Novel multidentate ligand composed of phosphorus-bridged ferrocene units

磷桥联二茂铁低聚物具有一种特殊的分子结构，这种结构源于具有圆柱形的二茂铁部分。低聚物可通过与金属碎片、主族元素和/或有机连接物的键进一步组装。在本项目中，选择环状二聚体作为合成目标，以阐明它们作为配体的功能。合成了两个P原子与两个1，1‘-二茂铁基团双键连接的P(Net_2)桥联[1.1]二茂铁。将[1.1]桥联的[1.1]二茂铁与HCl进行氯化反应，选择性地得到PC1桥联的[1.1]二茂铁的合成异构体，与PhLi、Me_3SiCH_2Li、p-TolMgBr或HNEt_2反应得到相应的二芳化、二烷化或二酰化的化合物，保持了合成的构象。在甲苯中加热时，PPH桥联的[1.1]二茂铁的AN和异构体几乎完全转化为合成异构体，这表明AND异构体在合成异构体上是热不稳定的。上述需要空间构型和给电子的双膦螯合物适用于动力学和/或热力学稳定不饱和络合物。在磷桥上含有Ph或Me_3SiCH_2基团的四面体钴(II)二氯配合物成功地进行了烷基化反应，得到了相应的二烷基配合物，而类似的CoCl2(Dppp)烷基化反应生成了Co^0(Dppp)_2。所得到的二烷基配合物是第一个分离并经X-射线分析表征的配位不饱和钴(II)(双膦)(二烷基)配合物。该络合物有望作为钴(II)催化的Heck反应的模型中间体。

Phosphorus-bridged ferrocene oligomers possess a peculiar molecular structure which stems from a ferrocene moiety bearing a cylindrical shape. The oligomers can be further assembled via bonds with metal fragments, main group elements, and/or organic linkers. In this project, cyclic dimers are chosen as synthetic targets in order to elucidate their functionality as a ligand.Preparation. P(NEt_2)-bridged [1.1]ferrocenophane, in which two P atoms are linked doubly with two 1,1'-ferrocenediy1 moieties, were prepared. Chlorination with HC1 of a mixture of syn-and anti-P(NEt_2)-bridged [1.1]ferrocenophane accompanied facile anti-to-syn conversion to give the syn isomer of PC1-bridged [1.1]ferrocenophane selectively, and treatment of the chlorophospine thus obtained with PhLi, Me_3SiCH_2Li, p-TolMgBr, or HNEt_2 afforded the corresponding diarylated, dialkylated, or diaminated compounds with the syn conformation retained.Relative Stability. An and isomer of PPh-bridged [1.1]ferrocenophane could be converted almost completely to a syn isomer upon heating in toluene, indicative of the thermal instability of the and isomer over the syn isomer.Utility. Sterically demanding and electron-donating diphosphine chelates described above are suitable for kinetically and/or thermodynamically stabilizing an unsaturated complex. Alkylation of a tetrahedral cobalt(II)dichloro complex bearing a Ph or Me_3SiCH_2 group on the phosphorus bridge gave a corresponding dialkyl-complex successfully, whereas similar alkylation of CoCl_2(dppp) resulted in a formation of Co^0(dppp)_2. The dialkyl complex obtained is the first coordinatively-unsaturated cobalt(II)(diphosphine)(dialkyl) complex isolated and characterized by X-ray analysis. This complex is expected to serve as a model intermediate in the cobalt(II)-catalyzed Heck-type reactions.