Tris(pyrazolyl)borate half-sandwich complexes of trivalent uranium incorporating the [C8H6{SiiPr3-1,4}2]2- and [C8H4{SiiPr3-1,4)2]2- ligands

The reaction of UI3 in THF with KTPme2 and the subsequent addition of [K2(C8H6{(SiPr3)-Pr-i-1,4)(2))] or [K-2(C8H4{(SiPr3)-Pr-i-1,4}(2))] yields dark red [U(K-3-T-P(Me2))(C8H6{(SiPr3)-Pr-i-1,4)(2))] 1and purple [U{K-3-T-P(Me2))(C8H4[(SiPr3)-Pr-i-1,4)(2))] 2, respectively The H-1 NMR of 1 at room temperature suggests a rigid structure, whereas 2 is fluxional in solution on the NMR timescale 1 is unreactive towards CO1 CO2 and MeNC under mild conditions: density functional calculations were used to compare the electronic and steric effects of the T-P(Me2) vs. CP* ligands in mixed sandwich complexes of the type [U(L)(C8H6{SiH3-1,4)2)] (L = Cp* Or (K-3-T-p(Me2))) On heating at 80 degrees C. 1 reacts with excess MeNC to yield [U(C8H6((SiPr3)-Pr-i-1,4)(2))(k(2)-dmpz)(2)(eta(1)-CNMe)] 3 The structures of 1-3 have been determined by single crystal X-ray diffraction. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved