Trepanier Steven J, Dennett James N L, Sterenberg Brian T, McDonald Robert, Cowie Martin
Department of Chemistry, University of Alberta Edmonton, AB, Canada T6G 2G2.
J Am Chem Soc. 2004 Jun 30;126(25):8046-58. doi: 10.1021/ja040054z.
The mixed-metal complex, [RhOs(CO)(4)(dppm)(2)][BF(4)] (1; dppm = micro-Ph(2)PCH(2)PPh(2)) reacts with diazomethane to yield a number of products resulting from methylene incorporation into the bimetallic core. At -80 degrees C the reaction between 1 and CH(2)N(2) yields the methylene-bridged [RhOs(CO)(3)(micro-CH(2))(micro-CO)(dppm)(2)][BF(4)] (2), which reacts further at ambient temperature to give the allyl methyl species, [RhOs(eta(1)-C(3)H(5))(CH(3))(CO)(3)(dppm)(2)][BF(4)] (4). At intermediate temperatures compounds 1 and 2 react with diazomethane to yield the butanediyl complex [RhOs(C(4)H(8))(CO)(3)(dppm)(2)][BF(4)] (3) by the incorporation and coupling of four methylene units. Compound 2 is proposed to be an intermediate in the formation of 3 and 4 from 1 and on the basis of labeling studies a mechanism has been proposed in which sequential insertions of diazomethane-generated methylene fragments into the Rh-C bond of bridging hydrocarbyl fragments occur. Reaction of the tricarbonyl species, [RhOs(CO)(3)(micro-CH(2))(dppm)(2)][BF(4)] with diazomethane over a range of temperatures generates the ethylene complex [RhOs(eta(2)-C(2)H(4))(CO)(3)(dppm)(2)][BF(4)] (7a), but no further incorporation of methylene groups is observed. This observation suggests that carbonyl loss in the formation of the above allyl and butanediyl species only occurs after incorporation of the third methylene fragment. Attempts to generate C(2)-bridged species by the reaction of 1 with ethylene gave no reaction, however, in the presence of trimethylamine oxide the ethylene adducts [RhOs(eta(2)-C(2)H(4))(CO)(3)(dppm)(2)][BF(4)] (7b; an isomer of 7a) and [RhOs(eta(2)-C(2)H(4))(2)(CO)(2)(dppm)(2)][BF(4)] (8) were obtained. The relationship of the above products to the selective coupling of methylene groups, and the roles of the different metals are discussed.
混合金属配合物[RhOs(CO)(4)(dppm)(2)][BF(4)]（1；dppm = μ-Ph(2)PCH(2)PPh(2)）与重氮甲烷反应，生成了许多因亚甲基掺入双金属核心而产生的产物。在-80℃下，1与CH(2)N(2)反应生成亚甲基桥连的[RhOs(CO)(3)(μ-CH(2))(μ-CO)(dppm)(2)][BF(4)]（2），其在室温下进一步反应生成烯丙基甲基物种[RhOs(η(1)-C(3)H(5))(CH(3))(CO)(3)(dppm)(2)][BF(4)]（4）。在中间温度下，化合物1和2与重氮甲烷反应，通过四个亚甲基单元的掺入和偶联生成丁二烯基配合物[RhOs(C(4)H(8))(CO)(3)(dppm)(2)][BF(4)]（3）。化合物2被认为是由1形成3和4的中间体，基于标记研究提出了一种机制，其中重氮甲烷生成的亚甲基片段依次插入桥连烃基片段的Rh-C键中。三羰基物种[RhOs(CO)(3)(μ-CH(2))(dppm)(2)][BF(4)]在一系列温度下与重氮甲烷反应生成乙烯配合物[RhOs(η(2)-C(2)H(4))(CO)(3)(dppm)(2)][BF(4)]（7a），但未观察到亚甲基的进一步掺入。这一观察结果表明，上述烯丙基和丁二烯基物种形成过程中的羰基损失仅在第三个亚甲基片段掺入后发生。尝试通过1与乙烯反应生成C(2)桥连物种未发生反应，然而，在三甲胺氧化物存在下，得到了乙烯加合物[RhOs(η(2)-C(2)H(4))(CO)(3)(dppm)(2)][BF(4)]（7b；7a的异构体）和[RhOs(η(2)-C(2)H(4))(2)(CO)(2)(dppm)(2)][BF(4)]（8）。讨论了上述产物与亚甲基选择性偶联的关系以及不同金属的作用。
