β‑Diketiminate Rare Earth Borohydride Complexes: Synthesis, Structure, and Catalytic Activity in the Ring-Opening Polymerization of ε‑Caprolactone and Trimethylene Carbonate

The synthesis of a series of divalent and trivalent β-diketiminate borohydrides [(dipp)₂NacNacLn­(BH₄)­(THF)₂] ((dipp)₂NacNac = (2,6-C₆H₃<i>i</i>Pr₂)­NC­(Me)­CHC­(Me)­N­(2,6-C₆H₃<i>i</i>Pr₂); Ln = Sm, Eu, Yb) and [(dipp)₂NacNac­Ln­(BH₄)₂­(THF)] (Ln = Sc, Sm, Dy, Yb, Lu) is reported. All compounds were obtained by salt metathesis in THF from [(dipp)₂NacNacK] and the corresponding homoleptic divalent and trivalent borohydrides [Ln­(BH₄)₂(THF)₂] (Ln = Sm, Eu, Yb), [Sc­(BH₄)₃(THF)₂], and [Ln­(BH₄)₃(THF)₃] (Ln = Sm, Dy, Yb, Lu), respectively. The complexes were fully characterized, and their solid-state structures were established by single-crystal X-ray diffraction. In both the divalent and trivalent compounds, the BH₄^– groups coordinate in a κ³(H) mode to the metal. Only in the lutetium complex [(dipp)₂NacNacLu­(BH₄)₂(THF)] does one BH₄^– group coordinate in a κ³(H) mode, whereas the other one coordinates as κ²(H). This kind of mixed κ²/κ³(H) coordination mode is rare. The application of the divalent and trivalent compounds as initiators in the ring-opening polymerization (ROP) of ε-caprolactone (CL) and trimethylene carbonate (TMC) was investigated. All complexes afforded a generally well-controlled ROP of both of these cyclic esters. High molar mass poly­(ε-caprolactone) diols (<i>M</i>_n,NMR < 92 700 g mol^–1, <i><i>Đ</i></i>_M = 1.51) and α-hydroxy,ω-formate telechelic poly­(trimethylene carbonate)­s (<i>M</i>_n,NMR < 16 000 g mol^–1, <i><i>Đ</i></i>_M = 1.59) were thus synthesized under mild operating conditions

Homoleptic Chiral Benzamidinate Complexes of the Heavier Alkaline Earth Metals and the Divalent Lanthanides

Reaction of the chiral amidine <i>N</i>,<i>N</i>′-bis­(1-phenyl­ethyl)­benzamidine ((<i>S</i>)-HPEBA), KCH­(SiMe₃)₂, and MI₂ (M = Ca, Sr, Ba) or LnI₂ (Ln = Eu, Yb) in a 2:2:1 stoichiometric ratio resulted in the chiral homoleptic monomeric alkaline earth metal compounds [Ca­(PEBA)₂­(THF)₂] (<b>1</b>) and [Sr­(PEBA)₂­(THF)₂] (<b>2</b>), the dimeric barium complex [Ba­(PEBA)₂]₂ (<b>3</b>), and the monomeric divalent lanthanide compounds [Eu­(PEBA)₂­(THF)₂] (<b>4</b>), and [Yb­(PEBA)₂­(THF)₂] (<b>5</b>). The solid-state structures of all compounds were established by single-crystal X-ray diffraction. Three different structures are observed in the solid state. Compounds <b>1</b>, <b>2</b>, <b>4</b>, and <b>5</b> form distorted coordination octahedra. For the alkaline earth element complexes <b>1</b> and <b>2</b>, the two THF molecules are located in a <i>trans</i>-position, whereas, for the lanthanide compounds <b>4</b> and <b>5</b>, they are arranged in a <i>cis</i>-position. In contrast, the barium complex <b>3</b> is dimeric with two amidinate ligands in an unusual “side-on” bridging mode. All five complexes were used as catalysts for hydrophosphination reactions of styrene and substituted analogues

Comparison of Decamethyldizincocene [(η⁵‑Cp*)₂Zn₂] versus Decamethylzincocene [Cp*₂Zn] and Diethylzinc Et₂Zn As Precatalysts for the Intermolecular Hydroamination Reaction

A comparison of the Zn–Zn bonded species [(η⁵-Cp*)₂Zn₂] versus the related organometallic zinc compound [Cp*₂Zn] and ZnEt₂ for the intermolecular hydroamination reaction in the presence of equimolar amounts of [PhNMe₂H]­[B­(C₆F₅)₄] is reported. All compounds show high reaction rates under mild conditions and a good functional group tolerance for the addition of aniline derivatives to primary alkynes. Within this series the metallocene [Cp*₂Zn] is the most active one, whereas the zinc–zinc bonded species [(η⁵-Cp*)₂Zn₂] shows the best selectivity. Most remarkable is the unexpected excellent catalytic performance of the zinc–zinc bonded species [(η⁵-Cp*)₂Zn₂]

Realgar as a Building Block for Lanthanide Clusters: Encapsulation of a Copper Cluster by a Lanthanide Cluster

The reactions of the divalent lanthanide metallocenes [Cp*₂Ln­(thf)₂] (Cp* = η⁵-C₅Me₅; Ln = Sm, Yb) with realgar (As₄S₄) gave the open cage tetrametallic complex [(Cp*₂Sm)­(Cp*Sm)₃AsS₃(Cp*AsS₂)₂(thf)₃] (<b>1</b>) or the trimetallic cage compound [(Cp*Yb)₃As₂S₄(Cp*AsS₂)­(thf)₂] (<b>2</b>), respectively, by reductive cleavage of the inorganic cage. As result of a Cp* transfer, the novel Cp*AsS₂^2– anion is formed. Moreover, the As₂S₄^4– anion, which is bound in <b>2</b>, is observed for the first time in coordination chemistry. Closed cage compounds are formed by either using bulkier ligands or a different As/S cage. The reaction of [Cp‴₂Sm] (Cp‴ = (1,2,4-(<i>t</i>-Bu)₃C₅H₂)) with As₄S₄ and the reaction of [Cp*₂Yb­(thf)₂] with dimorphite (As₄S₃) gave the closed 11-vertex cage clusters [(Cp‴Sm)₃(AsS₃)₂] (<b>3</b>) and [(Cp*Yb)₃(AsS₃)₂] (<b>4</b>), respectively. The reaction of <b>3</b> with [CuMes] resulted in the formation of the Sm/S/Cu cluster [(Cp‴Sm­(thf))₄Cu₄S₆] (<b>5</b>), in which the Sm atoms encapsulate a classical Cu₄S₆^8– cluster core. This is the first transition metal chalcogenide cluster encapsulated by f-elements. Alternatively, the endohedral cluster can thus be described as [Cu₄@{(Cp‴Sm­(thf))₄S₆}], in which a Cu₄ tetrahedron is encapsulated by the samarium sulfido cluster {(Cp‴Sm­(thf))₄S₆}

Manganese- and Lanthanide-Based 1D Chiral Coordination Polymers as an Enantioselective Catalyst for Sulfoxidation

The chiral 1D-coordination polymers (CP) {[Ln₂­(MnLCl)₂­(NO₃)₂­(dmf)₆­(H₂O)₂]·<i>x</i>H₂O}_<i>n</i> [Ln = Pr (<b>1</b>), Nd (<b>2</b>), Sm (<b>3</b>), and Gd (<b>4</b>)] were synthesized by the reaction of <i>N,N</i>′-bis­(4-carboxy­salicylidene)­cyclo­hexane­di­amine (H₄L) with [MnCl₂·4­(H₂O)] and [Ln­(NO₃)₃·<i>x</i>(H₂O)] in the presence of dmf/pyridine at 90 °C. The polymers consist of manganese-salen-based moieties having carboxylate linkers connected to rare earth atoms in a 1D-chain structure. The polymers are very easily accessible. A one-step synthesis for the ligand and a second step for the preparation of the 1D coordination polymers starting from commercially available material are needed. The solid state structures of <b>1</b>–<b>4</b> were established by single-crystal X-ray diffraction. Compounds <b>1</b>–<b>4</b> were investigated as heterogeneous catalysts for the sulfoxidation reaction of various alkyl and aryl sulfides. The influence of various solvents and oxidizing agents on the catalytic reaction was examined. It was found that the catalysts were active for more than one reaction cycle without significant loss of activity. For phenylsulfide with 1 mol % of the catalyst <b>4</b>, a maximum conversion 100% and a chemoselectivity 88% were observed

(Iminophosphoranyl)(thiophosphoranyl)methanide {CH(PPh₂NSiMe₃)(Ph₂PS)}⁻ as a Ligand in Rare-Earth-Element Chemistry

The (iminophosphoranyl)­(thiophosphoranyl)­methanide {CH­(PPh₂NSiMe₃)­(PPh₂S)}⁻ has been introduced as a ligand into the chemistry of yttrium and the lanthanides. First, the bimetallic potassium reagent [K­{CH­(PPh₂NSiMe₃)­(PPh₂S)}]₂ was synthesized by deprotonation of [CH₂(PPh₂NSiMe₃)­(PPh₂S)] with KH. [K­{CH­(PPh₂NSiMe₃)­(PPh₂S)}]₂ forms a dimeric structure in the solid state. The potassium atoms are bridged by the sulfur atom of the ligand. Moreover, an η⁶ coordination of one phenyl ring is observed. The salt metathesis of [K­{CH­(PPh₂NSiMe₃)­(PPh₂S)}]₂ with LnCl₃ led to the dichloro complexes [{CH­(PPh₂NSiMe₃)­(PPh₂S)}­LnCl₂(THF)] (Ln = Dy, Er). The bis­(amido) compounds [{CH­(PPh₂NSiMe₃)­(PPh₂S)}­Ln­{N­(SiHMe₂)₂}₂] (Ln = Y, Sm, Er, Lu) were obtained by amine elimination from [CH₂(PPh₂NSiMe₃)­(PPh₂S)] and [Ln­{N­(SiHMe₂)₂}₃(THF)₂]. The amido complex [{CH­(PPh₂NSiMe₃)­(PPh₂S)}­Er­{N­(SiHMe₂)₂}₂] could also be accessed by the reaction of [{CH­(PPh₂NSiMe₃)­(PPh₂S)}­ErCl₂(THF)] with KN­(SiHMe₂)₂

Synthesis, Structural Characterization, and Magnetic Properties of Lanthanide Arsolyl Sandwich Complexes

A series of trivalent lanthanide sandwich complexes [(η5-C4R4As)Ln(η8-C8H8)] using three different arsolyl ligands are reported. The complexes were obtained via salt elimination reactions between potassium arsolyl salts and lanthanide precursors [LnI(COT)(THF)2] (Ln = Sm, Dy, Er; COT = η8-C8H8). The resulting compounds exhibit classical sandwich complex structures with one notable exception. Characterization was conducted in both the solid state using single-crystal X-ray diffraction and in solution for the Sm compounds using NMR spectroscopy. Furthermore, the magnetic properties of an Er complex were investigated, revealing distinctive single-molecule-magnet behavior characterized by an energy barrier of Ueff = 323.3 K. Theoretical calculations were employed to support and interpret the experimental findings, with a comparative analysis performed against previously reported complexes

Chiral Mono(borohydride) Complexes of Scandium and Lutetium and Their Catalytic Activity in Ring-Opening Polymerization of dl-Lactide

The enantiopure mono­(borohydride) rare-earth complexes [Ln­{(<i>S</i>)-PETA)}₂(BH₄)] (Ln = Sc (<b>1</b>), Lu (<b>2</b>); PETA = <i>N</i>,<i>N</i>′-bis­((<i>S</i>)-1-phenylethyl)-<i>tert</i>-butylamidinate) are reported. The synthesis was achieved by salt metathesis reactions of the homoleoptic tris­(borohydrides) [Ln­(BH₄)₃(thf)_<i>n</i>] and (<i>S</i>)-LiPETA. Complexes <b>1</b> and <b>2</b> were fully characterized, including single-crystal X-ray diffraction. Compounds <b>1</b> and <b>2</b> were evaluated as initiators for the ring-opening polymerization (ROP) of racemic lactide. Both <b>1</b> and <b>2</b> were found to be active in the ROP of dl-lactide. Polymerizations carried out in toluene show a higher activity for <b>2</b> but a lower selectivity in comparison to the scandium derivative

Mononuclear and Tetranuclear Compounds of Yttrium and Dysprosium Ligated by a Salicylic Schiff-Base Derivative: Synthesis, Photoluminescence, and Magnetism

The Schiff-base (2-aminoethyl)­hydroxybenzoic acid (H₂L) as a proligand was prepared in situ from 3-formylsalicylic acid and ethanolamine (ETA). The mononuclear {[Y­(HL)₄]­[ETAH]·H₂O} (<b>1</b>) and {[Dy­(HL)₄] [ETAH]·3MeOH·H₂O} (<b>2</b>) and tetranuclear {[Y₄(HL)₂(L)₄(μ₃-OH)₂]·4MeOH·4H₂O} (<b>3</b>), {[Dy₄(HL)₂(L)₄(μ₃-OH)₂]·5­(MeOH)₂·7H₂O (<b>4</b>), and {[Dy₄(HL)₈(L)₂]·4MeOH·2H₂O}­(<b>5</b>) rare-earth metal complexes of this ligand could be obtained as single-crystalline materials by the treatment of H₂L in the presence of the metal salts [Ln­(NO₃)₃·(H₂O)_<i>m</i>] (Ln = Y, Dy). In the solid state, the tetranuclear compounds <b>3</b> and <b>4</b> exhibit butterfly structures, whereas <b>5</b> adopts a rectangular arrangement. Electrospray ionization mass spectrometry data of the ionic compounds <b>1</b> and <b>2</b> support single-crystal X-ray analysis. The yttrium compounds <b>1</b> and <b>3</b> show fluorescence with 11.5% and 13% quantum yield, respectively, whereas the quantum yield of the dysprosium complex <b>4</b> is low. Magnetic studies on the dysprosium compounds <b>4</b> and <b>5</b> suggest the presence of weak antiferromagnetic interactions between neighboring metal centers. Compound <b>4</b> shows single-molecule-magnet behavior with two relaxation processes, one with the effective energy barrier <i>U</i>_eff = 84 K and the preexponential factor τ₀ = 5.1 × 10^–9 s

Tetranuclear and Pentanuclear Compounds of the Rare-Earth Metals: Synthesis and Magnetism

The Schiff-base proligand 4-<i>tert</i>-butyl-2,6-bis-[(2-hydroxy-phenylimino)­methyl]­phenol (H₃L) was prepared in situ from 4-<i>tert</i>-butyl-2,6-diformylphenol and 2-aminophenol. The proligand (H₃L) was used with dibenzoylmethane (DBMH) or acetylacetone (acacH) with lanthanides giving compounds with varying arrangements of metal atoms and nuclearities. The tetranuclear compound {[Dy₄(L)₃(DBM)₄]­[Et₃NH]} (<b>1</b>) and pentanuclear compound {[Dy₅(μ₃-OH)₂(L)₃(DBM)₄(MeOH)₄]·4­(MeOH)} (<b>2</b>) were obtained from the ligand (L)^3– and dibenzoylmethane. The tetranuclear compounds {[Dy₄(μ₄-OH)­(L)₂(acac)₄(MeOH)₂(EtOH)­(H₂O)]·(NO₃)·2­(MeOH)·3­(EtOH)} (<b>3</b>) and {[Ln₄(μ₃-OH)₂(L)­(HL)­(acac)₅(H₂O)] (HNEt₃)­(NO₃)·2­(Et₂O)} (Ln = Tb (<b>4</b>), Dy (<b>5</b>), Ho (<b>6</b>), and Tm (<b>7</b>)) resulted when the ligand (L)^3– was used in the presence of acetylacetone. In the solid state structures, the tetranuclear compound <b>1</b> adopts a linear arrangement of metal atoms, while tetranuclear compound <b>3</b> has a square grid arrangement of metal atoms, and tetranuclear compounds <b>4</b>–<b>7</b> have a seesaw-shaped arrangement of metal atoms. The composition found from single-crystal X-ray analysis of compound <b>1</b> and <b>3</b>–<b>7</b> is supported by electrospray ionization mass spectrometry (ESI-MS). The magnetic studies on compounds <b>1</b> suggest the presence of weak ferromagnetic interactions, whereas compounds <b>2</b>–<b>6</b> exhibit weak antiferromagnetic interactions between neighboring metal centers. Compounds <b>1</b>,<b> 2</b>, and <b>3</b> also show single-molecule magnet behavior under an applied dc field