Coordination Chemistry of Cyclopropenylidene-Stabilized Phosphenium Cations: Synthesis and Reactivity of Pd and Pt Complexes
Coordination Chemistry of Cyclopropenylidene-Stabilized Phosphenium Cations: Synthesis and Reactivity of Pd and Pt Complexes
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DOI：
10.1002/chem.201303686
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发表时间：
2014-02-17
影响因子：
4.3
通讯作者：
Alcarazo, Manuel
中科院分区：
文献类型：
--
作者：
Kozma, Agnes;Deden, Tobias;Alcarazo, Manuel
通过[（iPr（2）N）（2）C3+Cl] BF_4与仲膦反应，直接合成了亚环丙烯基稳定的膦阳离子1a-g。通过对Rh配合物[RhCl（CO）L-2]（BF_4）（2）中CO伸缩频率的分析和电化学方法评价了它们的给电子能力。环丙烯鎓环诱导亚磷酸酯型行为，其可以通过连接到磷原子的另外两个取代基来调节。尽管它们带有正电荷，但膦阳离子1a-g仍然充当双电子供体配体，与Pd-II和Pt-II前体形成加合物。相反，在Pd-O物质存在下，发生Pd原子氧化插入到C-卡宾-磷键中，提供二聚体结构，其中每个Pd原子键合到环丙烯基卡宾，而两个二烷基/二芳基磷化物配体用作两个Pd中心之间的桥。测试所得Pt-II络合物库的催化性能;所有阳离子膦加速2-乙炔基-1，1-联苯的原型6-内切环化以提供五螺烯。最佳配体1g被用于合成两种天然产物：金鱼藻毒素和表麦冬异苷A。
A straightforward synthesis of cyclopropenylidene-stabilized phosphenium cations 1a-g through the reaction of [(iPr(2)N)(2)C3+Cl]BF4 with secondary phosphines is described. Their donor ability was evaluated by analysis of the CO stretching frequency in Rh complexes [RhCl(CO)L-2](BF4)(2) and electrochemical methods. The cyclopropenium ring induces a phosphite-type behavior that can be tuned by the other two substituents attached to the phosphorus atom. Despite of the positive charge that they bear, phosphenium cations 1a-g still act as two-electron donor ligands, forming adducts with Pd-II and Pt-II precursors. Conversely, in the presence of Pd-0 species, an oxidative insertion of the Pd atom into the C-carbene-phosphorus bond takes place, providing dimeric structures in which each Pd atom is bonded to a cyclopropenyl carbene while two dialkyl/diaryl phosphide ligands serve as bridges between the two Pd centers. The catalytic performance of the resulting library of Pt-II complexes was tested; all of the cationic phosphines accelerated the prototype 6-endo-dig cyclization of 2-ethynyl-1,1-biphenyl to afford pentahelicene. The best ligand 1g was used in the synthesis of two natural products, chrysotoxene and epimedoicarisosideA.