Understanding the Scarcity of Thorium Peroxide Clusters

Abstract

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.

Deciphering the Crystal Structure of a Scarce 1D Polymeric Thorium Peroxo Sulfate

“…Such a difference can be attributed to the ionic radius of the tetravalent actinides versus trivalent lanthanides and their related charge density. The Th−OP length in Th(O 2 )(SO 4 )(H 2 O) 2 ranges from 2.351(7) to 2.573(6) Å, which agrees with the literature data observed for Th (2.369(2) Å) and Pu peroxide clusters (2.33(1)–2.36(1) Å) but also with μ 3 peroxo complexes (Ln−OP ranges from 2.311(3) to 2.408(2) Å for Ln=Sm, Eu, Gd; from 2.289 to 2.501 Å for Ln=Dy; and from 2.35 to 2.36 Å for Ln=Tb)…”

“…1.486(7) Å, which is slightly lower than those reported for μ 3 ‐bridged Ln‐peroxo compounds (1.52 to 1.55 Å) . However, it is closer to those reported for the only two peroxide structures resolved for tetravalent actinides, where the peroxide ligands exhibit μ 2 ‐η 2 :η 2 coordination (O−O length is 1.496(6) Å in the Pu IV peroxy‐carbonate compound Na 8 Pu 2 (O 2 ) 2 (CO 3 ) 6 ⋅ 12 H 2 O and 1.516–1.515 Å in [Th(O 2 )(terpy)(NO 3 ) 2 ] 3 cluster) . Such a difference can be attributed to the ionic radius of the tetravalent actinides versus trivalent lanthanides and their related charge density.…”

“…[17] X-ray structural analysis. Th(O 2 )(SO 4 )(H 2 O) 2 ,3 96 gmol À1 ;w hite precipitate;o rthorhombic system; Pna2 1 space group; V = 717.31(5) 3 ; 1 calcd = 3.631; Z = 4; a = 10.2600(5), b = 16.3746(7) and c = 4.2696(1) .S ynchrotron powder X-ray diffraction data were recorded at the Rossendorf beamline-BM20 (ESRF) using aP ilatus 3 X2 Md etector (sample-detector:3 9.9 cm; l = 0.77490 ;S i(111) double-crystal monochromator). The first 30 peaks of the pattern were indexed using the X-Cell algorithm incorporated in the Reflex program of materials studio.…”

“…[5] Particularly,t horium peroxides of variable compositions have been reported to form in sulfuric acid medium. [4a,d, 5a, 6] The older literature reportst hat weakly acidic conditions lead to a precipitate crystallizing in the hexagonal system, [5a, 6] whereas higher acidic conditions (> 0.3 m)a re proposed to form at rihydrate Th(O 2 )(SO 4 )(H 2 O) 3 .Ac oordination number of 6w as proposed for this compound and the few structural interpretations have suggested an orthorhombic system comprising a bridging OÀOp eroxide ligand and ab identate chelating sulfato group. [4a,d, 6] The current paper describes the unprecedented structure of am ixed Th IV complex coordinated with peroxo and sulfate ligands.…”

“…Adeeper understanding of the structure of this materialw as obtainedb yp erforming synchrotron powder X-ray diffraction ( Figure S6 [a] %wt is the theoretical value calculated from releasedm olecules compound in an orthorhombic system in the space group Pna2 1 ,w ith four formula units per cell and lattice parameters of a = 10.2600(5), b = 16.3746(7), c = 4.2696(1) and V = 717.31(5) 3 .T he asymmetricu nit is composed of one Th atom surrounded by one sulfur atom and eight oxygen atoms. Four of the eight oxygen atoms belongt ot he sulfate group (labelled OS), two O-atoms belong to the peroxo group (labelled OP) and the remaining two belongt ot he water molecules (labelled OW).…”