Abstract:

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.

Key words: Density functional theory; Natural bond orbital; Fe—Hg Interaction; ³¹P NMR