A theoretical probe for pentavalent bis-imido uranium complexes containing diverse axial substituents and equatorial donors: U-N multiple bond and structural/electronic properties

摘要

Pentavalent trans-bis(imido) uranium complexes, [U-V(NR)(2)(THF)(2)(cis-I-2)](-) (2R), [U-V(NR)(2)(THF)(3)(trans-I-2)](-) (3R) and [U-V((NBu)-Bu-t)(2)(THF)(3)(cis-I-2)](-) (3(t)Bu'), have been examined using relativistic density functional theory, where the R substituent is changed from CF3, Ph, H, Me, Bu-t to Cy. The calculated electron -spin density indicates the 5f(1) configuration on the uranium center, which is mainly reflected by the HOMO with over 96% metal character. The U-V-N triple bond in these complexes is evidenced by computed bond length, bond order and electronic structure, although being weaker than U-VI-N in their hexavalent analogues and U-V-O in uranyl analogues. The U-NH stretching vibrational frequencies of 2H and 3H are calculated between 698 and 745 cm(-1), while the U-N-C ones of other complexes are found in the range from 1043 to 1285 cm(-1). This shift is caused by the strong coupled interaction between sizable substituent and U-N bond. The present study unravels that the changes of the R substituents as well as the number and the position of equatorial donors are capable of tuning structural and electronic properties of bis-imido complexes. (C) 2016 Elsevier B.V. All rights reserved.