No abstract

Understanding the bonding trends within, and the differences between, the 4f and 5f element series with soft donor atom ligands will aid elucidation of the fundamental origins of actinide (An) versus lanthanide (Ln) selectivity that is integral to many advanced nuclear fuel cycle separation concepts. One of the principal obstacles to acquiring such knowledge is the dearth of well characterized transuranic molecules that prevents the necessary comparison of 4f versus 5f coordination chemistry, electronic structure, and bonding. Reported herein is new chemistry of selenium analogues of dithiophosphinate actinide extractants. Ln III and An III/IV complexes with the diselenophosphinate [Se 2 PPh 2 ] À anion have been synthesized, structurally and spectroscopically characterized, and quantum chemical calculations performed on model compounds in which the phenyl rings have been replaced by methyl groups. The complexes [Ln III (Se 2 PPh 2) 3 (THF) 2 ] (Ln ¼ La (1), Ce (2), Nd (3)), [La III (Se 2 PPh 2) 3 (MeCN) 2 ] (4), [Pu III (Se 2 PPh 2) 3 (THF) 2 ] (5), [Et 4 N][M III (Se 2 PPh 2) 4 ] (M ¼ Ce (6), Pu (7)), and [An IV (Se 2 PPh 2) 4 ] (An ¼ U (8), Np (9)), represent the first f-element diselenophosphinates. In conjunction with the calculated models, complexes 1-9 were utilized to examine two important factors: firstly, bonding trends/differences between trivalent 4f and 5f cations of near identical ionic radii; secondly, bonding trend differences across the 5f series within the An IV oxidation state. Analysis of both experimental and computational data supports the conclusion of enhanced covalent bonding contributions in Pu III-Se versus Ce III-Se bonding, while differences between U IV-Se and Np IV-Se bonding is satisfactorily accounted for by changes in the strength of ionic interactions as a result of the increased positive charge density on Np IV compared to U IV ions. These findings improve understanding of soft donor ligand binding to the f-elements, and are of relevance to the design and manipulation of f-element extraction processes.

A series of tetravalent An(IV) complexes with a bis-phenyl β-ketoiminate N,O donor ligand has been synthesized with the aim of identifying bonding trends and changes across the actinide series. The neutral molecules are homoleptic with the formula An((Ar)acnac)(4) (An = Th (1), U (2), Np (3), Pu (4); (Ar)acnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-(t)Bu(2)C(6)H(3)) and were synthesized through salt metathesis reactions with actinide chloride precursors. NMR and electronic absorption spectroscopy confirm the purity of all four new compounds and demonstrate stability in both solution and the solid state. The Th, U, and Pu complexes were structurally elucidated by single-crystal X-ray diffraction and shown to be isostructural in space group C2/c. Analysis of the bond lengths reveals shortening of the An-O and An-N distances arising from the actinide contraction upon moving from 1 to 2. The shortening is more pronounced upon moving from 2 to 4, and the steric constraints of the tetrakis complexes appear to prevent the enhanced U-O versus Pu-O orbital interactions previously observed in the comparison of UI(2)((Ar)acnac)(2) and PuI(2)((Ar)acnac)(2) bis-complexes. Computational analysis of models for 1, 2, and 4 (1a, 2a, and 4a, respectively) concludes that both the An-O and the An-N bonds are predominantly ionic for all three molecules, with the An-O bonds being slightly more covalent. Molecular orbital energy level diagrams indicate the largest 5f-ligand orbital mixing for 4a (Pu), but spatial overlap considerations do not lead to the conclusion that this implies significantly greater covalency in the Pu-ligand bonding. QTAIM bond critical point data suggest that both U-O/U-N and Pu-O/Pu-N are marginally more covalent than the Th analogues.

The syntheses of two phenylamine-based ligand systems, N(o-PhNH(2))(3) and N(o-PhNHC(O)(i)Pr)(3), are reported. These ligands readily coordinate to Co(II) to form monomeric complexes. X-ray diffraction studies establish that the [N(o-PhNC(O)(i)Pr)(3)](3-) ligand stabilizes the Co(II) ion in a trigonal-monopyramidal coordination environment. The axial coordination site in this complex is accessible and, upon cyanide coordination, generates an electrochemically active species.

Introduction Electronic patient records are becoming more common in critical care. As their design and implementation are optimized for single users rather than for groups, we aimed to understand the differences in interaction between members of a multidisciplinary team during ward rounds using an electronic, as opposed to paper, patient medical record.