Studies on catalysts for selective functionalization of Group 14 compounds

烯丙基碳酸酯在三甲基硅基氰化物的催化下，在四氢呋喃中回流，高产率地氰化生成β，伽马不饱和碳腈。几种顺式和反式脂环底物的氰化反应进行得很干净(立体选择性为99%)，总保留率为99%。与本催化剂相关的钯配合物的表征和反应表明，ETA^3-烯丙基钯配合物与三甲基硅氰化物容易发生金属转移反应，而生成的氰基(ETA^3-烯丙基)钯配合物只有在存在过量的三甲基硅氰化物时才能生成相应的烯丙基氰化物。产物的立体化学表明，CN从钯一侧进攻ETA^3-烯丙基。两个顺-双(硅基)双(膦)铂配合物，顺-[铂(SiPh_2Me)_2(PMe_2Ph)_2]和顺-[铂(SiFMe_2)_2(Pet_3)_2]和两个顺-双(锡基)双(膦)钯配合物的结构和流动行为，测定了顺式[Pd(SnMe_3)_2(PMe_3)_2]和顺式-[Pd(SnMe_3)_2(PMePh_2)_2]，它们的结构均为扭曲的正方形平面结构。双(硅基)铂配合物在核磁共振时间尺度上表现出流动行为。在流动过程中，P、Si和铂之间的自旋-自旋耦合被保留，即这些核自旋态在分子内是保守的。络合物的流动性归因于通过准四面体过渡态的单分子扭转。双(锡基)钯配合物的类似流动性能通过利用溶液和固体核磁共振都很明显。

Allylic carbonates are cyanated in high yields to beta, gamma-unsaturated carbonitriles using trimethylsilyl cyanide in the presence of catalytic amount (5 mol%) of Pd(PPh_3)_4 in THF under reflux. The cyanations of several cis- and trans-alicyclic substrates proceed cleanly (stereoselectivity> 99%) with overall retention. Characterization and reaction of palladium complexes relevant to the present catalysis indicate that transmetallation of eta^3-allyl palladium complex with trimethylsilyl cyanide is facile, while the resulting cyano(eta^3-allyl)palladium complexes afford the corresponding allylic cyanides only when excess trimethylsilyl cyanide is present. Stereochemistry of the product indicates that the CN attacks the eta^3-allyl moieties from the palladium side.The structures and fluxional behavior of two cis-bis(silyl)bis(phosphine)platinum complex, cis- [Pt(SiPh_2Me)_2(PMe_2Ph)_2] and cis-[Pt(SiFMe_2)_2(PEt_3)_2], and two cis-bis(stannyl)bis(phosphine)palladium complex, cis-[Pd(SnMe_3)_2(PMe_3)_2] and cis-[Pd(SnMe_3)_2(PMePh_2)_2], were examined, The complexes have twisted square-planar structures with cis-orientation of the ligands. The bis(silyl)platinum complexes show fluxional behavior on the NMR time-scale. In the fluxional process, the spin-spin coupling between P, Si, and Pt are retained ; namely these nuclear spin states are intramolecularly conserved. The fluxionality of the complexes is attributed to the unimolecular twist-rotation via pseudo tetrahedral transition state. Similar fluxionality of the bis(stannyl)palladium complex is evident by utilizing both solution and solid state ^<31>P NMR.