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Berkelium is positioned at a crucial location in the actinide series between the inherently stable half-filled 5f(7) configuration of curium and the abrupt transition in chemical behavior created by the onset of a metastable divalent state that starts at californium. However, the mere 320-day half-life of berkelium's only available isotope, (249)Bk, has hindered in-depth studies of the element's coordination chemistry. Herein, we report the synthesis and detailed solid-state and solution-phase characterization of a berkelium coordination complex, Bk(III)tris(dipicolinate), as well as a chemically distinct Bk(III) borate material for comparison. We demonstrate that berkelium's complexation is analogous to that of californium. However, from a range of spectroscopic techniques and quantum mechanical calculations, it is clear that spin-orbit coupling contributes significantly to berkelium's multiconfigurational ground state.

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Raman spectra of all the actinide(V) (except Pa) and actinide(VI) complexes in 2 M Na2C03 solutions have been obtained.A resonance Raman effect was observed for Np(VI), Pu(VI), and Am(VI) and found to be related to the position of the charge-transfer bands observed in the corresponding electronic spectra and to the formal potential of actinide(VI)/actinide(V) couples in carbonate solution. No resonance effect was observed in the Raman spectrum of U(VI). The symmetric stretching frequency (¡q) of the M022+ group was shifted in carbonate solutions as compared to acidic noncomplexing solutions and decreased regularly with an increase in the atomic number of the actinide considered. In contrast, the iq frequencies of the M02+ group for actinide(V) species in carbonate solutions did not vary as the atomic number of the actinide increased. In comparison to the iq frequencies in acidic solutions, in carbonate solution a small negative shift was observed for vx of Np(V) and a positive shift was obtained for vx of Am(V). The Raman spectra of Na3M02(C03)2 solid compounds were obtained for M = Np, Pu, and Am. The iq frequencies of the M02+ ions decreased linearly with increasing atomic number of the actinide and were higher than the corresponding values for aqueous M02+ ions. The differences in behavior observed between actinide(V) and -(VI) species in noncomplexing media and in carbonate media may be related to possible hydrogen bonding between the oxygen of the actinide(V) oxycation and water molecules.

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An approach to obtaining substantial amounts of data from a hazardous starting material that can only be obtained and handled in small quantities is demonstrated by the investigation of a single small-scale reaction of cyclooctatetraene, C8H8, with a solution obtained from the reduction of Cp′3Pu (Cp′ = C5H4SiMe3) with potassium graphite. This one reaction coupled with oxidation of a product has provided single-crystal X-ray structural data on three organoplutonium compounds as well as information on redox chemistry thereby demonstrating an efficient route to new reactivity and structural information on this highly radioactive element. The crystal structures were obtained from the reduction of C8H8 by a putative Pu­(II) complex, (Cp′3PuII)1−, generated in situ, to form the Pu­(III) cyclooctatetraenide complex, [K­(crypt)]­[(C8H8)2PuIII], 1-Pu, and the tetra­(cyclopentadienyl) Pu­(III) complex, [K­(crypt)]­[Cp′4PuIII], 2-Pu. Oxidation of the sample of 1-Pu with Ag­(I) afforded a third organoplutonium complex that has been structurally characterized for the first time, (C8H8)2PuIV, 3-Pu. Complexes 1-Pu and 3-Pu contain Pu sandwiched between parallel (C8H8)2– rings. The (Cp′4PuIII)− anion in 2-Pu features three η5-Cp′ rings and one η1-Cp′ ring, which is a rare example of a formal Pu–C η1-bond. In addition, this study addresses the challenge of small-scale synthesis imparted by radiological and material availability of transuranium isotopes, in particular that of pure metal samples. A route to an anhydrous Pu­(III) starting material from the more readily available PuIVO2 was developed to facilitate reproducible syntheses and allow complete spectroscopic analysis of 1-Pu and 2-Pu. PuIVO2 was converted to PuIIIBr3(DME)2 (DME = CH3OCH2CH2OCH3) and subsequently PuIIIBr3(THF) x , which was used to independently synthesize 1-Pu, 2-Pu, and 3-Pu.

The effects of alpha-particle self-irradiation have been investigated in solutions of "'Pu in the pH range from 1.3 to > 2.2. The ionic strengths of the solutions ranged from 0.