Dau Phuong D, Shuh David K, Sturzbecher-Hoehne Manuel, Abergel Rebecca J, Gibson John K
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Dalton Trans. 2016 Aug 2;45(31):12338-45. doi: 10.1039/c6dt02414a.
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.
对于后几个锕系元素，二价氧化态相对于三价态越来越稳定，锎是第一个在中等条件下表现出二价化学性质的锕系元素。尽管有证据表明溶液和固体化合物中存在二价锎，但尚无关于Cf(II)由阴离子配体配位的离散配合物的报道。本文描述了二价甲磺酸锎配位配合物Cf(II)(CH3SO2)3(-)，它是通过从Cf(III)(CH3SO2)4(-)中还原消除CH3SO2在气相中制备的。与相应的钐和锔配合物的合成比较表明，Cf(III)和Sm(III)被还原，没有证据表明Cm(III)被还原。这反映了3+/2+的比较还原电位：Cf(3+)（-1.60 V）≈Sm(3+)（-1.55 V）≫Cm(3+)（-3.7 V）。O2与二价配合物的结合归因于超氧化物的形成，同时恢复了三价氧化态。锎的这种新的气相化学性质，现在是通过这种方式研究的最重的元素，为Cf(II)配位配合物以及Cf和Sm的类似化学性质提供了证据。
