Synthesis and crystallographic characterization of di-phenyl-amide rare-earth metal complexes Ln(NPh2)3(THF)2 and [(Ph2N)2 Ln(μ-NPh2)]2.

Studies of the coordination chemistry between the di-phenyl-amide ligand, NPh2, and the smaller rare-earth Ln III ions, Ln = Y, Dy, and Er, led to the structural characterization by single-crystal X-ray diffraction crystallography of both solvated and unsolvated complexes, namely, tris-(di-phenyl-amido-κN)bis-(tetrahydro-furan-κO)yttrium(III), Y(NPh2)3(THF)2 or [Y(C12H10N)3(C4H8O)2], 1-Y, and the erbium(III) (Er), 1-Er, analogue, and bis-[μ-1κN:2(η6)-di-phenyl-amido]-bis-[bis-(di-phenyl-amido-κN)yttrium(III)], [(Ph2N)2Y(μ-NPh2)]2 or [Y2(C12H10N)6], 2-Y, and the dysprosium(III) (Dy), 2-Dy, analogue. The THF ligands of 1-Er are modeled with disorder across two positions with occupancies of 0.627 (12):0.323 (12) and 0.633 (7):0.367 (7). Also structurally characterized was the tetra-metallic ErIII bridging oxide hydrolysis product, bis-(μ-di-phenyl-amido-κ2 N:N)bis-[μ-1κN:2(η6)-di-phenyl-amido]-tetra-kis-(di-phenyl-amido-κN)di-μ3-oxido-tetra-erbium(III) benzene disolvate, {[(Ph2N)Er(μ-NPh2)]4(μ-O)2}·(C6H6)2 or [Er4(C12H10N)8O2]·2C6H6, 3-Er. The 3-Er structure was refined as a three-component twin with occupancies 0.7375:0.2010:0.0615

Synthesis of rare-earth-metal-in-cryptand dications, [Ln(2.2.2-cryptand)]2+, from Sm2+, Eu2+, and Yb2+ silyl metallocenes (C5H4SiMe3)2Ln(THF)2.

Cp'2Ln(THF)2 metallocenes (Cp' = C5H4SiMe3) react with 2.2.2-cryptand (crypt) to form Ln2+-in-crypt complexes, [Ln(crypt)(THF)][Cp'3Ln]2 (Ln = Sm, Eu) and [Yb(crypt)][Cp'3Yb]2, that contain Ln2+ ions surrounded only by neutral ligands. A bimetallic, mixed-ligand metallocene/opened-crypt complex of Sm2+, [Sm(C16H32N2O6-κ2O:κ2O')SmCp''2], was obtained by KC8 reduction of Cp''2Sm(THF) [Cp'' = C5H3(SiMe3)2] in the presence of crypt

Synthesis of rare-earth-metal-in-cryptand dications, [Ln(2.2.2-cryptand)]2+, from Sm2+, Eu2+, and Yb2+ silyl metallocenes (C5H4SiMe3)2Ln(THF)2.

Cp'2Ln(THF)2 metallocenes (Cp' = C5H4SiMe3) react with 2.2.2-cryptand (crypt) to form Ln2+-in-crypt complexes, [Ln(crypt)(THF)][Cp'3Ln]2 (Ln = Sm, Eu) and [Yb(crypt)][Cp'3Yb]2, that contain Ln2+ ions surrounded only by neutral ligands. A bimetallic, mixed-ligand metallocene/opened-crypt complex of Sm2+, [Sm(C16H32N2O6-κ2O:κ2O')SmCp''2], was obtained by KC8 reduction of Cp''2Sm(THF) [Cp'' = C5H3(SiMe3)2] in the presence of crypt

Reactivity of the Ln²⁺ Complexes [K(2.2.2-cryptand)][(C₅H₄SiMe₃)₃Ln]: Reduction of Naphthalene and Biphenyl

The reductive capacity of the recently discovered Ln²⁺ complexes [K­(2.2.2-cryptand)]­[Cp′₃Ln], <b>1-Ln</b> (Cp′ = C₅H₄SiMe₃; Ln = Y, La, Ce, Dy), has been probed by examining their reactions with aromatic hydrocarbons. [K­(2.2.2-cryptand)]­[Cp′₃Y], <b>1-Y</b>, is capable of reducing naphthalene and forms a mixture of the naphthalenide dianion complex [K­(2.2.2-cryptand)]­[Cp′₂Y­(η⁴-C₁₀H₈)], <b>2-Y</b>, as well as the ligand redistribution product [K­(2.2.2-cryptand)]­[Cp′₄Y], <b>3-Y</b>, and the cyclopentadienyl ligand salt [K­(2.2.2-cryptand)]­[Cp′], <b>4</b>. Naphthalene is reduced analogously by <b>1-La</b>, <b>1-Ce</b>, and <b>1-Dy</b>. Each complex in the yttrium reaction was synthesized independently to confirm its identity in the mixture. Complex <b>2-Y</b> was prepared from [Cp′₂Y­(THF)₂]­[BPh₄], <b>5</b> (synthesized from [Et₃NH]­[BPh₄] and Cp′₃Y), and K/naphthalene. Complex <b>3-Y</b> was obtained by adding KCp′ to Cp′₃Y in the presence of 2.2.2-cryptand. [K­(2.2.2-cryptand)]­[Cp′] was synthesized from 2.2.2-cryptand and KCp′. Each C₁₀ unit in the reduced naphthalene products, <b>2-Y</b>, <b>2-La</b>, <b>2-Ce</b>, and <b>2-Dy</b>, is bent with four carbon atoms of one ring oriented toward the metal, while the remaining six carbon atoms form a planar ring consistent with (η⁴-C₁₀H₈)^2– coordination. In the solid state, <b>3-Y</b> contains one η¹-Cp′ ligand and three η⁵-Cp′ rings, whereas all four Cp′ rings in <b>3-La</b> have η⁵-coordination. In the solid-state structure of <b>4</b>, the (Cp′)⁻ anion is not coordinated to potassium, which is encapsulated by the cryptand and located 7.063 Å from the ring centroid. Complex <b>1-Y</b> also reduces biphenyl to form [K­(2.2.2-cryptand)]­[Cp′₂Y­(η⁶-C₆H₅Ph)], <b>6-Y</b>, which contains a dianion with a planar aromatic phenyl ring as a substituent on a nonplanar η⁶-C₆ ring oriented toward the metal ion

Isolation of +2 rare earth metal ions with three anionic carbocyclic rings: bimetallic bis(cyclopentadienyl) reduced arene complexes of La2+ and Ce2+ are four electron reductants.

A new option for stabilizing unusual Ln2+ ions has been identified in the reaction of Cp'3Ln, 1-Ln (Ln = La, Ce; Cp' = C5H4SiMe3), with potassium graphite (KC8) in benzene in the presence of 2.2.2-cryptand. This generates [K(2.2.2-cryptand)]2[(Cp'2Ln)2(μ-η6:η6-C6H6)], 2-Ln, complexes that contain La and Ce in the formal +2 oxidation state. These complexes expand the range of coordination environments known for these ions beyond the previously established examples, (Cp''3Ln)1- and (Cp'3Ln)1- (Cp'' = C5H3(SiMe3)2-1,3), and generalize the viability of using three anionic carbocyclic rings to stabilize highly reactive Ln2+ ions. In 2-Ln, a non-planar bridging (C6H6)2- ligand shared between two metals takes the place of a cyclopentadienyl ligand in (Cp'3Ln)1-. The intensely colored (ε = ∼8000 M-1 cm-1) 2-Ln complexes react as four electron reductants with two equiv. of naphthalene to produce two equiv. of the reduced naphthalenide complex, [K(2.2.2-cryptand)][Cp'2Ln(η4-C10H8)]

Isolation of +2 rare earth metal ions with three anionic carbocyclic rings: bimetallic bis(cyclopentadienyl) reduced arene complexes of La2+ and Ce2+ are four electron reductants.

A new option for stabilizing unusual Ln2+ ions has been identified in the reaction of Cp'3Ln, 1-Ln (Ln = La, Ce; Cp' = C5H4SiMe3), with potassium graphite (KC8) in benzene in the presence of 2.2.2-cryptand. This generates [K(2.2.2-cryptand)]2[(Cp'2Ln)2(μ-η6:η6-C6H6)], 2-Ln, complexes that contain La and Ce in the formal +2 oxidation state. These complexes expand the range of coordination environments known for these ions beyond the previously established examples, (Cp''3Ln)1- and (Cp'3Ln)1- (Cp'' = C5H3(SiMe3)2-1,3), and generalize the viability of using three anionic carbocyclic rings to stabilize highly reactive Ln2+ ions. In 2-Ln, a non-planar bridging (C6H6)2- ligand shared between two metals takes the place of a cyclopentadienyl ligand in (Cp'3Ln)1-. The intensely colored (ε = ∼8000 M-1 cm-1) 2-Ln complexes react as four electron reductants with two equiv. of naphthalene to produce two equiv. of the reduced naphthalenide complex, [K(2.2.2-cryptand)][Cp'2Ln(η4-C10H8)]

Tris(pentamethylcyclopentadienyl) Complexes of Late Lanthanides Tb, Dy, Ho, and Er: Solution and Mechanochemical Syntheses and Structural Comparisons

The tris­(pentamethylcyclopentadienyl) complexes, (C₅Me₅)₃Ln (Ln = Tb, Dy, Ho, and Er), have been synthesized to determine if structural trends observed with the larger rare-earth metals, La–Gd, extend to the smaller metals and to determine the level of steric crowding associated with C–H bond activation of benzene and toluene as found for the (C₅Me₅)₃Y complex of the smaller rare-earth metal, yttrium. Three different synthetic methods were used. (C₅Me₅)₃Tb was synthesized in benzene from (C₅Me₅)₂Tb­(μ-Ph)₂BPh₂ and KC₅Me₅, which established that it does not activate benzene. In contrast, complexes of Dy, Ho, and Er were not isolable in benzene or toluene. (C₅Me₅)₃Dy was synthesized in pentane from [(C₅Me₅)₂DyH]₂ and 1,2,3,4-tetramethylfulvene. Solvent-free mechanochemistry was utilized to synthesize the Ho and Er complexes by ball-milling (C₅Me₅)₂Ln­(μ-Ph)₂BPh₂ and KC₅Me₅ as solids. This route also provided the Tb, Dy, and Y complexes. Crystallographic analysis of these complexes of the smaller metals has allowed identification of a feature in the structures of (C₅Me₅)₃Ln that was less obvious with the larger metals. The displacements of the methyl substituents out of the cyclopentadienyl ring plane away from the metal do not change substantially for complexes of the metals smaller than Gd, but the cyclopentadienyl rings become increasingly less planar and continue to tilt away from the metal with increasing angles

Synthesis of rare-earth-metal-in-cryptand dications, [Ln(2.2.2-cryptand)] 2+

Cp'2Ln(THF)2 metallocenes (Cp' = C5H4SiMe3) react with 2.2.2-cryptand (crypt) to form Ln2+-in-crypt complexes, [Ln(crypt)(THF)][Cp'3Ln]2 (Ln = Sm, Eu) and [Yb(crypt)][Cp'3Yb]2, that contain Ln2+ ions surrounded only by neutral ligands. A bimetallic, mixed-ligand metallocene/opened-crypt complex of Sm2+, [Sm(C16H32N2O6-κ2O:κ2O')SmCp''2], was obtained by KC8 reduction of Cp''2Sm(THF) [Cp'' = C5H3(SiMe3)2] in the presence of crypt