Polyphenylcyclopentadienyl complexes of rare earth elements

Reaction of LnCl₃(thf) _x (Ln = Y, La, Yb, Lu) with NaCp^Phn (Cp^Phn = 1,3-Ph₂C₅H₃, 1,2,4-Ph₃C₅H₂, Ph₄C₅H) leads to formation of monocyclopentadienyl dichloride complexes Yb(Ph₂C₅H₃)Cl₂(thf)₃ (1), Ln(Ph₃C₅H₂)Cl₂(thf)₃ (Ln = Y (2), Lu (3)), La(Ph₄C₅H)Cl₂(thf)₃ (4). Molecular structures of 1, 2 and the polynuclear complex [(Ph₃C₅H₂)₃Lu₄(Cl)₇(O)(thf)₃] (5), which is a partial hydrolysis product of 3, have been established by the X-ray method.     

Europium is Different: Solvent and Ligand Effects on Oxidation State Outcomes and C-F Activation in Reactions Between Europium Metal and Pentafluorophenylsilver

Unique outcomes have emerged from the redox transmetallation/ protolysis (RTP) reactions of europium metal with [Ag(C₆F₅)(py)] (py=pyridine) and pyrazoles (RR′pzH). In pyridine, a solvent not normally used for RTP reactions, the products were mainly Eu^II complexes, [Eu(RR′pz)₂(py)₄] (RR′pz=3,5-diphenylpyrazolate (Ph₂pz) 1 ; 3-(2-thienyl)-5-trifluoromethylpyrazolate (ttfpz) 2 ; 3-methyl-5-phenylpyrazolate (PhMepz) 3 ). However, use of 3,5-di-tert-butylpyrazole (tBu₂pzH) gave trivalent [Eu(tBu₂pz)₃(py)₂] 4 , whereas the bulkier N,N′-bis(2,6-difluorophenyl)formamidine (DFFormH) gave divalent [Eu(DFForm)₂(py)₃] 5 . In tetrahydrofuran (thf), the usual solvent for RTP reactions, C−F activation was observed for the first time with [Ag(C₆F₅)(py)] in such reactions. Thus trivalent [{Eu₂(Ph₂pz)₄(py)₄(thf)₂(μ-F)₂}{Eu₂(Ph₂pz)₄(py)₂(thf)₄(μ-F)₂}] ( 6 ), [Eu₂(ttfpz)₄(py)₂(dme)₂(μ-F)₂] ( 7 ), [Eu₂(tBu₂pz)₄(dme)₂(μ-F)₂] ( 8 ) were obtained from the appropriate pyrazoles, the last two after crystallization from 1,2-dimethoxyethane (dme). Surprisingly 3,5-dimethylpyrazole (Me₂pzH) gave the divalent cage [Eu₆(Me₂pz)₁₀(thf)₆(μ-F)₂] ( 9 ). This has a compact ovoid core held together by bridging fluoride, thf, and pyrazolate ligands, the last including the rare μ₄-1η⁵(N₂C₃): 2η²(N,N′): 3κ(N): 4κ(N′) pyrazolate binding mode. With the bulky N,N′-bis(2,6-diisopropylphenyl)formamidine (DippFormH), which often favours C−F activation in RTP reactions, neither oxidation to Eu^III nor C−F activation was observed and [Eu(DippForm)₂(thf)₂] ( 10 ) was isolated. By contrast, Eu reacted with Bi(C₆F₅)₃ and Ph₂pzH or tBu₂pzH in thf without C−F activation, to give [Eu(Ph₂pz)₂(thf)₄] ( 11 ) and [Eu(tBu₂pz)₃(thf)₂] ( 12 ) respectively, the oxidation state outcomes corresponding to that for use of [Ag(C₆F₅)(py)] in pyridine.     

Metallorganische Verbindungen der Lanthanoide. 93 [1]. Tetramethylcyclopentadienyl-Komplexe ausgewählter 4f-Elemente

Organometallic Compounds of the Lanthanides. 93. Tetramethylcyclopentadienyl Complexes of Selected 4f-Elements The trichlorides of lanthanum, neodymium, samarium, and terbium react with Na(C₅Me₄H) in THF to yield the homoleptic complexes Ln(C₅Me₄H)₃ [Ln = La ( 1a ), Nd ( 1b ), Sm ( 1c ), Tb ( 1d )]. On the other hand the reactions of HoCl₃, TmCl₃, and LuCl₃ with Na(C₅Me₄H) result only with formation of the dicyclopentadienyl complexes (C₅Me₄H)₂LnCl(THF) [Ln = Ho ( 2e ), Tm ( 2f ), Lu ( 2h )]. The metallocenes (C₅Me₄H)₂Ln(THF)₂ [Ln = Sm ( 3c ), Yb ( 3g )] are obtained by the reactions of LnI₂ (Ln = Sm, Yb) with Na(C₅Me₄H). The ¹H- and ¹³C-NMR spectra as well as the X-ray crystal structure of the triscyclopentadienyl complexes 1 a and 1 c are discussed.     

Synthese und Charakterisierung donor-funktionalisierter ansa-Metallocene von Yttrium,Neodym, Samarium,Erbium und Lutetium

Organometallic Compounds of the Lanthanides. 133 Synthesis and Characterization of donor-functionalised ansa -Metallocenes of Yttrium, Neodymium, Samarium, Erbium, and Lutetium The reaction of Me₂SiCl₂ with K[C₅H₄^tBu], Li[C₅H₄SiMe₃] or K[C₅H₃^tBuMe-3] followed by treatment with K[C₅H₄CH₂CH₂NMe₂] yields mixed substituted dicyclopentadienyldimethylsilanes which after double deprotonation with KH afford the dipotassium salts K₂[Me₂Si(C₅H₃^tBu-3)(C₅H₃CH₂CH₂NMe₂-3)] ( 1 ), K₂[Me₂Si · (C₅H₃SiMe₃-3)(C₅H₃CH₂CH₂NMe₂-3)] ( 2 ), and K₂[Me₂Si · (C₅H₂^tBu-3-Me-5)(C₅H₃CH₂CH₂NMe₂-3)] ( 3 ), respectively. The reaction of 1 , 2 , or 3 with LnCl₃(THF)_x (Ln = Y, La, Nd, Sm, Er, Lu) leads to the complexes [Me₂Si(C₅H₃^tBu-3) · (C₅H₃CH₂CH₂NMe₂-3)]LnCl [Ln = Y ( 4 a ), Sm ( 4 c ), Lu ( 4 e )], [Me₂Si(C₅H₃SiMe₃-3)(C₅H₃CH₂CH₂NMe₂-3)]LnCl [Ln = Y ( 5 a ), Sm ( 5 c ), Lu ( 5 e )], and [Me₂Si(C₅H₂^tBu-3-Me-5)(C₅H₃CH₂CH₂NMe₂-3)]LnCl [Ln = Y ( 6 a ), Nd ( 6 b ), Sm ( 6 c ), Er ( 6 d ), Lu ( 6 e )], respectively. Alkylation of 4 a , 4 c , 5 a , and 6 b , 6 e with LiCH₃, LiCH₂SiMe₃, and LiCH(SiMe₃)₂ produces the alkylmetallocenes [Me₂Si(C₅H₃^tBu-3) · (C₅H₃CH₂CH₂NMe₂-3)]LnR [R = CH₃, Ln = Y ( 7 a ), Sm ( 7 c ); R = CH₂SiMe₃, Ln = Y ( 8 a )], [Me₂Si(C₅H₃SiMe₃-3) · (C₅H₃CH₂CH₂NMe₂-3)]YCH₃ ( 9 a ), and [Me₂Si(C₅H₂^tBu3-Me-5)(C₅H₃CH₂CH₂NMe₂-3)]LnR (R = CH₃, Ln = Lu ( 10 e ); R = CH₂SiMe₃, Ln = Lu ( 11 e ); R = CH(SiMe₃)₂, Ln = Nd ( 12 b ), Lu ( 12 e )], respectively. All new compounds were characterized by elemental analyses, NMR spectroscopy and mass spectrometry. The molecular structure of 6 c and 6 e was determined by single crystal X-ray structure analysis.     

New Homoleptic Rare Earth 3,5‐Diphenylpyrazolates and 3,5‐Di‐tert‐butylpyrazolates and a Noteworthy Structural Discontinuity

Direct thermally induced reactions between rare earth metals (Ln = Y,Ce, Dy, Ho, and Er) activated by Hg metal and 3,5‐diphenylpyrazole (Ph₂pzH) or 3,5‐di‐tert‐butylpyrazole (tBu₂pzH) yielded either homoleptic complexes [Ln_n(R₂pz)_3n] or a heteroleptic complex [Ln(Ph₂pz)₃(Ph₂pzH)₂] From Ph₂pzH, [Ce₃(Ph₂pz)₉], [Dy₂(Ph₂pz)₆], [Ho₂(Ph₂pz)₆], and [Y(Ph₂pz)₃(Ph₂pzH)₂] were isolated. The first has a bowed trinuclear Ce₃ backbone with two η² pyrazolate ligands on the terminal metal atoms and one on the middle, and bridging by both μ‐η²:η² and μ‐η²:η⁵ ligands between the terminal and the central Ce atoms. Although both the Dy and Ho complexes are dinuclear, the former has the rare μ‐η²:η¹ bridging whilst the latter has μ‐η²:η² bridging. Thus the dysprosium complex is seven‐coordinate and the holmium is eight‐coordinate, in contrast to any correlation with Ln³⁺ ionic radii, and the series has a remarkable structural discontinuity. The heteroleptic Y complex is eight coordinate with three chelating Ph₂pz and two transoid unidentate Ph₂pzH ligands. From tBu₂pzH, dimeric [Ln₂(tBu₂pz)₄] (Ln = Ce, Er) were isolated and are isomorphous with eight coordinate Ln atoms ligated by two chelating terminal tBu₂pz and two μ‐η²:η² tBu₂pz donor groups. They are also isomorphous with previously reported La, Nd, Yb, and Lu complexes.     

Organometallic Compounds of the Lanthanides. 127 [1] Synthesis of Monomeric Bis(cyclopentadienyl)lanthanide Tetrahydroborates with Bulky Cyclopentadienyl Ligands. Single Crystal X-ray Structures of [(η5-C5Me5)2SmBH4(THF)] and [(η5-C5Me4Et)2Y(μ-H)2BH2(THF)]

The trichlorides of yttrium, samarium, and lutetium react with 2 equivalents of Na[C₅H₄ ^tBu] and 1 equivalent of NaBH₄ to give [(η⁵-C₅H₄ ^tBu)₂LnBH₄(THF)] (Ln = Y ( 1 ), Sm ( 2 ), Lu ( 3 )) or with 2 equivalents of Na[C₅Me₄R] and 1 equivalent of NaBH₄ to form [(η⁵-C₅Me₄R)₂ · LnBH₄(THF)] (R = H, Ln = Y ( 4 ), Sm ( 5 ), Lu ( 6 ); R = Me, Ln = Y ( 7 ), Sm ( 8 ), Lu ( 9 ); R = Et, Ln = Y ( 10 ), Sm ( 11 ), Lu ( 12 ); R = ⁱPr, Ln = Y ( 13 ), Sm ( 14 ), Lu ( 15 )). The new compounds have been characterized by elemental analysis, NMR spectroscopy and mass spectrometry. The crystal structures of 8 and 10 were determined by single crystal X-ray diffraction.     

When Metathesis Reactions Go Wrong: Novel Structural Consequences

The complex [Yb(Ph₂pz)₃(LiOBu)]₂ ( 1 ) (Ph₂pz = 3,5‐diphenylpyrazolate), fortuitously obtained from reaction of Yb metal with a lithium containing sample of [SnMe₃(Ph₂pz)] at elevated temperatures forms a centrosymmetric butoxy‐ and pyrazolate‐bridged open box structure. Each ytterbium atom is eight coordinate with one chelating Ph₂pz ligand, one μ‐η²:η² bridging pyrazolate, one μ‐η²(Yb):η⁴(Li) Ph₂pz group and two bridging butoxide ligands. Each lithium atom is unsymmetrically chelated by an η²‐Ph₂pz group, η⁴(N,C(pz)C₂(Ph)) bonded by another pyazolate group, and bridged through a butoxide oxygen atom to two ytterbium atoms. The type of η⁴‐pyrazolate coordination is unprecedented and is the first observation of interactions to a metal by the Ph rings of the Ph₂pz ligand. The complex [Li(dme)₃][Eu(Ph₂pz)₃(dme)] ( 2 ) obtained from reaction of Eu metal with the same sample of [SnMe₃(Ph₂pz)] in dme at room temperature is a charged separated species with the first anionic pyrazolatolanthanoidate(II) complex in which europium is eight coordinate with three chelating Ph₂pz ligands and a chelating dme.     

Effective and Reversible Carbon Dioxide Insertion into Cerium Pyrazolates

The homoleptic pyrazolate complexes [Ce^III₄(Me₂pz)₁₂] and [Ce^IV(Me₂pz)₄]₂ quantitatively insert CO₂ to give [Ce^III₄(Me₂pz?CO₂)₁₂] and [Ce^IV(Me₂pz?CO₂)₄], respectively (Me₂pz=3,5‐dimethylpyrazolato). This process is reversible for both complexes, as observed by in situ IR and NMR spectroscopy in solution and by TGA in the solid state. By adjusting the molar ratio, one molecule of CO₂ per [Ce^IV(Me₂pz)₄] complex could be inserted to give trimetallic [Ce₃(Me₂pz)₉(Me₂pz?CO₂)₃(thf)]. Both the cerous and ceric insertion products catalyze the formation of cyclic carbonates from epoxides and CO₂ under mild conditions. In the absence of epoxide, the ceric catalyst is prone to reduction by the co‐catalyst tetra‐n‐butylammonium bromide (TBAB).     

Reactions of lanthanoid metals with 3,5-diphenylpyrazole at elevated temperatures: synthesis and structures of both homoleptic, [Ln3(Ph2pz)9] (Ln = La, Nd), [Ln2(Ph2pz)6] (Ln = Er, Lu), and heteroleptic, [Ln(Ph2pz)3(Ph2pzH)2] (Ln = La, Nd, Gd, Tb, Er or Yb), pyrazolate complexes

The direct reaction of lanthanoid metals with 3,5-diphenylpyrazole (Ph2pzH) at 300 degrees C under vacuum in the presence of mercury gives the structurally characterized [Ln3(Ph2pz)9] (Ln = La or Nd), [Ln2(Ph2pz)6] (Ln = Er or Lu). Similar reactions provided heteroleptic [Ln(Ph2pz)3(Ph2pzH)2] (Ln = La, Nd, Gd, Tb, Er and Y). The last was obtained only from impure Ph2pzH, but was subsequently prepared by treatment of [Yb(Ph2pz)3(thf)2] with Ph2pzH. Reactions of Yb with Ph2pzH at 200 degrees C gave a poorly soluble divalent species which was converted by 1,2-dimethoxyethane into [Yb(Ph2pz)2(dme)2]. Single crystal X-ray structures established a bowed trinuclear pyrazolate-bridged structure for [Ln3(Ph2pz)9] (Ln = La or Nd), Ln...Ln...Ln being 135.94(1) degrees (La) and 137.41(1) degrees(Nd). There are two eta2-Ph2pz ligands on the terminal Ln atoms and one on the central metal with adjacent Ln atoms linked by one mu-eta2:eta2 and one mu-eta5 (to terminal Ln):eta2 pyrazolate group. Thus the terminal Ln atoms are formally nine-coordinate and the central Ln, ten-coordinate. By contrast, [Ln2(Ph2pz)6] (Ln = Er or Lu) complexes are dimeric with two terminal (eta2) and two bridging (mu-eta2:eta2) pyrazolates and eight-coordinate lanthanoids. All six heteroleptic complexes [Ln(Ph2pz)3(Ph2pzH)2] (Ln = La, Nd, Gd, Tb, Er or Yb) are isomorphous with three equatorial eta2-Ph2pz groups, transoid(N-Ln-N 158.18(6)-161.43(9) degrees) eta1-pyrazole ligands, and eight-coordinate Ln throughout.     

An unusual organoyttrium alkyl complex containing a [C5HMe3(η(3)-CH2)-C5H4N-κ]- ligand and an elusive cyclopentadienide-based scandium tuck-over zwitterion obtained by C-H bond activation

The acid–base reaction between Y(CH₂SiMe₃)₃(thf)₂ and the pyridyl‐functionalized cyclopentadienyl (Cp) ligand C₅Me₄H? C₅H₄N (1 equiv) at 0 °C afforded a mixture of two products: (η⁵:κ‐C₅Me₄? C₅H₄N)Y(CH₂SiMe₃)₂(thf) ( 1 a ) and (η⁵:κ‐C₅Me₄? C₅H₄N)₂YCH₂SiMe₃ ( 1 b ), in a 5:2 ratio. Addition of the same ligand (2 equiv) to Y(CH₂SiMe₃)₃(thf)₂, however, generated 1 b together with the novel complex 1 c , the first well defined yttrium mono(alkyl) complex (η⁵:κ‐C₅Me₄? C₅H₄N)[C₅HMe₃(η³‐CH₂)‐C₅H₄N‐κ]Y(CH₂SiMe₃) containing a rare κ/η³‐allylic coordination mode in which the C? H bond activation occurs unexpectedly with the allylic methyl group rather than conventionally on Cp ring. If the central metal was changed to lutetium, the equimolar reaction between Lu(CH₂SiMe₃)₃(thf)₂ and C₅Me₄H? C₅H₄N exclusively afforded the bis(alkyl) product (η⁵:κ‐C₅Me₄? C₅H₄N)Lu(CH₂SiMe₃)₂(thf) ( 2 a ). Similarly, the reaction between the ligand (2 equiv) and Lu(CH₂SiMe₃)₃(thf)₂ gave the mono(alkyl) complex (η⁵:κ‐C₅Me₄? C₅H₄N)₂LuCH₂SiMe₃ ( 2 b ), in which no ligand redistribution was observed. Strikingly, treatment of Sc(CH₂SiMe₃)₃(thf)₂ with C₅Me₄H? C₅H₄N in either 1:1 or 1:2 ratio at 0 °C generated the first cyclopentadienide‐based scandium zwitterionic “tuck‐over” complex 3 , (η⁵:κ‐C₅Me₄? C₅H₄N)Sc(thf)[μ‐η⁵:η¹:κ‐C₅Me₃(CH₂)‐C₅H₄N]Sc(CH₂SiMe₃)₃. In the zwitterion, the dianionic ligand [C₅Me₃(CH₂)‐C₅H₄N]^2? binds both to Sc1³⁺ and to Sc2³⁺, in η⁵ and η¹/κ modes. In addition, the reaction chemistry, the molecular structures, and the mechanism are also discussed in detail.     

Elevated-temperature metathesis syntheses of structurally novel alkali-metal tetrakis(3,5-di-tert-butylpyrazolato)lanthanoidate(III) complexes: toluene-coordinated discrete bimetallic complexes and supramolecular chains

Sodium and potassium tetrakis(3,5-di-tert-butylpyrazolato)lanthanoidate(III) complexes [M[Ln(tBu(2)pz)(4)]] have been prepared by reaction of anhydrous lanthanoid trihalides with alkali metal 3,5-di-tert-butylpyrazolates at 200-300 degrees C, and a 1,2,4,5-tetramethylbenzene flux for M=K. On extraction with toluene (or occasionally directly from the reaction tube) the following complexes were isolated: [Na(PhMe)[Ln(tBu(2)pz)(4)]] (1 Ln; 1 Ln=1 Tb, 1 Ho, 1 Er, 1 Yb), [K(PhMe)[Ln(tBu(2)pz)(4)]].2 PhMe (2 Ln; 2 Ln=2 La, 2 Sm, 2 Tb, 2 Ho, 2 Yb, 2 Lu), [Na[Ln(tBu(2)pz)(4)]](n) (3 Ln; 3 Ln=3 La, 3 Tb, 3 Ho, 3 Er, 3 Yb), [K[Ln(tBu(2)pz)(4)]](n) (4 Ln; 4 Ln=4 La, 4 Nd, 4 Sm, 4 Tb, 4 Ho, 4 Er, 4 Yb, 4 Lu), with the last two classes generally being obtained by loss of toluene from 1 Ln or 2 Ln, and [Na(tBu(2)pzH)[Ln(tBu(2)pz)(4)]].PhMe (5 Ln; 5 Ln=5 Nd, 5 Er, 5 Yb). Extraction with 1,2-dimethoxyethane (DME) after isolation of 2 Ho yielded [K(dme)[Ho(tBu(2)pz)(4)]] (6 Ho). X-ray crystal structures of 1 Ln (=1 Tb, 1 Ho; P2(1)/c), 2 Ln (=2 La, 2 Sm, 2 Tb, 2 Yb, 2 Lu; Pnma), 3,4 Ln (=3 La, 3 Er, 4 Sm; P2(1)/m), and 5 Ln (=5 Nd, 5 Er, and 5 Yb; P1) show each group to be isomorphous regardless of the size of the Ln(3+) ion. All complexes contain eight-coordinate [Ln(eta(2)-tBu(2)pz)(4)] units. These are further linked to the alkali metal by bridging through two (1,2,5 Ln) or three (3,4 Ln) tBu(2)pz groups which show striking coordination versatility. Sodium is coordinated by an eta(4)-PhMe, a micro-eta(2):eta(2)-tBu(2)pz, and a micro-eta(4)(Na):eta(2)(Ln)-tBu(2)pz ligand in 1 Ln, and by one eta(1)-tBu(2)pzH and two micro-eta(3)(Na):eta(2)(Ln) ligands in 5 Ln. By contrast, potassium has one eta(6)-PhMe and two micro-eta(5)(K):eta(2)(Ln) ligands in 2 Ln. Classes 3,4 Ln form polymeric chains with the alkali metal bonded by two micro-eta(3)(NNC-M):eta(2)(Ln)-tBu(2)pz ligands within [MLn(tBu(2)pz)(4)] units which are joined together by eta(1)(C)-tBu(2)pz-Na, K linkages.     

Metallorganische Verbindungen der Lanthanoide. 113. [(tert-Butylcyclopentadienyl)(cyclopentadienyl)dimethylsilan]-Komplexe ausgewählter Lanthanoide

Organometallic Compounds of the Lanthanides. 113. [(tert-Butylcyclopentadienyl)(cyclopentadienyl)dimethylsilane] Complexes of selected Lanthanides The reaction of [Me₂Si(C₅H₄)(tBuC₅H₃)]Li₂ with LnCl₃ (Ln = Y, Nd, Sm, Lu) in THF results in the formation of the chiral, dimeric complexes [Me₂Si(C₅H₄)(tBuC₅H₃)]Ln(μ-Cl)₂Li(THF)(Et₂O) [Ln = Y ( 1 ), Nd ( 2 ), Sm ( 3 ), Lu ( 4 )]. The ¹H-, ¹³C-NMR- and the mass spectra of the new compounds as well as the X-ray crystal structures of 2 a and 3 a were discussed.     

Chemical Research Faculties: An International Directory : Edited by G.L. Pollock. The American Chemical Society, Washington, 1984, xxxv + ca. 530 pages. US $129.95 (U.S.A. and Canada); US $155.95 (elsewhere). ISBN 0-8412-0817-4.

Heterobinuclear complexes of formula [LMCl₂(pz)M′(tfb)] (M = Ru, L = p-cymene, M′ = Rh; M = Ir, L = C₅Me₅, M′ = Rh; M = Rh, L = C₅Me₅, M′ = Ir) and [(C₅Me₅)IrCl(pz)₂Rh(tfb)] (tfb = tetrafluorobenzo[5.6]bicyclo[2.2.2]octan-2,5,7-triene) have been prepared. The molecular structure of [(p-cymene)Ru(μ-Cl)2(μ-pz)Rh(tfb)] has been determined by X-ray diffraction. It consists of two moieties, (p-cymene)Ru and (tfb)Rh, triply-bridged by a pyrazolate group and two chlorine atoms.     

Cationic Allyl Complexes of the Rare‐Earth Metals: Synthesis,Structural Characterization,and 1,3‐Butadiene Polymerization Catalysis

Monocationic bis‐allyl complexes [Ln(η³‐C₃H₅)₂(thf)₃]⁺[B(C₆X₅)₄]^? (Ln=Y, La, Nd; X=H, F) and dicationic mono‐allyl complexes of yttrium and the early lanthanides [Ln(η³‐C₃H₅)(thf)₆]²⁺[BPh₄]₂^? (Ln=La, Nd) were prepared by protonolysis of the tris‐allyl complexes [Ln(η³‐C₃H₅)₃(diox)] (Ln=Y, La, Ce, Pr, Nd, Sm; diox=1,4‐dioxane) isolated as a 1,4‐dioxane‐bridged dimer (Ln=Ce) or THF adducts [Ln(η³‐C₃H₅)₃(thf)₂] (Ln=Ce, Pr). Allyl abstraction from the neutral tris‐allyl complex by a Lewis acid, ER₃ (Al(CH₂SiMe₃)₃, BPh₃) gave the ion pair [Ln(η³‐C₃H₅)₂(thf)₃]⁺[ER₃(η¹‐CH₂CH?CH₂)]^? (Ln=Y, La; ER₃=Al(CH₂SiMe₃)₃, BPh₃). Benzophenone inserts into the La? C_allyl bond of [La(η³‐C₃H₅)₂(thf)₃]⁺[BPh₄]^? to form the alkoxy complex [La{OCPh₂(CH₂CH?CH₂)}₂(thf)₃]⁺[BPh₄]^?. The monocationic half‐sandwich complexes [Ln(η⁵‐C₅Me₄SiMe₃)(η³‐C₃H₅)(thf)₂]⁺[B(C₆X₅)₄]^? (Ln=Y, La; X=H, F) were synthesized from the neutral precursors [Ln(η⁵‐C₅Me₄SiMe₃)(η³‐C₃H₅)₂(thf)] by protonolysis. For 1,3‐butadiene polymerization catalysis, the yttrium‐based systems were more active than the corresponding lanthanum or neodymium homologues, giving polybutadiene with approximately 90 % 1,4‐cis stereoselectivity.     

Metallorganische Verbindungen der Lanthanoide. 88. Monomere Lanthanoid(III)-amide: Synthese und Röntgenstrukturanalyse von [Nd{N(C6H5)(SiMe3)}3(THF)], [Li(THF)2(μ-Cl)2Nd{N(C6H3Me2-2,6)(SiMe3)}2(THF)] und [ClNd{N(C6H3-iso-Pr2-2,6)(SiMe3)}2(THF)]

Organometallic Compounds of the Lanthanides. 88. Monomeric Lanthanide(III) Amides: Synthesis and X-Ray Crystal Structure of [Nd{N(C₆H₅)(SiMe₃)}₃(THF)], [Li(THF)₂(μ-Cl)₂Nd{N(C₆H₃Me₂-2,6)(SiMe₃)}₂(THF)], and [ClNd{N(C₆H₃-iso-Pr₂-2,6)(SiMe₃)} ₂(THF)] A series of lanthanide(III) amides [Ln{N(C₆H₅) · (SiMe₃)}₃(THF)_x] [Ln = Y ( 1 ), La ( 2 ), Nd ( 3 ), Sm ( 4 ), Eu ( 5 ), Tb ( 6 ), Er ( 8 ), Yb ( 9 ), Lu ( 10 )] could be prepared by the reaction of lanthanide trichlorides, LnCl₃, with LiN(C₆H₅)(SiMe₃). Treatment of NdCl₃(THF)₂ and LuCl₃(THF)₃ with the lithium salts of the bulky amides [N(C₆H₃R₂-2,6)(SiMe₃)]^? (R = Me, iso-Pr) results in the formation of the lanthanide diamides [Li(THF)₂(μ-Cl)₂Nd{N(C₆H₃Me₂-2, 6)(SiMe₃)}₂(THF)] ( 11 ) and [ClLn{N(C₆H₃-iso-Pr₂-2,6)(SiMe₃)} ₂(THF)] [Ln = Nd ( 12 ), Lu ( 13 )], respectively. The ¹H- and ¹³C-NMR and mass spectra of the new compounds as well as the X-ray crystal structures of the neodymium derivatives 3 , 11 and 12 are discussed.     

Synthesis and structures of the C5Me4SiMe3-supported polyhydride complexes over the full size range of the rare earth series

The acid-base reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] with Cp'H gave the corresponding half-sandwich rare earth dialkyl complexes [(Cp')Ln(CH(2)SiMe(3))(2)(thf)] (1-Ln: Ln=Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; Cp'=C(5)Me(4)SiMe(3)) in 62-90% isolated yields. X-ray crystallographic studies revealed that all of these complexes adopt a similar overall structure, in spite of large difference in metal-ion size. In most cases, the hydrogenolysis of the dialkyl complexes in toluene gave the tetranuclear octahydride complexes [{(Cp')Ln(μ-H)(2)}(4)(thf)(x)] (2-Ln: Ln=Sc, x=0; Y, x=1; Er, x=1; Tm, x=1; Gd, x=1; Dy, x=1; Ho, x=1) as the only isolable product. However, in the case of Lu, a trinuclear pentahydride [(Cp')(2)Lu(3)(μ-H)(5)(μ-CH(2)SiMe(2)C(5)Me(4))(thf)(2)] (3), in which the C-H activation of a methyl group of the Me(3)Si unit on a Cp' ligand took place, was obtained as a major product (66% yield), in addition to the tetranuclear octahydride [{(Cp')Lu(μ-H)(2)}(4)(thf)] (2-Lu, 34%). The use of hexane instead of toluene as a solvent for the hydrogenolysis of 1-Lu led to formation of 2-Lu as a major product (85%), while a similar reaction in THF yielded 3 predominantly (90%). The tetranuclear octahydride complexes of early (larger) lanthanide metals [{Cp'Ln(μ-H)(2)}(4)(thf)(2)] (2, Ln=La, Ce, Pr, Nd, Sm) were obtained in 38-57% isolated yields by hydrogenolysis of the bis(aminobenzyl) species [Cp'Ln(CH(2)C(6)H(4)NMe(2)-o)(2)], which were generated in-situ by reaction of [Ln(CH(2)C(6)H(4)NMe(2)-o)(3)] with one equivalent of Cp'H. X-ray crystallographic studies showed that the fine structures of these hydride clusters are dependent on the size of the metal ions.     

Rare-earth metal allyl and hydrido complexes supported by an (NNNN)-type macrocyclic ligand: synthesis, structure, and reactivity toward biomass-derived furanics

The preparation and characterization of a series of neutral rare‐earth metal complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane anion (Me₃TACD^?) are reported. Upon treatment of the neutral allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] with Brønsted acids, monocationic allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)(thf)₂][B(C₆X₅)₄] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me₃TACD)H₂]_n (Ln=Y, n=3; La, n=4; Sm). X‐ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me₃TACD)R₂]_n (R=η³‐C₃H₅, n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring‐opening conditions.     

Synthesis and structural study of a lithium complex of 6-methyl-2-(trimethylsilylamino)pyridine and its use in the formation of some lanthanoid complexes

Lithiation of 6-methyl-2-(trimethylsilylamino)pyridine (APyTMSH) occurs smoothly in tetrahydrofuran (thf) affording [Li(APyTMS)(thf)]₂ (1). Treatment of anhydrous lanthanoid chlorides (LnCl₃, Ln=Gd, Er) with 1.5 equivalents of (1) yields the solvent-free homoleptic tris–amido complexes [Ln(APyTMS)₃], (Ln=Gd (2); Ln=Er (3)). Similar treatment of LnCl₃ (Ln=Gd, Er) with one equivalents of 1 putatively generates the heteroleptic species [Ln(APyTMS)₂Cl], (Ln=Gd (4); Ln=Er (5)) in situ, however, these compounds undergo redistribution in hexane to yield homoleptic 2 and 3 and the anhydrous lanthanoid halides (Ln=Gd, (6), Ln=Er (7)) and were therefore not fully characterised. These lanthanoid reagents are extremely moisture sensitive as examplified by the low yield isolation of [APyH₂·H]₂[ErCl₅(thf)] during one prepartion of 3. The structures of compounds 1, 2, 3 and 8 were characterised by X-ray crystallographic methods. The X-ray structure of 1 is a centrosymmetric dimer similar to its diethyl ether analogue. Compounds 2 and 3 are six-coordinate homoleptic mononuclear species and compound 8 comprises the unprecedented [ErCl₅(thf)]⁻ anion within an intricate hydrogen-bonded ionic system.     

Synthese,Struktur und Reaktivität von Tris‐, Bis‐ und Mono(2,4‐dimethylpentadienyl)‐Komplexen des Neodyms,Lanthans und des Yttriums

The tris(2,4‐dimethylpentadienyl) complexes [Ln(η⁵‐Me₂C₅H₅)₃] (Ln = Nd, La, Y) are obtained analytically pure by reaction of the tribromides LnBr₃·nTHF with the potassium compound K(Me₂C₅H₅)(thf)_n in THF in good yields. The structural characterization is carried out by X‐ray crystal structure analysis and NMR‐spectroscopically. The tris complexes can be transformed into the dimeric bis(2,4‐dimethylpentadienyl) complexes [Ln₂(η⁵‐Me₂C₅H₅)₄X₂] (Ln, X: Nd, Cl, Br, I; La, Br, I; Y, Br) by reaction with the trihalides THF solvates in the molar ratio 2:1 in toluene. Structure and bonding conditions are determined for selected compounds by X‐ray crystal structure analysis and NMR‐spectroscopically in general. The dimer‐monomer equilibrium existing in solution was investigated NMR‐spectroscopically in dependence of the donor strength of the solvent and could be established also by preparation of the corresponding monomer neutral ligand complexes [Ln(η⁵‐Me₂C₅H₅)₂X(L)] (Ln, X, L: Nd, Br, py; La, Cl, thf; Br, py; Y, Br, thf). Finally the possibilities for preparation of mono(2,4‐dimethylpentadienyl)lanthanoid(III)‐dibromid complexes are shown and the hexameric structure of the lanthanum complex [La₆(η⁵‐Me₂C₅H₅)₆Br₁₂(thf)₄] is proved by X‐ray crystal structure analysis.     

Emergence of a New [NNN] Pincer Ligand via Si−H Bond Activation and β-Hydride Abstraction at Tetravalent Cerium

The cerium(IV) pyrazolate complexes [Ce(Me₂pz)₄]₂ and [Ce(Me₂pz)₄(thf)] initiate β-hydride abstraction of the bis(dimethylsilyl)amido moiety, to afford a heteroleptic cerium(IV) species containing a dimethylpyrazolyl-substituted silylamido ligand, namely [Ce(Me₂pz)₃(bpsa)] (bpsa=bis((3,5-dimethylpyrazol-1-yl)dimethylsilyl)amido; Me₂pz =3,5-dimethylpyrazolato), along with some cerium(III) species. Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si−H-bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry. When [Ce(Me₂pz)₄]₂ is treated with [Li{N(SiMe₃)₂}], that is, in the absence of the SiH functionality, any redox chemistry did not occur. Instead, the ceric ate complex [LiCe₂(Me₂pz)₉] and the stable mixed-ligand ceric species [Ce(Me₂pz)₂{N(SiMe₃)₂}₂] were obtained.