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

The new bis-iminophosphorane complexes [UO2Cl{(eta)^3-CH(Ph2PNSiMe3)2}(thf)](1) and [UO2Cl{(eta)^3-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) (angstrom) in contrast to 2 where the U-N bond is close to the equatorial plane (0.154(3)(angstrom)). This difference in geometry results in an unusual low energy electronic absorption band for 1 originating from C (right arrow)U LMCT supported by molecular orbital calculations at the DFT level.