo redistribution reactions that produce unstable triiodides RPbI₃. Diiodides capable of intramolecular redistributions are particularly reactive. The resulting triiodides then decompose by a formal reductive elimination of RI and PbI₂. Since the iodinolysis of (cyclopropylmethyl)triphenylplumbane (11) yields mainly (iodomethyl)cyclopropane instead of ring-opened products derived from cyclopropylmethyl cations or radicals, we suggest that the reductive elimination of RI and PbI₂ from RPbI₃ is concerted.