Unusual addition of but-2-yne to a permethyltitanocene species

Mach, Karel; Gyepes, Róbert; Kubišta, Jiřı́; Horáček, Michal

doi:10.1016/j.inoche.2005.10.029

Cited by 9 publications

(7 citation statements)

References 33 publications

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“…In spite of the aforementioned interest in the reactivity of 1 , this compound has not been examined for its reactivity toward internal alkynes and olefins. We have entered an investigation of this topic in an effort to find out the mechanism of formation of the interesting paramagnetic product 2 , which formed in high yield when [TiCl 2 (η 5 -C 5 Me 5 ) 2 ] was reduced with an excess of magnesium in the presence of excess but-2-yne in tetrahydrofuran (Scheme ) …”

Section: Introductionmentioning

confidence: 99%

Insertion of Internal Alkynes and Ethene into Permethylated Singly Tucked-in Titanocene

et al. 2008

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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 of the paramagnetic [TiIII(η5-C5Me5){η5:η1-C5Me4(CH2CR1CR2)}] products 3a−g,k,l were determined by single-crystal X-ray diffraction analysis. These compounds and compounds 3h−j,m, whose crystal structures could not be determined, were chlorinated with PbCl2 to give the diamagnetic products [TiIVCl(η5-C5Me5){η5:η1-C5Me4(CH2CR1CR2)}] (4a−j) and the corresponding chlorotitanocene derivatives 4k−m. The solution structures of 4a−m were determined by 1H and 13C NMR spectroscopy, and crystal structures for 4b,e,g,l,m were found by single crystal X-ray diffraction analysis. DFT calculations threw light on the transition-state molecule for the formation of 3j and revealed a steric hindrance to be responsible for preventing the insertion of a second molecule of hex-3-yne, the closest homologue of but-2-yne, to react with 3i, forming a homologue of 2.

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Section: Introductionmentioning

confidence: 99%

Insertion of Internal Alkynes and Ethene into Permethylated Singly Tucked-in Titanocene

et al. 2008

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“…Hence, using Mg as the reducing agent and isolation of the alkyne complexes might exclude the formation of these during synthesis of the desired four‐membered 1‐metallacyclobuta‐2,3‐dienes. However, it should be noted that in all cases described hereafter, the formation of unidentified Ti III species as the side products was observed, thus giving comparably low yields of the reported products …”

Section: Methodsmentioning

confidence: 86%

Titanocene Silylpropyne Complexes: Promising Intermediates en route to a Four‐Membered 1‐Metallacyclobuta‐2,3‐diene?

Reiß

Spannenberg

et al. 2017

Chemistry A European J

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Coordination of the alkyl-substituted alkynes Me SiC CH R (1: R=SiMe ; 2: R=N(SiMe ) ) to titanocene centres [Cp' Ti] (Cp'=Cp, Cp*) yields stable alkyne complexes of the type Cp' Ti(η -Me SiC CH R) (3: Cp'=Cp, R=SiMe ; 5: Cp'=Cp, R=N(SiMe ) ; 6: Cp'=Cp*, R=SiMe ) that are not prone to alkyne/allene isomerisation. When reacting alkyne 2 with Cp TiCl and Mg formation of the complex Cp* Ti(III)(η -Me SiC CH ) (7) which displays a propargylic unit coordinated to the Ti centre takes place. All complexes were fully characterised, the molecular structures for 5, 6, and 7 are discussed.

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“…64 THF solutions of [Cp* 2 TiCl 2 ] react with but-2-yne in the presence of excess Mg forming predominantly (Z 5 :Z 1 -1,2,3,4-tetramethyl-5-(2,3,4,5-tetramethylpenta-2,4-dien-1,5-diyl-kC5)-cyclopentadienyl)(Z 5 -pentamethylcyclopentadienyl)titanium, in which two but-2ynes have linked to a ring methyl in forming an unusual pendant ligand (1). 65 Solutions of Zn-reduced [Cp 2 TiX 2 ] in HMPA contain mixtures of [Cp 2 Ti(HM-PA)] + , [Cp 2 Ti(HMPA) 2 ] + and [Cp 2 TiX(HMPA)], with the ionic components predominating as the halogen series is descended. However, there is an inverse correlation between HMPA concentration and rate of reduction of electrophiles such as PhCHO and PhCH 2 Cl, suggesting that it is the unsolvated Ti III species that are responsible.…”

Section: Organometallicsmentioning

confidence: 99%