Actinide chalcogenido and chalcogenolate compounds
Creators: name: Ringgold, Marissa
Publisher: name: No Publisher Supplied
Year: 2019

description: Actinide chemistry, specifically thorium and uranium chalcogenolate and chalcogenido complexes are relatively unexplored. Traditionally in literature they contain sterically hindered environments or are synthesized under aqueous conditions. However, it has been discovered that thorium metal reductively inserts into the E-E bond of REER (R= Ph, C6F5; E = S, Se) to from stable chalcogenolate compounds whose size is determined by the identity of the neutral donor ligand or additional chalcogen in air-free, water-free conditions without the use of large bulky ligands. Thorium cubanes (py)8Th4(μ3-E′)4(μ2-EPh)4(η-EPh)4 (E, E′ = S, Se) were prepared from ligand-based redox reactions of elemental E′ with Th(EPh)4. Products with all four possible E/E′ combinations (E,E′ = S,S; Se,Se; S,Se; Se,S) were isolated and structurally characterized, ligand exchange reactions were explored, and the heterochalcogen compounds (py)8Th4(μ3-S)4(μ2-SePh)4(η-SePh)4 and (py)8Th4(μ3-Se)4(μ2-SPh)4(η-SPh)4 were heated to deliver solid solutions of ThSxSe2−x. NMR spectroscopy indicated that the structure of (py)8Th4(μ3-Se)4(μ2-SePh)4(η-SePh)4 is static in pyridine solution, with no exchange between bridging and terminal PhE− ligands on the NMR time scale. A computational analysis of 77Se NMR shifts provides insight into the solution structure of both clusters and monomeric chalcogenolates.Thorium chalcogenolates Th(ER)4 react with 2,2’-bipyridine (bipy) to form complexes with the stoichiometry (bipy)2Th(ER)4 (E = S, Se; R = Ph, C6F5).  All four compounds have been isolated and characterized by spectroscopic methods and low-temperature single crystal x-ray diffraction.  Two of the products, (bipy)2Th(SC6F5)4 and (bipy)2Th(SeC6F5)4 , crystallize with lattice solvent, (bipy)2Th(SPh)4 crystallizes with no lattice solvent, and the selenolate (bipy)2Th(SePh)4 crystallizes in two phases, with and without lattice solvent.  In all four compounds the available volume for coordination bounded by the two bipy ligands is large enough to allow significant conformational flexibility of thiolate or selenolate ligands.  77Se NMR confirms that the structures of the selenolate products are the same in pyridine solution and in the solid state. Attempts to prepare analogous derivatives with 2,2′:6′,2″-terpyridine (terpy) were successful only in the isolation of (terpy)(py)Th(SPh)4, the first terpy compound of thorium.  These materials are thermochroic, with color attributed to ligand-to-ligand charge transfer excitations.  In addition, heterometallic compounds with both thorium and uranium have been explored. Four clusters (py)8Th4[Hg(EPh)2]4(μ3-E′)4(μ2-EPh)4(η-EPh)4, (py)8U4[Hg(EPh2)]4(μ3-E′)4(μ2-EPh)4(η-EPh)4 (E’ = S, Se; E = Se) and three cation anion pairs [U8S13I3py17][HgI4][HgI3py], [ThF2bipy2py3][Ag4SePh6], [Th8S13I4py18][HgI4]  have been synthesized, isolated, and structurally characterized. These compounds integrate mercury as an external ligand or counter ion instead of a bridging moiety inside the inner core structure as seen in previous lanthanide compounds. 100% occupancy of the mercury moiety in the cubane clusters is not consistent or easily achieved, yet all these compounds are of significant interest when compared to other heterometallic compounds.