Reductive Elimination of Diphosphine from a Thorium–NHC–Bis(phosphido) Complex

The synthesis, characterization, and reductive elimination reactivity of a bis­(NHC)­borate-supported thorium bis­(phosphido) complex (<b>2</b>^<b>Mes</b>) is described. Treating <b>2</b>^<b>Mes</b> with 2,2′-bipyridine leads to the reductive elimination of dimesityldiphosphine (<b>4</b>) and the formation of the previously reported NHC–thorium–bpy complex (<b>3</b>). The kinetics of the bpy-induced reductive elimination were studied by ³¹P NMR and suggest the presence of an intermediate. Treatment with alternative oxidants also leads to diphosphine elimination, but the corresponding thorium species have not been isolated cleanly. Additional primary (<b>2</b>^<b>Ph</b>) and secondary (<b>2</b>^<b>PPh2</b>) Th–bis­(phosphido) complexes were synthesized but do not demonstrate the same facile reductive elimination as <b>2</b>^<b>Mes</b>

A Thorium Chalcogenolate Series Generated by Atom Insertion into Thorium–Carbon Bonds

A new thorium monoalkyl complex, Th­(CH₂SiMe₃)­(L₃) (L = MeC­(N^<i>i</i>Pr)₂) (<b>2</b>), undergoes insertion of chalcogen atoms resulting in a series of thorium chalcogenolate complexes, Th­(ECH₂SiMe₃)­(L₃) (E = S, SS, Se, Te; <b>5</b>–<b>8</b>). Complex <b>6</b> represents the first alkyl disulfide thorium species and illustrates the ability of <b>2</b> to undergo controllable, stoichiometric atom insertion. All complexes have been characterized by ¹H and ¹³C NMR spectroscopy, FTIR, EA, and melting point, and in the case of <b>1</b>, <b>2</b>, and <b>4</b>–<b>8</b>, X-ray crystallography. Insertion was achieved by balancing the thermodynamic driving force of chalcogenolate formation versus the BDE of the pnictogen–chalcogen bond in the transfer reagent. Utilizing Me₃NO as an oxygen atom transfer reagent led to C–H activation and SiMe₄ extrusion rather than oxygen atom insertion, resulting in the alkoxide complex Th­(OCH₂NMe₂)­(L₃) (<b>4</b>)

A New Supporting Ligand in Actinide Chemistry Leads to Reactive Bis(NHC)borate-Supported Thorium Complexes

A versatile, monoanionic, chelating (bis)­carbene ligand (<b>2</b>) was used to prepare a thorium dihalide complex (<b>3</b>) and a direduced-bpy derivative (<b>4</b>). CASSCF calculations suggest the involvement of a multiconfigurational open-shell singlet, with the main configuration corresponding to a Th­(III)-bpy(−1) (f¹π*¹) electronic structure. The reactivity of <b>4</b> was explored in various transformations, including reactions with carbonyls and organic azides; the latter gave rise to an unusual terminal Th-imido bpy complex (<b>6</b>)

Thorium Metallacycle Facilitates Catalytic Alkyne Hydrophosphination

The bis­(NHC)­borate-supported thorium-bis­(mesitylphosphido) complex (<b>1</b>) undergoes reversible intramolecular C–H bond activation enabling the catalytic hydrophosphination of unactivated internal alkynes. Catalytic and stoichiometric experiments support a mechanism involving reactive Th–NHC metallacycle intermediates (<b>Int</b> and <b>2</b>)