Synthesis and molecular structures of lanthanocene amide complexes and their catalytic activity for addition of amines to nitriles

Reaction of (CH₃C₅H₄)₂LnCl(THF) with NaNHAr in a 1:1 molar ratio in THF afforded the amide complexes (CH₃C₅H₄)₂LnNHAr(THF) [(Ar = 2,6-Me₂C₆H_3, Ln = Yb (I), Y (III); Ar = 2,6-ⁱPr₂C₆H₃, Ln = Yb (II)]. X-ray crystal structure determination revealed that complexes I-III are isostructural. The central metal in each complex coordinated to two methylcyclopentadienyl groups, one amide group and one oxygen atom from THF to form a distorted tetrahedron. Complexes I-III and a known complex (CH₃C₅H₄)₂YbNⁱPr₂(THF) IV all can serve as the catalysts for addition of amines to nitriles to monosubstituted N-arylamidines. The activity depended on the central metals and amide groups, and the active sequence follows the trend IV ≈ III < I < II.     

Synthesis and characterization of phosphorous-bridged bisphenoxy titanium complexes and their application to ethylene polymerization

Phosphorous-bridged bisphenoxy titanium complexes were synthesized and their ethylene polymerization behavior was investigated. Bis[3-tert-butyl-5-methyl-2-phenoxy](phenyl)phosphine tetrahydrofuran titanium dichloride (4a) was obtained by treatment of 3 equiv of n-BuLi with bis[3-tert-butyl-2-hydroxy-5-methylphenyl](phenyl)phosphine hydrochloride salt (3a) followed by TiCl₄(THF)₂ in THF. THF-free complexes 5a-5d were synthesized more conveniently by the direct reaction of MOM-protected ligands (2a-2d) with TiCl₄ in toluene. X-ray analysis of 4a revealed that the ligand is bonded to the octahedral titanium (IV) center in a facial fashion and two chlorine atoms possess cis-geometry. Complexes 4a and 5a-5d were utilized as catalyst precursors for ethylene polymerization. Complex 5c gave high molecular weight polyethylene (M_w = 1,170,000, M_w/M_n = 2.0) upon activation with Al(ⁱBu)₃/[Ph₃C][B(C₆F₅)₄] (TB). Ethylene polymerization activity of 5d activated with Al(ⁱBu)₃/TB reached 49.0 × 10⁶ g mol (cat) ⁻¹ h⁻¹.     

Synthesis and structural characterisation of the palladium N-heterocyclic carbene cluster complexes [Pd3(μ-CO)3(NHC)3] and [Pd3(μ-SO2)3(NHC)3]

The reduction of trans-[Pd(NHC)₂Cl₂] (NHC = IMes, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; IⁱPr₂ = 1,3-bis-isopropylimidazol-2-ylidene) with potassium graphite under an atmosphere of CO affords the palladium NHC carbonyl clusters [Pd₃(μ-CO)₃(NHC)₃] (NHC = IMes, 1; IⁱPr₂, 3). Treatment of 1 with SO₂ at room temperature yields the bridging SO₂ complex [Pd₃(μ-SO₂)₃(IMes)₃] (4) in quantitative yield. Complexes 1, 3 and 4 have been structurally characterised by X-ray crystallography.     

Organometallic consequences of a redox reaction: Terminal trimethylsilylmethylidene titanium complexes prepared by a one-electron oxidation step

One-electron oxidation of the titanium(III) bis-trimethylsilylmethyl complex (nacnac)Ti(CH₂SiMe₃)₂ (1) (nacnac⁻ = [ArNC(Me)]₂CH, Ar = 2,6-ⁱPr₂C₆H₃), readily prepared from (nacnac)TiCl₂(THF) and 2 equiv. of LiCH₂SiMe₃ in Et₂O, with AgOTf results in formation of the five-coordinate and terminal titanium alkylidene complex (nacnac)TiCHSiMe₃(OTf)(THF) (2)-THF concurrent with extrusion of tetramethylsilane and precipitation of silver metal. Complex 2-THF eliminates THF slowly under dynamic vacuum to generate the four-coordinate alkylidene 2 along with some decomposition products. Alternatively, the four-coordinate and non-solvento alkylidene complex, 2, can be prepared from 1 and AgOTf in pentane. Complex 2 undergoes cross-metathesis transformation to afford [ArNC(Me)CHC(Me)CHSiMe₃]TiNAr(OTf) (3) as the major product after 34 h at room temperature. Complexes 1, 2, 2-THF, and 3 have been fully characterized spectroscopically, and single crystal X-ray diffraction analysis for 1 and 2-THF are presented.     

Synthesis and structural characterisation of rhodium hydride complexes bearing N-heterocyclic carbene ligands

Addition of excesses of N-heterocyclic carbenes (NHCs) IEt₂Me₂, IⁱPr₂Me₂ or ICy (IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene; IⁱPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene; ICy = 1,3-dicyclohexylimidazol-2-ylidene) to [HRh(PPh₃)₄] (1) affords an isomeric mixture of [HRh(NHC)(PPh₃)₂] (NHC = IEt₂Me₂ (cis-/trans-2), IⁱPr₂Me₂ (cis-/trans-3), ICy (cis-/trans-4) and [HRh(NHC)₂(PPh₃)] (IEt₂Me₂(cis-/trans-5), IⁱPr₂Me₂ (cis-/trans-6), ICy (cis-/trans-7)). Thermolysis of 1 with the aryl substituted NHC, 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (IMesH₂), affords the bridging hydrido phosphido dimer, [{(PPh₃)₂Rh}₂(μ-H)(μ-PPh₂)] (8), which is also the reaction product formed in the absence of carbene. When the rhodium precursor was changed from 1 to [HRh(CO)(PPh₃)₃] (9) and treated with either IMes (=1,3-dimesitylimidazol-2-ylidene) or ICy, the bis-NHC complexes trans-[HRh(CO)(IMes)₂] (10) and trans-[HRh(CO)(ICy)₂] (11) were formed. In contrast, the reaction of 9 with IⁱPr₂Me₂ gave [HRh(CO)(IⁱPr₂Me₂)₂] (cis-/trans-12) and the unusual unsymmetrical dimer, [(PPh₃)₂Rh(μ-CO)₂Rh(IⁱPr₂Me₂)₂] (13). The complexes trans-3, 8, 10 and 13 have been structurally characterised.     

Synthesis and structure of isopropyldimethylsilyl-substituted octamethyltitanocene

Reduction of isopropyldimethylsilyl-substituted titanocene dichloride [TiCl₂(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (1) by excess magnesium in the presence of excess bis(trimethylsilyl)ethyne (btmse) in tetrahydrofuran at 60 °C yielded a mixture of products amongst them only the trinuclear Ti-Mg-Ti hydrido-bridged complex Mg[Ti(μ-H)₂(η⁵-C₅Me₄SiMe₂Prⁱ)]₂ (3) was isolated and characterized. The precursor of titanocene, [Ti(η⁵-C₅Me₄SiMe₂Prⁱ)₂(η²-btmse)] (6), was obtained from the identical system which, after initial formation of [TiCl(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (2), reacted at −18 °C overnight and then the solution was rapidly separated from the remaining magnesium. Titanocene [Ti(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (7) was obtained by thermolysis of 6 at 75 °C in vacuum. Crystal structures of 1, 2, 3, 6, and 7 were determined.     

Organolanthanides with 3-(2-pyridylmethyl) indenyl ligands: synthesis, crystal structures and catalytic activities of divalent complexes for ε-caprolactone polymerization

Reaction of 3-(2-pyridylmethyl)indenyl lithium (1) with LnI₂(THF)₂ (Ln = Sm, Yb) in THF produced the divalent organolanthanides (C₅H₄NCH₂C₉H₆)₂Ln^II(THF) (Ln = Sm (2), Yb (3)) in high yield. 1 reacts with LnCl₃ (Ln = Nd, Sm, Yb) in THF to give bis(3-(2-pyridylmethyl)indenyl) lanthanide chlorides (C₅H₄NCH₂C₉H₆)₂Ln^IIICl (Ln = Nd (4), Sm (5)) and the unexpected divalent lanthanides 3 (Ln = Yb). Complexes 2-5 show more stable in air than the non-functionalized analogues. X-ray structural analyses of 2-4 were performed. 2 and 3 belong to the high symmetrical space group (Cmcm) with the same structures, they are THF-solvated 9-coordinate monomeric in the solid state, while 4 is an unsolvated 9-coordinate monomer with a trans arrangement of both the sidearms and indenyl rings in the solid state. Additionally, 2 and 3 show moderate polymerization activities for ε-caprolactone (CL).     

Synthesis and structural characterization of gallium and indium complexes obtained from redistribution reactions of mixed chalcogen-imidodiphosphinate ligands

The ionic complex [Ga{N(SPⁱPr₂)(SePⁱPr₂)-S, Se}₂]⁺[GaCl₄]⁻ (5) was prepared by a ligand redistribution process from the mono-chelate [Cl₂Ga{N(SPⁱPr₂)(SePⁱPr₂)-S, Se}] (3) complex in benzene. A similar phenomenon was observed for the heavier indium homologues, where the neutral complexes [ClIn{N(SPⁱPr₂)(SePⁱPr₂)-S, Se}₂] (7) and [ClIn{N(OPⁱPr₂)(SPⁱPr₂)-O, S}₂] (8) were isolated along with InCl₃ as the main reaction by-product. Complexes 5, 7 and 8 were characterized by single-crystal X-ray structural analysis.     

Synthesis of neutral and cationic monocyclopentadienyl alkyl niobium and tantalum complexes

Compound [NbCp′Me₄] (Cp′ = η⁵-C₅H₄SiMe₃, 1) reacted with several ROH compounds (R = tBu, SiiPr₃, 2,6-Me₂C₆H₃) to give the derivatives [NbCp′Me₃(OR)] (R = tBu 2a, SiiPr₃2b, 2,6-Me₂C₆H₃2c). The diaryloxo tantalum compound [TaCp^∗Me₂(OR)₂] (Cp^∗ = η⁵-C₅Me₅, R = 2,6-Me₂C₆H₃3) was obtained by reaction of [TaCp^∗Cl₂Me₂] with 2 equiv of LiOR (R = 2,6-Me₂C₆H₃). Abstraction of one methyl group from these neutral compounds 1-3 with the Lewis acids E(C₆F₅)₃ (E = B, Al) gave the ionic derivatives [NbCp′Me₂X][MeE(C₆F₅)₃] (X = Me 4-E. X = OR; R = SiiPr₃5b-E, 2,6-Me₂C₆H₃5c-E. E = B, Al) and [TaCp^∗Me(OR)₂][MeE(C₆F₅)₃] (R = 2,6-Me₂C₆H₃6-E; E = B, Al). Polymerization of MMA with the aryloxoniobium compound 2c and Al(C₆F₅)₃ gave syndiotactic PMMA in a low yield, whereas the tetramethylniobium compound 1 and the diaryloxotantalum derivative 3 were inactive.     

Structural studies of phosphor-1,1-diselenoato Mn(I) and Re(I) complexes

Mononuclear complexes of the type, M(CO)₄[Se₂P(OR)₂] (M = Mn, R = ⁱPr, 1a; Et, 1b; M = Re, R = ⁱPr, 3a; Et, 3b) can be prepared from either [-Se(Se)P(OⁱPr)₂]₂ (A) or [Se{-Se(Se)P(OEt)₂}₂] (B) with M(CO)₅Br. O,O′-dialkyl diselenophosphate ([(RO)₂PSe₂]^-, abbreviated as dsep) ligands generated from A and B act as a chelating ligand in these complexes. Upon refluxing in acetonitrile, these mononuclear complexes yield dinuclear complexes with a general formula of [M₂(CO)₆{Se₂P(OR)₂}₂] (M = Mn, R = ⁱPr, 2a; Et, 2b; M = Re, R = ⁱPr, 4a; Et, 4b). Dsep ligands display a triconnective, bimetallic bonding mode in the dinuclear compounds and this kind of connective pattern has never been identified in any phosphor-1,1-diselenoato metal complexes. Compounds 2b, 3b, and 4 are structurally characterized. Compounds 2b and 3b display weak, secondary Se?Se interactions in their lattices.     

Au(I) and Au(III) complexes of a sterically bulky benzimidazole-derived N-heterocyclic carbene

The reaction of [AuCl(SMe₂)] with in situ generated [AgCl(ⁱPr₂-bimy)] (ⁱPr₂-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene), which in turn was obtained by the reaction of Ag₂O with 1,3-diisopropylbenzimidazolium bromide (ⁱPr₂-bimyH⁺Br⁻, A), afforded the monocarbene Au(I) complex [AuCl(ⁱPr₂-bimy)] (1). Subsequent reaction of 1 and the ligand precursor ⁱPr₂-bimyH⁺BF₄⁻, (B) in acetone in the presence of K₂CO₃ yielded the bis(carbene) complex [Au(ⁱPr₂-bimy)₂]BF₄ (2) as a white powder in 80% yield. The oxidative addition of elemental iodine to complex 2 gave the bis(carbene) Au(III) complex trans-[AuI₂(ⁱPr₂-bimy)₂]BF₄ (3) as an orange-red powder in 92% yield. All complexes 1-3 have been fully characterized by multinuclear NMR spectroscopies, ESI mass spectrometry, elemental analysis, and X-ray single crystal diffraction. Complexes 1 and 2 adopt a linear geometry around metal centers as expected for d¹⁰ metals. The geometry around the Au(III) metal center in 3 is essentially square-planar with two carbene ligands in trans-position to each other. Complex 3 shows absorption and photoluminescence properties owing to a ligand to metal charge transfer.     

Synthesis, characterization, and ethylene polymerization behavior of [(RR′-admpzp)2Ti(OPr)2] complexes (RR′-admpzp = 1-dialkylamino-3-(3,5-dimethyl-pyrazol-1-yl)-propan-2-olate)

[(RR′-admpzp)₂Ti(OPrⁱ)₂] complexes (2a-c), synthesized from reaction of Ti(OPrⁱ)₃Cl (0.5 equiv) with 1-dialkylamino-3-(3,5-dimethyl-pyrazol-1-yl)-propan-2-ol compounds in the presence of triethylamine (0.5 equiv), are pseudo-octahedral with each RR′-admpzp ligand κ²-O,N(pyrazolyl) coordinated to the titanium center. In solution, 2a-c adopt isomeric structures that are in dynamic equilibrium. At 23 °C, 2a-c/1000 MAO catalyst systems furnished high molecular weight polymers with narrow molecular weight distributions (M_w/M_n = 2.7-2.8). At 100 °C, 2a-c/MAO catalyst systems exhibited increased polymerization activity and 2c/1000 MAO system furnished high molecular weight polyethylene with a molecular weight distribution (M_w/M_n = 2.1) that is close to that found for single-site catalysts.     

Dioxomolybdenum(VI) complexes containing N-heterocyclic carbenes

Compound MoO₂Cl₂(THF)₂ reacts with two equivalents of 1,3-dialkyl substituted 4,5-dimethylimidazol-2-ylidenes to give the dioxomolybdenum(VI) complexes MoO₂Cl₂(L^R)₂ [R = Me (1), i-Pr (2)]. Treatment of MoO₂Cl₂(THF)₂ with one equivalent of the N-heterocyclic carbenes L^Me, L^i-Pr and ^C1L^n-Bu (L^Me = 1,3,4,5-tetramethylimidazol-2-ylidene, L^i-Pr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, and ^C1L^n-Bu = 1,3-dibutyl-4,5-dichloroimidazol-2-ylidene) affords the monocarbene adducts MoO₂Cl₂(L^R) [R = Me (3), i-Pr (4)] and MoO₂Cl₂(^C1L^n-Bu) (5), respectively. Decomposition of complexes 1-5 affords a molybdenum oxychloride anion [Mo₂O₅Cl₄]²⁻ as an imidazolium salt.     

Synthesis and structure of functional spherosilicate building block molecules for materials synthesis

Cubic, trialkyl tin functionalized spherosilicates Si₈O₂₀(SnR₃)₈ (R = Me, ⁿBu) and the pentagonal prismatic tin-spherosilicate Si₁₀O₂₅(SnMe₃)₁₀ have been synthesized and characterized. Single crystal X-ray structures were obtained for Si₈O₂₀(SnMe₃)₈ (I), Si₈O₂₀(SnMe₃)₈ · 4H₂O (I · 4H₂O), and Si₁₀O₂₅(SnMe₃)₁₀ · 4H₂O (II). Structural metrics for the silicate cores observed in these structures were compared to other Si₈O₁₂ and Si₁₀O₂₅ cores reported in the CSD database. A pronounced tetragonal distortion of the Si₈O₂₀ cage leads to Si-O-Si bond angles that are considerably distorted in I · 4H₂O when compared to other analogous Si₈O₁₂ structures described in the literature. These octameric stannylated spherosilicates readily react with metal chlorides to produce mesocopically interesting metal oxide and hybrid materials. An illustration of this is found in the reaction of the octameric anhydrous tin compound I with titanocene dichloride to give the octatitanocene derivative Si₈O₂₀(Cp₂TiCl)₈ · 3CH₂Cl₂ (III). The single crystal structure of III is also described.     

New group 14 element(IV) β-diiminates and a Sn(II) analogue

Seven group 14 element(IV) compounds 2-7 have been prepared, derived either (2-5) from the potassium β-diketiminate K(L) [L = {N(Ar)C(Me)}₂CH, Ar = C₆H₃Prⁱ₂-2,6] (1) or the known lithium β-dialdiminate Li(L′)] [L′ = {N(Ar)C(H)}₂CPh, Ar = C₆H₃Prⁱ₂-2,6]. Treatment of 1 with Bu^tC(O)Cl, Me₃SiCl, Ph₃SnCl, or Me₃SnCl afforded {N(Ar)C(Me)}₂C(H)C(O)Bu^t (2), [ArNC(Me)C(H)C(Me)N(Ar)SiMe₃] (3), [HN(Ar)C(Me)C(H)C(CH₂SnPh₃)N(Ar)] (4), or (5), respectively. Compounds 4 and 5 are remarkable as they have arisen from a tautomer of 1; crystalline centrosymmetric 5 has a fused tricyclic structure, a central eight-membered ring flanked by two six-membered rings. The compounds [GeCl₂(L′)(OGeCl₃)] (6) or [SnCl(L′)Me₂] (7), the first group 14 metal β-dialdiminates, were obtained from Li(L′) and (GeCl₃)₂O or Me₂SnCl₂, respectively. The Sn(II) compound SnCl(L′) (8) was prepared from SnCl₂ and K(L′). The molecular structures of the crystalline compounds 3-8 are reported.     

A combined experimental and theoretical study of metallic salts of thiapentadienyl, sulfinylpentadienyl and butadienesulfonyls

Alternative methods for the synthesis of the following acyclic salts (CH₂CHCHCHS)M [M = K, 1(K); Na, 1(Na); Li, 1(Li)], (CH₂CHCHCHSO)M [M = K, 2(K); Na, 2(Na)], (CH₂CHCHCHSO₂)M [M = K, 3(K); Na, 3(Na); Li, 3(Li)], (CH(Me)CHC(Me)CHSO₂)M [Me5-syn, M = K, 9(K); Na, 9(Na); Li, 9(Li), (CH(Me)CHCHC(Me)S)M [Me5-syn, M = K, 10(K); Na, 10(Na); Me5-anti, M = K, 11(K); Na, 11(Na)] are described, as a result of the activation of C-S bond in dihydrothiophenes by deprotonation with different bases. The effect of methyl substituents in the dihydrothiophenes is significant, which modifies considerably the choice of the base. The influence of the reaction conditions, type of solvent, base and dihydrothiophenes is analyzed. The NMR spectroscopy, including NOESY, ROESY and difference NOE establish the preferred U conformation for all derivatives, and support a delocalization of charge on the thiapentadienyl (1M) and sulfinylpentadienyl (2M) complexes. However, a conjugated diene structure is proposed on the butadienesulfonyl compounds (3M), in which the negative charge is delocalized in the SO₂ fragment and stabilized with the corresponding cations (M = K, Na and Li). In presence of traces of base, compounds 3M suffer a rearrangement, to the most stable S conformer, 13M. The stability of 3M depends on the size of the cation, the greater the size, the greater stability. Furthermore, a theoretical study shows that electronic and geometrical properties (energy conformers, charge distributions and relative stabilities) of the thiapentadienyl, sulfinylpentadienyl and butadienesulfonyl anions and their corresponding metal salts 1M-3M (M = Li, Na and K) shows to be in good agreement with the experimental findings.     

Ruthenium and rhodium nitrosyl complexes containing dichalcogenoimidodiphosphinate ligands

Interaction of [Ru(NO)Cl₃(PPh₃)₂] with K[N(R₂PS)₂] in refluxing N,N-dimethylformamide afforded trans-[Ru(NO)Cl{N(R₂PS)₂}₂] (R = Ph (1), Prⁱ (2)). Reaction of [Ru(NO)Cl₃(PPh₃)₂] with K[N(Ph₂PSe)₂] led to formation of a mixture of trans-[Ru(NO)Cl{N(Ph₂PSe)₂}₂] (3) and trans-[Ru(NO)Cl{N(Ph₂PSe)₂}{Ph₂P(Se)NPPh₂}] (4). Reaction of Ru(NO)Cl₃ · xH₂O with K[N(Ph₂PO)₂] afforded cis-[Ru(NO)(Cl){N(Ph₂PO)₂}₂] (5). Treatment of [Rh(NO)Cl₂(PPh₃)₂] with K[N(R₂PQ)₂] gave Rh(NO){N(R₂PQ)₂}₂] (R = Ph, Q = S (6) or Se (7); R = Prⁱ, Q = S (8) or Se (9)). Protonation of 8 with HBF₄ led to formation of trans-[Rh(NO)Cl{HN(Prⁱ₂PS)₂}₂][BF₄]₂ (10). X-ray diffraction studies revealed that the nitrosyl ligands in 2 and 4 are linear, whereas that in 9 is bent with the Rh–N–O bond angle of 125.7(3)°.     

Substituted lithiumtrimethylsiloxysilanides LiSiRR′(OSiMe3) - Investigations of their synthesis, stability and reactivity

The reactions of the trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-h: R′ = Ph, 1a: R = H, 1b: R = Me, 1c: R = Et, 1d: R = ⁱPr, 1e: R = ^tBu, 1f: R = Ph, 1g: R = 2,4,6-Me₃C₆H₂ (Mes), 1h: R = 2,4,6-(Me₂CH)₃C₆H₂ (Tip); 1i: R = R′ = Mes) with lithium metal in tetrahydrofuran (THF) at −78 °C and in a mixture of THF/diethyl ether/n-pentane in a volume ratio 4:1:1 at −110 °C lead to mixtures of numerous compounds. Dependent on the substituents silyllithium derivatives (Me₃SiO)RR′SiLi (2b-i), Me₃SiO(RR′Si)₂Li (3a-g), Me₃SiRR′SiLi (4a-h), (LiO)RR′SiLi (12e, 12g-i), trisiloxanes (Me₃SiO)₂SiRR′ (5a-i) and trimethylsiloxydisilanes (6f^∗, 6h^∗, 6i^∗) are formed. All silyllithium compounds were trapped with Me₃SiCl or HMe₂SiCl resulting in the following products: (Me₃SiO)RR′SiSiMe₂R″ (6b-i: R″ = Me, 7c-i: R″ = H), Me₃SiO(RR′Si)₂SiMe₂R″ (8a-g: R″ = Me, 9a-g: R″ = H), Me₃SiRR′SiSiMe₂R″ (10a-h: R″ = Me, 11a-h: R″ = H) and (HMe₂SiO)RR′SiSiMe₂H (13e, 13g-i). The stability of trimethylsiloxysilyllithiums 2 depends on the substituents and on the temperature. (Me₃SiO)Mes₂SiLi (2i) is the most stable compound due to the high steric shielding of the silicon centre. The trimethylsiloxysilyllithiums 2a-g undergo partially self-condensation to afford the corresponding trimethylsiloxydisilanyllithiums Me₃SiO(RR′Si)₂Li (3a-g). (Me₃)Si-O bond cleavage was observed for 2e and 2g-i. The relatively stable trimethylsiloxysilyllithiums 2f, 2g and 2i react with n-butyllithium under nucleophilic butylation to give the n-butyl-substituted silyllithiums ⁿBuRR′SiLi (15g, 15f, 15i), which were trapped with Me₃SiCl. By reaction of 2g and 2i with 2,3-dimethylbuta-1,3-diene the corresponding 1,1-diarylsilacyclopentenes 17g and 17i are obtained.X-ray studies of 17g revealed a folded silacyclopentene ring with the silicon atom located 0.5 Å above the mean plane formed by the four carbon ring atoms.     

Redistribution reactions of heteroleptic barium iodide derivatives: Synthesis and structures of trans-BaI2(DME)(triglyme), cis-BaI2(DME)(tetraglyme) and [Ba(tetraglyme)2]I2 · C7H8

The reaction between BaI₂ · 2H₂O and NaHFIP [HFIP = OCH(CF₃)₂] in a 1:1 stoichiometry gave the heterometallic compound NaBaI₂(HFIP)(H₂O)(THF)_0.5 (1). Attempts to recrystallize 1 in the presence of N- or O-donor ligands lead to redistribution reactions. Barium iodide adducts such as BaI₂(DME)₃ (2), trans-BaI₂(DME)(triglyme) (3) and cis-BaI₂(DME)(tetraglyme) (4) were isolated with DME as solvent. A similar behavior was observed for the reaction between BaI₂ · 2H₂O and NaTFA (TFA = O₂CCF₃) in a 1:1 stoichiometry in THF, and [Ba(tetraglyme)₂]I₂ · C₇H₈ (6) was isolated in the presence of excess tetraglyme. All compounds have been characterized by elemental analysis, IR and ¹H NMR as well as single crystal X-ray studies for 3, 4 and 6. Compounds 3 and 4 are covalent adducts with eight- and nine-coordinate barium, respectively. Compound 6 is an ionic compound where two tetraglyme ligands wrap the 10-coordinate barium cation in a helical fashion. The presence of DME actually allows the coordination number of barium in the mixed-ligand adducts 3 and 4 to be tuned. The average Ba–O bond lengths (2.80 for 3 to 2.87 Å for 6) reflect the coordination number of the metal. The same observation is valid for the average Ba–I bond distance, 3.442 for 3 vs. 3.536 Å for 4.     

σ-Bonded organometallic derivatives of yttrium(III) and thulium(III): An unusual ligand coupling reaction mediated by thulium(III)

The reaction between LnI₃(THF)_3.5 and 2 equiv. of {(Me₃Si)₂(Me₂MeOSi)C}K (1) in THF at room temperature yields only the mono-substituted products {(Me₃Si)₂(Me₂MeOSi)C}LnI₂(THF)₂ [Ln = Y (5), Tm (6)]; under more forcing conditions decomposition occurs. In contrast, the metathesis reaction between TmI₃(THF)_3.5 and 2 equiv. of the lithium iodide-containing salt {(Me₃Si)₂(Me₂MeOSi)C}K(LiI)_x yields the highly unusual separated ion pair complex [[{(Me₃Si)₂C(SiMe₂)}₂O]TmI₂{Li(THF)₃}₂][[{(Me₃Si)₂C(SiMe₂)}₂O]TmI₂] (8). The dianionic ligand in 8 is derived from the coupling of 2 equiv. of (Me₃Si)₂(Me₂MeOSi)C⁻, accompanied by the formal elimination of Me₂O. The structures of compounds 5, 6, and 8 have been determined by X-ray crystallography; compound 8 crystallizes as an unusual ion pair, the cation and anion of which differ only in the inclusion of 2 equiv. of Li(THF)₃ in the former, bridged to thulium by iodide ions.