Mono(pentamethylcyclopentadienyl)uranium(III) Complexes:  Synthesis, Properties, and X-ray Structures of (η-C₅Me₅)UI₂(THF)₃, (η-C₅Me₅)UI₂(py)₃, and (η-C₅Me₅)U[N(SiMe₃)₂]₂

Abstract

The uranium(III) iodide complex UI 3 (THF) 4 reacts cleanly at ambient temperature with 1 equiv of sodium and potassium pentamethylcyclopentadienide salts in tetrahydrofuran to form the mono-ring uranium(III) complex (η-C 5 Me 5 )UI 2 (THF) 3 (1). Additionally, reaction of UI 3 (THF) 4 with 2 equiv or more of K(C 5 Me 5 ) in THF solution leads to the formation of the bis-ring adduct (η-C 5 Me 5 ) 2 UI(THF) (2) in high yield. In the solid state 1 exhibits a pseudooctahedral mer,trans ligand geometry with the C 5 Me 5 ligand occupying one axial position. U-I bond lengths range from 3.161(1) to 3.179(1) Å, while U-O distances to the THF ligands lie in the range 2.496(8)-2.594(10) Å. 1 also provides a convenient entry into a variety of other mono-ring complexes of uranium(III). In the presence of excess pyridine, the coordinated THF ligands of 1 are readily displaced to form the tris(pyridine) adduct (η-C 5 Me 5 )UI 2 (py) 3 (3), which exhibits a mer,trans ligand geometry in the solid state similar to that of 1. Metathesis of the iodide ligands in 1 with 2 equiv of KN(SiMe 3 ) 2 affords the bis(amido) complex (η-C 5 Me 5 )U[N(SiMe 3 ) 2 ] 2 (4). An X-ray diffraction study of this molecule reveals that methyl groups from both amido ligands are involved in agostic interactions with the uranium-(III) center.

Expanding the Family of Uranium(III) Alkyls: Synthesis and Characterization of Mixed‐Ligand Derivatives

“…The U–C(Cp*) avg. distance of 2.807 Å compares favorably to that of Cp*UI 2 (THF) 3 [2.80(1) Å], but is less than that found in Cp*UI 3 . Likewise, the U–O(THF) distance of 2.558(10) Å compares favorably to Cp*UI 2 (THF) 3 [2.496(8)–2.594(10) Å] and Tp*UI 2 (THF) 2 [2.582(5) and 2.615(6) Å].…”

“…Following the synthesis of the mixed‐Tp R complexes, the next aim was to synthesize a family of mixed Cp R /Tp R ligands targeting Cp* (Cp* = 1,2,3,4,5‐pentamethylcyclopentadienide) derivatives. Dropwise addition of an equivalent of KTp slurried in THF to a solution of Cp*UI 2 (THF) 3 at –35 °C caused an instantaneous color change, and allowed for isolation of a green solid, Cp*TpUI, following recrystallization. Initial characterization was accomplished by IR spectroscopy, which showed an absorption band at 2462 cm –1 (B–H) consistent with the presence of the Tp ligand.…”

Lanthanide(III)/Actinide(III) Differentiation in the Cerium and Uranium Complexes [M(C5Me5)2(L)]0,+ (L=2,2′‐Bipyridine, 2,2′:6′,2′′‐Terpyridine): Structural, Magnetic, and Reactivity Studies

“…NEt 3 HBPh 4 was prepared by mixing NEt 3 HCl and NaBPh 4 in water; the precipitate was filtered off, washed with ethanol and diethyl ether and dried under vacuum. The green powder of [U-(Cp*) 2 I(py)] was obtained by evaporation of a pyridine solution of [U-(Cp*) 2 I(thf)], which was prepared as previously reported; [40] in contrast to the cerium analogue, the pyridine ligand in [U(Cp*) 2 I(py)] is not labile and did not dissociate on heating under vacuum. 1 Synthesis of [Ce(Cp*) 2 (terpy)] (4 a): A flask was charged with 3 a (100 mg, 0.130 mmol) and 2 % Na(Hg) (540 mg, 0.47 mmol), and THF (12 mL) was condensed into it.…”

Synthesis, structure, spectroscopy and redox energetics of a series of uranium(IV) mixed-ligand metallocene complexes

“…Similar interactions have been observed for other uranium complexes bearing the [N(SiMe 3 ) 2 ] ligand. Three UÁ Á ÁH-C interactions (U-C ave = $3.31 Å ) were proposed to exist in the U IV complex [(Me 3 Si) 2 N] 3 U-S(2,6-Me 2 C 6 H 3 ) [38], while the U III metallocene complex (C 5 Me 5 )U[N(SiMe 3 ) 2 ] 2 featured two UÁ Á ÁH-C interactions (U-C ave = $2.83 Å ) [39]. Decreased U-N-Si angles were also hallmarks for UÁ Á ÁH-C interactions in these complexes.…”

“…All solvents (Aldrich) were purchased anhydrous and dried over KH for 24 h, passed through a column of activated alumina, and stored over activated 4 Å molecular sieves prior to use. The following compounds were prepared according to literature procedures: (C 5 Me 5 ) 2 UI(THF) [39], (C 5 Me 5 ) 2 U[N(SiMe 3 ) 2 ] [29], (C 5 Me 5 ) 2 U(NPh 2 )(THF) [8], (Ph 3 P)Au-N 3 [10], C and [56], and (C 5 Me 5 ) 2 U[N(SiMe 3 ) 2 ](I) (4) [9].…”