ABSTRACT
The reduction of a bimetallic yttrium ansa-metallocene hydride was examined to explore the possible formation of Y-Y bonds with 4d1 Y(II) ions. The precursor [CpAnY(µ-H)(THF)]2 (CpAn = Me2Si[C5H3(SiMe3)-3]2) was synthesized by hydrogenolysis of the allyl complex CpAnY(η3-C3H5)(THF), which was prepared from (C3H5)MgCl and [CpAnY(µ-Cl)]2. Treatment of [CpAnY(µ-H)(THF)]2 with excess KC8 in the presence of one equivalent of 2.2.2-cryptand (crypt) generates an intensely colored red-brown product crystallographically identified as [K(crypt)][(µ-CpAn)Y(µ-H)]2. The two rings of each CpAn ligand in the reduced anion [(µ-CpAn)Y(µ-H)]21- are attached to two yttrium centers in a "flyover" configuration. The 3.3992(6) and 3.4022(7) Å Y···Y distances between the equivalent metal centers within two crystallographically independent complexes are the shortest Y···Y distances observed to date. Ultraviolet-visible (UV-visible)/near infrared (IR) and electron paramagnetic resonance (EPR) spectroscopy support the presence of Y(II), and theoretical analysis describes the singly occupied molecular orbital (SOMO) as an Y-Y bonding orbital composed of metal 4d orbitals mixed with metallocene ligand orbitals. A dysprosium analogue, [K(18-crown-6)(THF)2][(µ-CpAn)Dy(µ-H)]2, was also synthesized, crystallographically characterized, and studied by variable temperature magnetic susceptibility. The magnetic data are best modeled with the presence of one 4f9 Dy(III) center and one 4f9(5dz2)1 Dy(II) center with no coupling between them. CASSCF calculations are consistent with magnetic measurements supporting the absence of coupling between the Dy centers.
ABSTRACT
The investigation of the coordination chemistry of rare-earth metal complexes with cyanide ligands led to the isolation and crystallographic characterization of the Ln III cyano-tri-phenyl-borate complexes di-chlorido-(cyano-tri-phenyl-borato-κN)tetra-kis-(tetra-hydro-furan-κO)lanthanide(III), [LnCl2(C19H15BN)(C4H8O)4] [lanthanide (Ln) = dysprosium (Dy) and yttrium Y)] from reactions of LnCl3, KCN, and NaBPh4. Attempts to independently synthesize the tetra-ethyl-ammonium salt of (NCBPh3)- from BPh3 and [NEt4][CN] in THF yielded crystals of the phenyl-substituted cyclic borate, tetra-ethyl-aza-nium 2,2,4,6-tetra-phenyl-1,3,5,2λ4,4,6-trioxatriborinan-2-ide, C8H20N+·C24H20B3O3 - or [NEt4][B3(µ-O)3(C6H5)4]. The mechanochemical reaction of BPh3 and [NEt4][CN] without solvent produced crystals of tetra-ethyl-aza-nium cyano-diphenyl-λ4-boranyl di-phenyl-borinate, C8H20N+·C25H20B2NO- or [NEt4][NCBPh2(µ-O)BPh2]. Reaction of BPh3 and KCN in THF in the presence of 2.2.2-cryptand (crypt) led to a crystal of bis-[(2.2.2-cryptand)potassium] 2,2,4,6-tetra-phenyl-1,3,5,2λ4,4,6-trioxatriborinan-2-ide cyano-methyl-diphenyl-borate tetra-hydro-furan disolvate, 2C18H36KN2O6 +·C24H20B3O3 -·C14H13BN-·2C4H8O or [K(crypt)]2[B3(µ-O)3(C6H5)4][NCBPh2Me]·2THF. The [NCBPh2(µ-O)BPh2]1- and (NCBPh2Me)1- anions have not been structurally characterized previously. The structure of 1-Y was refined as a two-component twin with occupancy factors 0.513â (1) and 0.487â (1). In 4, one solvent mol-ecule was disordered and included using multiple components with partial site-occupancy factors.
ABSTRACT
The complexes [Cp'2Ln(µ-CH3)]2, (Cp' = C5H4SiMe3; Ln = Y, Tb, Dy) were reduced to determine if these methyl-bridged complexes would form mixed valent 4f n 5d1 Ln(II)/4f n Ln(III) compounds or bimetallic 4f n 5d1 Ln(II) compounds containing 5d1-5d1 metal-metal bonds upon reduction. Reaction of the known bridged-chloride complexes, [Cp'2Ln(µ-Cl)]2, 1-Ln (Ln = Y, Tb, Dy), with MeLi forms the bridged-methyl complexes [Cp'2Ln(µ-CH3)]2, 2-Ln, which were crystallographically characterized for Tb and Dy. KC8 reduction of 2-Ln in the presence of 2.2.2-cryptand produced 3-Y, 3-Tb, and 3-Dy, which exhibited intense dark colors and broad absorbance peaks around 400 nm with molar extinction coefficients of 1700, 2300, and 1800 M-1 cm-1, respectively, which are characteristics of Ln(II) ions. The dark maroon 3-Y product had an axial electron paramagnetic resonance spectrum at 77 K (g 1 = 1.99, A 1 = 17.9 G; g 2 = 2.00, A 2 = 17.7 G) and a two-line isotropic spectrum at 273 K (g = 1.99, A = 18.4 G), which indicates that an Y(II) ion is present. Although these results are indicative of Ln(II) ions present in the solution, crystallographic evidence was not obtained to establish the structure of these complexes.
ABSTRACT
Small-scale reactions of the Pu analogues La, Ce, and Nd have been explored in order to optimize reaction conditions for milligram scale reactions of radioactive plutonium starting from the metal. Oxidation of these lanthanide metals with iodine in ether and pyridine has been studied, and LnI3(Et2O)x (1-Ln; x = 0.75-1.9) and LnI3(py)4 (2-Ln; py = pyridine, NC5H5) have been synthesized on scales ranging from 15 mg to 2 g. The THF adducts LnI3(THF)4 (3-Ln) were synthesized by dissolving 1-Ln in THF. The viability of these small-scale samples as starting materials for amide and cyclopentadienyl f-element complexes was tested by reacting KN(SiMe3)2, KCp' (Cp' = C5H4SiMe3), KCp'' (Cp'' = C5H3(SiMe3)2-1,3), and KC5Me4H with 1-Ln generated in situ. These reactions produced Ln[N(SiMe3)2]3 (4-Ln), Cp'3Ln (5-Ln), Cpâ³3Ln (6-Ln), and (C5Me4H)3Ln (7-Ln), respectively. Small-scale samples of Cp'3Ce (5-Ce) and Cp'3Nd (5-Nd) were reduced with potassium graphite (KC8) in the presence of 2.2.2-cryptand to check the viability of generating the crystallographically characterizable Ln2+ complexes [K(2.2.2-cryptand)][Cp'3Ln] (8-Ln; Ln = Ce, Nd).
