Mono‐ and Dinuclear Rare‐Earth Chlorides Ligated by a Mesityl‐Substituted β‐Diketiminate

Revealing unbound β-diketiminate anions: structural dynamics from caesium complexes

This study reports the first structural elucidation of β-diketiminate anions (BDI-), known for strong coordination, in their unbound form within caesium complexes. β-Diketiminate caesium salts (BDICs) were synthesised, and upon the addition of Lewis donor ligands, free BDI- anions and donor-solvated Cs+ cations were observed. Notably, the liberated BDI- anions exhibited an unprecedented dynamic cisoid-transoid exchange in solution.

Expanding the Utility of β-Diketiminate Ligands in Heavy Group VI Chemistry of Molybdenum and Tungsten

We report the synthesis of 17 molybdenum and tungsten complexes supported by the ubiquitous BDI ligand framework (BDI = β-diketiminate). The focal entry point is the synthesis of four molybdenum and tungsten(V) BDI complexes of the general formula [MO(BDI^R)Cl₂] [M = Mo, R = Dipp (1); M = W, R = Dipp (2); M = Mo, R = Mes (3); M = W, R = Mes (4)] synthesized by the reaction between MoOCl₃(THF)₂ or WOCl₃(THF)₂ and LiBDI^R. Reactivity studies show that the BDI^Dipp complexes are excellent precursors toward adduct formation, reacting smoothly with dimethylaminopyridine (DMAP) and triethylphosphine oxide (OPEt₃). No reaction with small phosphines has been observed, strongly contrasting the chemistry of previously reported rhenium(V) complexes. Additionally, the complexes 1 and 2 are good precursors for salt metathesis reactions. While 1 can be chemically reduced to the first stable example of a Mo(IV) BDI complex 15, reduction of 2 resulted in degradation of the BDI ligand via a nitrene transfer reaction, leading to MAD (4-((2,6-diisopropylphenyl)imino)pent-2-enide) supported tungsten(V) and tungsten(VI) complexes 16 and 17. All reported complexes have been thoroughly studied by VT-NMR and (heteronuclear) NMR spectroscopy, as well as UV-vis and EPR spectroscopy, IR spectroscopy, and X-ray diffraction analysis.

The crystal structure of aqua-bis{2-bromo-6-((2-(2-phenylacetyl)hydrazineylidene)methyl)phenolato-κ3 N,O,O′}-dimethylformamide-κ1 O-erbium(III) chloride – dimethylformamide – water (1/2/1), C39H49N7O9Br2ClEr

C39H49N7O9Br2ClEr, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 12.3164(9) Å, b = 12.7581(9) Å, c = 14.5023(11) Å, α = 70.873(2)°, β = 80.281(2)°, γ = 65.810(2)°, V = 1962.4(3) Å3, Z = 1, R gt (F) = 0.0383, wR ref (F 2) = 0.0765, T = 296.15 K.

Low-Coordinate Mixed Ligand NacNac Complexes of Rare Earth Metals

We report the synthesis and characterization of two types of new mixed-ligand rare earth complexes: tetracoordinate (NacNac^Mes)Ln(BIAN^dipp) (Ln = Dy (1), Er (2) and Y (3)) and pentacoordinate (NacNac^Mes)Ln(AP^dipp)(THF) (Ln = Dy (4), Er (5) and Y (6)). The first three compounds were prepared by the reaction of [(BIAN^Dipp)LnI] with potassium β-diketiminate. The salt metathesis of β-diketiminato-supported rare earth dichlorides (NacNac^Mes)LnCl₂(THF)₂ with sodium o-amidophenolate results in compounds 4-6. The crystal structures of complexes 1-6 were determined by single-crystal analysis. The combination of bulky monoanionic N-mesityl-substituted β-diketiminates with sterically hindered redox-active ligands led to the very low coordination numbers of rare earths and strong distortion of the chelate ligands.

Structural Diversity and Multielectron Reduction Reactivity of Samarium(II) Iodido-β-diketiminate Complexes Dependent on Tetrahydrofuran Content

The molecular structures of complexes [Sm(Nacnac)I(thf)_n] (Nacnac = HC(C(Me)Ndipp)₂^-, dipp = 2,6-diisopropylphenyl, thf = tetrahydrofuran) depending on the number of thf ligands are studied. The complete removal of thf from a known complex [Sm(Nacnac)I(thf)₂] leads to a tetranuclear product [Sm(Nacnac)I]₄ (4). The partial removal of thf results in mixtures of dinuclear [Sm₂(Nacnac)₂I₂(thf)] (2), trinuclear [Sm₃(Nacnac)₃I₃(thf)] (3), and tetranuclear [Sm₄(Nacnac)₄I₄(thf)₂] (4*) complexes and 4, depending on the conditions. The reaction of solvent-free SmI₂ with 1 equiv of K(Nacnac) results mainly in [Sm(Nacnac)₂] (1), while the interaction of 4 with certain amounts of thf allows obtaining pure 2 and 3 (with the admixture of 4*). Complex 4* is the exact dimer of 2, and both compounds are stable in solutions. Reactions with 3 and 4 as reductants are studied. 4 is oxidized by I₂ to stoichiometrically yield two products, mixed-valent tetranuclear [Sm₄(Nacnac)₄I₅] (5) and binuclear [Sm(Nacnac)I₂]₂ (6) complexes. In the reaction of 4 with ⁿBu₃PTe, a trinuclear complex [Sm₃(Nacnac)₃(μ-I)₃(μ₃-E)₂] (8, E = I or Te) is formed in small amounts, with the formation of 6 as the second product. 3 serves as a two-electron reductant in the reaction with ⁿBu₃PTe to yield a trinuclear complex [Sm₃(Nacnac)₃I₃(μ-Te₂)] (7). Complexes 2, 4, 4*, 5, 6, and 8 possess a unique flat Sm_xI_y core of heavy atoms, which is assumed to be a consequence of the Nacnac ligand geometry.

3D-Frameworks and 2D-networks of lanthanide coordination polymers with 3-pyridylpyrazole: photophysical and magnetic properties

A series of 15 lanthanide-containing coordination polymers, both 3D- and 2D-networks, as well as complexes of Ln-trichlorides with 3-(3-pyridyl)pyrazole (3-PyPzH), were synthesized. A large structural diversity is observed depending on the ligand content: 3∞[Ln(3-PyPzH)Cl₃], Ln = Eu and Gd, of sra topology, 2∞[Sm(3-PyPzH)Cl₃], 2∞[Ln₂(3-PyPzH)₃Cl₆]·2solv, Ln = Eu³⁺, Tb³⁺, Dy³⁺, Ho³⁺ and Er³⁺, solv = Tol and MeCN, of sql topology and 2∞[Ln(3-PyPzH₂)Cl₄], Ln = La and Nd, of hcb topology with salt like complexes of the formula [(3-PyPzH₂)][Ln(3-PyPzH)₂Cl₄], Ln = Eu, Tb, Dy and Ho. The products were characterized by single-crystal and powder X-ray diffraction, high-temperature X-ray diffraction, differential thermal analysis and thermogravimetry (DTA/TG) combined with mass spectrometry, differential scanning calorimetry (DSC), IR-spectroscopy, UV-visible spectrophotometry, photoluminescence spectroscopy, and magnetic susceptibility. Absorption spectroscopy shows ion-specific 4f-4f transitions that can be assigned to Sm³⁺, Eu³⁺, Dy³⁺, Ho³⁺ and Er³⁺ in a wide range from the UV-VIS to NIR region. An excellent antenna effect through ligand-metal energy transfer was observed in 2∞[Tb₂(3-PyPzH)₃Cl₆]·2solv, leading to high efficiency of the luminescence indicated by a quantum yield up to 76%. Direct current magnetic susceptibility studies reveal the absence of interatomic interaction for Dy³⁺ and Er³⁺ and weak ferromagnetic interaction for Ho³⁺. Thermal analysis shows good stability up to 365 °C for 2∞[Ho₂(3-PyPzH)₃Cl₆]·2MeCN.

A Sodium Sodate as Precursor for Lanthanide Bis(4-R-benzoxazol-2-yl)methanide Single-Molecule Magnets

From the sodium sodate precursor [(Na(thf)₆][Na{(4-Me-NCOC₆H₃)₂CH}₂] (1) three isostructural dinuclear lanthanide complexes [(μ-Cl)Ln^III{(4-MeNCOC₆H₃)₂CH}₂]₂ with Ln = Gd (2), Dy (3), and Er (4) based on the N,N'-chelating monoanionic bis(4-methylbenzoxazol-2-yl)methanide ligand (titled "Mebox") were synthesized and characterized by X-ray diffraction and magnetic measurements. The sodium precursor 1 was analyzed via X-ray diffraction and diffusion-ordered NMR spectroscopy experiments (DOSY-NMR) in order to investigate its aggregation in solution and the solid state. The sodium analog [(thf)₃Na(NCOC₆H₄)₂CH] (1') based on the bis(benzoxazol-2-yl)-methanide ligand (titled "box") was prepared and analyzed for comparison reasons. From the lanthanide derivatives 2-4, the Dy^III complex 3 displays slow relaxation of magnetization at zero field, with a relaxation barrier of U = 315.7 cm^-1. The coupling strength between the two lanthanide centers was estimated with the Gd^III equivalent 2, giving a weak antiferromagnetic coupling of J = -0.035 cm^-1.

Enhancing Steric Hindrance via Ligand Design in Dysprosium Complexes: From Induced Slow Relaxation to Zero-Field Single-Molecule Magnet Properties

The synthesis and magnetic characterization of three novel Dy compounds, [Dy{PPh₂S(N^tBu)₂}₂(μ-Cl₂)Li(THF)₂] (1), [Dy{PhS(N^tBu)₂}₂(μ-Cl₂)Li(THF)₂] (2), and [Dy{MeS(N^tBu)₃}₂(μ-Cl₂)Li(THF)₂] (3), based on the sulfur-nitrogen ligands RS(N^tBu)_x^- (where R = PPh₂, x = 2 for (1); R = Ph, x = 2 for (2); and R = Me, x = 3 for (3)) are reported. They represent rare examples of lanthanide-based complexes containing sulfur-nitrogen ligands, whose suitability to enhance the magnetic anisotropy in 3d metals was only recently established. Changes in the ligand field environment drastically affect the magnetic properties, with compounds 1 and 2 displaying field-induced single-molecule magnet (SMM) behavior, while compound 3 shows slow relaxation at zero field. These trends strongly suggest that ligand engineering strategies toward linear dysprosium complexes, similar to those for dysprosocenium complexes, should enhance the SMM performances of SN-based lanthanide compounds.

Slow Magnetic Relaxation in Mono- and Bimetallic Lanthanide Tetraimido-Sulfate S(NtBu)4 2- Complexes

Lanthanide ions are particularly well-suited for the design of single-molecule magnets owing to their large unquenched orbital angular momentum and strong spin-orbit coupling that gives rise to high magnetic anisotropy. Such nanoscopic bar magnets can potentially revolutionize high-density information storage and processing technologies, if blocking temperatures can be increased substantially. Exploring non-classical ligand scaffolds with the aim to boost the barriers to spin-relaxation are prerequisite. Here, the synthesis, crystallographic and magnetic characterization of a series of each isomorphous mono- and dinuclear lanthanide (Ln=Gd, Tb, Dy, Ho, Er) complexes comprising tetraimido sulfate ligands are presented. The dinuclear Dy complex [{(thf)2 Li(NtBu)2 S(tBuN)2 DyCl2 }2  ⋅ ClLi(thf)2 ] (1c) shows true signatures of single-molecule magnet behavior in the absence of a dc field. In addition, the mononuclear Dy and Tb complexes [{(thf)2 Li(NtBu)2 S(tBuN)2 LnCl2 (thf)2 ] (2b,c) show slow magnetic relaxation under applied dc fields.

Structure and magnetism of a tetrahedral uranium(iii) β-diketiminate complex

We describe the functionalisation of the previously reported uranium(iii) β-diketiminate complex (BDI)UI₂(THF)₂ (1) with one and two equivalents of a sterically demanding 2,6-diisopropylphenolate ligand (ODipp) leading to the formation of two heteroleptic complexes: [(BDI)UI(ODipp)]₂ (2) and (BDI)U(ODipp)₂ (3). The latter is a rare example of a tetrahedral uranium(iii) complex, and it shows single-molecule magnet behaviour.

Single-molecule magnet behavior in heterolopetic Dy3+-chloro-diazabutadiene complexes: influence of the nuclearity and ligand redox state

We report the synthesis, structure and magnetic properties investigations of a series of new dysprosium mono- and dinuclear chloro complexes based on different diazabutadiene ligands (DAD^2R = [2,6-iPr₂C₆H₃N–CRCR–NC₆H₃iPr₂-2,6]; R = H, Me).

Synthesis and luminescence studies of lanthanide complexes (Gd, Tb, Dy) with phenyl- and 2-pyridylthiolates supported by a bulky β-diketiminate ligand. Impact of the ligand environment on terbium(iii) emission

Structure-dependent photoluminescence was studied for lanthanide complexes with widespread Nacnac ligands, supplemented by thiolates; notable antenna properties of the latter are revealed.

Relaxation dynamics in see-saw shaped Dy(iii) single-molecule magnets

Unusual see-saw shaped Dy(iii) single-molecule magnets, [K(DME)_n][L^ArDy(X)₂] (L^Ar = {C₆H₄[(2,6-ⁱPrC₆H₃)NC₆H₄]₂}²⁻), X = Cl (1) and X = I (2) were synthesized and display high effective energy barriers (U_eff = 1278–1334 K) in zero field.

Synthesis, characterization and catalytic activity of rare-earth metal amides incorporating cyclohexyl bridged bis(β-diketiminato) ligands

The bridged bis(β-diketiminato) ligands supported rare-earth amides exhibited high catalytic activity towards the hydrophosphination of β-nitroalkene and α,β-unsaturated carbonyl derivatives with an excellent regioselectivity.