Coordination of bistriflimide and triflate to the uranyl bis(diphenylphosphino)methane dication, {UO2(DPPMO2)2}2+

The {UO2(DPPMO2)(2)}(2+) dication (where DPPMO2=bis(diphenylphosphino)methane contains the linear uranyl group, {UO2}(2+), with two bidentate P=O donor ligands. Previously, we have shown that the weakly coordinating oxoanions [ReO4](-) and [TcO4](-) (as well as Cl-) will fill a fifth equatorial coordination site yielding complexes of general formula [UO2(DPPMO2)(2)X][X] (where X = [ReO4](-), [TcO4](-) and Cl-), with the X- anion acting in both monodentate coordinated and uncoordinated modes. Seven coordinate pentagonal bipyramidal uranyl complexes with the same general formula have now also been prepared with both the bistriflimide, ((CF3SO2)(2)N-, NTf2-) and triflate (CF3SO3- OTf-) anions and we report the structural characterisation of both [UO2(NTf2)(DPPMO2)(2)][NTf2] (1) and [UO2(OTf)(DPPMO2)(2)][OTf] (2). In the case of 1 the anion is coordinated through a terminal oxygen. representing the first structural characterization of an actinide-bistriflimide complex. Both the solid state uranium-anion bond lengths (for O-donor ligands only) and P-31[H-1) NMR solution competition studies indicate that the strength of the Uranyl-anion bond decreases along the series Cl- > [ReO4](-) > [OTf](-) > [NTf2](-). In addition, P-31(H-1) NMR competition studies show that both nitrate and excess DPPMO2 will readily displace the weakly coordinating X- anions. (c) 2008 Elsevier Ltd. All rights reserved.