The synthesis, coordination chemistry and ethylene polymerisation activity of ferrocenediyl nitrogen-substituted ligands and their metal complexes

Treatment of aminoferrocene with substituted 2-hydroxybenzaldehydes yields the air- and moisture-stable ligands 1–4, which were then reacted to form the chromium dichloride complexes 5–7 and the nickel bis-chelate species 8 and 9. The metal compounds are very air-sensitive but the chromium compounds act as pre-catalysts for the polymerisation of ethylene. Reaction of 1,1′-bis(amino)ferrocene with similarly substituted 2-hydroxybenzaldehyes or simple benzaldehyde gives the ligands 10–12 and 17, respectively. The X-ray crystal structure of 11 shows the molecule to have non-crystallographic C₂ symmetry and to be linked by C–Hπ interactions between the anthracene rings. Titanium-containing complexes 13–16 can be formed utilising ligands 10–12 and there is a change in geometry within the complexes dependent on the adjacent co-ligands, whilst ligand 17 can be reacted with PdClMe(COD) to form the chelate complex 18. Cyclic voltammetric studies have been carried out on 18 and its oxidised analogue 19, but both complexes are inactive towards ethylene polymerisation.     

Synthesis, characterization, and activity in ethylene polymerization of silica supported cationic cyclopentadienyl zirconium complexes

Cp*ZrMe3 reacts with silica pretreated at 800 degrees C, SiO(2-(800)) through two pathways: (a) protolysis of a Zr-Me group by surface silanols and (b) transfer of a methyl group to the surface by opening of strained siloxane bridges, in a relative proportion of ca. 9/1, respectively, affording a well-defined surface species [([triple bond]SiO)ZrCp*(Me)2], 3, but with two different local environments 3a, [([triple bond]SiO)ZrCp*(Me)2][[triple bond]Si-O-Si[triple bond]], and the other with 3b, [structure: see text]. The reaction of the species 3 with B(C6F5)3 is controlled by this local environment and gives three surface species [([triple bond]SiO)ZrCp*(Me)](+)[MeB(C6F5)3]- [[triple bond]Si-O-Si[triple bond]], 4a (20%), [([triple bond]SiO)ZrCp*(Me)](+)[(Me)B(C6F5)3]- [[triple bond]Si-Me], 4b (10%), and [([triple bond]SiO)2ZrCp*](+)[(Me)B(C6F5)(3)](-)[[triple bond]Si-O-Si[triple bond]], 5 (70%). On the contrary, the reaction of Cp*Zr(Me)3, Cp2Zr(Me)2 with [[triple bond]SiO-B(C6F5)3](-)[HNEt2Ph]+, 6, leads to a unique species [([triple bond]SiO)B(C6F5)3](-)[Cp*Zr(Me)2.NEt2Ph]+, 7, and [([triple bond]SiO)ZrCp2](+)[(Me)B(C6F5)3]-, 9 respectively. The complexes 4 and 7 are active catalysts in ethylene polymerization at room temperature, 93 and 67 kg PE mol Zr1- atm(-1) bar(-1), respectively, indicating that covalently bounded Zr catalyst 4 is slightly more active than the "floating" cationic catalyst 7.     

Novel cyclopentadienyl silanes and disilanes: synthesis, structure and gas-phase pyrolysis

The new chloro(cyclopentadienyl)silanes Cp′SiH_yCl_3−y (Cp′=Me₄EtC₅, y=1: 1; Cp′=Me₄C₅H, y=1: 2; y=0: 3; Cp′=Me₃C₅H₂, y=1: 4 and pentachloro(cyclopentadienyl)disilanes Cp′Si₂Cl₅ (Cp′=Me₅C₅ 5, Me₄EtC₅ 6, Me₄C₅H 7, Me₃C₅H₂ 8, Me₃SiC₅H₄ 9) are synthesized in good yields via metathesis reactions. Treatment of 1–9 with LiAlH₄ leads under Cl–H exchange to the hydridosilyl compounds Cp′SiH₃ (Cp′=Me₄EtC₅ 10, Me₄C₅H 11, Me₃C₅H₂ 12) and to the hydridodisilanyl compounds Cp′Si₂H₅ (Cp′=Me₅C₅ 13, Me₄EtC₅ 14, Me₄C₅H 15, Me₃C₅H₂ 16, Me₃SiC₅H₄ 17). Complexes 1–17 are characterized by ¹H, ¹³C, and ²⁹Si-NMR spectroscopy, IR spectroscopy, mass spectrometry and CH-analysis. The structures of 6, 7 and 9 are determined by single-crystal X-ray diffraction analysis. Pyrolysis studies of the cyclopentadienylsilanes 10–12 and disilanes 13–17 show their suitability as precursors in the MOCVD process.     

The synthesis,structure, and ethylene polymerization of dimeric salicylaldiminato titanium complexes

A series of dimeric titanium complexes bearing salicylaldiminates, [4-R-6-^tBu-2-(CH=NⁿBu)C₆H₂OTiCl₂(µ-Cl)]₂ [R?=?H (1); R?=?^tBu (2); R?=?NO₂ (3)], have been synthesized in high yield (>90%) by the reaction of corresponding 4-R-6-^tBu-2-(CH=NⁿBu)C₆H₂OSiMe₃ with TiCl₄. The molecular structure of 2 has been confirmed by single-crystal X-ray diffraction analysis. When activated with methylaluminoxane, these complexes exhibit good catalytic activity for ethylene polymerization.     

The zwitterion effect in proton exchange membranes as synthesised by polymerisation of bicontinuous microemulsions

The bicontinuous microemulsions consisting of a polymerisable zwitterionic surfactant 3-((11-acryloyloxyundecyl)imidazolyl) propyl sulfonate (AIPS) and other monomers can be cross-polymerised to form good proton conductive membranes.     

Hybrid catalysts: the synthesis, structure and ethene polymerisation activity of (salicylaldiminato)(pyrrolylaldiminato) titanium complexes

The mono(salicylaldiminato) complexes Ti{3-tBu-2-(O)C6H3CH=N(R)}Cl3(THF)(where R = C6H5, C6F5) react with the metallated pyrrolylaldiminato ligand, K[2-(C6H5NCH)C4H3N], to afford the first examples of hybrid salicylaldiminato-ligated octahedral titanium complexes; the pre-catalysts give from very high to extremely high ethene polymerisation productivities when activated with MAO.     

The synthesis, structure and ethene polymerisation catalysis of mono(salicylaldiminato) titanium and zirconium complexes

The silyl ethers 3-But-2-(OSiMe3)C6H3CH=NR (2a-e) have been prepared by deprotonation of the known iminophenols (1a-e) and treatment with SiClMe3 (a, R = C6H5; b, R = 2,6-Pri2C6H3; c, R = 2,4,6-Me3C6H2; d, R = 2-C6H5C6H4; e, R = C6F5). 2a-c react with TiCl4 in hydrocarbon solvents to give the binuclear complexes [Ti{3-But-2-(O)C6H3CH=N(R)}Cl(mu-Cl3)TiCl3] (3a-c). The pentafluorophenyl species 2e reacts with TiCl4 to give the known complex Ti{3-But-2-(O)C6H3CH=N(R)}2Cl2. The mononuclear five-coordinate complex, Ti{3-But-2-(O)C6H3CH=N(2,4,6-Me3C6H2)}Cl3 (4c), was isolated after repeated recrystallisation of 3c. Performing the dehalosilylation reaction in the presence of tetrahydrofuran yields the octahedral, mononuclear complexes Ti{3-But-2-(O)C6H3CH=N(R)}Cl3(THF) (5a-e). The reaction with ZrCl4(THF)2 proceeds similarly to give complexes Zr{3-But-2-(O)C6H3CH=N(R)}Cl3(THF) (6b-e). The crystal structures of 3b, 4c, 5a, 5c, 5e, 6b, 6d, 6e and the salicylaldehyde titanium complex Ti{3-But-2-(O)C6H3CH=O}Cl3(THF) (7) have been determined. Activation of complexes 5a-e and 6b-e with MAO in an ethene saturated toluene solution gives polyethylene with at best high activity depending on the imine substituent.     

New zirconocenes with 4,5,6,7-tetrahydroindene ligands. Synthesis and catalytic activity in the polymerization of ethylene and copolymerization of ethylene with hex-1-ene

A series of symmetric and nonsymmetric tetrahydroindenyl zirconium complexes was obtained by the reaction of ZrCl₄ or (CpTMS)ZrCl₃ with lithium salts of the corresponding tetrahydroindenes. Activated with methylalumoxane, these complexes exhibit high activity in polymerization of ethylene (up to 6.8?10⁶ g PE (mol Zr h)^–1), as well as in copolymerization of ethylene and hex-1-ene (up to 8.6?10⁶ g PE (mol Zr h)^–1).     

New possibilities of 1,2,4-triazines functionalization: first examples of synthesis and structure of boron-containing 1,2,4-triazines

By oxidation of 3-thioderivatives of 1,2,4-triazine 1a,b 3-alkylsulfonic derivatives 2a,b were obtained. Interaction of the sulfonic derivative 2a with indole leads to 3-oxo-5-indolyl-5-phenyl-as-triazine 4. The sulfone 2a reacts with 1-ethyl-2,6-dimethylquinolinium iodide to give 3-(1-ethyl-6-methyl-1,2-dihydroquinoline-2-methylene)-5-phenyl-1,2,4-triazine 5. The 3-morpholino- 3 and 3-thioderivatives 6, 7a,b of as-triazine were obtained by interaction of the sulfone 2 with morpholine and organic boron-containing thiols. The crystal structure of boron-containing derivative of as-triazine 7b was investigated by X-ray analysis.     

Thio-Pybox and Thio-Phebox complexes of chromium, iron, cobalt and nickel and their application in ethylene and butadiene polymerisation catalysis

A series of bis(thiazolinyl)- and bis(thiazolyl)pyridine Thio-Pybox ligands and their metal complexes of chromium(III), iron(II), cobalt(II) and nickel(II) has been prepared, as well as a nickel(II) complex containing a monoanionic bis(thiazolinyl)phenyl Thio-Phebox ligand. These new metal complexes have been characterised and used as catalysts, in combination with the co-catalyst MAO, for the polymerisation of ethylene and for the polymerisation of butadiene. In the case of ethylene polymerisation, the Thio-Pybox and Thio-Phebox metal complexes have shown relatively low polymerisation activities, much lower compared to the related bis(imino)pyridine complexes of the same metals. In the polymerisation of butadiene, several Thio-Pybox cobalt(II) complexes show very high activities, significantly higher than the other metal complexes with the same ligand. It is the metal, rather than the ligand, that appears to have the most profound effect on the catalytic activity in butadiene polymerisation, unlike in the polymerisation of ethylene, where bis(imino)pyridine ligands provide highly active catalysts for a range of 1st row transition metals.     

The first examples of anthracene capped chiral carbohydrate derived dendrimers: synthesis, fluorescence and chiroptical properties

The first examples of anthracene capped chiral dendrimers derived from a 1,3,5-trisubstituted aromatic core and carbohydrate units in the interior and periphery are described. Excimer formation was evident from the fluorescence spectrum, and both fluorescence and chiroptical properties indicated that the dendrimer does not undergo aggregation in the ground state.     

Cationic benzyl zirconium heteroscorpionates: synthesis and characterization of a novel ethylene polymerisation catalyst showing an unusual temperature dependent polymerisation mechanism

The reaction of (bpzmp)Zr(CH2Ph)3 with B(C6F5)3 produces the active ethylene polymerisation catalyst [(bpzmp)Zr(CH2Ph)2]+[PhCH2B(C6F5)3]- which showed a temperature dependent polymerisation mechanism identified by variable temperature 1H NMR analysis of the catalyst solution.     

Probing the effects of ligand structure on activity and selectivity of Cr(III) complexes for ethylene oligomerisation and polymerisation

A series of distorted octahedral Cr(III) complexes containing tridentate S-, S/O- or N-donor ligands comprised of three distinct architectures: facultative {S(CH(2)CH(2)SC(10)H(21))(2) (L(1)) and O(CH(2)CH(2)SC(10)H(21))(2) (L(2))}, tripodal {MeC(CH(2)S(n)C(4)H(9))(3) (L(3)), MeC(CH(2)SC(10)H(21))(3) (L(4))} and macrocyclic {(C(10)H(21))[9]aneN(3) (L(5)), (C(10)H(21))(3)[9]aneN(3) (L(6)), with [9]aneN(3)=1,4,7-triazacyclononane} are reported and characterised spectroscopically. Activation of [CrCl(3)(L)] with MMAO produces very active ethylene trimerisation, oligomerisation and polymerisation catalysts, with significant dependence of the product distribution upon the ligand type present. The properties of the parent [CrCl(3)(L)] complexes are probed by cyclic voltammetry, UV-visible, EPR, EXAFS and XANES measurements, and the effects upon activation with Me(3)Al investigated similarly. Treatment with excess Me(3)Al leads to substitution of Cl ligands by Me groups, generation of an EPR silent Cr species (consistent with a change in the oxidation state of the Cr to either Cr(II) or Cr(IV)) and substantial dissociation of the neutral S and S/O-donor ligands.     

Cationic rare-earth metal bis(tetrahydridoborato) complexes: direct synthesis, structure and ring-opening polymerisation activity toward cyclic esters

Rare-earth metal tris(borohydrides) [Ln(BH4)3(thf)3] (Ln = Y, La, Nd, Sm) are converted with one equivalent of the Br?nsted acid [NEt3H]+[BPh4]- in thf into the monocationic bis(borohydride) complexes [Ln(BH4)2(thf)5]+[BPh4]-. They efficiently initiate the ring-opening polymerisation of epsilon-caprolactone.     

Studies of bimetallic carboxylates: their synthesis, characterization, biological activity and X-ray structure

Ten novel diorganotin dicarboxylates containing germanium in the carboxylate ligand have been synthesized and their structures have been characterized by IR, Mössbauer and multinuclear NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopies and X-ray diffraction. Also, the twodiastereotopic protons of the methylene group which are directly attached to the chiral center in these compounds have been successfully analyzed for the first time. The resulted ABX system gives three coupling constants and three chemical shifts. The single crystal X-ray analysis of precursor (p-CH₃C₆H₄)₃GeCH(p-CH₃C₆H₄)CH₂COOH revealed the dimeric structure of the molecule through H-bonding between carboxylic acid groups in a conventional manner. The results of their biological activity suggest that the materials have potential to be used as drugs.     

The first examples of seco-prezizaane-type norsesquiterpenoids with neurotrophic activity from Illicium jiadifengpi

Two seco-prezizaane-type sesquiterpenoids (2R)-hydroxy-norneomajucin (1) and jiadifenone (2) that represent the first examples of nor-type were isolated from the methanol extract of the pericarps of Illicium jiadifengpi. Their structures and the absolute configuration of 1 were established by the analysis of spectroscopic data and chemical conversion of (2S)-hydroxyneomajucin to 1, respectively. In addition, compound 1 exhibited neurotrophic activity to significantly promote neurite outgrowth in the primary cultured rat cortical neurons at concentrations ranging from 1 to 10 μmol L^?1.     

From symmetrical to unsymmetrical bimetallic nickel complexes bearing aryl-linked iminopyridines; synthesis, structures and ethylene polymerisation studies

Both symmetrical and unsymmetrical tetramethylphenyl-linked iminopyridines, 1,4-{(2-C₅H₄N)RCN}₂-2,3,5,6-Me₄C₆ [R = H (L1a), Me (L1b)] and 1-{(2-C₅H₄N)HCN}-4-{(2-C₅H₄N)MeCN}-2,3,5,6-Me₄C₆ (L1c), have been prepared in good yield using straightforward condensation strategies. The molecular structures of L1a and L1c reveal the adjacent imino and pyridyl nitrogen atoms to adopt transoid configurations. Interaction of L1x with two equivalents of NiX₂ [NiX₂ = (DME)NiBr₂ (DME = 1,2-dimethoxyethane), NiCl₂] in n-BuOH at elevated temperature affords the paramagnetic bimetallic complexes, [(L1x)Ni₂X₄] [L1x = L1a, X = Br (1a); L1x = L1b, X = Br (1b); L1x = L1c, X = Br (1c); L1x = L1a, X = Cl (1d)] in moderate to good yield. Adduct formation results on treatment of bromide-containing 1a-1c with DMF (dimethylformamide) to yield dicationic [(L1x)Ni₂Br₂(DMF)₆]Br₂ [L1x = L1a (2a), L1b (2b), L1c (2c)], while with chloride-containing 1d the neutral species [(L1a)Ni₂Cl₄(DMF)₄] (3) is obtained. Activation of 1a-1d and 2c with excess methylaluminoxane (MAO) generates active ethylene polymerisation catalysts (1b/MAO > 1c/MAO > 1a/MAO ∼ 1d/MAO > 2c/MAO) affording mixtures of waxes and low molecular weight solid polyethylene. Multinuclear NMR and GC analysis of the waxy components reveal methyl branched materials that contain mostly internal unsaturation along with low levels of α-olefins. Broad molecular weight distributions are observed for all the polymers obtained, with that from 1b/MAO leading to the highest molecular weight. Single crystal X-ray diffraction studies have been performed on L1a, L1c, 2a-2c and 3.     

Synthesis of zirconocenes bearing benz[f]indenyl ligand and their use as a catalyst in ethylene polymerization

Benz[f]indenyl zirconium complexes have been successfully synthesized and characterized. Their catalytic activities were evaluated for the polymerization of ethylene. The complexes combined with MAO can be highly active single site catalysts, which display activities comparable with that of the Cp₂ZrCl₂/MAO system and provide very high molecular weight polyethylenes. The melting point of the polymers indicates the formation of linear polyethylene.     

Chromium and molybdenum pentacarbonyl complexes of phosphinocarbodithioates: synthesis, molecular structure and behaviour in RAFT polymerisation

Molybdenum and chromium pentacarbonyldiphenylphosphinocarbodithioate complexes have been prepared in a one‐pot reaction from the corresponding metallocarbonyldiphenylphosphine. The complexes have been characterised by IR, ¹H, ³¹P and ¹³C NMR spectroscopies and by mass spectrometry. The solid‐state structures of [Cr(CO)₅{PPh₂CS₂CH(Ph)CH₃}] ( 1 ) and [Mo(CO)₅{PPh₂CS₂CH(Ph)CH₃}] ( 2 ) are reported. Compounds 1 and 2 are isostructural and crystallise in the triclinic P$\bar 1Molybdenum and chromium pentacarbonyldiphenylphosphinocarbodithioate complexes have been prepared in a one-pot reaction from the corresponding metallocarbonyldiphenylphosphine. The complexes have been characterised by IR, (1)H, (31)P and (13)C?NMR spectroscopies and by mass spectrometry. The solid-state structures of [Cr(CO)(5){PPh(2)CS(2)CH(Ph)CH(3)}] (1) and [Mo(CO)(5){PPh(2)CS(2)CH(Ph)CH(3)}] (2) are reported. Compounds 1 and 2 are isostructural and crystallise in the triclinic P1 space group. These new organometallic compounds are highly efficient reversible chain-transfer agents for reversible addition-fragmentation chain-transfer (RAFT) polymerisation of styrene (St) and n-butyl acrylate (nBA), with controlled number-average molar mass values and narrow dispersities (<1.2). The controlled character of the polymerisation was further exemplified by the synthesis of St and nBA diblock copolymers.     

(Diphenylphosphinoethyl)cyclopentadienyl complexes of yttrium and lutetium: synthesis and structure

The reaction of LnCl₃·xTHF with Na(C₅H₄CH₂CH₂PPh₂) followed by the in situ reaction with Na₂(C₁₄H₁₀) afforded the (C₅H₄CH₂CH₂PPh₂)Ln(C₁₄H₁₀)L complexes (Ln = Y or Lu and L = THF or DME). The structure of (C₅H₄CH₂CH₂PPh₂)Lu(C₁₄H₁₀)(DME) was established by X-ray diffraction. In solution, there is an equilibrium between the complexes with the coordinated and uncoordinated phosphorus atom. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1687–1689, September, 2007.