Homoleptic Perchlorophenyl "ate" Complexes of Thorium(IV) and Uranium(IV)

The reaction of AnCl4(DME)n (An = Th, n = 2; U, n = 0) with 5 equiv of LiC6Cl5 in Et2O resulted in the formation of homoleptic actinide-aryl "ate"complexes [Li(DME)2(Et2O)]2[Li(DME)2][Th(C6Cl5)5]3 ([Li][1]) and [Li(Et2O)4][U(C6Cl5)5] ([Li][2]). Similarly, the reaction of AnCl4(DME)n (An = Th, n = 2; U, n = 0) with 3 equiv of LiC6Cl5 in Et2O resulted in the formation of heteroleptic actinide-aryl "ate"complexes [Li(DME)2(Et2O)][Li(Et2O)2][ThCl3(C6Cl5)3] ([Li][3]) and [Li(Et2O)3][UCl2(C6Cl5)3] ([Li][4]). Density functional calculations show that the An-Cipso σ-bonds are considerably more covalent for the uranium complexes vs the thorium analogues, in line with past results. Additionally, good agreement between experiment and calculations is obtained for the 13Cipso NMR chemical shifts in [Li][1] and [Li][3]. The calculations demonstrate a deshielding by ca. 29 ppm from spin-orbit coupling effects originating at Th, which is a direct consequence of 5f orbital participation in the Th-C bonds.