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Reduction of ansa-titanocene dichlorides [X(η5-C5H4)2TiCl2] (X = SiMe2 (1) and CMe2 (2)) in tetrahydrofuran (THF) by preactivated magnesium in the presence of bis(trimethylsilyl)acetylene (BTMSA) yielded complexes [X(η5-C5H4)2Ti(η2-BTMSA)] (X = SiMe2 (3) and CMe2 (4)). The prolonged action of excess magnesium and BTMSA resulted in the formation of ansa-titanium-magnesium complexes [μ-X{(η5-C5H4)Ti(η2-SiMe3C≡CSiMe3)2}{(η5-C5H4)Mg(THF)}] (X = SiMe2 (5) and CMe2 (6)), which had their metals bounded via the ansa-ligand and ionic bonding between magnesium and the BTMSA ligands. Compounds 5 and 6 easily isomerized to 5a and 6a through rotation of their {(C5H4)Mg(THF)} moiety around the ansa- X–C bond. This rotation canceled the interaction of magnesium with the BTMSA ligands, which resulted in a large high-field shift of acetylenic carbon resonances. The geometry of both structures optimized by Density Functional Theory (DFT) computations together with the good correlation of computed magnetic shieldings and experimental 13C NMR shifts of 5 and its isomer 5a approved the above isomerization. The simultaneous ionic bonding of Mg2+ to the cyclopentadienyl ligand, which is η5-coordinated to the {Ti(η2-BTMSA)2} moiety in 5a got also confirmed by computational results. Reduction by magnesium was used to obtain Ti(III) dimers of ansa-titanocene acetylides [{X(η5-C5H4)2Ti (μ-η1:η2-C≡CSiMe3)}2] (X = SiMe2 (7) and X = CMe2 (8)) via redox splitting of 1,4-bis(trimethylsilyl)buta-1,3-diyne (BSD) by transient Ti(II) titanocene. The thermally stable Ti(II) compounds 3 and 4 were also shown to react with BSD yielding respectively 7 and 8. The reduction of 1 and 2 with magnesium in THF afforded Ti(III) monochloride dimers [{ansa-X(η5-C5H4)2Ti(μ-Cl)}2] (X = SiMe2 (10); CMe2 (11)), which in contrast to the non-ansa dimer [(η5-C5H5)2Ti(μ-Cl)}2] were silent in toluene glass EPR spectra. No evidence of obtaining quadruply bridged dititanium complexes capped with the ansa-ligands was encountered among crystal structures of 7–11, even though the total energy of optimized molecules 7 and 10 and their capped congeners differed by more than 45 kJ/mol, favouring the capped isomers in both cases.

A series of Miocene fossil resin from the northwest part of the Czech Republic, called duxite, has been analyzed by elemental, microscopic, gas chromatography (GC/MS), pyrolysis-gas chromatography, Fourier Transform infrared (FTIR), and Raman techniques. The set of samples consisted of museum, contemporary and artificially altered samples. The results of GC/MS revealed fine variances in chemical structure among the samples, which could be attributed to the geologic paleosituation during resin deposition, as was verified by alteration of a sample under different conditions. Sesquiterpenes, including α-cedrene and cuparene, were identified in sample extracts and sample pyrolysates together with diterpenoid members abietanes, pimaranes, and dehydroabietanes. The distribution and intensity of functional groups of FTIR spectra also confirmed that the duxite samples were fossilised exudates from a member of the Cupressaceae conifer family. Raman spectra supported this record indicating aromatic character of duxite and higher maturity of the samples. The chemical composition indicated that duxite is a member of Class IV resins of the fossil resin classification system. Members of this group do not have a polymeric structure. This nonpolymerizable behaviour was confirmed by their excellent solubility in an organic solvent and the low softening point of the material. Our results therefore provide a valuable insight into the duxite-producing process and its potential for evaluating the geological environment and diagenetic conditions.

The singly tucked-in titanocene [(η5-C5Me5)TiIII{η5:η1-C5Me4(CH2)}] (1) reacted with one equivalent of 1-tert-butylpropyne to yield the propenyl-tethered regioisomer [(η5-C5Me5)Ti(η5:η1-C5Me4CH2C(t-Bu) = κCMe)] (3). The exclusive formation of paramagnetic 3 was proved experimentally and steric reasons were clarified by DFT calculation of transition state which involves both π-systems on the alkyne for bonding interaction with the metal and with sp2 carbon atom of exomethylene group of 1. The obtained compound 3 is by 40 kJ/mol lower in energy than its hypothetical isomer having t-Bu group on Cα of the tether.

Two novel half-sandwich Ti complexes, both incorporating two adamantoxy (OAd) ligands coordinated to their central atoms were synthesized. The complexes were characterized by 1 H, 13 C, 19 F NMR, EI-MS and IR spectroscopy and by single-crystal X-ray diffraction. In both complexes, the coordination environment is pseudo-tetrahedral and is assembled of two O-coordinated adamantoxy and one η 5 -coordinated permethylcyclopentadienyl ligand. The fourth ligand in complex 1 is a methyl group coordinated through a regular σ-bond, whereas in complex 2 the same coordination site is occupied by the methyl group of the balancing (C 6 F 5 ) 3 BMeˉ anion. DFT computations complemented with NBO analyses of 2 have unveiled, that in addition to the electrostatic interactions occurring between the half-sandwich titanocene moiety and the anionic ligand, delocalization of one methyl C H bond into the available acceptor orbital on the central atom takes place. AIM analyses of 2 have revealed the presence of a Bond Critical Point between the metal atom and the anionic methyl group. These results prove foundation for the description of 2 as a zwitterionic complex coupled with a concurrent Ti⋯C H agostic interaction in its molecule. The comparison of 2 with its analogous complex equipped with two O t -Bu ligands instead of both OAd has suggested only a minor change in the extent of the agostic interaction, despite significant geometric differences between the two complexes.

Sunlight photolysis of the triplet state (S = 1) dititanium compound 1 induced its rearrangement to diamagnetic 2, which was a molecule containing two hydrogens less. The cage structure of 2 was determined by single crystal X-ray diffraction and was corroborated fully by 1H and 13C NMR spectra that identified three simple bridging moieties — a hydrogen atom, a methine carbon and a methylene carbon. Its extremely short Ti−Ti distance 2.7537(7) A causes a strong distortion of the bridging fulvalene ligand, which becomes η5- bonded to one Ti(IV) and connected by two σ-bonds from nearest carbon atoms of its other ring to the other Ti(IV) of 2. Other photolytical byproducts in very minor amounts were also isolated, which differed from 2 by the absence of one bridging moiety: compound 4 lacked the methine group and compound 5 had no bridging hydrogen. In the latter cases, the Ti−Ti distance fell in the range 3.2077(8) – 3.5543(12) A and the fulvalene ligand was coordinated in the common µ-η5: η5-mode to both titanium atoms. The octamethylfulvalene ligands in 4 and 5 had their ring planes rotated mutually by about 40° in order to relieve the steric hindrance between their methyl groups. The thermally robust µ-oxo complex 3 obtained from reacting 2 with water showed a very similar structure.

Solutions of permethylcyclopentadienyl-tethered titanium(IV) chlorides incorporating one double bond in their tethers were exposed in glass vessels to sunlight, which triggered their photolytical reactions providing mixtures of products. Although the formation of several different products was apparent from 1H NMR spectra, only a single product could be identified in the crude reaction mixtures. This product was dicyclopentadiene [C10Me10], which arose from the recombination of the generally photodissociated C5Me5 radical. Amongst products that contained titanium, three complexes (3a, 3b and 4a) could be isolated after employing fractional crystallization and these complexes were characterized. The mechanism of 3a formation involves photodissociation of one η5-C5Me5 ligand from the parent complex, complemented by chlorine abstraction from another reactant molecule. Complexes 3b and 4a become formed via tether rearrangement, which starts with dissociating the tether Ti–C bond and is followed by rotating the tether, reattaching it subsequently through its available radical terminus.

The permethylcyclopentadienyl diphenylsilylene-bridged titanium constrained geometry complex [TiCl2{η5-C5Me4(SiPh2NCMe3-κN)}] (2) was synthesised following the common synthetic route and subsequently characterised by spectral analyses and by single-crystal X-ray diffraction. The comparison of its solid-state structure with that of the parent dimethylsilylene CGC complex [TiCl2{η5-C5Me4(SiMe2NCMe3-κN)}] (1) revealed only negligible geometry differences between their cyclopentadienyl centroid-Ti-N-Si skeletons. A significantly different positioning was however observed for the amine tBu substituent of the DFT-optimised methyl-substituted cationic catalytical species (1a, 2a), which are supposed to be generated from 1 and 2 in the presence of methylaluminoxane (MMAO). A lower ethylene polymerisation activity of 2-MMAO system compared to that of 1-MMAO is compatible with the higher steric congestion at the metallic centre due to the tBu ligand becoming rotated more into the open space in 2b. This arrangement aggravates monomer access throughout the catalytical process and decreases the coordination unsaturation of the central atom through the formation of auxiliary agostic interaction.

Thirty samples of the lacustrine sediments from three localities of the Most Basin including coal samples were studied by petrological and organic geochemical methods. The consistent results indicate the relatively stable surface development of the sediments in the environment of the Holesice, Lom and Osek Members. Biological material with contribution of microbial activity participated in the storing, which led to the formation of clayey coal. In the results of the chemical composition dominated sesqui-, diand triterpene compounds. Completely different sediments of Libkovice Member contained low proportions of small organic particles dispersed in the sediment. In the extracts of these samples prevailed hopanes, perylene and sulphur after the action of microorganisms. The base of the organic fraction also formed remains of terrestrial plants and liptinite macerals, especially alginite, liptodetrinite and bituminite that are typical for lacustrine sediments.

New titanocene dihydrosulfide compounds [(C 5 Me 4 CH 2 Ph) 2 Ti(SH) 2 ] ( 6 ) and [(C 5 Me 4 t -Bu) 2 Ti(SH) 2 ] ( 7 ) were obtained by addition of hydrogen sulfide to the corresponding doubly tucked-in titanocenes, and titanocene hydrosulfide compounds [(C 5 Me 4 CH 2 Ph) 2 TiSH] ( 8 ) and [(C 5 Me 4 t -Bu) 2 TiSH] ( 9 ) by H 2 S-induced protonolysis of σ-Ti–C bonds in [(η 5 -C 5 Me 4 CH 2 Ph)Ti(III)(η 5 :η 1 -C 5 Me 4 CH 2 - o -C 6 H 4 )] and [(C 5 Me 4 t -Bu)Ti(III)(η 5 :η 1 -C 5 Me 4 CMe 2 CH 2 )], respectively. The crystal structures of 6 , 8 , and 9 and electronic absorption spectra of 6 – 9 in hexane solution highly resemble those of corresponding [Cp* 2 Ti(SH) 2 ] ( 1 ) and [Cp* 2 TiSH] ( 2 ), however, compounds 6 and 7 strongly differ in their sensitivity to sunlight mutually and with respect to 1 . The sunlight photolysis of 6 in toluene proceeded similarly to the process described previously for 1 except that about three times longer exposition (300 h) was required to obtain the cyclopentadienyltitanium sulfide cage cluster [{(C 5 Me 4 CH 2 Ph)Ti} 4 S 6 ] ( 10 ) in 48% yield. In contrast, compound 7 photo-decomposed very efficiently to give compound 9 as the only isolated titanium-containing product in 87% yield. The formation of 10 can be accounted for the redox elimination of the cyclopentadiene followed by elimination of hydrogen sulfide in intramolecular condensation reaction whereas the formation of 9 requires the dissociation of SH radicals. Both the processes were recognized by Rosenthal and Beweries to concur in photodecomposition of [Cp* 2 Ti(OH) 2 ].

Five fossil resins from various localities in the Czech Republic were investigated. To arrive at more detailed description of the resins, pyrolysis-gas chromatography/mass spectrometry with derivatisation using tetramethylammonium hydroxide, gas chromatography-mass spectrometry, and micropetrography were applied. The content of organic macerals, composition of biomarkers in the solvent extracts and in the pyrolysates have been determined and compared to amber samples. The analyses clearly indicate that all resins belong to the Class Ib type derived from regular labdane structures that lacked succinic acid. The presence of labdane type diterpenoids and the absence of plant triterpenoids in the resin point to a conifer (gymnosperm) source which contrasts with the angiosperm source of Sarawak amber from Malaysia. According to their chemical composition, all Czech resins can be assigned to the Cupressaceae family. There was an obvious difference between a Duxite sample (Miocene) and other resins that could be attributed to deposition inside wood, which did not allow degradation of the resin.

article i nfo Numerous coalified tree stumps remained preserved in-situ in the so-called "Stump Horizon" (the palaeontologic horizon No.31), which represents clayey overburden of themain coal seam in the Bilina open cast mine in the Most Basin (Czech Republic). The petrological and chemical composition, palaeobotanical origin and preservation of 24 selected tree stumps were studied by optical and scanning electron microscopy and gas chromatography-mass spectrometry (GC-MS). Composition of the fossil wood is dominated by ulminite, particularly texto-ulminite B. Textinite forms up to 38 vol.% in the decomposed tree stumps. Corpohuminite dominates in bark and root tissues. Partly gelified and deformed woody tissuescontain both corpohuminite and resinite fillings.Randomreflectance of ulminite ranges from 0.33% to 0.39% and carbon content from 49 wt.% to 78 wt.%. Samples represent pure woody material with small admixtures of clay minerals, siderite, and very rare pyrite. Observations by scanning electron microscopy revealed various levels of deformed secondary xylem with more or less swollen cell walls, conspicuous tracheids, uniseriate rays of a different height, and round or cylinder-like resin or corpohuminite bodies. According to our results and other published data the wood might belong to Glyptostroboxylon and Taxodioxylon genera that are supposed to belong to Glyptostrobus and Quasisequoia plants respectively, representatives of the coniferous family Cupressaceae. The biomarker composition in the extracts of the fossil wood includes sesquiterpenoids (α-cedrane, drimane, eudesmane), diterpenoids (abietane, fichtelite, 16α(H)-phyllocladane) and their degraded compounds. The terpenoids are derived from precursors produced by the source plants and microorganisms. The terpenoid signatures support a relationship to the Cupressaceae family with input of microbial species. These characteristics were identical for all studied samples. Significant variations have been observed in sesquiterpenoid α-cedrane and diterpenoid 16α(H)-phyllocladane contents.

Exposures in the Bilina opencast mine provide a direct evidence that the 3.5 m thick upper bench of the Main Seam in the Most Basin passes over a distance of about a kilometre into a hundred metres thick equivalent of clastic deltaic sediments with Gilbert-type mouth bars and thus clearly corroborates the co-existence of lacustrine delta–mire system. Deposition of the delta and the upper bench of the Main Seam were affected by five short-term lacustrine incursions, possibly related to tectonic subsidence before final lacustrine transgression took place. Between the temporary lacustrine incursions, delta mouth bars prograded into an extensive mire being separated only by a shallow compaction lake along mouth bars foreland. However, most clastics, introduced from delta were caught by dense vegetation in a narrow proximal zone of mire and did not affect more distal parts of relatively dry woodland mire with water table fluctuating around the surface. It is therefore characterised by low ash yield and increased resinite, fusinite and inertodetrinite contents. Palynological data indicate that the peat-forming vegetation of the upper bench of the Main Seam was dominated by Taxodiaceae ( Glyptostrobus , Athrotaxis ) and Calamus palm accompanied by paludal species of the family Pinaceae and rich undergrowth of ferns and Vaccinium -type Ericaceae . Progradation of delta mouth bars to the proximity of the study section is documented by increasing proportion of allochthonous elements produced by plants colonizing the flood plain and delta plain areas ( Nyssa – Taxodium , Parrotia – Ulmus pyramidalis and Comptonia – Pinus oviformis associations). In contrast, during periods of temporary lacustrine transgressions the mire was replaced by open water environment, which favoured deposition of clay-rich coals or partings (> 30% of ash yield) of the flooding horizons in spite of fact that delta body retreated to the basin margin and the clastics were introduced from a larger distance. Rare palynomorphs indicate only sparse vegetation cover of aquatic plants during this time. Clay content seems to be the best indicator of the water level fluctuations. Facies indices (e.g. TPI and GI) show only poor correlation to hydrological and floristic changes detected in the mire–lake system.

Decamethylchromocene [Cr(η5-C5Me5)2] reacted with cyclopentadienyltitanium trichlorides [Ti(η5-C5H5-nMen)Cl3] (n = 0–5) in toluene to precipitate yellow finely crystalline ion pairs [Cr(η5-C5Me5)2]+[Ti(η5-C5H5-nMen)Cl3]− (1–6). Evidence for the chromocenium cation and titanate anions was obtained by paramagnetic 1H NMR spectra of 1–6 in CD2Cl2. The resonance of the cation was invariant at δ 6.9 ppm (Δν1/2 ~ 0.4 kHz) whereas resonances of the titanate anions were shifting in response to the number of methyl groups (δ 10.5–8.4 ppm (CpMe) and δ 26.6–39.0 ppm (CpH)). The presence of toluene of crystallization in 1–6 was observed by 1H NMR spectra, and in the crystal structure of 6. Crystallization of 6 from tetrahydrofuran afforded solvent-free crystals of 6A. In crystal structures of both 6 and 6A the [Ti(η5-C5Me5)Cl3]– titanate anion possessed shorter Ti–Cg distances and longer Ti–Cl bonds than the neutral species.

Emplacement mode and original shape and dimensions of a well exposed phonolite body in the Ceske středohoři Mountains (Czech Republic) were reconstructed using combined techniques of structural analysis of magmatic fabrics and columnar jointing together with analogue and thermal mathematical modeling of cooling for different shapes of experimental bodies. Phreatomagmatic rocks in the vicinity of some phonolite stocks in the area of interest suggest that the phonolite bodies were likely emplaced into maar-diatremes. Our modeling revealed that intrusion of magma into phreatomagmatic maar-diatreme craters can result in cryptodomes, extrusive domes, lava lakes or branched intrusions. The fabric and columnar jointing pattern of the selected phonolite body reveals best fit with an asymmetric extrusive dome emplaced into the maar crater. The scaling analysis and thermal modeling also suggest that the phonolite extrusion could have formed within 6–66 days and cooled to the background temperature after 10,000 years. Combined analogue and thermal modeling also revealed that the phonolite extrusions into maar-diatreme craters are marked by upper tier (collonade) of vertical columns and lower tier of curved and outward flaring columns. Both tiers in the phonolite extrusions are divided by a subhorizontal suture.

The singly tucked-in titanocene [Ti(η5-C5Me5)(η5:η1-C5Me4CH2)] (1) reacts smoothly with ethylene glycol or hydroquinone to give bis(titanoceneoxide) (TiIII) complexes [CH2OTi(η5-C5Me5)2]2 (2) and [(η5-C5Me5)2TiOC6H4OTi(η5-C5Me5)2] (3) containing dimethylene and 1,4-phenylene link, respectively. EPR spectra of 2 in 2-methyltetrahydrofuran glass and 3 in toluene glass revealed that the unpaired d1 electrons are in interaction to form triplet state molecules. The Ti–Ti distance derived from the zero-field splittings D for the two conformations of 2 (7.42 A and 7.66 A) are in good agreement with the Ti–Ti distance of 7.2430(7) A from the X-ray diffraction single-crystal analysis. For 3, however, the Ti–Ti distance derived from D (7.65 A) is by 1.47 A shorter than the crystallographic distance of 9.1230(8) A that indicates an enhancement of the through-space dipole–dipole interaction due to the presence of a conjugated quinonide link.

The new ansa -titanocene dichloride [{(SiMePh)(η 5 -C 5 H 4 ) 2 }TiCl 2 ] ( 1 ) was prepared by one pot reaction, whereas synthesis of its methylated analogue [{(SiMePh)(η 5 -C 5 Me 4 ) 2 }TiCl 2 ] ( 3 ) was performed in two steps with isolation of corresponding silane intermediate SiMePh(HC 5 Me 4 ) 2 ( 2 ). The reaction of 1 and 3 with TiCl 4 afforded the dinuclear complexes [(SiMePh){(η 5 -C 5 R 4 )TiCl 3 } 2 ] (R = H ( 4 ) and R = Me ( 5 )). The catalysts formed from 4 and 5 after their activation with excess MAO exhibited a modest activity in ethylene polymerization. The polymer products consisted of high molar mass linear polyethylenes with a broad molar mass distribution. The presence of three paramagnetic titanium species in the mixture 4 /MAO was revealed by EPR spectroscopy. All new prepared compounds 1 – 5 were characterized by multinuclear NMR, EI-MS, IR, and solid-state structures of 1 , 3 and 5 were determined by X-ray single crystal diffraction.

Elimination of methane during thermolysis of title compounds results in the formation of σ-Ti–C bond to t-butyl or benzyl group. The t-butyl-containing titanocene methyl compound [Ti(III)Me(η5-C5Me4t-Bu)2] (5) eliminates methane at 110 °C to give cleanly [Ti(III)(η5:η1-C5Me4CMe2CH2)(η5-C5Me4t-Bu)] (6). The methyl derivative of analogous benzyl-containing titanocene [Ti(III)Me(η5-C5Me4CH2Ph)2] was not isolated because it eliminated methane at ambient temperature to give [Ti(III)(η5:η1-C5Me4CH2-o-C6H4)(η5-C5Me4CH2Ph)] (7) with one phenyl ring linked to titanium atom in ortho-position. The corresponding titanocene dimethyl compound [TiMe2{η5-C5Me4t-Bu)}2] (9) eliminates two methane molecules at 110 °C to give the singly tucked-in 1,1-dimethylethane-1,2-diyl-tethered titanocene [Ti{η5:η1:η1-C5Me3(CH2)(CMe2CH2)}(η5-C5Me4t-Bu)] (11). In distinction, the analogous benzyl derivative [TiMe2(η5-C5Me4CH2Ph)2] (10) eliminates at 110 °C only one methane molecule to afford [TiMe(η5:η1-C5Me4CH2-o-C6H4)(η5-C5Me4CH2Ph)] (12) containing one phenyl group attached to titanium in o-position and one methyl group persisting on the titanium atom. This compound is stable at 150 °C for at least 3 h. The crystal structures of 5, 6, 7, and 10 were determined.

Thermolysis of [TiMe 2 (η 5 -C 5 Me 4 Ph) 2 ] ( 4 ) at 145 °C for 5 h afforded the singly tucked-in paramagnetic titanocene [Ti(III)(η 5 -C 5 Me 4 Ph){η 5 :η 1 -C 5 Me 3 Ph(CH 2 )}] ( 9 ). In distinction to the singly tucked-in permethyltitanocene [Ti(III)(η 5 -C 5 Me 5 ){η 5 :η 1 -C 5 Me 4 (CH 2 )}] ( 1 ) which was found crystallographically disordered [J.M. Fischer, W.E. Piers, V.G. Young, Jr., Organometallics 15 (1996) 2410] the single crystal X-ray diffraction analysis of 9 afforded molecular parameters with nearly by one order better precision as measured by esd-values.

Thermally stable zwitterionic complex [(η5-C5Me5)Ti(Ot-Bu)2](δ+)[(μ-Me)B(C6F5)3](δ−) (5) was formed by mixing equimolar quantities of [(η5-C5Me5)TiMe(Ot-Bu)2] and [B(C6F5)3]. The compound was recrystallized from hot toluene and has been stable so far for 1 year at ambient temperature in the solid state and in toluene solution. The 1H, 19F and 1D NOESY NMR spectra in C6D6 solution proved the inner sphere ion pair structure of 5. The X-ray crystal structure of 5 revealed that the bridging methyl group is σ-bonded to boron, and all its C–H bonds fulfil criteria for agostic bonding interaction with the titanium atom. In contrast to the stable solution in C6D6 compound 5 decomposed in CD2Cl2 solvent within hours at room temperature.

In the series of the methylated compounds (η5-C5H5−nMen)TiCl3 (n = 0–5) 1–6, linear correlations of λmax of the absorption band and δ 49,47Ti chemical shift with the number of Me groups were found. It is due to the dependence of both the magnitudes on the HOMO–LUMO energy gap which is influenced by electron donating methyl substituents. The catalysts made by combining 1–6 with MAO (molar ratio Al/Ti 500) showed only a gross dependence of decreasing activity with the number of methyl groups. For compounds (η5-C5Me4R)TiCl3 7–14 and (η5-C5H(1,2,3-)Me3R)TiCl3 15–20 where R = alkyl, silyl or phenyl no correlation between λmax and δ was found. Limited DFT calculations were performed to assign HOMO/LUMO orbitals involved. Crystal structures of 16 and 20 were determined and some other inspected to prove the absence of steric hindrance. The poor correlation of the spectroscopic properties with the catalytic activity is not surprising because steric effects of cyclopentadienyl ligands at cationic polymerization centers are generally anticipated.

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.

The [TiCl 2 (η 5 -C 5 Me 5 ) 2 ]/Mg excess /tetrahydrofuran system reacts with but-2-yne in excess to give paramagnetic (η 5 :η 1 -1,2,3,4-tetramethyl-5-(2,3,4,5-tetramethylpenta-2,4-dien-1,5-diyl-κC5)cyclopentadienyl)(η 5 -pentamethylcyclopentadienyl)titanium(III) ( 1 ) as the main product. The crystal structure of 1 shows a minimum steric hindrance between the methylated cyclopentadienyl ligands and non-coplanar conjugated double bonds in the C 5 tether.

Single tucked-in titanocene [Ti(η5-C5Me5)(η5:η1-C5Me4CH2)] adds to B(C6F5)3 to give the paramagnetic cationic complex [Ti(η5-C5Me5){η5-C5Me4CH2B(C6F5)3}] (1). Doubly tucked-in titanocene [Ti(η5-C5Me5){η3:η4-C5Me3(CH2)2}] reacts with B(C6F5)3 by one methylene group to give [Ti(η5-C5Me5){η5:η1-C5Me3(CH2)CH2B(C6F5)3}] (6). The crystal structure of 6 revealed that one hydrogen of the methylene group attached to boron agostically interacts with Ti(IV).

The five new silanes C5Me3RSiMenCl3 − n (n = 3, R = i-Pr (5); n = 2, R = i-Pr (6); n = 2, R = s-Bu (7); n = 2, R = cyclohexyl (8); and n = 3, R = t-Bu (9)) were synthesized by reaction of 1-alkyl-2,3,4-trimethylcyclopentadienyl lithium salts with appropriate chlorosilane and characterized by NMR, MS, and IR spectra. At elevated temperatures (250–360 K), all the silanes undergo a non-degenerate sigmatropic silyl rearrangement, which generates non-equivalent structures a and b. The presence of minor structure c was observed in compounds 5 and 7 only. The Diels–Alder cycloaddition of 5 with strong dienophiles tetracyanoethylene (TCNE), and dimethylacetylenedicarboxylate (DMAD) provides compounds 10 and 11, which confirmed isomers a and b, respectively. The free energy of activation of b → a isomerization for compounds 5–8 evaluated from variable temperature NMR spectra show only marginal influence of group R on the 1,2-silyl shift rate. Moreover, in compounds 5 and 7, the process b → a was found significantly faster than b → c process in the above-mentioned temperature range.

The ethene–styrene copolymerization has been investigated using the dimethylsilylene-bridged (amidocyclopentadienyl)dichlorotitanium(IV) complexes [TiCl 2 {η 5 -1-(SiMe 2 N t -Bu-κN)-2,3,4-Me 3 -5-R-C 5 }], where R = Me ( 1 ), H ( 2 ), Bu ( 3 ), Ph ( 4 ), 4-fluorophenyl ( 5 ), and but-2-en-2-yl ( 6 ) in combination with methylalumoxane (MAO) as catalysts. The nature of the substituent R strongly influenced the catalyst activity and selectivity and the copolymer microstructure and molecular weight. The catalysts derived from 1 to 3 were by about one order more active than those derived from 4 to 6 . At the optimum Al/Ti molar ratio of 900, the highly active catalysts produced a pseudo-random copolymer (95–97 wt.%) containing up to 47.8 mol% of incorporated styrene. The low-active catalysts gave mixtures of a pseudo-random copolymer (76–85 wt.%) with polyethene (10 wt.%) and polystyrene sequences (3–7 wt.%). The X-ray diffraction crystal structures of 2 and 4 were determined. Comparison of crystal structures of 1 and 2 versus 4 and 5 revealed a slightly shorter distances Ti–Cg (Cg – centroid of the cyclopentadienyl ring) and slightly larger Cl–Ti–Cl angles in 1 and 2 , indicating a higher electron density at the titanium atom. An electron attracting effect of phenyl or alkenyl substituents as well as their steric hindrance can account for a low catalytic performance of 4 – 6 /MAO catalysts.

Paramagnetic titanocene complexes containing the unsaturated carbyl group which consists of one and half molecule of 1,4-bis(trimethylsilyl)buta-1,3-diyne (BSD) are formed by the reduction of titanocene dichlorides with one molar equivalent of magnesium in the presence of 1.5 molar equivalent BSD in tetrahydrofuran (THF) for titanocene moieties Ti(η5-C5H5 − nMen)2 (n = 5 (1), 4 (2), and 3 (3)) and Ti{Me2Si(η5-C5Me4)2} (4). The non-methylated titanocene moiety affords under identical conditions known diamagnetic bis(η5-cyclopentadienyl)-2,4-bis(trimethylsilylethynyl)-3,5-bis(trimethylsilyl)titanacyclopenta-2,4-diene (5) as the major product. Crystal structures of 3 and 4 show the same bonding scheme for the 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl ligand as previously found for compound 1 [P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, A. Spannenberg, K. Mach, U. Rosenthal, Chem. Commun. (1999) 2505]. Compound 1 is stable against weak proton donors like methanol or alk-1-ynes even at 90 °C, however, it undergoes retroreaction when oxidized by PbCl2 in THF, yielding nearly quantitatively BSD and [TiCl2(η5-C5Me5)2].

Bis{η5-(N,N-dimethylaminodimethylsilyl)tetramethylcyclopentadienyl}dichlorotitanium(IV), [TiCl2{η5-C5Me4(SiMe2NMe2)}2] (1), reacts with sulfane under cleavage of both Si–N and Ti–Cl bonds to give sulfido-tethered titanocene compound bis{η5-1,2,3,4-tetramethyl-5-(dimethylsilylsulfido-κS)cyclopentadienyl}titanium(IV), [Ti{η5-C5Me4(SiMe2S- κS)}2] (4), and dimethylamine hydrochloride as the byproduct. The crystal structure of compound 4 has been determined by single-crystal X-ray diffraction.

Reduction of methyl-substituted titanocene dichlorides bearing pendant double bonds [TiCl2{η5-C5Me4(CH2CMeCH2)}2] (1) and [TiCl2{η5-C5Me4(SiMe2(CH2)2CHCH2)}2] (2) with magnesium yielded diamagnetic Ti(IV) compound [Ti{η1:η1:η5-C5Me3(CH2)(CH2CH(Me)CH2)}{η5-C5Me4(CH2C(Me)CH2)}] (4) and paramagnetic Ti(III) compound [Ti{η5-C5Me4(SiMe2CH2CHCHMe)}(μ-η3,η1:η5,η1(Ti:Mg){C5Me3(CH2)(SiMe2CHCHCMe)})Mg(OC4H8)2] (6), respectively. The reluctance of titanocene intermediates to undergo intramolecular cyclization to cyclopentadienyl-ring-tethered titanacycles (as typically observed) can be explained by a shortness of the 2-methylallyl group and steric hindrance of its double bond in the former case and, in the latter case, by an attack of magnesium on the titanocene intermediate, faster than cyclization reactions. The crystal structures of 4 and 6 were determined by single-crystal X-ray diffraction.

Paramagnetic complexes ansa-[Ti(C CCMe3){η5:η5-C5Me4SiMe2CH CHCH2CH2SiMe2C5Me4}] (1) and ansa-[Ti(OH){η5:η5-C5Me4SiMe2CH2CH CHCH2SiMe2C5Me4}] (2) were prepared by reactions of ansa-[Ti(III){η3:η5:η5-C5Me4SiMe2CHCHCHCH2SiMe2C5Me4}] (3) with t-butylethyne or water, respectively. The X-ray single crystal diffraction analysis of 1 and 2 showed that the cis-double bond is situated asymmetrically in the ansa-bridge of 1 whereas, in 2, the double bond is trans, and lies in the bridge centre. ESR and UV-near IR spectra indicated a weaker oxygen π-electron donation into the Ti–O bond of 2 compared to analogous methoxide ansa-[Ti(III)(OMe){η5:η5-C5Me4SiMe2CH2CH CHCH2SiMe2C5Me4}] (4) or decamethyltitanocene hydroxide (5).

An easy and inexpensive three-step synthesis of new 2,3-dimethyl-1,4-diphenylcyclopentadiene (3) ligand and the titanium and zirconium homometallocene dichlorides [TiCl2(η5-C5H-2,3-Me2-1,4-Ph2)2] (4), [ZrCl2(η5-C5H-2,3-Me2-1,4-Ph2)2] (5), and the mixed ligand zirconium complex [ZrCl2(η5-C5H-2,3-Me2-1,4-Ph2)(η5-C5H5)] (6) prepared thereof are described. The polymerization of ethene using 4–6/MAO catalysts revealed that zirconocene complexes 5 and 6 displayed moderate and high activity, respectively, whereas the titanium catalyst 4/MAO was inactive. The crystal structures of 4 and 5 were determined by X-ray crystallography.

Fully methylated titanocene hydroxide [Ti(OH) (η5-C5Me5)2] (1) was obtained by the reaction of single tucked-in decamethyltitanocene [Ti(η5-C5Me5){η5:η1-C5Me4(CH2)}] (2) with one equivalent of water dissolved in toluene. The X-ray single crystal diffraction of 1 revealed the bent Ti–O–H bonds (112(4)°) where the oxygen atom is only 0.038(4) A away from the Cg(1), Ti, Cg(2) (Cg – centroid of the cyclopentadienyl ring) plane, and the hydroxyl bond is directed to the cyclopentadienyl ring C(1–5). The Ti–O bond length (1.889(2) A) and energy of 1a1→b2 transition (6770(50) cm−1) indicate that the π-donation effect of the hydroxyl group is weaker compared to alkoxy groups.

Two novel half-sandwich Ti(IV) complexes, [η5:η1-O-C5(CH3)4CH2CH2OCH3]TiCl3 (3) and (η5:η1-P-C5H4CH2CH2PPh2)TiCl3 (6), were prepared and structurally characterised. At elevated temperatures, complex 3 undergoes a conversion into [η5:σ-C5(CH3)4CH2CH2O–]TiCl2 (4). The dynamic behaviour of complexes 3 and 6 in solutions has been studied by variable-temperature 1H, 13C and 31P NMR spectroscopy. Thermodynamic parameters of the intramolecular dissociation-coordination processes for 3 and 6 were elucidated by the numerical analysis of the δ(T) dependencies. The intramolecular M(IV)←E (M=Ti, Zr; E=O, P) coordination in half-sandwich cyclopentadienyl complexes is discussed.

The η3:η4-allyldiene-(η5-cyclopentadienyl)titanium(II) complex [Ti(η5-C5Me5){η3:η4-C5Me3(CH2)2}] (1) reacts with three molar equivalents of substituted propargylic alcohols FcCCCMe2(OH) (2a) and PhCCCH2OH (2b) at elevated temperature to give (η5-pentamethylcyclopentadienyl)titanium(IV) alkoxides [Ti(η5-C5Me5)(FcCCCMe2O-κO)3] (3a) and [Ti(η5-C5Me5)(PhCCCH2O-κO)3] (3b), respectively. The crystal structure of 3a has been determined by single-crystal X-ray diffraction.

Fully methylated η3:η4-allyldiene(η5-cyclopentadienyl)titanium(II) (1) reacts with alkynylketones RCCC(O)Me (R=SiMe3 (3a) and ferrocenyl (3b)) to give the expected products of the CO group insertion into one Ti–CH2 bond 4a and 4b, respectively. Compound 4a could not be isolated in pure form due to its high solubility; a minor product of two-fold addition (5) was isolated instead. Complex 5, formally [ 1 +2 3a ], was characterized as a monocyclopentadienyl bis(alkoxy)organyl complex, where the alkoxyorganyl ligand arises from CO insertion into one Ti–CH2 and the Ti–C(cyclopentadienyl) bonds. The structures of compounds 4b and 5 were determined by single-crystal X-ray diffraction.

Reduction of isomeric, fully-substituted titanocene dichlorides having a pendant double bond, [TiCl2(η5-C5Me4R)(η5-C5Me5)] (R=CH2CH2CHCH2 (1); R=CH(Me)CHCH2, (2)), with magnesium in THF in the presence of bis(trimethylsilyl)ethyne (btmse) affords different products depending on the alkenyl chain length. Whereas the reduction of 1 yields a compound with intramolecularly η2-coordinated double bond, [Ti(η5-C5Me5){η2:η5-C5Me4(CH2CH2CHCH2)}] (3), compound 2 affords under identical conditions a product with two new TiC bonds, [Ti{(η1:η1:η5-C5Me3(CH2)(CH(Me)CH2CH2)}(η5-C5Me5)] (4). The formation of 3 can be rationalized as a simple intramolecular stabilization of a titanocene intermediate formed by reductive removal of the chloride ligands. The formation of 4 from the respective titanocene, however, requires formally an activation (oxidative addition) of one CH bond at the methyl group adjacent to the unsaturated chain followed by a hydrogen shift (hydrometallation). Under similar conditions, the complex with asymmetric unsaturated ansa-bridge [TiCl2{η5:η5-C5Me4CH2CHCH(CH2)5C5Me4}] (5) is reduced to a titanocene–η2-alkene complex with the double bond shifted to the central position, ansa-[Ti{η2:η5:η5-C5Me4(CH2)3CHCH(CH2)3C5Me4}] (7). In the absence of btmse, analogous complex with saturated bridge ansa-[TiCl2{η5:η5-C5Me4(CH2)8C5Me4}] (6) undergoes a hydrogen abstraction to give 7 as well albeit in a lower yield. The reduction of 6 in the presence of btmse gives η2-alkyne complex ansa-[Ti{η5:η5-C5Me4(CH2)8C5Me4}(η2-Me3SiCCSiMe3)] (8) which is converted upon thermolysis at 150 °C to a mixture of asym- and sym-isomers of the doubly tucked-in complex ansa-[Ti{(η3:η4-C5Me2(CH2)2)(CH2)8(η5-C5Me4)}] (9) in 2:1 ratio; no CH activation involving methylene groups of the ansa tether was observed. The crystal structures of 4, 7, and 8 have been determined by X-ray crystallography.

Reduction of fully substituted titanocene dichlorides [TiCl2(η5-C5Me4R)2] (R=SiMe2CH2CH2Ph, 3; SiMe2Ph, 4; and SiMePh2, 5) with magnesium in THF proceeds via the formation of titanocene monochlorides [TiCl(η5-C5Me4R)2] 6–8 to afford monomeric titanocenes, [Ti(η5-C5Me4R)2], 9–11. Titanocene monochlorides give the expected EPR spectra in toluene solution and glass. The structure of 7 was further corroborated by single-crystal X-ray diffraction. Titanocenes 9–11 are EPR silent down to −196 °C but exhibit paramagnetic broadening of the signals in solution NMR spectra. The positions of the NMR signals are temperature-dependent, obeying the Curie Law in the range investigated (0–60 °C). As revealed by X-ray crystallography, titanocenes 9 and 11 possess bent metallocene structures with the cyclopentadienyl rings tilted at an angle of 9.8(1) and 14.4(2)°, respectively. Titanocenes 9–11 are easily oxidized with PbCl2 to the parent dichloride complexes 3–5. Titanocenes 9 and 10 react with bis(trimethylsilyl)ethyne (btmse) only in large excess of the alkyne to give an equilibrium concentration of the respective [Ti(η5-C5Me4R)2(η2-Me3SiCCSiMe3)] complexes. On the other hand, titanocene 11 does not observably react with btmse.

Reduction of dichloro-{1,3-bis(η 5 -tetramethylcyclopentadienyl)-1,1,3,3-tetramethyldisiloxane}titanium(IV), [TiCl 2 {η 5 :η 5 -(C 5 Me 4 SiMe 2 ) 2 O}] ( 1 ), with magnesium in the presence of bis(trimethylsilyl)ethyne affords the ansa -[Ti{η 5 :η 5 -(C 5 Me 4 SiMe 2 ) 2 O}(η 2 -Me 3 SiCCSiMe 3 )] ( 2 ) complex in high yield. Compound 2 is thermally robust, decomposing at 170 °C in high vacuum with liberation of 1,2-bis(trimethylsilyl)ethene to give predominantly an asymmetric, allydiene complex ansa -[Ti{(η 5 -C 5 Me 4 )SiMe 2 OSiMe 2 {η 3 :η 4 -C 5 Me 2 (CH 2 ) 2 }] ( 3 ) as a result of twofold CH bond activation. Crystal structures of 2 and 3 were determined by X-ray diffraction.

The paramagnetic compounds exo,exo-bis(η5-isodicyclopentadienyl)chlorotitanium(III) (3) and its analogue with trimethylsilyl-substituted isodicyclopentadienide (isodiCp) ligand (4), and the similar pair of diamagnetic exo,exo-bis(isodicyclopentadienyl)[η2-bis(trimethylsilyl)ethyne]titanium(II) complexes 5 and 6 were obtained by common reduction procedures from exo,exo-bis(isodicyclopentadienyl)titanium(IV) dichloride (1) and exo,exo-bis[η5-2-(trimethylsilyl)isodicyclopentadienyl]titanium(IV) dichloride (2), respectively. As indicated by ESR spectroscopy compound 3 is a dimer in the solid state and in frozen toluene glass but monomeric in toluene solution. Compound 4 is monomeric in solution as well as in the solid state. As judged from the red shift of the ν(CC) vibration, compound 6 binds bis(trimethylsilyl)ethyne more strongly than compound 5. A comparison of their wavenumbers with those of the [Ti(C5H5−nMen)2(η2-Me3SiCCSiMe3)] (n=2–5) complexes shows that Lewis acidity of the central titanium atom decreases in the order of ligands 1,3-dimethylcyclopentadienyl>isodiCp∼1,2,3-trimethylcyclopentadienyl>(trimethylsilyl)isodiCp∼tetramethylcyclopentadienyl. The crystal structure of the most bulky complex 6 shows a bis-lateral (anti) conformation of the isodiCp ligands with the π-coordinated five-membered rings nearly eclipsed.

A series of three ansa-titanocene monochlorides containing η5-tetramethylcyclopentadienyl ligands bridged by five- or eight-membered aliphatic chains were prepared via reduction of the corresponding dichlorides with half molar equivalent of magnesium and characterized by spectral methods. The solid-state structures of the monochloride complexes ansa-[TiCl{η5:η5-C5Me4CH(Me)CH2CH2CH(Me)CH(Me)C5Me4}] (1a) and ansa-[TiCl{η5:η5-C5Me4(CH2)3CH(Me)CH(Me)CHCHCH2C5Me4}] (4a), and of the bridge-unsaturated titanocene dichloride complex ansa-[TiCl2{η5:η5-C5Me4CH2CHCH(CH2)5C5Me4}] (3) were determined by single-crystal X-ray diffraction. All the compounds show bent metallocene structures with the ansa-chain situated in a side position with respect to Cg, Ti, Cg (Cg=centroid of the cyclopentadienyl ligand) plane. Angles subtended by the least-squares planes of the cyclopentadienyl rings and conformation of the ansa-chains indicates the absence of steric strain in the metallocene framework.

Bis{η5-(N,N-dimethylaminodimethylsilyl)tetramethylcyclopentadienyl}dichlorotitanium(IV), [TiCl2{η5-C5Me4(SiMe2NMe2)}2] (1), easily undergoes hydrolytic cleavage of the Si–N bonds to give dimethylamine and {1,3-bis(η5-tetramethylcyclopentadienyl)-1,1,3,3-tetramethyldisiloxane}dichlorotitanium(IV), ansa-[TiCl2{(η5-C5Me4SiMe2)2O}] (2), in almost quantitative yields. The crystal structures of compounds 1 and 2 were determined by single-crystal X-ray diffraction.

Titanocene complexes [Ti(η 5 -C 5 H 5− n Me n ) 2 (η 2 -Me 3 SiCCSiMe 3 )] ( n =0, 4 and 5) react uniformly with siladiynes R 2 2 Si(CCR 1 ) 2 , where R 1 =Ph, and R 2 =Ph or Me, at elevated temperature in hydrocarbon solvents to give the corresponding silacyclobutene-annelated titanacyclobutene complexes, 3-bis(η 5 -cyclopentadienyl)titana-6-diorganylsilabicyclo[2.2.0]hexa-1(2),4(5)-dienes, [(η 5 -C 5 H 5− n Me n ) 2 Ti{R 1 2 C 4 (SiR 2 2 )}]. Products arising from [Ti(η 5 -C 5 H 5− n Me n ) 2 (η 2 -Me 3 SiCCSiMe 3 )] ( n =0, 2 (1,3-isomer), 4 and 5) and Me 2 Si(CCCMe 3 ) 2 vary with n : the non-methylated titanocene complex affords a mixture of an analogous silacyclobutene-annelated titanacyclobutene and [{Ti(η 5 -C 5 H 5 ) 2 } 2 {μ-η(3–5):η(4–6)-Me 3 CCCCCCMe 3 }], the permethylated titanocene precursor gives mainly the allyldiene complex [Ti(η 5 -C 5 Me 5 )(η 3 :η 4 -C 5 Me 3 (CH 2 ) 2 )] while no titanium-containing product could be isolated for n= 4. The reaction of [Ti(η 5 -1,3-C 5 H 3 Me 2 ) 2 (η 2 -Me 3 SiCCSiMe 3 )] with Me 2 Si(CCCMe 3 ) 2 , however, cleanly affords the expected silacyclobutene–titanacyclobutene complex. All complexes were studied by spectral methods and solid-state structure of two representatives, [(η 5 -C 5 Me 5 ) 2 Ti{Ph 2 C 4 (SiMe 2 )}] and [(η 5 -1,3-C 5 H 3 Me 2 ) 2 Ti{(Me 3 C) 2 C 4 (SiMe 2 )}] was determined by single-crystal X-ray diffraction.

We have studied the fabrication and properties of the Cu+-containing waveguides. These waveguides were fabricated in a special soda-lime silicate glass as well as in commercial optical glass substrates, by using an ion exchange in the melts containing either Cu+ or Cu2+, at temperatures from 350°C to 500°C, and for periods from 5 min to 21 h. The optical properties of the fabricated waveguides were characterized using both mode and photoluminescence spectroscopy. The composition of waveguiding layers was studied using Rutherford Backscattering Spectrometry (RBS) and ESCA. The presence of divalent copper was determined using Electron Paramagnetic Resonance (EPR). After ion exchange, the refractive index increased, depending on the fabrication conditions, up to Δn=+0.0693, and the waveguides supported up to 16 TE and TM modes. The depths of the fabricated waveguides varied between 6.0 and 27.5 μm. The most intensive blue-green luminescence was achieved with the samples that were ion-exchanged in the Cu2Cl2·ZnCl2 melt, where the presence of Zn2+ strongly impeded the oxidation of Cu+ to Cu2+. Both oxidation states of copper (Cu+ as well as Cu2+) were found in the waveguides fabricated in the pure Cu2Cl2. The main advantage of the copper-containing waveguides is the possibility of integrating the passive and active functions of the waveguides on the same substrate.

The titanocene–bis(trimethylsilyl)acetylene (BTMSA) complexes Cp′2Ti[η2-C2(SiMe3)2] (Cp′C5H5−nMen; n=0–5) react with acetone azine Me2CNNCMe2 (AA) in two different ways depending on the number of Me substituents at the Cp′ ligands (n). For n=0–2, BTMSA is replaced by AA, which then undergoes an oxidative addition accompanied by a proton transfer, affording titana-2-isopropyl-4-methyl-2,3-diazacyclopent-3-ene complexes A0–A2. For n=3–5, replacement of the acetylene is followed by the splitting of AA to give either (C5Me5)2Ti(III)(NCMe2) (C5) or the Ti(IV) (Cp′A)2Ti complexes B3 and B4 for n=3 and 4, respectively. The intramolecularly bridging Cp′A ligand 1-(η5-2,3,5-trimethylcyclopentadienide)-2-(η1-amide)-2,2′-dimethylethane arises from a formal insertion of the CN bond of isopropylidene amide into a CH bond of one methyl group of the cyclopentadienyl ligands before or after splitting of AA. Crystal structures of C5 and (η5:η1-C5HMe3CH2CMe2NH)2Ti(IV) (B4) were determined.

The reduction of (C5Me4Ph)2TiCl2 by magnesium in tetrahydrofuran affords a mixture of the diamagnetic doubly tucked-in titanocene complex (C5Me4Ph)[C5Me2(CH2)2Ph]Ti (1), the paramagnetic trinuclear Ti–Mg–Ti hydride bridged complex [(C5Me4Ph)2Ti(μ-H)2]2Mg (2) and the paramagnetic binuclear titanocene hydride–magnesium hydride complex (C5Me4Ph)[C5Me4(o-C6H4)]Ti(μ-H)2Mg(THF)2 (3). The X-ray diffraction analysis of 3 revealed that the magnesium atom forms the σ-bond to the ortho-carbon atom of one of the phenyl rings and binds 2 molecules of THF.

The reduction of {[η8-1,4-(SiMe3)2C8H6]Ti(μ-Cl)}2(THF) by magnesium in the presence of bis(trimethylsilyl)acetylene in tetrahydrofuran affords diamagnetic bis[μ-η5:η5-1,4-bis(trimethylsilyl)cyclooctatetraenetitanium](Ti–Ti) (1) in low yield. The X-ray crystal analysis of 1 revealed that bridging cyclooctatetraene ligands in the centrosymmetric dimer are concave-bent. An extremely short Ti–Ti distance of 2.326(2) A is compatible with the presence of a double Ti–Ti bond.

Redox properties of the substituted zirconocene dichlorides: (C 5 H 5− n Me n ) 2 ZrCl 2 ( n =0–5), [C 5 H 5− n (SiMe 3 ) n ] 2 ZrCl 2 ( n =0–3), [C 5 Me 4 (SiMe 3 )](C 5 HMe 4 )ZrCl 2 and two ansa -analogues Me 2 Si(C 5 H 4 ) 2 ZrCl 2 and Me 2 Si[C 5 H 2 (SiMe 3 ) 2 ] 2 ZrCl 2 were investigated by cyclic voltammetry on a mercury electrode in tetrahydrofuran. In the (C 5 H 5− n Me n ) 2 ZrCl 2 ( n =0–4) compounds, standard electrode potential ( E °) of the one-electron uptake shifts to more negative values by 0.071 V per one methyl group. A deviation from this linear dependence to a less negative E ° is observed for (C 5 Me 5 ) 2 ZrCl 2 . This effect is attributed to the steric hindrance between rotating C 5 Me 5 ligands which tends to decrease the angle between the cyclopentadienyl ring planes ( φ ) and consequently, the energy difference between MO frontier orbitals. In the trimethylsilylated compounds, the net effect of SiMe 3 is negligible, giving virtually the same value of E ° for n =0–3. In μ-SiMe 2 -bridged ansa -compounds the difference in E ° of 147 mV corresponds to the negative shift of 37 mV per one SiMe 3 group. Owing to the rigid angle φ , this shift can be tentatively accounted for the electronic effect of the SiMe 3 groups. In the non- ansa -compounds, the negative shift due to the electronic effect of SiMe 3 groups is assumed to be roughly compensated by a positive shift resulting from a sterically controlled diminution of φ .

The reaction between equimolar quantities of TiCl 3 (THF) 3 and 1,4-bis(trimethylsilyl)cyclooctatetraene dianion (COT″) yields a mixture of (COT″) 2 Ti ( 1 ), [(COT″)Ti] 2 (μ-Cl) 3 ( 2 ) and [(COT″)Ti(μ-Cl)] 2 (THF) ( 3 ). Crystalline 2 and 3 were isolated on the basis of different solubility in hexane. Their X-ray diffraction analyses revealed dimeric structures linked by chlorine bridges. In 3 , only one of the Ti atoms coordinates one molecule of THF. The mixed-valency Ti(III)/Ti(IV) compound 2 shows an ESR spectrum typical of mononuclear (COT″)Ti(III) complexes. The ESR spectra of 3 in toluene or 2-methyltetrahydrofuran glasses prove the triplet state of coupled Ti(III) d 1 electrons.

Methyl-substituted titanocene dichlorides (C5H5−nMen)2TiCl2 (n=0–5), [C5Me4(SiMe3)]2TiCl2, (C5Me4Ph)2TiCl2 (Ph=phenyl), [C5Me4(FPh)]2TiCl2 (FPh=para-fluorophenyl), [C5Me4(CH2Ph)]2TiCl2 and ansa-compounds Me2Si(C5H4)2TiCl2 and Me2Si(C5Me4)2TiCl2 were investigated by means of cyclic voltammetry at a mercury electrode in tetrahydrofuran. The standard potential (E°1) of the first electron uptake shifts to more negative values proportionally to the number of methyl groups in the (C5H5−nMen)2TiCl2 (n=0–3) compounds, with an increment of 0.093 V per one methyl group. A decline from this linear dependence is observed for (C5HMe4)2TiCl2 and a positive shift for (C5Me5)2TiCl2. The [C5Me4(R)]2TiCl2 (R=SiMe3, Ph, FPh and CH2Ph) compounds show even larger positive shifts of E°1. These positive shifts can be brought about by a steric strain between the cyclopentadienyl ligands which lowers the dihedral angle between cyclopentadienyl ring planes (φ) and thus decreases energies of bent titanocene 1a1 and b2 LUMO orbitals. This opinion is corroborated by the voltammetry of ansa-compounds Me2Si(C5H4)2TiCl2 and Me2Si(C5Me4)2TiCl2, having a large and fixed angle φ. Their E°1 values are close to those of (C5H5)2TiCl2 and (C5HMe4)2TiCl2, respectively.

Addition of excess ferrocenylacetylene (FcCCH) to [η 5 -(C 5 H 5 )Ti][μ:η 2 :η 2 -C 2 (SiMe 3 ) 2 ] 2 [η 5 -(C 5 H 5 )Mg] ( 1 ) affords the novel ferrocene–pseudotitanocene complex [η 5 -1,2,5,6-tetrakis(trimethylsilyl)-4-ferrocenylcyclohexa-1,4-dienyl](η 5 -cyclopentadienyl)titanium(II), [η 5 -(Me 3 Si) 4 FcC 6 H 2 ]Ti(η 5 -C 5 H 5 ) ( 2 ), as the sole isolated titanium-containing product. Its structure was established by EI MS, NMR and UV–vis spectroscopy. The formation of 2 follows the general reaction route of terminal acetylenes with 1 .