Uranium rhodium bonding in heterometallic complexes

Abstract

The heterotetra- and bimetallic uranium(iv)-rhodium(i) complexes [U^IVI₂(μ-OAr^P-1κ¹O,2κ¹P)₂Rh^I(μ-I)]₂ (2) (Ar^PO^- = 2-(diphenylphosphino)-6-tert-butyl-4-methylphenoxide) and U^IVI(μ-I)(μ-OAr^P-1κ¹O,2κ¹P)₃Rh^I (3) were prepared by treatment of U^IVI(OAr^P-κ²O,P)₃ (1) with rhodium(i) iodide olefin complexes. The reaction of 1 with the monodentate cyclooctene (coe) rhodium(i) precursor [(coe)₂Rh^II]₂ gives only the bimetallic complex [U^IVRh^I] 3, and with the diene [(cod)Rh^II]₂ (5) (cod = 1,5-cyclooctadiene), mixtures of [U^IVRh^I]₂ complex 2 and [U^IVRh^I] 3 along with (cod)Rh^IOAr^P-κ²O,P (4), a Rh^I side-product from the formation of 2. The complexes were characterised by single crystal X-ray diffraction, NMR and UV-vis-NIR spectroscopy, and electrochemistry. The U^IV-Rh^I intermetallic distances in 2 (2.7601(5) Å) and 3 (2.7630(5) Å) are among the shortest between f-elements and transition metals reported to date. Despite almost identical U-Rh bond lengths in the solid state, in solution only weak, and very different interactions between the metal centres are found.