Theoretical Study On Bonding Properties Of Actinide-silicon/actinide-carbon In Actinide Metal Complexes

The organometallic complexes have been widely used in various catalytic reactions and good research results have been obtained.Further understanding of the geometric structure and bonding properties of complexes can enrich the contents of structural chemistry and coordination chemistry.In this thesis,we have systematically studied the electronic structures and bonding in actinide organometallic complexes using scalar-relativistic density functional theory(DFT).The main creative results are as follows:(1)The electronic structures of the complexes(Cp Si Me₃)₃An Si(NCHMes)₂(An=Th-Am)were investigated using the density functional theory(DFT)by changing the valence states(II,III,IV)of actinides and actinides atoms.An-Si bond length for a series of[An-Si]with different oxidation state may be contributed by the synergistic effect of the steric hindrance and the ability of actinide atom to accept electrons.The An-Si bonds are highly polarized and have donor-acceptor interaction.In addition,the binding energies suggest that the tetravalent complexes[An ^IV-Si]⁺are thermodynamically accessible.The electron affinity analysis suggests that the reduction reaction of[An ^III-Si]?[An ^II-Si]^-should become increasingly facile across the actinide series from Th to Am.This work expands the knowledge on the An-Si bonding,especially for the transuranium-silicon bonding and guides synthesis of the actinide silicon complexes with different oxidation state.(2)The structure and properties of M(CH₂Ph)₄(M=Mo?U?Th?Ce?Zr?Hf)and its derivatives(U(2-picolyl)₄and U(o-OMe Bn)₄have been studied by DFT.The structures,bonding nature and thermodynamic properties of the complexes are explored.The results show that in the lanthanide/actinide metal complexes,the d and f valence orbitals are involved in the formation of M-C/N?bonds,while in the transition metal complexes,the metal d orbitals are involved in the formation of?bonds,and the bonding between Zr(benzyl)₄and Hf(benzyl)₄complexes has obvious similarities.QTAIM and EDA analysis showed that the metal-ligand bond was mainly ionic character,and there was little charge accumulation between the two nuclei.The negative values of binding energy show that the formation of metal complexes is thermodynamically favorable.