Divalent and trivalent gas-phase coordination complexes of californium: evaluating the stability of Cf(ii)

Abstract

The divalent oxidation state is increasingly stable relative to the trivalent state for the later actinide elements, with californium the first actinide to exhibit divalent chemistry under moderate conditions. Although there is evidence for divalent Cf in solution and solid compounds, there are no reports of discrete complexes in which Cf(II) is coordinated by anionic ligands. Described here is the divalent Cf methanesulfinate coordination complex, Cf(II)(CH3SO2)3(-), prepared in the gas phase by reductive elimination of CH3SO2 from Cf(III)(CH3SO2)4(-). Comparison with synthesis of the corresponding Sm and Cm complexes reveals reduction of Cf(III) and Sm(III), and no evidence for reduction of Cm(III). This reflects the comparative 3+/2+ reduction potentials: Cf(3+) (-1.60 V) ≈ Sm(3+) (-1.55 V) ≫ Cm(3+) (-3.7 V). Association of O2 to the divalent complexes is attributed to formation of superoxides, with recovery of the trivalent oxidation state. The new gas-phase chemistry of californium, now the heaviest element to have been studied in this manner, provides evidence for Cf(II) coordination complexes and similar chemistry of Cf and Sm.

Genome-wide toxicogenomic study of the lanthanides sheds light on the selective toxicity mechanisms associated with critical materials

“…1A), but these deletion mutants include only a small number of overrepresented GO terms, suggesting that at IC20 concentration, this metal affects many aspects of cell biology in a nonspecific manner. Eu is the lanthanide with the most accessible divalent chemistry (higher standard reduction potential) (35), which may contribute to its greater involvement in chemical bonding with biological receptors. Although the exact reasons for the three different trends within the lanthanide series are not fully understood, distinct behaviors between lighter and heavier lanthanides had been previously observed in other biological systems, including bacteria (36,37).…”

Contemporary Chemistry of Berkelium and Californium

“…[52,53] In the + II state these studies provide important comparisons with Sm II , which is the closeste lectrochemical analog of Cf II ,a nd similar gas-phase speciation was observed for Sm II and Cf II complexes. [54,55] Albeit, divalent californium chemistry has been historically somewhat developed in simple binary compounds such as halides, little else is known about californium's divalent character. [21,54] Studies of the pentavalent states revealed more non-intuitive trends in which covalency in the An=Ob onds from Pu V to Cf V is observed across the actinide series concomitant with distortions of the linear geometry of AnO 2 + cation from the linear, trans-PuO 2 + cation to bents tructures for AmO 2 + ,C mO 2 + ,a nd BkO 2 + ,a nd finally to a cis-geometryf or CfO 2 + as shown in Figure 4.…”

“…Gas‐phase studies on californium complexes have been used to investigate all oxidation states from Cf II to Cf V . In the +II state these studies provide important comparisons with Sm II , which is the closest electrochemical analog of Cf II , and similar gas‐phase speciation was observed for Sm II and Cf II complexes . Albeit, divalent californium chemistry has been historically somewhat developed in simple binary compounds such as halides, little else is known about californium's divalent character .…”

Covalency in AnCl3 (An = Th–No)

“…For a long time, the second part of this statement was moot, as the radioactivity and scarcity of the later actinides precluded experimental study. However, thanks to the heroic recent efforts of a number of researchers, [1][2][3][4][5] we are now beginning to explore the chemistry of the later actinides, including the nature of the metal-ligand bonding. [6][7][8][9] An interesting subtlety of the bonding in the actinide series concerns the nature of any covalent bonding present.…”