Magnesium In THF Research Articles

Protolysis of five-membered metallacyclocumulene complexes of zirconocene and hafnocene

The reactions of the five-membered metallacyclocumulene complexes Cp2M[η4ButC4But] (M = Zr, Hf) with an equimolar amount of HCl in dioxane at 20 °C result in linear complexes Cp2M(Cl)–C(But)=CH–CCBut, whereas the reaction with an excess of HCl affords Cp2MCl2 and trans-ButCH=CH–CCBut. The reaction of the latter hydrocarbon with an equivalent amount of the bis(trimethylsilyl)acetylene complex of zirconocene Cp2Zr(Me3SiC2SiMe3)(Py) leads to bis(trimethylsilyl)acetylene and a five-membered zircona-cycloallene complex. This complex can also be obtained in ‘one-pot’ via the reactions of five-membered zircona-cyclocumulene with two equivalents of HCl and subsequent treatment with magnesium in THF.

3 a,6 a-Diaza-1,4-Diphosphapentalenes: Synthesis and Complexation with the Organic π-Acceptor 1,2,4,5-Tetracyanobenzene.

The reaction of PCl3 with diethyl ketazine and 4-phenylcyclohexanone azine results in the formation of 1,4-dichloro-3a,6a-diaza-1,4-diphosphapentalenes which were reduced by magnesium in THF to give corresponding diazadiphosphapentalenes EtMeDDP and PhcHexDDP, containing two-coordinate phosphorus atoms. According to the CVA data, the new diazadiphosphapentalenes are strong electron donors showing oxidation peak potentials at 0.34 and 0.10 V, respectively, (vs. Ag/AgCl). Interaction of 1,2,4,5-tetracyanobenzene (TCNB) with the obtained diazadiphosphapentalenes in any stoichiometry produces sandwich complexes of the composition DDP-TCNB-DDP. Black-purple crystals of π-complexes contain infinite molecular chains with short P⋅⋅⋅P contacts between DDP molecules and short (Csp2 -H⋅⋅⋅N) contacts between TCNB molecules. Calculations showed that each TCNB molecule is an acceptor of ∼0.3e from two DDP molecules. Estimation of the HOMO-LUMO gap from the onset of optical absorption give values of 1.25 eV and 1.31 eV for [(EtMeDDP)2 (TCNB)] and [(PhcHexDDP)2 (TCNB)] respectively.

Isolation of a 1-Magnesium-2,3-disilacyclopropene and a Related Bis(disilenide).

Herein we report the first synthesis of a 1-magnesium-2,3-disilacyclopropene and a related bis(disilenide). Reduction of (boryl)tribromosilane (1, boryl = (HCArN)2B, Ar = 2,6-iPr2C6H3) with magnesium in THF afforded boryl-substituted magnesium complex [(boryl)Si]2Mg(THF)3 (2) in good yield, whereas reduction of (boryl)trichlorosilane (3) with KC8 in THF led to the isolation of bridged alkoxy alkyl bis(disilenide) (THF)K(boryl)Si═Si(boryl)O(CH2)4(boryl)Si═Si(boryl)K(THF) (4) via ring opening of a THF molecule. X-ray diffraction analysis of 2 confirmed the presence of the novel Si2Mg three-membered ring as well as the Si═Si double bond, which existed in a noticeably twisted B-Si-Si-B array. Complex 2 also represents the first reported example of a stable disilyne dianion.

Synthesis of 5-(dimethylsilyl)pentylalkylferrocene-grafted HTPB (alkylFc-HTPB) via platinum-catalyzed hydrosilylation

In this work, at first alkylferrocene derivatives were synthesized according to procedure described in the literature. (5-Chloropentanoyl)ferrocene derivatives were prepared by Friedel–Crafts acylation of ferrocene and alkylferrocene derivatives with 5-chloropentanoyl chloride in dichloromethane, and AlCl3 was used as catalyst. The corresponding 5-chloropentylferrocene derivatives were synthesized from reduction of these products by NaBH4 in diglyme at 0 °C. Finally (5-alkylferrocenylpentyl)dimethylsilane was synthesized from reaction of 5-chloropentylferrocene derivatives with magnesium in THF and reaction of corresponding Grignard reagents with chlorodimethylsilane in 82–87% yields. 1H and 13C NMR, FT-IR spectroscopy supported the predicted structure of the product. Nine samples of alkylferrocene-grafted hydroxyl-terminated polybutadiene (alkylFc-HTPB) derivatives, containing different percent of iron, were synthesized by hydrosilylation reaction of [5-(alkylferrocenyl)pentyl]dimethylsilane with hydroxy-terminated polybutadiene (HTPB), in the presence of catalytic amount of the hexachloroplatinic acid (Speier’s catalyst). FT-IR spectroscopy was utilized to follow the progress of the reaction, by monitoring the loss of the Si–H absorption at 2110 cm−1, and the reaction was completed in 24 h. Some properties of resulting prepolymer like viscosity, glass transition temperature and iron percentage as important parameters in production of composite propellants were investigated. For example, the viscosity increased with increasing iron content because of the greater extent of ferrocene grafting in the polymer.

Addition of phenylacetylene to a magnesium complex of monoiminoacenaphtheneone (dpp-mian).

In the presence of formic acid, acenaphthenequinone (AQ) reacts with one molar equivalent of 2,6-diisopropylaniline in toluene to give monoiminoacenaphtheneone (3, dpp-mian) in good yield. Reduction of compound 3 with an excess of magnesium in thf results in green crystalline amido-alcoholate [(dpp-mian)Mg(thf)2]2 (4). Crystallization of complex 4 from toluene affords a blue tetramer [(dpp-mian)Mg(thf)]4 (5). Reactions of compounds 4 and 5 with phenylacetylene proceed with C-C bond formation between the alkyne and the dpp-mian ligand to give the monomeric alkynyl-magnesium derivative [(dpp-mian)(PhC=CH2)Mg(C≡CPh)2(thf)]2 (7). Hydrolysis of complex 5 gives metal-free dpp-mian(PhC=CH2)H (8). Reaction of 7 with acetylacetone yields [{dpp-mian(PhC=CH2)}Mg(acac)]2 (9). Compounds 3-5 and 7-9 have been characterized by IR and NMR spectroscopy; molecular structures of 3, 5, 7, 8 and 9 have been determined by single crystal X-ray analysis.

Microwave-Assisted Efficient One-Pot Synthesis of 9-Phenyl-9,10-disilatriptycene and Its Bridgehead Functionalization

9-Phenyl-9,10-disilatriptycene (2) was synthesized by the reaction of bis(2-bromophenyl)silane (1) with magnesium in THF. On conventional heating, 2 and cis-9,10-diphenyl-9,10-dihydro-9,10-disilaanthracene (cis-3) were obtained in 31% and 36% yields, respectively. However, the yield of 2 was significantly increased to 71% on microwave irradiation. Theoretical calculations suggest that the intermediary Grignard reagents generated from trans- and cis-9,10-diaryl-9,10-dihydro-9,10-disilaanthracenes have quite different reactivity for construction of the 9,10-disilatriptycene skeleton. The bridgehead Si–H moiety of 2 was readily functionalized to give several 9,10-disilatriptycene derivatives.

Synthesis of Styrene Monomers Hydroxyl Functionalized

Bifunctional monomers provide the possibility of preparing new polymeric and nano structures such as random or graft copolymers. These materials can potentially be used as surfactants or coupling agents in polymeric blends, especially where each functionality in the monomer has different chemical properties. This article describes the organic synthesis of bifunctional monomers derived from styrene through the Grignard reaction with aldehydes and ketones. The Grignard reagent was synthesized from 4-bromostyrene and magnesium in THF. At the end of the synthesis four different bifunctional monomers were obtained bearing two terminal substituents: a vinyl and a hydroxyl group. These monomers were obtained in high yield and purity. The reactivities of the monomers were probed via the random copolymerization of one of these monomers with styrene and acrylonitrile.

Ethene Complexes of Bulky Titanocenes, Their Thermolysis, and Their Reactivity toward 2-Butyne

Ethene complexes of titanocenes [Ti(II)(η2-C2H4)(Cp′)2] for Cp′ = η5-C5Me5 (1), η5-C5Me4t-Bu (2), η5-C5Me4SiMe3 (3), and η5-C5HMe4 (4) were prepared by reduction of corresponding titanocene dichlorides with magnesium in THF in the presence of ethene. Thermolysis of 1–3 in toluene solution at a maximum of 100 °C resulted in elimination of ethane, affording cleanly doubly tucked-in titanocene compounds 5–7, respectively. Experiments with 2 and 3 in NMR tubes proved that symmetrical isomers 6a and 7a were formed first, and these thermally isomerized to thermodynamically more stable asymmetrical isomers 6b and 7b. The energy difference between 7a and 7b calculated by DFT methods was 15.3 kJ/mol. Thermolysis of 4 in m-xylene required a temperature of 135 °C, affording a mixture of 8b > 8a and “dimeric dehydro-titanocene” 9 as a concurrent product of hydrogen abstraction. In contrast to thermolysis in solvents, heating of 1 and 2 in high vacuum to 135 °C resulted in sublimation of known titanocenes [Ti(C5Me5)2]...

Dehydrocoupling of SiMe2H substituents in permethylated zirconocene complexes

Complex [Zr{η5-C5Me4(SiMe2H)}2Cl2] (1) was prepared by the reaction of lithium salt of 2,3,4,5-tetramethyl-1-(dimethylsilyl)cyclopenta-2,4-diene with [ZrCl4] in boiling THF. The reduction of 1 with excess magnesium in THF in the presence of excess bis(trimethylsilyl)acetylene (btmsa) afforded the bivalent metal ansa-disilylene complex with π-coordinated btmsa [Zr(η2-btmsa){η5-C5Me4(SiMe2)}2] (2). The dehydrocoupling of SiMe2H groups was accompanied by a hydrogen transfer to releasing btmsa to give a mixture of cis- and trans-1,2-bis(trimethylsilyl)ethene. Chlorination of 2 with PbCl2 afforded ansa-[Zr{η5-C5Me4(SiMe2)}2Cl2] (3) and liberated btmsa. The crystal structures of complexes, 1, 2 and 3 have been determined by X-ray crystallography.

ChemInform Abstract: Silatranes from Reactions of Chloromethylsilatrane with Chlorosilanes and Magnesium in Tetrahydrofuran.

Abstract Some silatranylmethylsilanes have been obtained by reaction of chloromethylsilatrane with chloro- silanes and magnesium in THF (i.e. under Barbier conditions).

ChemInform Abstract: Tetrahydrofuran-Soluble Magnesium Dihydride by Catalytic Hydrogenation of Magnesium

Upon hydrogenation of magnesium in THF using homogeneous magnesium-anthracene transition-metal halide catalysts in the presence of small amounts of MgCl2 and solubilizing agents L, a dissolved form of magnesium hydride (MgH'2) is produced. The preferred L's are quinuclidine (QC) or organomagnesium compounds; however, organoaluminium and -boron compounds can also be used. The fraction n of magnesium hydride produced in the dissolved form and the stability of the MgH'2 solutions are investigated as a function of the kind and the amount of solubilizing agents and catalysts. The optimized method for the preparation of MgH'2 is described. The magnesium hydride dissolved in THF is characterized by IR spectroscopy. In order to elucidate the role of the solubilizing agents, THF-soluble MgCl2-containing stoichiometric MgH2 · QC model complexes are also prepared and characterized by IR spectra. Advantages and disadvantages of using MgH'2 for synthetic purposes instead of catalytically prepared suspensions of magnesium hydride (MgH2) are discussed.

ChemInform Abstract: An α-Aminomethyl Carbanion Equivalent via a Novel Barbier Reaction: (1H-Naphtho[1,8-de]-1,2,3-triazin-2-yl)methyl Anion.

Abstract A novel sonication-promoted Barbier reaction putatively generated the titled species from the corresponding naphthotriazinylmethyl chloride and magnesium in THF: its formal addition to a variety of carbonyl compounds in situ, occurred in excellent yields. Subsequent catalytic hydrogenolysis of the triazine moiety demasked the amine, thus defining a route to various phenylethylamines (including the alkaloid ‘mescaline’), or ethanolamines (in two cases), in excellent overall yields.

Si−H Bond Activation of Alkynylsilanes by Group 4 Metallocene Complexes

The reactivity of variously substituted alkynylsilanes toward selected group 4 metallocene complexes was investigated. Reactions of the alkynylsilanes R(1)C(2)SiR(2)(2)H (R(1) = SiMe(3), R(2) = Me, 1; R(1) = SiMe(3), R(2) = Ph, 2; R(1) = SiMe(2)H, R(2) = Me, 5) with Cp(2)TiMe(2) (Cp = eta(5)-cyclopentadienyl) resulted, upon methyl group transfer to the silyl group, in the previously described titanocene alkyne complexes Cp(2)Ti(R(1)C(2)SiR(2)(2)R(3)) (R(1) = Me(3)Si, R(2) = R(3) = Me, 3; R(1) = HMe(2)Si, R(2) = R(3) = Me, 6) or the unreported complex 4 (R(1) = Me(3)Si, R(2) = Ph, R(3) = Me). The Cp(2)TiCl(2)/n-BuLi system yielded alkyne complexes 6 and 7 (R(1) = HMe(2)Si, R(2) = Me, R(3) = H); no alkyl group transfer was detected. On the other hand, reactions utilizing the Cp(2)ZrCl(2)/n-BuLi system afforded inseparable mixtures; however, complexes of the type Cp(2)Zr[R(1)C(2)SiMe(2)(n-Bu)] (R(1) = Me(3)Si, 8; R(1) = HMe(2)Si, 9) were detected. Cp(2)Hf(n-Bu)(2) reacted with the alkynylsilanes in a diverse way, depending on the substituents of the alkyne substrate. The reaction with an excess of alkyne 1 (R(1) = Me(3)Si, R(2) = Me) afforded only an intractable mixture, which contained Me(3)SiC(2)SiMe(2)(n-Bu) (10). Hafnacyclopentadienes 13-15 as precedented product types were obtained when alkyne 12 (R(1) = Ph, R(2) = Me) was used. In sharp contrast, the symmetrically substituted alkynes 5 (R(1) = HMe(2)Si, R(2) = Me) and H(2)PhSiC(2)SiPhH(2) (18) yielded the hitherto unknown Si-containing metallacycles 16 and 19. A reaction mechanism leading to these products was proposed and subsequently supported by DFT calculations. In addition, the reduction of Cp(2)HfCl(2) with magnesium in THF in the presence of alkynylsilanes was shown to be an alternative route to compounds 14-16 and 19. Presumably due to steric reasons, alkyne 1 could not form any of the product types described above. Nevertheless, it was utilized for the preparation of the PMe(3)-stabilized hafnocene alkyne complex 11.

Stable “Inverse” Sandwich Complex with Unprecedented Organocalcium(I): Crystal Structures of [(thf)2Mg(Br)-C6H2-2,4,6-Ph3] and [(thf)3Ca{μ-C6H3-1,3,5-Ph3}Ca(thf)3

The reaction of bromo-2,4,6-triphenylbenzene with activated magnesium in THF yielded the Grignard reagent [(thf)(2)Mg(Br)-C(6)H(2)-2,4,6-Ph(3)] (1) with a Mg-C bond length of 214.8(3) pm. A similar reaction of bromo-2,4,6-triphenylbenzene with activated calcium led to an "inverse" sandwich complex [(thf)(3)Ca{mu-C(6)H(3)-1,3,5-Ph(3)}Ca(thf)(3)] (2) with the calcium atoms on opposite sides of the central arene ring showing small Ca-Ca' and Ca-C distances of 427.9(3) and 259.2(3) pm. This extremely air- and moisture-sensitive complex exhibits thermochomic and solvatochromic behavior. It is paramagnetic with spin of S = 1 (triplet) with an ESR resonance at g = 2.0023. Quantum chemical calculations shed light on the bonding situation in this very unusual dinuclear Ca(I) compound.

The Grignard Reagent Formation Reaction of 2‐Chloro‐1,1,1‐triphenylethane Revisited

AbstractThe reaction of 2‐chloro‐1,1,1‐triphenylethane (1) with magnesium in THF has been reinvestigated. The reaction produced a dark‐red solution and after deuterolysis with D2O, 1,1,1‐triphenylethane (2; 16 %), 2‐D‐1,1,1‐triphenylethane (3; 52 %) and 1,1,2‐triphenylethene (4; 26 %) were isolated. Rate constants for phenyl migration in the 2,2,2‐triphenylethyl radical were measured directly between 23 °C and 55 °C; the reaction is described by log k = 11.2 – 7.5/2.3 RT [kcal/mol] and the rate constant for rearrangement at 20 °C is 4.0 × 105 s–1. The combined results support the intermediate formation of radicals in the reaction of chloride 1 with magnesium. The red colour of the reaction mixture, however, indicates the formation of a carbanionic species, which has not yet been identified. The diffusion model for Grignard formation reactions of Garst et al. is in line with the product distribution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Reactivity of SiMe2H Substituents in Permethylated Titanocene Complexes: Dehydrocoupling and Ethene Hydrosilylation

The complex [TiCl2{η5-C5Me4(SiMe2H)}2] (3) was prepared by reacting the lithium salt of 2,3,4,5-tetramethyl-1-(dimethylsilyl)cyclopenta-2,4-diene (1) with [TiCl3(THF)3] followed by chlorination of the formed [TiCl{η5-C5Me4(SiMe2H)}2] (2) with PbCl2. The reduction of 3 with excess magnesium in THF in the presence of excess bis(trimethylsilyl)ethyne (btmse) afforded the bivalent metal ansa disilylene complex with π-coordinated btmse [Ti{η5-C5Me4(SiMe2)}2(η2-btmse)] (4). The dehydrocoupling of the SiMe2H groups was accompanied by hydrogen transfer to the free btmse. Analogous reduction of 3 with magnesium in the presence of ethene gave a mixture of titanocene [Ti{η5-C5Me4(SiMe2Et)}2] (5) and its ethene complex [Ti{η5-C5Me4(SiMe2Et)}2(η2-C2H4)] (6). The latter complex is however unstable in this mixture and rearranges with evolution of ethane to [Ti{η5-C5Me4(SiMe2Et)}{η5:η2-C5Me4(SiMe2CH═CH2)}] (7), which has its vinyl group attached by π-coordination to Ti(II). The chlorination of 4 by PbCl2 yields ansa-[TiCl2{η5-C5Me4(SiMe2)}2] (8), liberating the btmse ligand. Complex 8 is reduced with a half-equivalent of Mg to give ansa-[TiCl{η5-C5Me4(SiMe2)}2] (9). Compounds 5, 6, and 7 were identified by 1H, 13C, and 29Si NMR spectra. The crystal structures of complexes 3, 4, and 9 have been determined by X-ray crystallography.

Synthesis and reactions of poly[(ethoxysilylene)phenylenevinylene]s and chain-to-pendant energy transfer in the resulting polymer

Reactions of (bromophenylethenyl)diethoxysilanes with magnesium in THF gave poly[(ethoxysilylene)phenylenevinylene]s. The ethoxy group of the polymers could be readily replaced with other substituents by treating them with nucleophiles. Optical properties of the resulting poly(silylenephenylenevinylene)s were examined with respect to their UV absorption and emission spectra. Of those, pyrenylethynyl-substituted one exhibited energy transfer from the backbone to the substituent in the photo-excited state.

Reduction of 2-( N, N-dimethylamino)ethyl substituted zirconocene dichlorides: Intramolecular activation of NCH 2–H bond. The crystal structures of [η 5:η 2( C, N)-C 5(CH 3) 4CH 2CH 2N(CH 3)CH 2][η 5-C 5(CH 3) 5]ZrX (X = Cl, H)

Treatment of zirconocene dichloride [η 5-C 5(CH 3) 4CH 2CH 2N(CH 3) 2][η 5-C 5(CH 3) 5]ZrCl 2 ( 1) with amalgamated magnesium in THF results in cleavage of a C–H bond in one of the methyl groups of the N(CH 3) 2 fragment yielding [η 5:η 2( C, N)-C 5(CH 3) 4CH 2CH 2N(CH 3)CH 2][η 5-C 5(CH 3) 5]ZrH ( 2). An analogous reduction of [η 5-C 5(CH 3) 4CH 2CH 2N(CH 3) 2] 2ZrCl 2 ( 4) proceeds similarly only in the presence of great excess of P(CH 3) 3, otherwise no identifiable products are formed. Heterogeneous reaction of the hydride complex 2 with NH 4Cl in THF produces the corresponding chloride complex [η 5:η 2( C, N)-C 5(CH 3) 4CH 2CH 2N(CH 3)CH 2][η 5-C 5(CH 3) 5]ZrCl ( 3), with the Zr–CH 2 bond retained. The molecular structures of compounds 2 and 3 were established by X-ray diffraction analyses.

Radical clocks and electron transfer. Comparison of crown ether effects on the reactivity of potassium and magnesium towards 1-bromo-2-(3-butenyl)benzene. The incidence of homogeneous versus heterogeneous electron transfer on selectivity

The reaction of the title precursor of the aryl radical clock 1-bromo-2-(3-butenyl)benzene, 1Br, towards potassium and magnesium in THF was studied in the presence and absence of various additives, at ambient and low temperatures. The additives were cis-dicyclohexano-18-crown-6 or tert-butyl alcohol; the first one to render soluble potassium by forming its alkalide, the second to distinguish carbanionic from radical cyclization. The addition of 1Br to a THF stirred suspension of potassium pieces yields remarkably low amounts of products resulting from radical cyclization, in contrast to the amounts reported by Bunnett and Beckwith's group for the reaction in 67% ammonia–33% tert-butyl alcohol medium. The amount of cyclized products obtained with potassium pieces in THF is in the same range as that observed in the reaction of magnesium with 1Br in THF. This similarity allows us to discard the earlier triad hypothesis that we proposed to account for the unexpectedly low amounts of cyclized products of aryl halides radical clocks in Grignard reagent formation. The addition of crown ethers to the THF reaction medium induces contrasting effects for potassium and magnesium. A distinctive increase in the radical cyclization is observed for potassium, whereas the addition of crown inhibits the formation of Grignard reagent more efficiently when the solvent is diethyl ether than when it is THF. The observed effects are explained by putting in perspective the metal reactive dissolution with elementary steps occurring in the vicinity of a cathode. The reaction of potassium pieces or magnesium turnings is comparable to the heterogeneous electron transfer occurring at a cathode whereas the reaction of potassium in the presence of crown ether is comparable to homogeneous conditions of electron transfer obtained in redox catalysis. A discussion of the dianion hypothesis for the Grignard reaction of aryl halides is provided and the importance of considering the reactivity of reactive metal dissolution (or organic corrosion) in the framework of recent progress made in the modelling of electrode reactivity is emphasized. This paper shows that caution should be taken when radical clocks are used to study reactions at the metal–solution interface. More specifically, the non-observation of rearranged products from the radical clock (even for the very rapid ones) under these conditions does not necessary imply that there is no radical intermediate along the dominant reaction channel. This pattern of reactivity strongly contrasts with that usually observed when radical clocks are used in homogeneous media. The leading parameters in the rearranged/unrearranged products ratio seem to be the time that the reactive species (radical anions) created by the first electron transfer spend in the close vicinity of this surface, the rate constant of rearrangement of the radical formed by the cleavage of the radical anion and the redox properties of this radical. Copyright © 2005 John Wiley & Sons, Ltd.

Reduction-induced double bond coordination and multiple CH activation in fully-substituted titanocenes bearing a pendant double bond or an eight-membered hydrocarbyl ansa-chain

Reduction of isomeric, fully-substituted titanocene dichlorides having a pendant double bond, [TiCl 2(η 5-C 5Me 4R)(η 5-C 5Me 5)] (R=CH 2CH 2CHCH 2 ( 1); R=CH(Me)CHCH 2, ( 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 η 2-coordinated double bond, [Ti(η 5-C 5Me 5){η 2:η 5-C 5Me 4(CH 2CH 2CHCH 2)}] ( 3), compound 2 affords under identical conditions a product with two new TiC bonds, [Ti{(η 1:η 1:η 5-C 5Me 3(CH 2)(CH(Me)CH 2CH 2)}(η 5-C 5Me 5)] ( 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 [TiCl 2{η 5:η 5-C 5Me 4CH 2CHCH(CH 2) 5C 5Me 4}] ( 5) is reduced to a titanocene–η 2-alkene complex with the double bond shifted to the central position, ansa-[Ti{η 2:η 5:η 5-C 5Me 4(CH 2) 3CHCH(CH 2) 3C 5Me 4}] ( 7). In the absence of btmse, analogous complex with saturated bridge ansa-[TiCl 2{η 5:η 5-C 5Me 4(CH 2) 8C 5Me 4}] ( 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 η 2-alkyne complex ansa-[Ti{η 5:η 5-C 5Me 4(CH 2) 8C 5Me 4}(η 2-Me 3SiCCSiMe 3)] ( 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{(η 3:η 4-C 5Me 2(CH 2) 2)(CH 2) 8(η 5-C 5Me 4)}] ( 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.