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.     

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.     

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.     

Supramolecular Architecture and a New Mode of Pyrazolate Coordination (η3) in the First Homoleptic Lanthanide Pyrazolate Complexes

A linear supramoleculecular array of anions and cations is present in the solvent-free potassium salt of the homoleptic erbium pyrazolate complex [K{Er(η²-tBu₂pz)₄}_n] ( 1 ). Treatment of 1 with [18]crown-6 in toluene/dimethoxyethane leads to formation of a charge-separated salt [Eq. (a)] in which the methyl group of a toluene molecule interacts with the potassium ion. tBu₂pz=3,5-di-tert-butylpyrazolate.     

Organoamido- and aryloxo-lanthanoids. XIII [1]. Organometallic compounds of the lanthanoids. CV [2]. New Lanthanoid(III) Complexes with Pyrazolate Ligands

The complexes Er(Me₂pz)₃(thf) and Ln(Ph₂pz)₃(thf)_n (Ln = Sc, Y, Gd, Er, n = 2; Ln = Lu, n = 3) (Me₂pz^? = 3,5-dimethylpyrazolate, thf = tetrahydrofuran, Ph₂pz^? = 3,5-diphenylpyrazolate) have been prepared by reaction of the lanthanoid metal with bis(pentafluorophenyl)mercury and the pyrazole in thf. The Ln(Ph₂pz)₃(thf)₂ complexes are considered to be eight coordinate with three η²-Ph₂pz ligands. Other lanthanoid pyrazolate complexes, Y(pz)₃(thf)₂, La(Me₂pz)₃(thf), Cp₂Ln(Me₂pz)(thf)_n (Ln = Y, Lu, n = 0; Ln = Lu, n = 1), (C₅Me₅)₂Y(pz)(thf), (C₅Me₅)₂Y(Mepz)(thf), (C₅Me₅)₂Y(Me₂pz)(thf)₂ (pz^? = pyrazolate, Mepz^? = 3-methylpyrazolate, Cp = cyclopentadienyl) have been synthesized by reaction of LnCl₃, Cp₂LnCl, or (C₅Me₅)₂LnCl with the appropriate sodium pyrazolate in thf. The structure of Ln(Me₂pz)₃(thf) (Ln = La or Er) is considered to be a symmetrical dimer with four chelating and two bridging Me₂pz groups, and two bridging thf ligands, whereas the cyclopentadienyl complexes are most likely dimers with bridging pyrazolate groups, and lattice thf of solvation.     

Synthesis and Chloride Affinity of Sterically Demanding Ditopic Lithium Bis(pyrazol‐1‐yl)borates

The synthesis and full characterization of the sterically demanding ditopic lithium bis(pyrazol‐1‐yl)borates Li₂[p‐C₆H₄(B(Ph)pz^R₂)₂] is reported (pz^R = 3‐phenylpyrazol‐1‐yl ( 3 ^Ph), 3‐t‐butylpyrazol‐1‐yl ( 3 ^tBu)). Compound 3 ^Ph crystallizes from THF as THF‐adduct 3 ^Ph(THF)₄ which features a straight conformation with a long Li···Li distance of 12.68(1) Å. Compound 3 ^tBu was found to function as efficient and selective scavenger of chloride ions. In the presence of LiCl it forms anionic complexes [ 3 ^tBuCl]⁻ with a central Li‐Cl‐Li core (Li···Li = 3.75(1) Å).     

Synthesis and X-ray crystal structures of [Ph2PMe2][(η-C5H4Bu)2Li] and [(η-C5H4Bu)2Yb(Cl)CH2P(Me)Ph2]

The interaction of [(η⁵-C₅H₄Bu^t)₂YbCl · LiCl] with one equivalent of Li[(CH₂) (CH₂)PPh₂] in tetrahydrofuran gave [Ph₂PMe₂][(η⁵-C₅H₄Bu^t)₂Li] (1) and [(η⁵-C₅H₄Bu^t)₂Yb(Cl)CH₂P(Me)Ph₂] (2) in 10% and 30% yields, respectively. 1 could also be prepared in 70% yield from the reaction of [Ph₂PMe₂][CF₃SO₃] with two equivalents of (C₅H₄Bu^t)Li. Both compounds have been fully characterized by analytical, spectroscopic and X-ray diffraction methods. The solid state structure of 1 reveals a sandwich structure for the [(η⁵-C₅H₄Bu^t)₂Li]⁻ anion.     

Syntheses of the Antimonides R2Sb− (R = Ph,Mes, tBu,tBu2Sb) and Sb73− by Reactions of Organoantimony Hydrides or cyclo‐(tBuSb)4 with Li,Na, K,or BuLi

Reactions of R₂SbH with BuLi at ?70 °C in tetrahydrofuran (thf) lead to [R₂SbLi(thf)₃] [R = Ph ( 1 ) or R = Mes ( 2 )]. The antimonides [tBu₂SbK(pmdeta)] ( 3 ) (pmdeta = pentamethyldiethylenetriamine), [Li(tmeda)₂][tBu₄Sb₃]·benzene ( 4 ) (tmeda = tetramethylethylenediamine), and [tBu₄Sb₃Na(tmeda, thf)] ( 5 ) result from the reduction of cyclo‐(tBuSb)₄ by Li, Na, or K with pmdeta or tmeda in thf. The primary stibanes RSbH₂ [R = Mes ( 6 ), 2‐(Me₂NCH₂)C₆H₂ ( 7 )] are synthesized by reactions of RSbCl₂ with LiAlH₄. PhSbH₂ reacts with BuLi, and tmeda in toluene to give [Sb₇Li₃(tmeda)₃]·toluene ( 8 ). [Sb₇Na₃(pmdeta)₃]·toluene ( 9 ) is obtained from PhSbH₂, Na in liqu. NH₃, pmdeta and toluene. Crystal structures are reported for 1 – 5 and 9 .     

1,3-Diphosphacyclobutene Cobalt Complexes

The synthesis and characterization of rare 1,3-diphosphacyclobutene transition-metal complexes is described. Reactions of the cobalt-hydride complex [Co(P₂C₂tBu₂)₂H] ( G ) with nBuLi, tBuLi, or PhLi afforded [Li(solv)_x{Co(η³-P₂C₂tBu₂HR)(η⁴-P₂C₂tBu₂)}] ( 1 : R=nBu, (solv)_x=(Et₂O)₂; 2 : R=tBu, (solv)_x=(thf)₂; 3 : R=Ph, (solv)_x=(Et₂O)(thf)₂), with an η³-coordinated 1,3-diphosphacyclobutene ligand as a result of organyl-anion attack at one of the phosphorus atoms of the bis(1,3-diphosphacyclobutadiene) backbone. In contrast to the reactions with PhLi, the aryl-magnesium compounds p-tolyl magnesium chloride and p-fluorophenyl magnesium bromide deprotonate [Co(P₂C₂tBu₂)₂H] to give the magnesium salt [Mg(MeCN)₆][Co(η⁴-P₂C₂tBu₂)₂]₂ ( 4 ), which contains a bis(1,3-diphosphacyclobutadiene)-cobaltate anion. The [Co(η⁴-P₂C₂tBu₂)₂]⁻ anions are well separated from the octahedral [Mg(MeCN)₆]²⁺ cation in the molecular structure of 4 . Compound 1 reacts with Me₃SiCl to give neutral [Co(η³-P₂C₂tBu₂HnBu)(η⁴-P₂C₂tBu₂SiMe₃)] ( 5 , 52 % yield) with an SiMe₃ group attached to one of the P atoms of the previously unfunctionalized backbone.     

Flexidentate Coordination Behavior and Chemical Non-Innocence of a Bis(1,3-Diphosphacyclobutadiene) Sandwich Anion

The homoleptic 1,3-diphosphacyclobutadiene sandwich complex [Co(η⁴-1,3-P₂C₂tBu₂)₂]⁻ behaved as a versatile and highly flexible metalloligand toward Ni²⁺, Ru²⁺, Rh⁺, and Pd²⁺ cations, forming a range of unusual oligonuclear compounds. The reaction of [K(thf)₂{Co(η⁴-1,3-P₂C₂tBu₂)₂}] with [Ni₂Cp₃]BF₄ initially afforded the σ-complex [CpNi{Co(η⁴-1,3-P₂C₂tBu₂)₂}(thf)] ( 2 ), which converted into [Co(η⁴-CpNi{1,3-P₂C₂tBu₂-κP,κC})(η⁴-1,3-P₂C₂tBu₂)] ( 3 ) below room temperature. The structure of 3 contains an unprecedented 1,4-diphospha-2-nickelacyclopentadiene moiety formed by an oxidative addition of a ligand P−C bond onto nickel. At elevated temperatures, 3 isomerized to [Co(η⁴-CpNi{1,4-P₂C₂tBu₂-κ²P,P})(η⁴-1,3-P₂C₂tBu₂)] ( 4 ), which features a 1,3-diphospha-2-nickelacyclopentadiene unit. Transmetalation of [K(thf)₂{Co(η⁴-1,3-P₂C₂tBu₂)₂}] with [Cp*RuCl]₄ (Cp*=C₅Me₅) afforded tetranuclear [(Cp*Ru)₃(μ-Cl)₂{Co(η⁴-1,3-P₂C₂tBu₂)₂}] ( 5 ), in which the [Co(η⁴-1,3-P₂C₂tBu₂]⁻ anion acts as a chelate ligand toward Ru²⁺. The diphosphido complex [(Cp*Ru)₂(μ,η²-P₂)(μ,η²-C₂tBu₂)] ( 6 ) was formed as a byproduct. Pure compound 6 was isolated after prolonged heating of the reaction mixture. The reaction of [K(thf)₂{Co(η⁴-1,3-P₂C₂R₂)₂}] (R=tBu; adamantyl, Ad) with [RhCl(cod)]₂ (cod=1,5-cyclooctadiene) afforded unprecedented π-complexes [Rh(cod){Co(η⁴-1,3-P₂C₂R₂)₂}] ( 7 : R=tBu; 8 : R=Ad), in which one μ:η⁴:η⁴-P₂C₂R₂ ligand bridges two metal atoms. The pentanuclear complex [Pd₃(PPh₃)₂{Co(η⁴-1,3-P₂C₂tBu₂)₂}₂] ( 10 ), featuring a Pd₃ chain and a rare 1,4-diphospha-2-butene ligand, was synthesized by reacting [K(thf)₂{Co(η⁴-1,3-P₂C₂tBu₂)₂}] with cis-PdCl₂(PPh₃)₂. The redox properties of selected compounds were analyzed by cyclic voltammetry, whereas DFT calculations gave additional insight into the electronic structures. The results of this study revealed several remarkable and previously unrecognized properties of the [Co(P₂C₂tBu₂)₂]⁻ anion.     

Reduction of Digallane [(dpp‐bian)Ga?Ga(dpp‐bian)] with Group 1 and 2 Metals

The reduction of digallane [(dpp‐bian)Ga? Ga(dpp‐bian)] ( 1 ) (dpp‐bian=1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene) with lithium and sodium in diethyl ether, or with potassium in THF affords compounds featuring the direct alkali metal–gallium bonds, [(dpp‐bian)Ga? Li(Et₂O)₃] ( 2 ), [(dpp‐bian)Ga? Na(Et₂O)₃] ( 3 ), and [(dpp‐bian)Ga? K(thf)₅] ( 7 ), respectively. Crystallization of 3 from DME produces compound [(dpp‐bian)Ga? Na(dme)₂] ( 4 ). Dissolution of 3 in THF and subsequent crystallization from diethyl ether gives [(dpp‐bian)Ga? Na(thf)₃(Et₂O)] ( 5 ). Ionic [(dpp‐bian)Ga]^?[Na([18]crown‐6)(thf)₂]⁺ ( 6 a ) and [(dpp‐bian)Ga]^?[Na(Ph₃PO)₃(thf)]⁺ ( 6 b ) were obtained from THF after treatment of 3 with [18]crown‐6 and Ph₃PO, respectively. The reduction of 1 with Group 2 metals in THF affords [(dpp‐bian)Ga]₂M(thf)_n (M=Mg ( 8 ), n=3; M=Ca ( 9 ), Sr ( 10 ), n=4; M=Ba ( 11 ), n=5). The molecular structures of 4 – 7 and 11 have been determined by X‐ray crystallography. The Ga? Na bond lengths in 3 – 5 vary notably depending on the coordination environment of the sodium atom.     

N2 Activation in NiI–NN–NiI Units: The Influence of Alkali Metal Cations and CO Reactivity

After single electron reduction of the dinitrogen complex [L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( I ) with KC₈, reaction of the resulting compound K[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( II ) with sodium sand yields KNa[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( 1 ), which contains two different alkali metal ions. Treatment of I with two equivalents of sodium sand leads to the symmetric complex Na₂[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( 2 ). Complexes 1 and 2 were investigated by single crystal X‐ray diffraction analysis as well as by Raman spectroscopy, and the results were compared with the data of K₂[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( III ), which contains two K⁺ ions. Thus, it became obvious that the nature of the alkali metal ion M in compounds M₂[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] has hardly any influence on the degree of NN bond activation. Furthermore, it was shown that treatment of the dinickel(I) complex III with CO leads to the dinickel(0) compound K₂[L^tBuNi(CO)]₂ ( 4 ) and N₂. Reaction of the unreduced dinickel(I) complex I with CO leads to a more simple replacement of the N₂ ligand and formation of [L^tBuNi(CO)] ( 3 ).     

Bildung und Struktur des [{η2‐tBu2P–P}Pt(PHtBu2)(PPh3)]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XX Formation and Structure of [{η²‐^tBu₂P–P}Pt(PH^tBu₂)(PPh₃)] [{η²‐^tBu₂P¹–P²}Pt(P³Ph₃)(P⁴Ph₃)] ( 2 ) reacts with ^tBu₂PH exchanging only the P³Ph₃ group to give [{η²‐^tBu₂P¹–P²}Pt(P³H^tBu₂)(P⁴Ph₃)] ( 1 ). The crystal stucture determination of 1 together with its ³¹P{¹H} NMR data allow for an unequivocal assignment of the coupling constants in related Pt complexes. 1 crystallizes in the triclinic space group P1 (no. 2) with a = 1030.33(15), b = 1244.46(19), c = 1604.1(3) pm, α = 86.565(17)°, β = 80.344(18)°, γ = 74.729(17)°.     

Effect of Substituents of Cerium Pyrazolates and Pyrrolates on Carbon Dioxide Activation

Homoleptic ceric pyrazolates (pz) Ce(RR’pz)₄ (R = R’ = tBu; R = R’ = Ph; R = tBu, R’ = Me) were synthesized by the protonolysis reaction of Ce[N(SiHMe₂)₂]₄ with the corresponding pyrazole derivative. The resulting complexes were investigated in their reactivity toward CO₂, revealing a significant influence of the bulkiness of the substituents on the pyrazolato ligands. The efficiency of the CO₂ insertion was found to increase in the order of tBu₂pz < Ph₂pz < tBuMepz < Me₂pz. For comparison, the pyrrole-based ate complexes [Ce₂(pyr)₆(µ-pyr)₂(thf)₂][Li(thf)₄]₂ (pyr = pyrrolato) and [Ce(cbz)₄(thf)₂][Li(thf)₄] (cbz = carbazolato) were obtained via protonolysis of the cerous ate complex Ce[N(SiHMe₂)₂]₄Li(thf) with pyrrole and carbazole, respectively. Treatment of the pyrrolate/carbazolate complexes with CO₂ seemed promising, but any reversibility could not be observed.     

Zum Einfluß der PR3‐Liganden auf Bildung und Eigenschaften der Phosphinophosphiniden‐Komplexe [{η2‐tBu2P–P}Pt(PR3)2] und [{η2‐tBu2P1–P2}Pt(P3R3)(P4R′3)]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes XXI The Influence of the PR₃ Ligands on Formation and Properties of the Phosphinophosphinidene Complexes [{η²‐^tBu₂P–P}Pt(PR₃)₂] and [{η²‐^tBu₂P¹–P²}Pt(P³R₃)(P⁴R′₃)] (R₃P)₂PtCl₂ and C₂H₄ yield the compounds [{η²‐C₂H₄}Pt(PR₃)₂] (PR₃ = PMe₃, PEt₃, PPhEt₂, PPh₂Et, PPh₂Me, PPh₂ⁱPr, PPh₂^tBu and P(p‐Tol)₃); which react with ^tBu₂P–P=PMe^tBu₂ to give the phosphinophosphinidene complexes [{η²‐^tBu₂P–P}Pt(PMe₃)₂], [{η²‐^tBu₂P–P}Pt(PEt₃)₂], [{η²‐^tBu₂P–P}Pt(PPhEt₂)₂], [{η²‐^tBu₂P–P}Pt(PPh₂Et)₂], [{η²‐^tBu₂P–P}Pt(PPh₂Me)₂], [{η²‐^tBu₂P–P}Pt(PPh₂ⁱPr], [{η²‐^tBu₂P–P}Pt(PPh₂^tBu)₂] and [{η²‐^tBu₂P–P}Pt(P(p‐Tol)₃)₂]. [{η²‐^tBu₂P–P}Pt(PPh₃)₂] reacts with PMe₃ and PEt₃ as well as with ^tBu₂PMe, PⁱPr₃ and P(c‐Hex)₃ by substituting one PPh₃ ligand to give [{η²‐^tBu₂P¹–P²}Pt(P³Me₃)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Ph₃)(P⁴Me₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Et₃)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Me^tBu₂)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³ⁱPr₃)(P⁴Ph₃)] and [{η²‐^tBu₂P¹–P²}Pt(P³(c‐Hex)₃)(P⁴Ph₃)]. With ^tBu₂PMe, [{η²‐^tBu₂P–P}Pt(P(p‐Tol)₃)₂] forms [{η²‐^tBu₂P¹–P²}Pt(P³Me^tBu₂)(P⁴(p‐Tol)₃)]. The NMR data of the compounds are given and discussed with respect to the influence of the PR₃ ligands.     

Synthesis and Characterization of Methylzinc Tri(tert‐butyl)silylphosphanide as well as Related Sodium and Potassium Phosphanylzincates

The reaction of dimethylzinc and tri(tert‐butyl)silylphosphane in toluene yielded dimeric methylzinc tri(tert‐butyl)silylphosphanide ( 1 ) which crystallized tetrameric. Compound 1 was deprotonated with sodium in DME and the solvent‐separated dimeric ion pair [(dme)₃Na]⁺ [(dme)Na(MeZn)₂(μ‐PSitBu₃)₂]^? ( 2 ) was isolated. The reaction of 1 in THF with two equivalents of potassium and one equivalent of tri(tert‐butyl)silylphosphane gave dimeric [{tBu₃Si(H)P}{(thf)₂K}₂(MeZn)(PSitBu₃)]₂ ( 3 ). Both of these phosphanylzincates contain Zn₂P₂ cycles with Zn‐P bond lengths of approximately 237 pm, whereas in 1 larger Zn‐P bond lengths of 248.5 pm were found due to the larger coordination numbers of the phosphorus and zinc atoms.     

Reaktionen von tBu2P–P=P(Me)tBu2 mit (Et3P)2NiCl2 und [{η2‐C2H4}Ni(PEt3)2]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XXIII. Reactions of ^tBu₂P–P=P(Me)^tBu₂ with (Et₃P)₂NiCl₂ and [{η²‐C₂H₄}Ni(PEt₃)₂] ^tBu₂P–P=P(Me)^tBu₂ ( 1 ) forms with (Et₃P)₂NiCl₂ ( 2 ) and Na(Nph) the [μ‐(1,3 : 2,3‐η‐^tBu₂P₄^tBu₂){Ni(PEt₃)Cl}₂] ( 3 ) as main product. Using Na/Hg instead as reducing agent the Ni⁰ compounds [{η²‐^tBu₂P–P}Ni(PEt₃)₂] ( 4 ), [{η²‐^tBu₂P–P=P–P^tBu₂}Ni(PEt₃)₂] ( 5 ) and [(Et₃P)Ni(μ‐P^tBu₂)]₂ ( 6 ) with four‐membered Ni₂P₂ ring result. [{η²‐C₂H₄}Ni(PEt₃)₂] yields with 1 also 4 . The compounds were characterized by ¹H and ³¹P{¹H} NMR investigations and 3 also by a single crystal X‐ray analysis. It crystallizes triclinic in the space group P 1 with a = 1129.4(2), b = 1256.8(3), c = 1569.5(3) pm, α = 72.44(3)°, β = 70.52(3)° and γ = 74.20(3)°.     

Dinuclear Rare‐Earth Metal Alkyl Complexes Supported by Indolyl Ligands in μ‐η2:η1:η1 Hapticities and their High Catalytic Activity for Isoprene 1,4‐cis‐Polymerization

Two series of new dinuclear rare‐earth metal alkyl complexes supported by indolyl ligands in novel μ‐η²:η¹:η¹ hapticities are synthesized and characterized. Treatment of [RE(CH₂SiMe₃)₃(thf)₂] with 1 equivalent of 3‐(tBuN?CH)C₈H₅NH ( L₁ ) in THF gives the dinuclear rare‐earth metal alkyl complexes trans‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH(CH₂SiMe₃)}Ind)RE(thf)(CH₂SiMe₃)]₂ (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L₁ is deprotonated by the metal alkyl species and the imino C?N group is transferred to the amido group by alkyl CH₂SiMe₃ insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ‐η²:η¹:η¹ bonding modes, forming the dinuclear rare‐earth metal alkyl complexes. When L₁ is reduced to 3‐(tBuNHCH₂)C₈H₅NH ( L₂ ), the reaction of [Yb(CH₂SiMe₃)₃(thf)₂] with 1 equivalent of L₂ in THF, interestingly, generated the trans‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH₂}Ind)Yb(thf)(CH₂SiMe₃)]₂ (major) and cis‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH₂}Ind)Yb(thf)(CH₂SiMe₃)]₂ (minor) complexes. The catalytic activities of these dinuclear rare‐earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio‐ and stereoselectivities for isoprene 1,4‐cis‐polymerization.     

Ansa‐Complexes of [Mn(η5‐C5H5)(η6‐C6H6)]: Preparation,Characterization, and Reactivity of [n]Manganoarenophanes (n=1, 2, 3)

We report the synthesis of [n]manganoarenophanes (n=1, 2) featuring boron, silicon, germanium, and tin as ansa‐bridging elements. Their preparation was achieved by salt‐elimination reactions of the dilithiated precursor [Mn(η⁵‐C₅H₄Li)(η⁶‐C₆H₅Li)]?pmdta (pmdta=N,N,N′,N′,N′′‐pentamethyldiethylenetriamine) with corresponding element dichlorides. Besides characterization by multinuclear NMR spectroscopy and elemental analysis, the identity of two single‐atom‐bridged derivatives, [Mn(η⁵‐C₅H₄)(η⁶‐C₆H₅)SntBu₂] and [Mn(η⁵‐C₅H₄)(η⁶‐C₆H₅)SiPh₂], could also be determined by X‐ray structural analysis. We investigated for the first time the reactivity of these ansa‐cyclopentadienyl–benzene manganese compounds. The reaction of the distannyl‐bridged complex [Mn(η⁵‐C₅H₄)(η⁶‐C₆H₅)Sn₂tBu₄] with elemental sulfur was shown to proceed through the expected oxidative addition of the Sn?Sn bond to give a triatomic ansa‐bridge. The investigation of the ring‐opening polymerization (ROP) capability of [Mn(η⁵‐C₅H₄)(η⁶‐C₆H₅)SntBu₂] with [Pt(PEt₃)₃] showed that an unexpected, unselective insertion into the C_ipso?Sn bonds of [Mn(η⁵‐C₅H₄)(η⁶‐C₆H₅)SntBu₂] had occurred.     

Synthesis and evaluation of substituted pyrazoles palladium(II) complexes as ethylene polymerization catalysts

The substituted pyrazole palladium complexes, (3,5-^tBu₂pz)₂PdCl₂ (1) (3,5-Me₂pz)₂PdCl₂ (2), (3-Mepz)₂PdCl₂ (3) and (pz)₂PdCl₂ (4) (pzH=pyrazole), can be prepared from the reaction of (COD)PdCl₂ with the appropriate pyrazole. The chloromethyl derivative, (3,5-^tBu₂pz)₂PdCl(Me) (5), was prepared from (COD)PdClMe and ^tBu₂pzH. X-ray crystal structure determination of 1 and 5 established their structures in the solid state to be the trans-isomer. After activation of 1-4 and 5 with methylaluminoxane (MAO) the resulting palladium complexes were used as catalysts in ethylene polymerization, yielding linear high-density polyethylene (HDPE). The highest activity was observed for (3,5-^tBu₂pz)PdClMe.