配合物[Fe(CO)x(Ph2Ppy)y(HgCl2)z](x=3, 4; y=1, 2; z=0, 1, 2)的Fe-Hg相互作用及31P化学位移的理论研究

用密度泛函理论PBE0法计算配合物[Fe(CO)x(Ph2Ppy)y(HgCl2)z](1: x=4, y=1, z=0; 2: x=3, y=2, z=0; 3: x=4, y=1, z=1; 4: x=3, y=2, z=1; 5: x=4, y=1, z=2; 6: x=3, y=2, z=2)的几何构型, 用PBE0-GIAO法计算配合物1~6的31P化学位移. 计算结果表明, 含2个Ph2Ppy的配合物5和6的Fe—Hg相互作用略大于含单个Ph2Ppy的配合物3和4. 含2个HgCl2的配合物4和6存在Fe—Hg σ键, 比含单个HgCl2的配合物3和5的Fe—Hg相互作用强, 配合物3和5的Fe—Hg相互作用以Fe→Hg和Fe←Hg离域为主. 配合物3中Fe的负电荷比5的小, 故配合物5的Fe—Hg相互作用比配合物3的强且Fe→Hg离域比较显著, 而配合物3的Fe←Hg离域更显著. Fe—Hg相互作用增大了双核配合物中P核周围的电子密度, 其31P化学位移比相应的单核配合物小, 且含2个HgCl2的双核配合物的31P化学位移更小. 含单个Ph2Ppy的配合物的31P化学位移小于含2个Ph2Ppy的配合物.

Theoretical Studies on the Fe-Hg Interactions and the 31P NMR in [Fe(CO)x(Ph2Ppy)y(HgCl2)z](x=3, 4;y=1, 2;z=0, 1, 2)

To study the Fe—Hg interactions and their effects on 31P NMR, [Fe(CO)x(Ph2Ppy)y(HgCl2)z](1: x=4, y=1, z=0; 2: x=3, y=2, z=0; 3: x=4, y=1, z=1; 4: x=3, y=2, z=1; 5: x=4, y=1, z=2; 6: x=3, y=2, z=2) were calculated by DFT PBE0 method. PBE0-GIAO method was employed to calculate the 31P chemical shifts. The conclusions can be drawn: (1) The Fe—Hg interactions in complexes with two Ph2Ppy are slightly stronger than those with one Ph2Ppy, and which in complexes with two HgCl2 are stronger than those with one HgCl2. (2) There is a Fe—Hg σ bond in complexes with two HgCl2. Fe—Hg interactions mainly exhibit the Fe→Hg and Fe←Hg indirect charge-transfer. Contrasted to complex 5, the CO→Fe σ-donation and CO←Fe π-back donation in complex 3 decrease the electron density of Fe. So the Fe—Hg interaction in complex 5 is stronger and acts as Fe→Hg charge-transfer, while that in complex 3 mainly acts as Fe←Hg. (3) Through Fe—Hg interaction, the charge-transfer from Ph and py towards the P, Fe and Hg atoms increases the electron density on P nucleus. So, compared with mononuclear complexes, the 31P chemical shifts in binuclear complexes show some reduction. The 31P chemical shifts in complexes with two HgCl2 or one Ph2Ppy are less than those with one HgCl2 or two Ph2Ppy.