Uranyl bis-iminophosphorane complexes with in- and out-of-plane equatorial coordination

Abstract

The new bis-iminophosphorane complexes [UO₂Cl{η³-CH(Ph₂PNSiMe₃)₂}(thf)] (1) and [UO₂Cl{η³-N(Ph₂PNSiMe₃)₂}(thf)] (2) are synthesised from the reaction of [UO₂Cl₂(thf)₃] with Na[CH(Ph₂PNSiMe₃)₂] (NaI) and Na[N(Ph₂PNSiMe₃)₂] (NaII), respectively. Both 1 and 2 form dinuclear complexes in the absence of a coordinating solvent. The reactivity of 1 has been explored. The crystal structures of 1 and 2 have been determined. They display distorted pentagonal bipyramidal geometry with ligands I and II both bonding in a tridentate chelating manner which is shown to remain intact in solution. Complex 1 contains a U–C bond that is out of the equatorial plane by 0.842(3) Å in contrast to 2 where the U–N bond is close to the equatorial plane (0.154(3) Å). This difference in geometry results in an unusual low energy electronic absorption band for 1 originating from C → U LMCT supported by molecular orbital calculations at the DFT level.