含三齿席夫碱配体锇(Ⅵ)的氮合物与CN^(-)的反应活性研究

Study on the reactivity of an osmium(Ⅵ)nitrido complex bearing a tridentate Schiff base ligand with CN^(-)

通过含三齿席夫碱配体锇(Ⅵ)的氮合物mer-[Os^(Ⅵ)(L^(1))(N)(Cl)(H_(2)O)]和不同比例的CN^(-)在乙腈中反应,分别得到了fac-(PPh_(4))[Os^(Ⅵ)(N)(L^(1))(CN)_(2)]和fac-(PPh_(4))_(2)[Os^(Ⅵ)(N)(L^(2))(CN)_(2)]两个配合物。当相同的反应在水中进行时,发现配合物mer-[Os^(Ⅵ)(L^(1))(N)(Cl)(H_(2)O)]易于分解,并分离出产率较低的锇(Ⅵ)的氮合物(PPh_(4))_(2)[Os(L^(3))(CN)_(4)]。通过X射线晶体学确定了配合物fac-(PPh_(4))[Os^(Ⅵ)(N)(L^(1))(CN)_(2)]、fac-(PPh_(4))_(2)[Os^(Ⅵ)(N)(L^(2))(CN)_(2)]和(PPh_(4))_(2)[Os(L^(3))(CN)_(4)]的晶体结构。配合物fac-(PPh_(4))[Os^(Ⅵ)(N)(L^(1))(CN)_(2)]结晶于单斜晶系,P2_(1)/n空间群。通过对堆积图的观察发现,碳与苯环质心的距离为3.508A,说明存在边界面的π--π堆积作用。配合物fac-(PPh_(4))_(2)[Os^(Ⅵ)(N)(L^(2))(CN)2]结晶于三斜晶系,P-1空间群。两个芳香环形成的二面夹角为99.3°,这与配合物fac-(PPh4)[Os^(Ⅵ)(N)(L^(1))(CN)_(2)]中的二面夹角相比要大一点。配合物(PPh_(4))_(2)[Os(L^(3))(CN)_(4)]结晶于正交晶系,Pnma空间群,金属锇中心也是由一个双齿配体L^(3)和四个CN^(-)配体构成的6配位的扭曲的八面体几何构型。配合物mer-[Os^(Ⅵ)(L^(1))(N)(Cl)(H_(2)O)]、fac-(PPh_(4))[Os^(Ⅵ)(N)(L1)(CN)_(2)]和fac-(PPh4)2[Os^(Ⅵ)(N)(L^(2))(CN)_(2)]均通过IR,UV/Ⅵs,CV,ESI/MS和元素分析进行了充分的表征,结果表明,含三齿席夫碱配体锇(Ⅵ)的氮合物与CN^(-)的反应主要发生在配体的C==N官能团上,这可能是含三齿席夫碱配体锇(Ⅵ)的氮合物作为催化剂的催化效率较低的主要原因。

Treatment of an osmium(Ⅵ)nitrido complex,mer-[Os^(Ⅵ)(L^(1))(N)(Cl)(H2O)]bearing a tridentate Schiff base ligand with different ratios of CN^(-) in CH3CN produced two complexes,fac-(PPh_(4))[Os^(Ⅵ)(N)(L^(1))(CN)_(2)]and fac-(PPh_(4))2[Os^(Ⅵ)(N)(L^(2))(CN)_(2)],respectively.When the same reaction was carried out in H_(2)O,ready decomposition of mer-[Os^(Ⅵ)(L^(1))(N)(Cl)(H2O)]was found and an osmium(Ⅵ)nitrido complex(PPh_(4))_(2)[Os(L^(3))(CN)4]with a low yield was isolated.The crystal structures of fac-(PPh_(4))[Os^(Ⅵ)(N)(L^(1))(CN)_(2)],fac-(PPh_(4))2[Os^(Ⅵ)(N)(L^(2))(CN)_(2)]and(PPh_(4))2[Os(L^(3))(CN)4]were also determined by X-ray crystallography.The complex fac-(PPh_(4))[Os^(Ⅵ)(N)(L^(1))(CN)_(2)]crystallizes in monoclinic system,P21/n space group.By obserⅥng the packing diagram,the distance between carbon to centroid of phenyl ring is found to be 3.508A,indicating the existence of the edge-to-face π--π stacking interactions.The complex fac-(PPh_(4))2[Os^(Ⅵ)(N)(L^(2))(CN)_(2)]crystallizes in triclinic crystal system,P-1 space group.The dihedral angle of the two aromatic rings is 99.3°,which are remarkably larger than that in the complex fac-(PPh_(4))[Os^(Ⅵ)(N)(L^(1))(CN)_(2)].The complex(PPh_(4))_(2)[Os(L^(3))(CN)_(4)]crystallizes in orthorhombic system,Pnma space group.The osmium center is also 6-coordinated by a bi-dentate ligand L^(3)and four CN^(-)ligands in a distorted octahedron geometry.Compounds mer-[Os^(Ⅵ)(L^(1))(N)(Cl)(H2O)],fac-(PPh_(4))[Os^(Ⅵ)(N)(L^(1))(CN)_(2)]and fac-(PPh_(4))_(2)[Os^(Ⅵ)(N)(L^(2))(CN)_(2)]have been well characterized by IR,UV/Ⅵs,CV,ESI/MS and elemental analysis.This study shows that the reaction of the osmium(Ⅵ)nitrido complex bearing Schiff base ligand with CN-mainly occurs on the C==N functional group of the ligand,which may be the main reason for the low catalytic efficiency of the osmium(Ⅵ)nitrido complex bearing Schiff base ligand as catalysts.