Fe–Hg Interactions and 31P Chemical Shifts in [Fe(CO) 3 (PPh 2R) 2(HgCl 2)] (R=pym, fur, py, thi)

Abstract

In order to study the effects of R group on Fe–Hg interactions and 31P chemical shifts, the structures of mononuclear complexes Fe(CO) 3(PPh 2R) 2 (R=pym: 1, fur: 2, py: 3,thi: 4; pym=pyrimidine, fur=furyl, py=pyridine, thi=thiazole) and binuclear complexes [Fe(CO) 3(PPh 2R) 2(HgCl 2)] (R=pym: 5, fur: 6, py: 7, thi: 8) were studied using the density functional theory (DFT) PBE0 method. The 31P chemical shifts were calculated by PBE0-GIAO method. Nature bond orbital (NBO) analyses were also performed to explain the nature of the Fe–Hg interactions. The conclusions can be drawn as follows: (1) The complexes with nitrogen donor atoms are more stable than those with O or S atoms. The more N atoms there are, the higher is the stabilility of the complex. (2) The Fe–Hg interactions play a dominant role in the stabilities of the complexes. In 5 or 6, thereisa σ-bond between Fe and Hg atoms. However, in 7 and 8, the Fe–Hg interactions act as σ P–Fe→ n Hg and σ C–Fe→ n Hg delocalization. (3) Through Fe→Hg interactions, there is charge transfer from R groups towards the P, Fe, and Hg atoms, which increases the electron density on P nucleus in binuclear complexes. As a result, compared with their mononuclear complexes, the 31P chemical shifts in binuclear complexes show some reduction.