Some oxygen-donor complexes of cyclopentadienyluranium(IV)N-thiocyanate; steric considerations and stability

Abstract

The oxygen-donor complexes [U(cp)(NCS)₃L₂][cp =η-C₅H₅, L = Me₃CCONMe₂(dmpva), Me₂CHCONMe₂(dmiba), PPh₃O, and P(NMe₂)₃O (tdpo)] have been prepared and i.r. and u.v.–visible (solution and solid reflectance) spectra are reported for them. Analogous complexes with L = MeCONMe₂(dma), EtCONMe₂(dmpa), EtCONEt₂(depa), pyridine, and 2,2′-bipyridyl could not be isolated and disproportionation to [U(cp)₃(NCS)] and [U(NCS)₄L_x] occurred. The observations are discussed in terms of the steric crowding about the uranium atom using a cone-packing model.