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Titanocene hydride [Cp*2TiH] (Cp* = η5-C5Me5) (1) readily inserts simple internal alkynes R1C≡CR2 into its Ti–H bond, yielding titanocene alkenyl Ti(III) compounds of two structural types. The less sterically congested products [Cp*2Ti(R1C═CHR2)] (2a–e) contain a σ1-bonded alkenyl group, whereas the products bearing at least one trimethylsilyl substituent and other bulky substituents (R1 = SiMe3; R2 = SiMe3, 4a; CMe3, 4b; and Ph, 4c) possess a remarkable Ti–H agostic bond of the σ1-bonded alkenyl group. This feature is consistent with solution EPR spectra of 4a–4c showing a doublet due to coupling of the hydrogen nucleus with the Ti(III) d1 electron. Compound 1 reacts with one molar equivalent of conjugated buta-1,3-diynes (RC≡C)2 to give η3-butenyne complexes (R = SiMe3, 5a; CMe3, 5b). The Ti(III) complexes 2a–2e and 5a and 5b were oxidatively chlorinated with PbCl2 to give Ti(IV) chloro-alkenyl complexes [Cp*2TiCl(R1C═CHR2)] 3a–3e and chloro-alkenynes 6a and 6b, respectively. 1H and 13C NMR spectra of 3...

Bis(decamethyltitanocene) oxide, [(Cp*2Ti)2O] (1; Cp* = η5-C5Me5) has been obtained as a yellow crystalline solid after reacting equimolar amounts of the hydride [Cp*2TiH] and the hydroxide [Cp*2Ti(OH)]. The solid-state structure of 1 revealed a linear Ti–O–Ti arrangement and a mutual, nearly perpendicular orientation of the bent-sandwich titanocene moieties; the length of both Ti–O bonds amounted to 1.9080(3) A. A unique structural feature was a close-to-eclipsed conformation of the cyclopentadienyl ligands, attributed to the high steric congestion of 1. The molecule in toluene glass exhibited a triplet state EPR spectrum of rhombic symmetry, having zero field splitting D = 0.02159 cm–1 and E = 0.00230 cm–1. The 1H NMR spectrum of 1 in toluene-d8 displays a paramagnetic resonance at δ 4.3 ppm (Δν1/2 ≈ 270 Hz). Compound 1 reacts with 1 molar equiv of water to give [Cp*2Ti(OH)]. In CD2Cl2, 1 is oxidized to yield the major product [(Cp*TiCl2)2O] and minor product [{Cp*Ti(Cl)O}3].

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]...

Thermolysis of [TiMe2{η5-C5Me4(CH2CH2CH═CH2)}2] (1) in toluene at 120 °C for 4 h resulted in the formation of the cyclopentadiene ring-tethered titanacyclobutane [TiIV{η5-C5Me4CH2CH2CH(κ-CH)}2CH2] (2) in virtually quantitative yields. Thermolysis in an NMR tube at 100 °C revealed that initial elimination of methane is followed by addition of one 3-butenyl double bond to a titanocene−methylidene moiety. The formed titanacyclobutane intermediate [Ti{η5-C5Me4(CH2CH2CH═CH2)}{η5-C5Me4CH2CH2CH(κ-CH)CH2CH2(κ-CH2)}] (4) then underwent a metathesis reaction with the pendant 3-butenyl to give 2 and free ethene. Cleavage of Ti−C bonds of 2 with HCl afforded stable ansa-[TiCl2{η5-C5Me4(CH2)7η5-C5Me4}] (3). Sunlight photolysis of 1 gave rise to the cyclopentadiene ring-tethered titanacyclopentane [TiIV{η5-C5Me4(CH2CH2CH(κ-CH)CH2}2] (5), the known product of cycloaddition reactions following the removal of chlorine atoms from [TiCl2{η5-C5Me4(CH2CH2CH═CH2)}2] with magnesium (as found by Horacek, M.Chem. Eur. J. 2000, 6,...

Hydrogen sulfide reacts with tucked-in titanocene complexes [Ti(III){η5:η1-C5Me4(CH2)}Cp*] (Cp* = η5-C5Me5) (2) and [Ti{η4:η3-C5Me3(CH2)2}Cp*] (3) and their precursors [Cp*2TiMe] (2a) and [Cp*2Ti(η2-Me3SiC≡CSiMe3)] (3a), respectively, to give the corresponding titanocene hydrosulfides [Cp*2Ti(SH)] (4) and [Cp*2Ti(SH)2] (1), respectively. Hydrogen sulfide also cleaves intramolecular σ- or π-Ti−C bonds in ansa-[TiIII(η1:η5:η5-C5Me4SiMe2CHCH2SiMe2C5Me4)] (5) and ansa-[TiII(η2:η5:η5-C5Me4SiMe2CH═CHSiMe2C5Me4)] (6), affording hydrosulfides ansa-[(η5-CH2Me2SiC5Me4)2Ti(SH)] (7) and ansa-[(η5-CH2Me2SiC5Me4)2Ti(SH)2] (8). The S−H bonds of hydrosulfides 4 and 7 were able to react with the Ti−C bonds in 2 and 5, affording titanocene sulfides [(Cp*2TiIII)2S] (11) and ansa-[{(η5-CH2Me2SiC5Me4)2TiIII}2S] (12), respectively. Combination of 7 with 2a gave rise to the mixed titanocene sulfide [ansa-{(η5-CH2SiMe2C5Me4)2Ti}S(TiCp*2)] (13). The titanium(III) d1 electrons in 11−13 form an electronic triplet state well observa...

The constrained geometry alkoxide [Ti(III)(η5-C5Me5){η5-C5Me4CH2CMe2O-κO}] (2) and titanocene alcoholates [Cp*2TiOR] for R = 1-adamantyl (3) and pentafluorophenyl (4) were prepared by reacting acetone and the respective alcohols with the singly tucked-in titanocene [Ti(III)(η5-C5Me5)(η5:η1-C5Me4CH2)] (1) in order to add the simplest member to constrained geometry alkoxides 5 and 6 and to extend the series of [Cp*2TiOR] (R = Me (8), tBu (7), Ph (9), and H (10)) compounds for one of the most bulky and the most electron attracting substituent. The titanocene alkoxides with the alkoxy carbon atom tethered to one of the cyclopentadienyl ligands showing the crystallographic Ti−O−C angle close to 133° are a suitable group of compounds to be compared with the [Cp*2TiOR] compounds, where the Ti−O−C angle is about 174° for 3 and 7 and 180° for 4. In spite of these Ti−O−C angle differences, the wavelength of the first electronic transition λexp(1a1 → b2), supposed to indicate the extent of the oxygen π-electron dona...

The ansa-1,2-bis(dimethylsilylene)ethane chain is exclusively activated when the parent ansa-permethyltitanocene compounds are reduced to titanium(II) either by thermolysis of titanium−methyl bonds...

Reaction of [(η5-C5Me5)TiMe3] with [(c-C5H9)7Si8O12(OH)] (SIPOSS) or [(c-C5H9)7Si7O9(OSiMe3)(OH)2)] (DIPOSS′) affords stoichiometrically the half-sandwich titanium-disiloxy-methyl complexes [(η5-C5Me5){(c-C5H9)7Si8O12O}2TiMe] (1) and [(η5-C5Me5){(c-C5H9)7Si7O9(OSiMe3)O2}TiMe] (2), respectively. Compound 2 consists of the two stereoisomers possessing the (η5-C5Me5) ligand and OSiMe3 group in syn- (2a) and anti-position (2b). The more abundant 2a (2a/2b ≈ 2:1) was isolated by fractional crystallization. Compounds 1 and 2a reacted rapidly with B(C6F5)3 to give zwitterionic complexes [(η5-C5Me5){(c-C5H9)7Si8O12O}2Ti](+)[(μ-Me)B(C6F5)3](−) (3) and syn-[(η5-C5Me5){(c-C5H9)7Si7O9(OSiMe3)O2}Ti](+)[(μ-Me)B(C6F5)3](−) (4a), respectively. Infrared spectra proved that 3 and 4a were thermally stable in the solid state, and the structure of 4a was determined by X-ray single-crystal analysis. In contrast, 1H, 13C, and 19F NMR spectra of 3 in toluene C7D8 revealed that it was completely dissociated into initial component...

A series of compounds [Cp*2Ti(III)OR′] where R′ is iPr3Si (2), Ph3Si (3), (tBuO)3Si (4), (c-C5H9)7Si8O12 (5), and tBu (6) were prepared by protolysis of the titanium−methylene bond in singly tucked...

The singly tucked-in permethyltitanocene 1 reacts with an excess of internal alkynes to give the 1:1 adducts 3a−c,f−i, arising from insertion of the alkyne triple bond into the titanium−methylene bond. Only the simplest species, 2-butyne, inserted two molecules to give the known compound 2; however, at a 1:1 stoichiometric ratio the 1:1 adduct 3j was also smoothly formed. 1,4-Disubstituted conjugated diynes with CMe3 or SiMe3 substituents reacted in the same way by only one triple bond to give 3d,e, respectively. The dimethylsilylene-bridged dialkynes Me2Si(C≡CR)2 (R = SiMe3, CMe3) afforded compounds 3k,l with both triple bonds reacting. After insertion of the first triple bond, the second one underwent a rearrangement which resulted in substituent shift and formation of a silacyclobutene ring linked to the titanium atom. Alkynes bearing the bulky substituents CMe3 and SiMe3 were unreactive. Among a number of olefins and 1,3-butadiene, only ethene reacted to give cleanly the 1:1 adduct 3m. The structures ...

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-[TiC...

The presence of a trimethylsilyl substituent in place of one of the methyl groups of each of the cyclopentadienyl ligands of decamethyltitanocene enhances the thermal stability of the resulting complex, [TiII{η5-C5Me4(SiMe3)}2] (1), and controls the products formed in thermolysis of its methyl derivatives. Titanocene 1 was found to be stable in toluene solution up to 90 °C, while under vacuum at 140 °C it liberated hydrogen to give the asymmetrical doubly tucked-in titanocene [TiII{η3:η4-C5Me2(SiMe3)(CH2)2}{η5-C5Me4(SiMe3)}] (3). The mono- and dimethyl derivatives of 1, the complexes [TiIIIMe{η5-C5Me4(SiMe3)}2] (5) and [TiIVMe2{η5-C5Me4(SiMe3)}2] (6), undergo thermolysis at lower temperature than do the corresponding permethyltitanocene derivatives and eliminate hydrogen from their trimethylsilyl group. Thus, the known [TiIII{η5:η1-C5Me4(SiMe2CH2)}{η5-C5Me4(SiMe3)}] (4) was obtained from 5, and compound 6 afforded [TiII{η6:η1-C5Me3(CH2)(SiMe2CH2)}{η5-C5Me4(SiMe3)}] (7) at only 90 °C, both with liberation ...

Reactions at elevated temperatures (150 °C) of titanocene−η2-bis(trimethylsilyl)ethyne (btmse) complexes [(η5-C5H5-nMen)2Ti(η2-btmse)] (n = 3−5; 1b−d) with bis((trimethylsilyl)ethynyl)dimethylsilane (2a) afford the unusual 1,1-bis(η5-cyclopentadienyl)-4,4-dimethyl-3,5-bis(trimethylsilyl)-1-titana-4-silacyclohexa-2,5-diene complexes [(η5-C5H5-nMen)2Ti{CC(SiMe3)}2SiMe2] (4b−d), whereas the nonmethylated precursor [(η5-C5H5)2Ti(η2-btmse)] (1a) gives under similar conditions the known dinuclear, acetylide-bridged complex [{(η5-C5H5)2Ti(μ-η1:η2-C⋮CSiMe3)}2] (3a). In contrast, analogous reactions with bis((trimethylsilyl)ethynyl)diphenylsilane (2b) give the product of simple ligand exchange [(η5-C5Me5)2Ti(η2-Me3SiC⋮CSiPh2C⋮CSiMe3)] (6d) from 1d and mixtures containing the similar complex [(η5-C5HMe4)2Ti(η2-Me3SiC⋮CSiPh2C⋮CSiMe3)] (6c) and the titanasilacyclohexadiene [Ti(η5-C5HMe4)2Ti{CC(SiMe3)}2SiPh2] (5c) from 1c. Hydrogenolysis of 5c (1 bar/3 h) affords 1,4-bis(trimethylsilyl)-5,5-diphenyl-5-silacyclopenta-1...

The complexes [Zr(η 2 -Me 3 SiC≡CSiMe 3 )(η 5 -C 5 Me 4 R) 2 ] (R = Me (5), H (6), SiMe 3 (7)) reacted smoothly with terminal alkynes HC≡CR'(R' = CMe 3 , SiMe 3 , ferrocenyl (Fc), Ph) to give the agostic alkenyl-alkynyl complexes [Zr(η 1 -C≡CR'){η 3 -C(SiMe 3 )=CH(SiMe 3 )}(η 5 -C 5 Me 4 R) 2 ] (R/ R' = Me/CMe 3 (5a), Me/SiMe 3 (5b), H/CMe 3 (6a), H/SiMe 3 (6b), H/Fc (6c), H/Ph (6d), SiMe 3 / CMe 3 (7a), SiMe 3 /Fc (7c)). Complex 7a, formed in situ from 7 and HC≡CCMe 3 , dimerized tert-butylethyne exclusively to give the head-to-tail dimer Me 3 CC≡CC(CMe 3 )=CH 2 , and when all the terminal alkyne was consumed, 7 was restored. Complex 7 reacted similarly with 1-hexyne, phenylethyne, and (trimethylsilyl)ethyne, affording the respective alkenyl-alkynyl complexes, which also changed back to 7 on evaporation of the reaction solutions; none of these terminal alkynes was dimerized with 5-7. Heating of complex 6 with LiC≡CSiMe 3 in toluene or THF yielded the diamagnetic zirconate complex Li[Zr(η 1 -C≡CSiMe 3 )(η 2 -Me 3 SiC≡ CSiMe 3 )(η 5 -C 5 HMe 4 ) 2 ] (6e) and its solvatomorph Li[Zr(η 1 -C≡CSiMe 3 )(η 2 -Me 3 SiC≡CSiMe 3 )(η 5 -C 5 HMe 4 ) 2 ].C 4 H 8 O (6f), respectively. The lithium cation in 6e and 6f is placed in a position at the side of the alkynyl triple bond and close to C β of the η 2 -Me 3 SiC≡CSiMe 3 ligand, apparently interacting with both moieties. All presented complexes were characterized by the standard spectral methods, and the structures of 5a, 6a, 6c, 6d, and 6e were determined by single-crystal X-ray diffraction.

Reduction of [ZrCl2{η5-C5Me4(SiMe3)}2] (1) with excess magnesium in tetrahydrofuran affords a mixture of the monomeric zirconocene hydride [ZrH{η1:η5-C5Me4(SiMe2CH2)}{η5-C5Me4(SiMe3)}] (2) and the dimeric, tetranuclear Zr(III)− and Zr(IV)−magnesium hydride complexes 3 and 4, respectively. In the presence of bis(trimethylsilyl)ethyne (btmse), a similar reduction yields the η2-alkyne complex [Zr{η5-C5Me4(SiMe3)}2(η2-btmse)] (5) as the major product and compounds 2−4 as minor impurities. Upon thermolysis under vacuum, 5 undergoes a 2-fold hydrogen transfer from trimethylsilyl groups in the zirconocene intermediate to leaving btmse to afford [Zr{η5:η1-C5Me4(SiMe2CH2)}2] (6) and a mixture of alkenes (E)- and (Z)-Me3SiCHCHSiMe3 (E ≫ Z). Crystal structures of compounds 2 and 4−6 were determined by X-ray crystallography.

Reduction of titanocene dichlorides bearing (ω-alkenyl)dimethylsilyl substituents [TiCl2{η5-C5Me5(SiMe2R)}2], where R = CHCH2 (3) and CH2CHCH2 (4), affords highly reactive Ti(II) intermediates, which immediately undergo intramolecular reactions with the pendant double bonds in a way dependent on the length of the alkenyl chain. The reduction of 4 with magnesium at 60 °C affords cleanly the cyclopentadienyl-ring-tethered titanacyclopentane, [Ti(η1:η1:η:5η5-C5Me4SiMe2CH(Ti)CH(Me)CH(Me)CH(Ti)SiMe2C5Me4] (5), which can be opened by HCl to an ansa-titanocene dichloride with a six-membered saturated bridging chain, [TiCl2{η:5η5-C5Me4SiMe2CH2CH(Me)CH(Me)CH2SiMe2C5Me4)2}] (6). An analogous reaction of 3 can be accomplished at low temperatures and only to some extent, providing a mixture of titanacyclopentane complex [Ti(η1:η1:η:5η5-C5Me4SiMe2CH(Ti)CH2CH2CH(Ti)SiMe2C5Me4] (10) and the fluxional η2-alkene complex [Ti(η5-C5Me4SiMe2CHCH2)(η2:η5-C5Me4SiMe2CHCH2)] (9). At 60 °C, the reduction of 3 yields a mixture of a...

The new class of compounds arising from unconventinal additions of 1,4-disubstituted 1,3-butadiynes to activated permethylmetallocene species of Ti and Zr can be used in facile functionalizations. For example, the chiral product 5, obtained from the addition of tBuC⋮CC⋮CtBu to activated permethyltitanocene, has been derivatized by simple means, e.g., hydrogen chloride, bromine, or dihydrogen, affording practically useful functionalized titanocene compounds containing a chiral auxiliary ligand with an intramolecularly coordinated (compound 7) or a free double bond (compounds 8a,b). The new complexes have been characterized spectroscopically. Additionally, X-ray crystal structure analyses were performed for 7 and 8a,b.

Thermally induced elimination of bis(trimethylsilyl)acetylene from its titanocene complex [{η5-C5Me4(SiMe3)}2Ti(η2-Me3SiC⋮CSiMe3)] (1) afforded the stable titanocene [{η5-C5Me4(SiMe3)}2TiII] (2) in...

The reduction of (η5-C5H5-nMen)2TiCl2 (n = 0, 4, and 5) complexes by magnesium metal in tetrahydrofuran and in the presence of [(trimethylsilyl)ethynyl]ferrocene (2) or [(phenyl)ethynyl]ferrocene (...

The reduction of [C5Me4(SiMe3)]2TiCl2 by excess Mg in THF yields the paramagnetic compound {[η5-C5Me4SiMe2(μ-CH2{Mg,Mg})][η5-C5Me4(SiMe3)]TiIII(μ-H)2Mg(THF)}2 (3). In the presence of Me3SiC⋮CSiMe3 ...

Thermolysis of bis(tetramethylcyclopentadienyl)-stabilized titanium(III) compounds (C(5)HMe(4))(2)TiR (R = Me (2), Ph (3)) yields, in marked contrast with the bis(pentamethylcyclopentadienyl) analog, the dimeric product [(C(5)HMe(4))(mu-eta(1):eta(5)-C(5)Me(4))Ti](2) (4), With a bridging metalated tetramethylcyclopentadienyl ligand. The hydride (C(5)HMe(4))(2)TiH (5), synthesized by hydrogenolysis of 2 or 3, reacts with N-2 to form the dinuclear Ti(II) dinitrogen compound [(C(5)HMe(4))(2)Ti]N-2(2) (8) Under a dynamic vacuum, the dinitrogen complex 8 loses the N-2 ligand to give the titanocene (C(5)HMe(4))(2)Ti (10). The molecular structures of both 4 and 8 were determined by X-ray diffraction methods.

The (C5H5-nMen)2Zr[η2-C2(SiMe3)2] (n = 2−5; 1,3-dimethyl, 1,2,3-trimethyl) (2C−F) complexes were prepared by the reduction of corresponding zirconocene dichlorides with magnesium in THF in the presence of bis(trimethylsilyl)acetylene (BTMSA). All of them are stable in the absence of THF. Crystal structures of (C5HMe4)2Zr[η2-C2(SiMe3)2] (2E) and (C5Me5)2Zr[η2-C2(SiMe3)2] (2F) and of the analogous titanium complexes are isomorphous. The red shift of the ν(C⋮C) vibration and the downfield shift of 13C δ(C⋮C) indicate that BTMSA in 2C−F is more strongly coordinated than in analogous titanocene complexes. The nonisolated complex (C5H4Me)2Zr[η2-C2(SiMe3)2](THF) (2B·THF) rearranges after the loss of THF to give the dimer [(η5-C5H4Me)(η1-C(SiMe3)CH(SiMe3)Zr(μ-η1:η5-C5H3Me)]2 (3B).

The titanium−magnesium complex [(η5-C5H5)Ti][μ-η2:η2-C2(SiMe3)2]2[(η5-C5H5)Mg] (1) containing perpendicularly bridging bis(trimethylsilyl)acetylene ligands reacts with excess (trimethylsilyl)ethyne to give mainly (η5-1,2,4,5,6-pentakis(trimethylsilyl)cyclohexadienyl)(η5-cyclopentadienyl)titanium(II) (2). The X-ray crystal structure of 2 showed that the SiMe3 group at C(6) is in an exo-position and that the planes of the Cp ring and of the dienyl part of the Chx ring are nearly parallel. The dihedral angle 4.9° between these planes is mainly due to tilting of the cyclohexadienyl ring by the C(1) and C(5) side toward the titanium atom. Analogous reactions of 1 with tert-butylethyne, cyclohexylethyne, 1-hexyne, and phenylethyne afforded (η5-1,2,5,6-tetrakis(trimethylsilyl)cyclohexadienyl)(η5-cyclopentadienyl)titanium(II) derivatives 3−6 containing the 1-alkyne substituent at C(4).