SHORT COMMUNICATION DOI: 10.1002/ejic.200600562 Actinide-Transition Metal Heteronuclear Ions and Their Oxides: {IrUO} + as an Analogue to Uranyl Marta Santos, [a] Joaquim Marçalo,* [a] António Pires de Matos, [a] John K. Gibson,* [b] and Richard G. Haire [b] Keywords: Actinides / Ion–molecule reactions / Isolobal relationship / Mass spectrometry / Metal–metal interactions / Uranium Recent theoretical calculations have shown that Ir should be- have as a chemical analogue to N, with the result that IrUO + , like known NUO + , is predicted to be a stable species isoelec- tronic with UO 2 2+ , the uranyl dication. The target hetero- metallic analogue to uranyl has now been prepared by direct laser desorption/ionization of a U/Ir alloy, and by oxidation Introduction Despite that actinide–transition metal (An–M nd ) bond- ing has been an important goal in molecular actinide chem- istry, remarkably few complexes have been characterized in which an An–M nd bond has been clearly identified (An = Th, U). [1,2] In these complexes, the An–M nd bonding is either mediated by phosphido bridges, [1] or is between the An and a M nd -containing fragment, M nd Cp(CO) 2 (Cp = cy- clo-C 5 H 5 ), [2] which can be considered an “organometallic pseudohalogen”. [3] Accordingly, there to date seem to be no well-established molecular complexes with a direct, unsup- ported covalent An–M nd bond. Gaseous AnM nd bimetallics are elementary molecular species incorporating distinct An–M nd bonding. The ThRu, ThRh, ThIr, ThPt, and URh molecules, synthesized in high-temperature vapors, have bond energies of 500 to 600 kJ mol –1 . [4] Direct An–M 5d bonding was also demon- strated with the preparation of the ThFe + and UFe + ions by collision-induced dissociation (CID) of AnFe(CO) x + (x = 2, 3). [5] In a recent theoretical study, Gagliardi and Pyykkö [6] predicted several stable triatomic species which would incorporate covalent bonds between uranium and 5d transition metals (M 5d ), including IrUO + . According to the concept of “autogenic isolobality”, [6,7] Au can behave as a pseudohalogen, Pt as a pseudochalcogen, and Ir as a pseu- dopnictogen. Thus, IrUO + can be formally represented as [a] Departamento de Química, Instituto Tecnológico e Nuclear, 2686-953 Sacavém, Portugal Fax: +351-21-994-6185 E-mail: jmarcalo@itn.pt [b] Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6375, USA Fax: +1-865-574-4987 E-mail: gibsonjk@ornl.gov © 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2006, 3346–3349 3346 of UIr + with N 2 O and C 2 H 4 O. Properties of UIr + , UPt + , and UAu + bimetallic ions have been studied. They demonstrate direct actinide–transition metal bonding, and support the concept of “autogenic isolobality”. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) {IrU=O} + , which is nominally isoelectronic with {NU=O} + and {O=U=O} 2+ (the uranyl dication); [6] both of the latter have been prepared in the gas phase. [8,9] In view of recent theoretical predictions of strong U–M 5d covalent bonds and stable triatomic species incorporating such bonds, we employed laser desorption/ionization (LDI) of binary An/M 5d alloys to synthesize gaseous AnM 5d + bi- metallic ions. The synthesis of these ions, and their reac- tions with nitrous oxide, ethylene oxide, and ethane, are in- terpreted in the context of “autogenic isolobality”, [6,7] and the nature of An–M 5d bonds. [6] Results and Discussion In the initial experiments that employed dilute ( 2–5 wt.-%) An/Pt alloys (An = Th, Pa, U, Np, Pu, Am, Cm), [10] several diatomic and triatomic ions were produced. These included the bimetallics, ThPt + , PaPt + , UPt + , NpPt + , PuPt + , AmPt + and CmPt + , the trimetallics ThPt 2 + and UPt 2 + , and the bimetallic oxides OThPt + , OPaPt + , OUPt + and ONpPt + . The appearance of the OAnPt + (from O con- tamination in the alloys) only for Th through Np reflects the particularly strong O–An + bonds there; [10] the suggested atomic connectivities of the oxides are consistent with this strong bonding. Generation of the AnPt + ions motivated a LDI study of U/M 5d alloys (M 5d = Os, Ir, Pt, Au;  20 wt.-% U). The following three bimetallics were produced in the indicated order of relative yields: UAu +  UPt +  UIr + ; UOs + was not observed. Illustrative LDI spectra are shown in Fig- ure 1. For each U/M 5d (M 5d = Au, Pt, Ir) alloy, U + and M 5d + were produced by LDI, both in an abundance very roughly an order of magnitude greater than that of UM 5d + .