Organometallics 1991,10, 2908-2913
2908
Attempted Synthesis of 1,3,5-Triphenyl-2,4,9-trithia-l,3,5-triplumbaadamantane. Decomposition of Organoiead Iodides Michio Kobayashi, St6phan Latour, and James D. Wuest' D6partemnt de Chlmk, Universit6 de Montr&l, Montr6a1, Qhbec, H3C 3J7 Canada Received January 25, 199 1 MNDO calculations suggest that the strength of the bridgehead carbon-hydrogen bond in 2,4,9-trithia1,3,5-triplumbaadamantane(2a) should be only 54 kcal/mol and the hydride affmity 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 la. Unfortunately, substituted derivative 2b could not be prepared from (Ph3PbCH2)3CHby controlled iodinolysis followed by treatment of the intermediate hexaiodide (Ph12PbCH2)&Hwith Ph3SnSSnPhp This failure results in part from the tendency of organolead diiodides &PbIz to undergo redistribution reactions that produce unstable triiodides RPbIp Diiodides capable of intramolecular redistributions are particularly reactive. The resulting triiodides then decompose by a formal reductive elimination of RI and PbIP Since the iodinolysis of (cyclopropylmethy1)triphenylplumbane(11) yields mainly (iodomethy1)cyclopropaneinstead of ring-opened products derived from cyclopropylmethyl cations or radicals, we suggest that the reductive elimination of RI and PbIz from RPb13 is concerted.
Carbon-hydrogen bonds antiperiplanar to several lone pairs or carbon-metal bonds are unusually reactive donors of hydride or hydrogen atoms.' For example, the bridgehead carbon-hydrogen bond in hypothetical stannaadamantane la is activated as a donor of hydrogen by three antiperiplanar carbon-tin bonds. MNDO calcula-
la (M-Sn.R-H)
11. ( M - S n )
