Models of surface-confined metallocene derivatives

The silsesquioxane [((C₆H₁₁)₇Si₇O₉)(OH)₃] (LH₃) was reacted with [M(C₅H₅)₂Cl₂] (M = Ti, Zr, Hf) and with [Ti(C₅H₅)Cl₃]. The reaction with [Ti(C₅H₅)Cl₃] produced [Ti(C₅H₅)L], whereas the reaction with [Ti(C₅H₅)₂Cl₂] produced a mixture of [Ti(C₅H₅)L]_n. (n = 1, 2) as determined by NMR spectroscopy. Only [Ti(C₅H₅)L] could be isolated from the mixture. The reaction with [M(C₅H₅)₂Cl₂] (M = Zr, Hf) produced oligomeric species which contained no cyclopentadienyl ligands and which were formulated as containing trimeric [M₃L₄Cl]⁻ anions on the basis of analytical and spectroscopic data.     

Some data on the character of the titanium -cyclopentadienyl ring bond in C5H5Ti(OC2H5)3 and (C5H5)2 Ti(OCOCH3)2

Summary On the basis of the formation of ferrocene during the reaction of C₅H₅Ti(OC₂H₅)₃ and (C₅H₅)₂Ti(OCOCH₃)₂ with FeCl₂ and the ease with which the bond of the cyclopentadienyl ring with the metal in these compounds may be hydrolyzed the hypothesis has been stated that the bond of the titanium atom with the cyclopentadienyl rings in (C₅H₅)₂Ti(OCOCH_{5 2} and C₅H₅Ti(OC₂H₅)₃ has an ionic character to a considerable degree.     

Ethylene polymerization with novel bridged tri- and tetranuclear titanocene/MAO systems

Two benzene centered tri- and tetracyclopentadienyl ligands C₆H₃(CH₂C₅H₅)₃-1,3,5 (1) and C₆H₂(CH₂C₅H₅)₄-1,2,4,5 (2) and their titanium complexes C₆H₃[CH₂C₅H₄Ti(C₅H₅)Cl₂]₃-1,3,5 (3), C₆H₃[CH₂C₅H₄Ti(C₅H₄CH₃)Cl₂]₃-1,3,5 (4), as well as C₆H₂[CH₂C₅H₄Ti(C₅H₅)Cl₂]₄-1,2,4,5 (5) were synthesized and characterized by mass and ¹H NMR spectra. In the presence of methylaluminoxane (MAO), 3, 4 and 5 are efficient catalysts for ethylene polymerization in toluene. The influence of the polymerization conditions such as catalyst concentration, MAO/Ti molar ratio, polymerization time and temperature were investigated in detail. 3, 4 and 5 produce linear polyethylene (PE) with broad molecular weight distributions (MWD) and a little lower molecular weight.     

Monomer-isomerization polymerization. XXIII.. Monomer-isomerization polymerization of 5-phenyl-2-pentene with ziegler–natta catalysts

5-Phenyl-2-pentene (5Ph2P) was found to undergo monomer-isomerization polymerization with TiCl₃–R₃Al (R = C₂H₅ or i-C₄H₉, Al/Ti > 2) catalysts to give a polymer consisting of exclusively 5-phenyl-1-pentene (5Ph1P) unit. The geometric and positional isomerizations of 5Ph2P to its terminal and other internal isomers were observed to occur during polymerization. The catalyst activity of alkylaluminum examined to TiCl₃ was in the following order: (C₂H₅)₃Al > (i-C₄H₉)₃Al > (C₂H₅)₂AlCl. The rate of monomer-isomerization polymerization of 5Ph2P with TiCl₃–(C₂H₅)₃Al catalyst was influenced by both the Al/Ti molar ratio and the addition of nickel acetylacetonate [Ni(acac)₂], and the maximum rate was observed at Al/Ti = 2.0 and Ni/Ti = 0.4 in molar ratios.     

Optisch aktive Ubergangsmetall-Komplexe XXI. Optisch aktive komplexe mit vier verschiedenen liganden am titanatom

Chiral C₅H₅(C₉H₇Ti(Cl)SCH(CH₃)₂ shows diastereotopic CH₃ resonances; the diasteroisomers of C₅H₅(CH₃C₅H₄Ti(Cl)OC₁₀H₁₉ could be separated by fractional crystallisation.     

Zur Wechselwirkung einiger Übergangsmetallhalogenide mit o-Mercaptophenol

The interaction of some transition metal halides with o-mercaptophenol o-Mercaptophenol reacts with WCl₆, TiCl₄, ZrCl₄, NbCl₅ and TaCl₅ giving the corresponding tris-chelat-komplexe W(C₆H₄OS)₃, H₂[M(C₆H₄OS)₃] (M = Ti, Zr), H[M(C₆H₄OS)₃] (M = Nb, Ta). (C₅H₅)₂TiCl₂ and (C₅H₅)₂ZrBr₂give in presence of triethylamine the compounds (C₅H₅)₂M(C₆H₄OS) (M = Ti, Zr). By reaction of nickel(II) acetyl-acetonate with o-mercaptophenol the polymeric octahedral complex nickel-bis-(o-hydroxy-thiophenolate) results.     

1,1′-Disubstituierte Titanocen-dithiolen-Chelate des Typs (η5-Me3EC5H4)2Ti(S2C2R2) (E = C,Si, Ge)

1,1′-Disubstituted Titanocene Dithiolene Chelates of Type (η⁵-Me₃EC₅H₄)₂Ti(S₂C₂R₂) (E = C, Si, Ge) Reaction of the titanocene dichlorides (η⁵-Me₃EC₅H₄)₂TiCl₂ (E = C, 1a ; E = Si, 1b ; E = Ge, 1c ) with the 1,2-dithiolates (NaS)₂C₂H₂, (NaS)₂C₂(CN)₂ or (LiS)₂C₆H₃Me-4 gave the new titanocene dithiolene chelates (η⁵-Me₃EC₅H₄)₂Ti(S₂C₂H₂) ( 2a–c ), (η⁵-Me₃EC₅H₄)₂Ti[S₂C₂(CN)₂] ( 3a–c ) and (η⁵-Me₃EC₅H₄)₂Ti(S₂C₆H₃Me-4) ( 4a–c ). These have been characterized by ¹H NMR, IR, and mass spectroscopy, and have been compared with the unsubstituted η⁵-C₅H₅ analogues 2d, 3d and 4d . Activation energies for the chelate ring inversion in solution of 2a–c, 3a–d and 4a–c have been estimated by temperature-dependent ¹H NMR spectroscopy.     

Facile Access to Silicon‐Functionalized Bis‐Silylene Titanium(II) Complexes

A series of unprecedented bis‐silylene titanium(II) complexes of the type [(η⁵‐C₅H₅)₂Ti(LSiX)₂] (L=PhC(NtBu)₂; X=Cl, CH_3, H) has been prepared using a phosphane elimination strategy. Treatment of the [(η⁵‐C₅H₅)₂Ti(PMe₃)₂] precursor ( 1 ) with two molar equivalents of the N‐heterocyclic chlorosilylene LSiCl ( 2 ), results in [(η⁵‐C₅H₅)₂Ti(LSiCl)₂] ( 3 ) with concomitant PMe₃ elimination. The presence of a Si? Cl bond in 3 enabled further functionalization at the silicon(II) center. Accordingly, a salt metathesis reaction of 3 with two equivalents of MeLi results in [(η⁵‐C₅H₅)₂Ti(LSiMe)₂] ( 4 ). Similarly, the reaction of 3 with two equivalents of LiBHEt₃ results in [(η⁵‐C₅H₅)₂Ti(LSiH)₂] ( 5 ), which represents the first example of a bis‐(hydridosilylene) metal complex. All complexes were fully characterized and the structures of 3 and 4 elucidated by single‐crystal X‐ray diffraction analysis. DFT calculations of complexes 3 – 5 were also carried out to assess the nature of the titanium–silicon bonds. Two σ and one π‐type molecular orbital, delocalized over the Si‐Ti‐Si framework, are observed.     

Synthesis and properties of a thermally stable methyltitanium(IV) compound: Cyclopentadienylmethyldichlorotitanium(IV)

η⁵C₅H₅Ti(CH₃)Cl₂ and η⁵-C₅H₅Ti(C₂H₅TiCl₂ have been synthesized. The reactivity of the methyl compound is much greater than that of the closely related sandwich compound, (η⁵-C₅H₅)₂Ti(CH₃)Cl, but the thermal stability is comparable.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XXXV. Zum Reaktionsverhalten von Tetrabenzyltitan gegenüber Lithiumalkylen

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXXV. Reactions in Tetrabenzyl Titanium/Alkyllithium Systems Organotitanium(IV) complexes of the type Li[(C₆H₅CH₂)₄TiR] (R = CH₃, C₂H₅, n-C₄H₉) were isolated from tetrabenzyl titanium and lithium alkyls at deep temperature. The reddish brown, crystalline compounds decompose between ?30 and 0°C with formation of benzyltitanates(II) which composition differs between Li₂[Ti(CH₂C₆H₅)₄] and Li[Ti(CH₂C₆H₅)₃]. From these complexes pure dibenzyl titanium can be isolated. The reaction mechanism is discussed. Experiments for isolation of a benzyl titanium(III) compound from (C₆H₅CH₂)₄Ti/RLi systems failed in all cases. Recent informations about stable tribenzyl titanium obtained from tetrabenzyl titanium and ethyl lithium could not be confirmed.     

Zur Kenntnis von Tribenzylzinn- und Tribenzyltitancyclopentadienyl

About Tribenzyltin- and Tribenzyltitaniumcyclopentadienyl The organocerium(III) compound Na(THF)[(π-C₅H₅)₃Ce(σ-C₅H₅)] ( I ) reacts with (C₆H₅CH₂)₃SnCl and (C₆H₅CH₂)₃TiCl after a S_N-reaction under separation of Nacl and (C₅H₅)₃Ce to tribenzyltin- resp.-titaniumcyclopentadienyl (C₆H₅CH₂)₃MC₅H₅ [M = Sn, ( II ); Ti, ( III )]. A special characterization of II and III was carried out by their elementary analysis, I.R. spectroscopy and ¹H, ¹³C, and ¹¹⁹Sn N.M.R. spectroscopy. These results allow the statement that II and III are better to be described by the formulae (C₆H₅CH₂)₃Sn(σ-C₅H₅) and (C₆H₅CH₂)₃Ti(π-C₅H₅), respectively.     

Etudes sur les composés organométalliques. XI [1]. Action du tétrabutoxytitane sur des solutions de Grignard

The reaction of titanium tetra-n-butoxide with phenylmagnesium bromide inether has been investigated. The species (C₆H₅)₂Mg in the Grignard reagent leads to (C₆H₅)₄Ti, whereas the dimeric species (C₆H₅)₂Mg · MgBr₂ produces an insoluble complex mTi(OBu)₄ · n[(C₆H₅)₂Mg · MgBr₂]. Applied to other Grignard reagents, the use of R₂Mg allowed the preparation of tetrabenzyltitanium, tetracyclohexyltitanium and tetramethyltitanium. Cristalline (C₆H₅)₄Ti and (C₆H₅CH₂)₄ Ti have been isolated.     

A dimeric constrained‐geometry titanium complex linked by double Ti–CH2–Al–CH2 heterocycles

In the structure of bis({N‐[di­methyl(1η⁵‐2,3,4,6‐tetra­methyl­in­den­yl)­silyl]­cyclo­hexyl­amido‐1κN}(methyl‐3κC)‐di‐μ₃‐methyl­ene‐1:2:3κ³C;1:3:3′κ³C‐tris(pentafluorophenyl‐2κC)titanium) benzene disolvate, [Me₂Si(η⁵‐2,3,4,6‐Me₄C₉H₂)(C₆H₁₁N)]Ti[(μ₃‐CH₂)Al(C₆F₅)₃][AlMe(μ₃‐CH₂)]₂ or [Ti₂(C₂₁H₇AlF₁₅)₂(C₂₁H₃₁NSi)₂]·2C₆D₆, the dimer is located on an inversion center, and the two Ti centers are linked by double Ti(μ₃‐CH₂)Al(C₆F₅)₃AlMe(μ₃‐CH₂) heterocycles. The electron‐deficient Ti centers are further stabilized by two α‐agostic interactions between Ti and one H atom of each bridging methyl­ene group.     

A cyclopentadienyl ring exchange method for the attachment of early transition metal metallocene dichlorides to a polymer support

PMR and mass spectral analysis have been used to study the interchange of π-bonded cyclopentadienyl rings with σ-bonded cyclopentadienyl rings in the compounds (C₅H₅)₄M (M = Ti, Zr, Hf, Nb, Ta, Mo and W) and (C₅H₅)₃V or a-bonded benzylcyclopentadienyl rings in the compounds (C₆H₅CH₂C₅H₄) (C₅H₅)₂MC1 (M = Ti, Zr, Hf, Nb, Ta, Mo and W). As soon as the Cp₄M species are generated (indicated by a color change), the interchange occurs and the equilibrium is established. As reported, no such interchange was observed in (C₅H₅) ₄Mo in the PMR time scale; however, it does occur after a longer time. By using this interchange behavior of the cyclopentadienyl ring, metallocene dichlorides of Ti, Zr, Hf, V, Nb, Ta, Mo and W have been attached to polystyrene-divinylbenzene beads.     

Preparation of dicyclopentadienylmetal-bis(trimethyl phosphite) complexes of titanium(II) and zirconium(II) by sodium atom reduction

The complexes (C₅H₅)₂M[P(OCH₃)₃]₂ (M = Ti and Zr) can be prepared by condensing sodium atoms at ?100°C into tetrahydrofuran solutions containing (C₅H₅)₂MCl₂ and excess trimethyl phosphite.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. 59. Cyclopentadienyl-2-(dimethylaminomethyl)ferrocenyl-Verbindungen elektronenarmer 3 d-Elemente

Contributions to the Chemistry of Transition Metal Alkyl Compounds. 59. Cyclopentadienyl-2-(dimethylaminomethyl)ferrocenyl Compounds of Early 3 d-Elements Compounds of the type (C₅H₅)₂M(FcN) (M = Sc ( 1 ), Ti ( 2 ), V ( 3 ), Cr ( 4 ); FcN = 2-dimethylaminomethyl)ferrocenyl group), and (C₅H₅)M(FcN)₂ (M = Ti ( 5 ), Cr ( 6 ) were synthesized and investigated. A detailled characterization with respect to the existence of chelate structures was realized by the uv-vis, ¹H-n.m.r. spectroscopic measurements and determination of magnetic moments.     

[μ‐1κ2O,O′:2(η5)‐Cyclopentadienylcarboxylato][2(η5)‐diphenylphosphinocyclopentadienyl]bis[1,1(η5)‐tetramethylcyclopentadienyl]iron(II)titanium(III)

Reacting stoichiometric amounts of 1‐(diphenylphosphino)ferrocene­carboxylic acid and [Ti(η⁵‐C₅HMe₄)₂(η²‐Me₃SiC[triple‐bond]CSiMe₃)] produced the title carboxyl­atotitanocene complex, [{μ‐1κ²O,O′:2(η⁵)‐C₅H₄CO₂}{2(η⁵)‐C₅H₄P(C₆H₅)₂}{1(η⁵)‐C₅H(CH₃)₄}₂Fe^IITi^III] or [FeTi(C₉H₁₃)₂(C₆H₄O₂)(C₁₇H₁₄P)]. The angle subtended by the Ti/O/O′ plane, where O and O′ are the donor atoms of the κ²‐carboxy­late group, and the plane of the carboxyl‐substituted ferrocene cyclo­penta­dienyl is 24.93 (6)°.     

Transition metal derivatives of 1,1′-dichloroferrocene

Complexes of the general formula [Cl₂Fc] _nML, (Cl₂Fc = C1C₅H₄FeC₅H₃Cl; ML = Fe(CO)₂C₅H₅, AuP(C₆H₅)₃, Mn(CO)₅ or Ir(CO)[P(C₆H₅)₃]₂ when n = 1; ML = Ti(C₅H₅)₂ when n = 2) have been prepared from a salt elimination reaction between 1,1′-dichloro-2-lithioferrocene and transition metal halide complexes. Spectroscopic properties of the compounds are reported. The titanium complex exists in meso and dl forms.     

Coordinatively Unsaturated Amidotitanocene Cations with Inverted σ and π Bond Strengths: Controlled Release of Aminyl Radicals and Hydrogenation/Dehydrogenation Catalysis

Cationic amidotitanocene complexes [Cp₂Ti(NPhAr)][B(C₆F₅)₄] (Cp=η⁵-C₅H₅; Ar=phenyl ( 1 a ), p-tolyl ( 1 b ), p-anisyl ( 1 c )) were isolated. The bonding situation was studied by DFT (Density Functional Theory) using EDA-NOCV (Energy Decomposition Analysis with Natural Orbitals for Chemical Valence). The polar Ti−N bond in 1 a–c features an unusual inversion of σ and π bond strengths responsible for the balance between stability and reactivity in these coordinatively unsaturated species. In solution, 1 a–c undergo photolytic Ti−N cleavage to release Ti(III) species and aminyl radicals ⋅ NPhAr. Reaction of 1 b with H₃BNHMe₂ results in fast homolytic Ti−N cleavage to give [Cp₂Ti(H₃BNHMe₂)][B(C₆F₅)₄] ( 3 ). 1 a–c are highly active precatalysts in olefin hydrogenation and silanes/amines cross-dehydrogenative coupling, whilst 3 efficiently catalyzes amine-borane dehydrogenation. The mechanism of olefin hydrogenation was studied by DFT and the cooperative H₂ activation key step was disclosed using the Activation Strain Model (ASM).