Theoretical Studies On M-M' Interactions And Spectral Properties Of The Binuclear Complexes Containing 2-(Diphenyl Phosphino) Pyridine Ligands

Binuclear complexes containing metal-metal interactions have been extensively studied due to their unique structures and properties including catalysis and spectroscopy. Recently, much interest is focused on the study of the binuclear complexes containing bidentate ligands with P or N donor atoms like 2-(diphenylphosphino)pyridine (Ph₂Ppy). The metal-metal interactions in this kind of complexes have notable effects on catalytic behaviour and spectroscopy. The researches about complexes with Ph₂Ppy ligands mainly focus synthesis and characterization experimentally. With the development of researches in this kind of complexes, some theoretical questions concerning catalytic mechanism and emission mechanism, such as molecular architecture, charge transport, the metal-metal interaction and its effect on catalytic activities and spectroscopy, become increasing important.In the present work, the metal-metal interactions and their effects on NMR chemical shifts and CO stretching vibrational frequencies of the organometallic complexes containing Ph₂Ppy ligands have been investigated by quantum chemistry calculations. The results suggest new theoretical basis and direction for design of novel organometallic materials. Our work will focus on four aspects:1. The stabilities, the nature of Ru-M interactions and their effects on ³¹P NMR in complexes [Ru(CO)3(Ph₂Ppy)2MCl2] (M=Zn, Cd, Hg) and [Ru(CO)₃(Ph₂Ppy)₂(MCl)]⁺ have been studied systematically by density functional theory (DFT) PBE0 method. The binding energies indicate that neutral Ru-Hg complex is stable and can be synthesized experimentally. As it is less stable than its cation complex, the reaction only gave the cation complex experimentally. The Ru-Zn cation complex is theoretically stable and experimental synthesis is in turn possible. The Ru-M interactions, those in cation complexes are stronger than corresponding neutral complexes, follows Fe-Hg>Fe-Zn≈Fe-Cd. The calculated ³¹P chemical shifts in 1³ are consistent to experimental results. Therefore, the ³¹P chemical shift with 52.09ppm in neutral Ru-Hg complex was predicted. The Ru→M or Ru←M charge-transfer interactions are revealed by NBO analysis. The interaction of Ru→M, corresponding to the delocalization from 4d orbital of Ru to s valence orbital of M2+, results in the delocalization of P-Ru→M, which decreases the electron density of P nucleus and causes the downfield ³¹P chemical shifts. Except 2, the back-donation effect of Ru←M, arising from the delocalization from s valence orbital of M2+ to the valence orbital of Ru, is against the P-Ru→M delocalization and results in the upfield ³¹P chemical shifts in 4.2. The Fe-M interactions and their effects on ³¹P NMR chemical shifts and carbonyl stretching vibrations in complexes [Fe(CO)₃(Ph₂Ppy)₂(MCl₂)]( 2:M=Zn; 3:M=Cd; 4:M=Hg )...