Sulphoxide complexes of actinoid tetrahalides

Complexes of actinoid tetrachlorides with sulphoxides MCl4,xR2SO [R = Et, x= 4(Th), 3(Th, U, or Np). and 2·5(Np or Pu); R = Ph, x= 4(Th, U, or Np) and 3(U, Np, or Pu); R = C10H7, x= 3(Th or U)] have been prepared. I.r. spectra, including tentative assignments for metal–halogen stretching frequencies in these complexes and the uranium tetrabromide complexes UBr4,yR2SO (R = Me, y= 8 and 6; R = Et, y= 5; R = Ph, y= 4), are reported. X-Ray powder diffraction data are also presented and the electronic spectra of the uranium tetrachloride complexes are discussed.