Hydrolysis of Bis(p-nitrophenyl)phosphate by Tetravalent Metal Complexes with Kläui’s Oxygen Tripodal Ligand

Oxidizing Cerium(IV) Alkoxide Complexes Supported by the Kläui Ligand [Co(η5-C5H5){P(O)(OEt)2}3]-: Synthesis, Structure, and Redox Reactivity

Tetravalent cerium alkoxide complexes supported by the Kläui tripodal ligand [Co(η⁵-C₅H₅){P(O)(OEt)₂}₃]^- (L_OEt^-) have been synthesized, and their nucleophilic and redox reactivity have been studied. Treatment of the Ce(IV) oxo complex [Ce^IV(L_OEt)₂(O)(H₂O)]·MeCONH₂ (1) with ⁱPrOH or reaction of [Ce^IV(L_OEt)₂Cl₂] (2) with Ag₂O in ⁱPrOH afforded the Ce(IV) dialkoxide complex [Ce^IV(L_OEt)₂(OⁱPr)₂] (3-iPr). The methoxide and ethoxide analogues [Ce^IV(L_OEt)₂(OR)₂] (R = Me (3-Me), Et (3-Et)) have been prepared similarly from 2 and Ag₂O in ROH. Reaction of 3-iPr with an equimolar amount of 2 yielded a new Ce(IV) complex that was formulated as the chloro-alkoxide complex [Ce^IV(L_OEt)₂(OⁱPr)Cl] (4). Treatment of 3-iPr with HX and methyl triflate (MeOTf) afforded [Ce(L_OEt)₂X₂] (X^- = Cl^-, NO₃^-, PhO^-) and [Ce^IV(L_OEt)₂(OTf)₂], respectively, whereas treatment with excess CO₂ in hexane led to isolation of the Ce(IV) carbonate [Ce^IV(L_OEt)₂(CO₃)]. 3-iPr reacted with water in hexane to give a Ce(III) complex and a Ce(IV) species, presumably the reported tetranuclear oxo cluster [Ce^IV₄(L_OEt)₄(O)₅(OH)₂]. The Ce(IV) alkoxide complexes are capable of oxidizing substituted phenols, possibly via a proton-coupled electron transfer pathway. Treatment of 3-iPr with ArOH afforded the Ce(III) aryloxide complexes [Ce^III(L_OEt)₂(OAr)] (Ar = 2,4,6-tri-tert-butylphenyl (5), 2,6-diphenylphenyl (6)). On the other hand, a Ce(III) complex containing a monodeprotonated 2,2'-biphenol ligand, [Ce^III(L_OEt)₂(^tBu₄C₁₂H₄O₂H)] (7) (^tBu₄C₁₂H₄O₂H₂ = 4,4',6,6'-tetra-tert-butyl-2,2'-biphenol), was isolated from the reaction of 3-iPr with 2,4-di-tert-butylphenol. The crystal structures of complexes 3-iPr, 3-Me, 3-Et, and 5-7 have been determined.

Organophosphorus-Modified Lanthanide Nitrates as Potential Actinide Oxide Aerosol Surrogates

In search of suitable simulants for aerosol uranium waste products from Plutonium Uranium Redox Extraction (PUREX) process burns, a series of lanthanide nitrate hydrates ([Ln(κ²-NO₃)₃·nH₂O]) were dissolved in the presence of tributylphosphate (O═P(O(CH₂)₃CH₃)₃) referred to as TBP) in kerosene or triphenylphosphate (O═P(O(C₆H₅) referred to as TPhP) in acetone. The crystal structure of the TPhP derivatives of the lanthanide nitrate series and uranium nitrate were solved as [Ln(κ²-NO₃)₃(TPhP)₃] (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and [U(O)₂(κ²-NO₃)₂(TPhP)₂] (U), respectively. The lanthanide-TBP, Ln, and U were further characterized using FTIR spectroscopy, ³¹P NMR spectroscopy, thermogravimetric analysis, and X-ray fluorescence spectroscopy. Further, thermal treatment of the lanthanide-TBP, Ln, and U using a box furnace to mimic pyrolysis conditions was found by PXRD analyses to generate a phosphate phase [LnP₃O₉ or UP₂O₇) for all systems. The resultant nuclear waste fire contaminant particulates will impact both aerosol transport and toxicity assessments.

Organometallic Zirconium Compounds in an Oxygen-Rich Coordination Environment: Synthesis and Structural Characterization of Tris(oxoimidazolyl)hydroboratozirconium Compounds

A series of tris(oxoimidazolyl)hydroborato ligands, which serve as L₂X [O₃] donors, have been employed to obtain organometallic zirconium compounds in an uncommon oxygen-rich coordination environment. For example, Cp[To^MeBenz]ZrCl₂ has been synthesized via the reaction of [To^MeBenz]Na with CpZrCl₃ and bears a structural resemblance to the bent metallocene dichloride derivative Cp₂ZrCl₂. In addition, the half-sandwich counterparts [To^MeBenz]ZrCl₃ and [To^But]ZrCl₃ have been obtained by metathesis of ZrCl₄ with [To^MeBenz]Na and [To^But]Na, respectively. The structurally related zirconium benzyl compounds [To^RBenz]Zr(CH₂Ph)₃ (R = Me, Bu^t, 1-Ad) have also been synthesized via the reactions of [To^RBenz]Tl with Zr(CH₂Ph)₄, and X-ray diffraction studies demonstrate that the benzyl ligands in these compounds are conformationally flexible and exhibit a large range of Zr-CH₂-Ph bond angles (94.7-131.7°). Protolytic cleavage of one of the benzyl ligands of [To^RBenz]Zr(CH₂Ph)₃ (R = Bu^t, 1-Ad) may be achieved by treatment with [PhNHMe₂][B(C₆F₅)₄] to generate {[To^RBenz]Zr(CH₂Ph)₂}[B(C₆F₅)₄], which are catalysts for the polymerization of ethylene. The molecular structure of the ether adduct, {[To^ButBenz]Zr(CH₂Ph)₂(OEt₂)}[B(C₆F₅)₄], has been determined by X-ray diffraction. In addition to the use of tris(oxoimidazolyl)hydroborato ligands, bis(oxoimidazolyl)hydroborato ligands have also been used to obtain zirconium benzyl compounds in oxygen-rich environments, namely, [Bo^MeBenz]₂Zr(CH₂Ph)₂ and [Bo^AdBenz]₂Zr(CH₂Ph)₂.

Structural insights into the multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate–n-dodecane solvent extraction system

Macroscopic phase behaviors in the liquid–liquid extraction are explained by microscopic, reverse micellar fluid structures containing tetranuclear Ce(iv) clusters revealed by use of X-ray spectroscopy and scattering of the light and dense organic phases.

Heterobimetallic cerium(iv) oxo clusters supported by a tripodal oxygen ligand

Heterometallic Ce^IV/M (M = Mo^VI, Re^VII, V^V) oxo clusters supported by the Kläui tripodal oxygen ligand [(η⁵-C₅H₅)Co{P(O)(OEt)₂}₃]⁻ (L_OEt⁻) have been synthesized and the catalytic activity of the Ce^IV/V^V oxo cluster in the oxidation of thioanisoles has been studied.

Tetravalent cerium pseudohalide complexes supported by the Kläui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]−

Cerium(iv) pseudohalide complexes supported by the Kläui tripodal ligand [Co(η⁵-C₅H₅){P(O)(OEt)₂}₃]⁻ (L_OEt⁻) have been synthesized and structurally characterized.