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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.
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) = 3122, 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 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- 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 mon onuclear 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 * CO 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.