1073193-06-2Relevant academic research and scientific papers
Sunlight photolysis of cyclopentadienyl–tethered titanium(iv) permethyltitanocene chlorides
Gyepes, Róbert,Horá?ek, Michal,Kubi?ta, Ji?í,Mach, Karel,Pinkas, Ji?í
, (2020/10/02)
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.
Insertion of internal alkynes and ethene into permethylated singly tucked-in titanocene
Pinkas,Cisarova,Gyepes,Horacek,Kubista,Cejka,Gomez-Ruiz,Hey-Hawkins,Mach
, p. 5532 - 5547 (2009/03/12)
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 [TFiIII- (η5-C5Me5)(η5: η1-C5Me4(CH2CR2)}] 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-C5Me 5){η5:η1-C5Me 4(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.
