Characterizing how actinide properties change across the f-element series is critical for improving predictive capabilities and solving many nuclear problems facing our society. Unfortunately, it is difficult to make direct comparisons across the 5f-element series because so little is known about trans-plutonium elements. Results described herein help to address this issue through isolation of An(S2CNEt2)3(N2C12H8) (Am, Cm, and Cf). These findings included the first single crystal X-ray diffraction measurements of Cm-S (mean of 2.86 ± 0.04 Å) and Cf-S (mean of 2.84 ± 0.04 Å) bond distances. Furthermore, they highlight the potential of An(S2CNEt2)3(N2C12H8) for providing a test bed for comparative analyses of actinide versus lanthanide bonding interactions.

The reaction of Th(NO)·5HO with 3 equiv of 2,2',6',2″-terpyridine (terpy) in a mixture of acetonitrile and methanol results in formation of the trinuclear thorium peroxide cluster [Th(O)(terpy)(NO)]. This cluster is assembled via bridging by μ-η:η peroxide anions between thorium centers. It decomposes upon removal from the mother liquor to yield Th(terpy)(NO) and Th(terpy)(NO)(EtOH). The peroxide formation appears to be radiolytic in origin and is, most likely, generated from radiolysis of water by short-lived daughters generated from Th decay. This cluster does not form when freshly recrystallized Th(NO)·5HO is used as the starting material and requires an aged source of thorium. Analysis of the bonding in these clusters shows that, unlike uranium(VI) peroxide interactions, thorium(IV) complexation by peroxide is quite weak and largely ionic. This explains its much lower stability, which is more comparable to that observed in similar zirconium(IV) peroxide clusters.

The CCDC number for [Th(O 2 )(terpy)(NO 3 ) 2 ] 3 was inadvertently omitted during conversion of the manuscript to the final proofs. The CCDC number is 1509348. The original paper has been updated online.