In order to study the Fe-Cu interactions and their effects on 31P NMR,the structures of mononuclear complex Fe(CO)3(Ph2Ppy)2 1 and binuclear complexes Fe(CO)3(Ph2Ppy)2(CuXn) (2:Xn=Cl22-,3:Xn=Cl-,4:Xn=Br-) are calculated by density functional theory (DFT) PBE0 method. For complexes 1,3 and 4,the 31P NMR chemical shifts calculated by PBE0-GIAO method are in good agreement with experimental results. The 31P chemical shift is 82.10 ppm in the designed complex 2. The Fe-Cu interactions (including Fe→Cu and Fe←Cu charge transfer) mainly exhibit the indirect interactions. Moreover,the Fe-Cu(I) interactions (mostly acting as σFe-P→4sCu and σFe-C→4sCu charge transfer) in complexes 3 and 4 are stronger than Fe-Cu(II) interactions (mostly acting as σ*Fe-C←4sCu and σ*Fe-P←4sCu) in complex 2. In complex 2,the stronger Fe←Cu interac-tions,acting as σ*Fe-P←4sCu charge transfer,increase the electron density on P nucleus,which causes the upfield 31P chemical shift compared with mononuclear complex 1. For 3 and 4,although a little deshielding for P nucleus is derived from the delocalization of σFe-P→4sCu due to the Fe→Cu interactions,the stronger σFe-C→nP charge-transfer finally increases the electron density on P nucleus. As a result,an upfield 31P chemical shift is observed compared with 1. The stability follows the order of 2>3≈4,indicating that Fe(CO)3(Ph2Ppy)2(CuCl2) is stable and could be synthesized experimentally. The N-Cu(II) interaction plays an important role in the stability of 2. Because the delocalization of σFe-C→4sCu and σFe-C→π*C-O weakens the σ bonds of Fe-C and π bonds of CO,it is favorable for increasing the catalytic activity of binuclear complexes. Complexes 3 and 4 are expected to show higher catalytic activity compared to 2.
