Synthesis of bis(cyclopentadienyl)diazadiene complexes of ytterbium. An X-ray structural study of the Cp2Yb(μ-η2:Ti2-But-N=CH-CH=N-But)Li(DME) complex

Ytterbium complexes, Cp₂Yb(-₂:²-DAB)Li(DME) (1) and CpYb(DAB)K(THF)₂ (2), containing a bridging diazadiene ligand were prepared by the reaction of CpYbCl₂(THF)₃ with (DAB)Li₂ (11) and (DAB)^–K⁺ (12) (DAB = Bu^t-N=CH-CH=N-Bu^t). The structure of complex1 was established by X-ray diffraction analysis. The complex is binuclear: the Yb atom of the Cp₂Yb fragment and the Li atom, which is bonded as well with the chelating DME molecule, are linked by the DAB ligand.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 148–151, January, 1994.     

Diazabutadiene derivatives of ytterbocenes. Syntheses,properties, and crystal structures of the (C5Me5)2Yb(ButNCHCHNBut) and [CpYb(μ2-OC13H8—C13H8O)(THF)]2 complexes

Oxidation of (C₅Me₅)₂Yb(THF)₂ with diazabutadiene Bu^tN=CHCH=NBu^t (DAD) afforded the (C₅Me₅)₂Yb(Bu^tNCHCHNBu^t) complex (1). The magnetic measurements and X-ray diffraction study confirmed the trivalent state of the ytterbium atom and the radical nature of the DAD ligand in complex 1. The oxidation state of ytterbium in the (C₅Me₅)₂YbDAD—solvent system depends on the coordinating properties of the solvent, whereas the ytterbium atom in the Cp₂YbDAD complex (2) remains trivalent regardless of the solvent nature. In complex 2, the redox replacement of DAD^·– with 9-fluorenone accompanied by the pinacol dimerization of 9-fluorenone and detachment of one Cp ligand from the ytterbium atom gave rise to the dimeric [CpYb(²-OC₁₃H₈-C₁₃H₈O)(THF)]₂ complex (3). The structure of complex 3 was established by X-ray diffraction analysis.     

New homo- and heteroleptic derivatives of trivalent ytterbium containing radical anion 1,4-diazadiene ligands. Synthesis, properties, and crystal structures of the complexes (C9H7)2Yb[2-MeC6H4NC(Me)C(Me)NC6H4Me-2] and [PhNC(Ph)C(Ph)NPh]3Yb

The interaction of the ytterbium bis(indenyl) complex (C₉H₇)₂Yb^II(THF)₂ (1) with the 1,4-diazabutadiene 2-MeC₆H₄N=C(Me)-C(Me)=NC₆H₄Me-2 (^MeDAD) is accompanied by the oxidation of the metal atom to the trivalent state and results in a paramagnetic compound of the metallocene type (C₉H₇)₂Yb^III(^MeDAD^−·) (3) containing the radical anion of 1,4-diazabutadiene. The structure of the complex 3 was determined by X-ray diffraction analysis. The reactions of the bis(indenyl) (1) and bis(fluorenyl) (C₁₃H₉)₂Yb^II(THF)₂ (2) derivatives of divalent ytterbium with the 1,4-diazabutadiene PhN=C(Ph)-C(Ph)=NPh (^PhDAD) (with the molar ratio of the reactants 1:2) proceed with a complete cleavage of the bonds Yb-C and the oxidation of the ytterbium atom to the trivalent state and result in a homoligand complex (^PhDAD^−·)₃Yb (6) containing three radical anion 1,4-diazadiene ligands. Complex 6 was also obtained by an exchange reaction of YbCl₃ with ^PhDAD^−·K⁺ (1: 3) in THF. Complex 6 was characterized by X-ray diffraction analysis.     

Bis(di-tert-butylcyclopentadienyl)ytterbium(ii). Synthesis and catalytic properties

Polymeric (Cp₂Yb·THF) _n (1), ionicate-complex Cp₃YbNa (2), and mono-adduct (Bu^t ₂C₅H₃)₂Yb·THF (3) were prepared through a reaction of CpNa (Cp = C₅H₅ or C₅H₃Bu^t ₂) with Ybl₂ in THF. Cooling complex (3) in THF at –100 °C gives a bis-adduct, which reversibly dissociates to give the mono-adduct, The (Bu^t ₂C H , Yb·THF complex shows catalytic activity in the homogeneous hydrogenation of hex-l-ene and in the polymerization of styrene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 7, pp. 1833–1837, July, 1996.     

Synthesis, properties, and reactivity of the stilbene complex of ytterbium (PhCH=CHPh)Yb(THF)2. Crystal structure of (2,4,6-But 3C6H2O)2Yb(THF)3

The stilbene complex of ytterbium (PhCH=CHPh)Yb(THF)₂ (1) was prepared by the reaction of YbI₂(THF)₂ with a twofold excess of (PhCH=CHPh)⁻ Li⁺. Based on the data of IR and ESR spectroscopy and on the results of magnetic measurements, compound1 was characterized as a complex of divalent ytterbium with the stilbene dianion. The reactivity of complex1 toward different types of reagents was studied. The structure of the product of the reaction of1 with 2,4,6-tri(tert-butyl)phenol (2,4,6-Bu^t ₃C₆H₂O)₂Yb(THF)₃ was established by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2345–2350, November, 1998.     

Reaction of a naphthalene complex C10H8Yb(THF)2 with cyclopentadienyl-substituted alcohols and amines as a convenient synthetic route to the half-sandwich complexes of divalent ytterbium

The reactions of ytterbium naphthalene complex C₁₀H₈Yb(THF)₂ with 2-cyclopentadienylethanol, 1-cyclopentadienylpropan-2-ol, 3-cyclopentadienyl-1-butoxypropan-2-ol, and cyclopentadienyldimethylsilyl-tert-butylamine were studied. The bivalent ytterbium complexes with chelate bifunctional cyclopentadienyl ligands [(η⁵−C₅H₅)CH₂CH₂(η¹−O)]Yb(THF), [(η⁵−C₅H₅)CH₂CH₂(η¹−O)]Yb(DME). [(η⁵−C₅H₅)CH₂CH(Me)(η¹−O)]Yb(THF), [(η⁵−C₅H₅)CH₂CH(CH₂OC₄H₉)(η¹−O)]Yb(THF), and [(η⁵−C₅H₅)SiMe₂(η¹−N(Bu¹))]Yb(THF) were obtained and characterized. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 742–745, April, 2000.     

Molecular and Crystal Structures of Cp2YbX(THF) (X = Cl,Br)

Cp₂YbCl(THF) crystallizes in the orthorhombic space group Pnma (Z = 4, a = 13.109(5), b = 11.851(4), c = 9.377(3) Å, R1 = 0.0412, wR2 = 0.0482), while Cp₂YbBr(THF) is monoclinic (P2₁/n, Z = 4, a = 8.149(2), b = 12.997(2), c = 14.388(3) Å, β = 105.73(2)°, R1 = 0.0425, wR2 = 0.0436). The ligand arrangements around the formally eight coordinate Yb atoms are pseudo tetrahedral. These two determinations complete the first series of [Cp₂LnX(L)] (X = F, Cl, Br, I) structures covering all halogens for one lanthanoid and cyclopentadienyl group.     

Study of reactions of some halides, cyclopentadienyl dichlorides, and bis(cyclopentadienyl) chlorides of lanthanides withtrans-stilbene adducts with alkali metals [PhCHCHPh]·−M+ (M=Li, Na)

Reaction of Sml₂(THF)₂ with metallic lithium andtrans-stilbene in 1:2:2 ratio in DME gives the stilbene complex of divalent samarium (PhCHCHPh)Sm(DME)₂. This complex reacts with hydrogen in THF to give SmH₂(THF)₂ and 1,2-diphenylethane. The reaction with (Me₃Si)₂NH gives the amide [(Me₃Si)₂N]₂Sm(DME)₂ and the reaction with triphenylgermane yields Ph₃GeGePh₃. Reaction of CpLuCl₂(THF)₂ with 2 equivalents of [PhCHCHPh]·⁻Na⁺ in DME results in the dimerization of stilbene fragments to give anate-complex {Cp₂Lu[μ-CH (Ph)CH(Ph)CH(Ph)CH(Ph)]}Na(DME)₃. In the reaction of Cp₂GdCl with [PhCHCHPh]·⁻Na⁺, the known complex Cp₃Gd(THF) was isolated as the only lanthanidecontaining product. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1442–1446, August, 2000.     

Reactions of ytterbium(II) bis(indenyl) complex (C9H7)2Yb(thf)2 with 2,2’-bipyridine and 1,4-bis(2,6-diisopropylphenyl)-1,4-diazabuta-1,3-diene. Structures and properties of (C9H7)2Yb(bipy) and (C9H7)2Yb(2,6-Pri 2C6H3NCHCHNC6H3Pri 2-2,6) complexes

The reaction of the ytterbium(II) bis(indenyl) complex (C₉H₇)₂Yb(thf)₂ (1) with 2,2’-bipyridine afforded the diamagnetic (C₉H₇)₂Yb(bipy) compound (2), whose structure was established by X-ray diffraction analysis. Under similar conditions, the reaction of complex 1 with 1,4-bis(2,6-diisopropylphenyl)-1,4-diazabuta-1,3-diene (DAD) led to oxidation of ytterbium giving rise to the paramagnetic (C₉H₇)₂Yb(DAD) complex (3). Magnetic measurements, X-ray diffraction study, and ¹H NMR spectroscopy in benzene confirmed the trivalent state of the ytterbium atom and the radical-anionic nature of the diazadiene ligand in complex 3. In the complex 3—solvent system, the oxidation state of metal depends on the coordination ability of the solvent. In benzene, complex 3 exists as (C₉H₇)₂Yb^III(DAD^·-), whereas (C₉H₇)₂Yb^II(thf)₂ and DAD⁰ are present in THF.     

Interaction of immobilized 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene with Na+, Cs+, and NH4 + ions and organic cations

The equilibrium in the system water—electrolyte—cross-linked polymer containing immobilized 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene was studied. Immobilized calixarene 1 was shown to form 1∶1, 1∶2, 1∶3, and 1∶4 compounds with inorganic cations (Na⁺, Cs⁺, and NH₄ ⁺), and with organic cations (hexamethylen-tetramine and β-diethylaminoethylp-aminobenzoate) 1∶1 compounds are formed. The affinity of immobilized calixarene1 increases in the series of cations: hexamethylenetetramine <Na⁺, Cs⁺, NH₄ ⁺<β-diethylaminoethylp-aminobenzoate. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2214–2216, November, 1998.     

Lanthanide(II) Complexes of the Dihydrotriazinido Ligand [N{C(Ph)=N}2C(tBu)Ph]−

The potassium dihydrotriazinide K(L^Ph,tBu) ( 1 ) was obtained by a metal exchange route from [Li(L^Ph,tBu)(THF)₃] and KOtBu (L^Ph,tBu = [N{C(Ph)=N}₂C(tBu)Ph]). Reaction of 1 with 1 or 0.5 equivalents of SmI₂(thf)₂ yielded the monosubstituted Sm^II complex [Sm(L^Ph,tBu)I(THF)₄] ( 2 ) or the disubstituted [Sm(L^Ph,tBu)₂(THF)₂] ( 3 ), respectively. Attempted synthesis of a heteroleptic Sm^II amido‐alkyl complex by the reaction of 2 with KCH₂Ph produced compound 3 due to ligand redistribution. The Yb^II bis(dihydrotriazinide) [Yb(L^Ph,tBu)₂(THF)₂] ( 4 ) was isolated from the 1:1 reaction of YbI₂(THF)₂ and 1 . Molecular structures of the crystalline compounds 2 , 3· 2C₆H₆ and 4· PhMe were determined by X‐ray crystallography.     

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.     

Density functional theory study of the interaction of CP2*ZrCH 3+ (Cp* = C5H5, C5Me5, and C13H9) with ethylene molecule

Density functional theory was used to study gas-phase reactions between the Cp₂*ZrMe⁺ cations, where Cp* = C₅H₅ (1), Me₅Cp = C₅Me₅ (2), and Flu = C₁₃H₉ (3), and the ethylene molecule, Cp₂*ZrMe⁺ + C₂H₄ → Cp₂*ZrPr⁺ → Cp₂*ZrAllyl⁺ + H₂. The reactivity of the Cp₂*ZrMe⁺ cations with respect to the ethylene molecule decreased in the series 1 > 3 ≈ 2. Substitution in the Cp ring decreased the reactivity of the Cp₂*ZrMe⁺ cations toward ethylene, in agreement with the experimental data on the comparative reactivities of complexes 1 and 3. The two main energy barriers along the reaction path (the formation of the C-C bond leading to the primary product Cp₂*ZrPr⁺ and hydride shift leading to the secondary product Cp₂*Zr(H₂)Allyl⁺) vary in opposite directions in the series of the compounds studied. For Flu (3), these barriers are close to each other, and for the other compounds, the formation of the C-C bond requires the overcoming of a higher energy barrier. A comparison of the results obtained with the data on the activity of zirconocene catalysts in real catalytic systems for the polymerization of ethylene led us to conclude that the properties of the catalytic center changed drastically in the passage from the model reaction in the gas phase to real catalytic systems.     

Interaction of the Negishi reagent Cp2ZrBun 2 with 1,4-bis(tert-butyl)butadiyne

The interaction of the Negishi reagent Cp₂ZrBuⁿ ₂ with 1,4-bis(tert-butyl)butadiyne Bu^tC≡C-C≡CBu^t leads to four products: a five-membered zirconacyclocumulene complex Cp₂Zr(η⁴-Bu^tC₄Bu^t) (2) synthesized earlier by another method, the previously unknown seven-membered zirconacyclocumulene Cp₂Zr[η⁴-Bu^tC₄(Bu^t)-C(C₂Bu^t)=CBu^t] (3) as well as small amounts of the zirconocene binuclear butatrienyl complex Cp₂(Buⁿ)Zr(Bu^tC₄Bu^t)Zr(Buⁿ)Cp₂ (4), and the dimeric acetylide [Cp₂ZrC≡CBu^t]₂ (5). The structure of complexes 2–5 was established by X-ray diffraction studies.     

Reactions of CpCuPPh3 with Lanthanides and Their Compounds

CpCuPPh₃ reacts with Pr, Er, Yb, Cp₂Yb, and SmI₂(THF)₄ to form, in high yields, lanthanide cyclopentadienyl derivatives Cp₂Yb, Cp₃Ln (Ln = Pr, Er, Yb), and CpSmI₂(THF)₂. The initial agent CpCuPPh₃ can be prepared in 95-98% yield by the reaction of t-BuOCu with CpH in the presence of PPh₃.     

Titanium ketimide complexes as α-olefin homo- and copolymerisation catalysts. X-ray diffraction structures of [TiCp(NCBu2)Cl2] (Cp=Ind, Cp*)

The synthesis of [TiInd(NC^tBu₂)Cl₂] and the applications of [TiCp^′(NC^tBu₂)Cl₂] (Cp^′=Ind, Cp*, Cp) as ethylene and propylene homopolymerisation catalysts, as well as its behaviour as catalysts of ethylene and 10-undecen-1-ol copolymerisation are described. The optimisation of the catalytic reactions showed that all compounds are very active homopolymerisation catalysts, particularly [TiInd(NC^tBu₂)Cl₂] that gives 123.37 × 10⁶ g/(molTi [E] h) and 50.77 × 10⁶ g/(molTi [P] h) of linear polyethylene and atatic polypropylene, respectively. The less active homopolymerisation catalyst, [TiCp(NC^tBu₂)Cl₂], is the most effective ethylene/10-undecen-1-ol copolymerisation catalyst, leading to the highest degree of polar monomer incorporation. The polymers obtained were characterised by NMR and DSC. The molecular structures of [TiCp^′(NC^tBu₂)Cl₂] (Cp^′=Ind, Cp*) were determined by X-ray diffraction studies.     

Synthesis, crystal structure, and reduction of bis(2-phenylindenyl)hafnium dichloride

Reduction of the bent-sandwich [·⁵-(Ph)Ind]₂HfCl₂ complex (1) (where (Ph) Ind is the 2-phenylindenyl anion) in a THF medium was studied by low-temperature cyclic voltammetry. Complex1 is stable in THF at a temperature lower than −50°C and undergoes reversible one-electron reduction to radical anion1 ^{. −}. Further one-electron reduction of1 ^{. −} to dianion1 ²⁻ is accompanied by the elimination of two Cl⁻ ions to form the bisindenyl sandwich [·⁵-(Ph)Ind]₂Hf complex (2). This complex can undergo reversible one-electron reduction to the corresponding radical anion2 ^{. −}, which is stable within the cyclic voltammetry time scale. AtT=−30°C in a THF solution, complex1 was reduced to a diamagnetic (apparently, binuclear) Hf^III complex, which was characterized by cyclic voltammetry. Synthesis and the crystal structure of complex1 are reported. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2161–2165, December, 1997.     

Isolation and Characterization,Including by X‐ray Crystallography,of Contact and Solvent‐Separated Ion Pairs of Silenyl Lithium Species

Reaction of bromoacylsilane 1 (pink solution) with tBu₂MeSiLi (3.5 equiv) in a 4:1 hexane:THF solvent mixture at −78 °C to room temperature yields the solvent separated ion pair (SSIP) of silenyl lithium E‐[(tBuMe₂Si)(tBu₂MeSi)C=Si(SiMetBu₂)]⁻ [Li⋅4THF]⁺ 2 a (green–blue solution). Removal of the solvent and addition of benzene converts 2 a into the corresponding contact ion pair (CIP) 2 b (violet–red solution) with two THF molecules bonded to the lithium atom. The 2 a ⇌ 2 b interconversion is reversible upon THF⇌ benzene solvent change. Both 2 a and 2 b were characterized by X‐ray crystallography, NMR and UV/Vis spectroscopy, and theoretical calculations. The degree of dissociation of the Si−Li bond has a large effect on the visible spectrum (and thus color) and on the silenylic ²⁹Si NMR chemical shift, but a small effect on the molecular structure. This is the first report of the X‐ray molecular structure of both the SSIP and the CIP of any R₂E=E′RM species (E=C, Si; E′=C, Si; M=metal).     

Isolation and Characterization,Including by X‐ray Crystallography,of Contact and Solvent‐Separated Ion Pairs of Silenyl Lithium Species

Reaction of bromoacylsilane 1 (pink solution) with tBu₂MeSiLi (3.5 equiv) in a 4:1 hexane:THF solvent mixture at ?78 °C to room temperature yields the solvent separated ion pair (SSIP) of silenyl lithium E‐[(tBuMe₂Si)(tBu₂MeSi)C=Si(SiMetBu₂)]^? [Li?4THF]⁺ 2 a (green–blue solution). Removal of the solvent and addition of benzene converts 2 a into the corresponding contact ion pair (CIP) 2 b (violet–red solution) with two THF molecules bonded to the lithium atom. The 2 a ? 2 b interconversion is reversible upon THF? benzene solvent change. Both 2 a and 2 b were characterized by X‐ray crystallography, NMR and UV/Vis spectroscopy, and theoretical calculations. The degree of dissociation of the Si?Li bond has a large effect on the visible spectrum (and thus color) and on the silenylic ²⁹Si NMR chemical shift, but a small effect on the molecular structure. This is the first report of the X‐ray molecular structure of both the SSIP and the CIP of any R₂E=E′RM species (E=C, Si; E′=C, Si; M=metal).     

Synthesis and structure of the platinum complexes [Bu4N]+[PtBr5(DMSO)]?, [Ph4P]+[PtBr5(DMSO)]?, and [Ph3(n-Am)P]+[PtBr5(DMSO)]?

The complexes [Bu₄N]₂⁺[PtBr₆]²⁻ (I), [Ph₄P]₂⁺[PtBr₆]²⁻ (II), and [Ph₃(n-Am)P]₂⁺ (III) are synthesized by the reactions of tetrabutylammonium bromide, tetraphenylphosphonium bromide, and triphenyl(n-amyl)-tetraphenylphosphonium bromide, respectively, with potassium hexabromoplatinate (mole ratio 2: 1). After recrystallization from dimethyl sulfoxide, complexes I, II, and III transform into [Bu₄N]⁺[PtBr₅(DMSO)]⁻ (IV), [Ph₄P]⁺[PtBr₅(DMSO)]⁻ (V), and [Ph₃(n-Am)P]⁺[PtBr₅(DMSO)]⁻ (VI). According to the X-ray diffraction data, the cations of complexes IV–VI have a slightly distorted tetrahedral structure. The N-C and P-C bond lengths are 1.492(7)–1.533(6) and 1.782(10)–1.805(10) ?, respectively. The platinum atoms in the mononuclear anions are hexacoordinated. The dimethyl sulfoxide ligands are coordinated with the Pt atom through the sulfur atom (Pt-S 2.3280(18)–2.3389(11) ?). The Pt-Br bond lengths are 2.4330(6)–2.4724(6) ?.