Diphosphinoamido complexes of thorium(IV) and uranium-(IV) and -(V). Crystal structures of [{ThCl2[N(CH2CH2PPri2)2]2}2] and [{UCl2[N(CH2CH2PEt2)2]2}2]

Abstract

The complexes [MCl_x{N(CH₂CH₂PR₂)₂}_{4 – x}](M = Th or U; R = Et or Prⁱ; x= 1–3) and [UCl₂{N(CH₂CH₂PPrⁱ₂)₂}₃] have been isolated in moderate to good yields from the reaction of MCl₄ with Li[N(CH₂CH₂PR₂)₂]. The uranium(V) complex is shown to be formed by adventitious oxidation. The complexes isolated depend on the stoichiometry of the reaction, the bulk of the tertiary phosphine donors and the oxidation state of the metal (for uranium); they all have pendant donors and are labile in solution involving exchange of co-ordinated for unco-ordinated tertiary phosphine. The solid-state structure of [ThCl₂{N(CH₂CH₂CH₂PPrⁱ₂)₂}₂] has been determined: triclinic, space group P, a= 11.47(1), b= 13.18(1), c= 15.08(4)Å, α= 103.98(4), β= 96.01(5), γ= 99.17(4)°. It is dimeric in the solid state with two bidentate PNP ligands, one bridging and one terminal chloride per thorium. The geometry of the thorium centres is shown to be distorted capped octahedral. The solid-state structure of [UCl₂{N(CH₂CH₂PEt₂)₂}₂] was also determined: monoclinic, space group P2₁/a, a= 26.274(3), b= 10.782(4), c= 24.659(7)Å, β= 90.31(14). It is dimeric in the solid state, containing one tri- and one bi-dentate chelating PNP ligand, one bridging and one terminal chloride per uranium centre. The geometry of the uranium centres is shown to be distorted dodecahedral.