1473-61-6Relevant articles and documents
Fridman et al.
, (1971)
CATALYTIC PROPERTIES OF IRON TETRACARBONYL ?-COMPLEXES OF VINYLSILANES IN THE ADDITION OF POLYHALOMETHANES AND HYDROSILANES TO VINYLSILANES
Gailyunas, G. A.,Nurtdinova, G. V.,Yur'ev, V. P.,Tolstikov, G. A.,Rafikov, S. R.
, p. 806 - 812 (1982)
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Olofson,R.A. et al.
, p. 1677 - 1680 (1978)
Comparative Study of the Electronic Structures of μ-Oxo, μ-Nitrido, and μ-Carbido Diiron Octapropylporphyrazine Complexes and Their Catalytic Activity in Cyclopropanation of Olefins
Cailler, Lucie P.,Clémancey, Martin,Barilone, Jessica,Maldivi, Pascale,Latour, Jean-Marc,Sorokin, Alexander B.
, p. 1104 - 1116 (2020/02/04)
The electronic structure of three single-Atom bridged diiron octapropylporphyrazine complexes (FePzPr8)2X having Fe(III)-O-Fe(III), Fe(III)-N-Fe(IV) and Fe(IV)-C-Fe(IV) structural units was investigated by M?ssbauer spectroscopy and density functional theory (DFT) calculations. In this series, the isomer shift values decrease, whereas the values of quadrupole splitting become progressively greater indicating the increase of covalency of Fe-X bond in the μ-oxo, μ-nitrido, μ-carbido row. The M?ssbauer data point to low-spin systems for the three complexes, and calculated data with B3LYP-D3 show a singlet state for μ-oxo and μ-carbido and a doublet state for μ-nitrido complexes. An excellent agreement was obtained between B3LYP-D3 optimized geometries and X-ray structural data. Among (FePzPr8)2X complexes, μ-oxo diiron species showed a higher reactivity in the cyclopropanation of styrene by ethyl diazoacetate to afford a 95% product yield with 0.1 mol % catalyst loading. A detailed DFT study allowed to get insight into electronic structure of binuclear carbene species and to confirm their involvement into carbene transfer reactions.
Decamethyltitanocene hydride intermediates in the hydrogenation of the corresponding titanocene-(η2-ethene) or (η2-alkyne) complexes and the effects of bulkier auxiliary ligands
Pinkas, Ji?í,Gyepes, Róbert,Císa?ová, Ivana,Kubi?ta, Ji?í,Horá?ek, Michal,Mach, Karel
, p. 8229 - 8244 (2017/07/10)
1H NMR studies of reactions of titanocene [Cp?2Ti] (Cp? = η5-C5Me5) and its derivatives [Cp?(η5:η1-C5Me4CH2)TiMe] and [Cp?2Ti(η2-CH2CH2)] with excess dihydrogen at room temperature and pressures lower than 1 bar revealed the formation of dihydride [Cp?2TiH2] (1) and the concurrent liberation of either methane or ethane, depending on the organometallic reactant. The subsequent slow decay of 1 yielding [Cp?2TiH] (2) was mediated by titanocene formed in situ and controlled by hydrogen pressure. The crystalline products obtained by evaporating a hexane solution of fresh [Cp?2Ti] in the presence of hydrogen contained crystals having either two independent molecules of 1 in the asymmetric part of the unit cell or cocrystals consisting of 1 and [Cp?2Ti] in a 2:1 ratio. Hydrogenation of alkyne complexes [Cp?2Ti(η2-R1CCR2)] (R1 = R2 = Me or Et) performed at room temperature afforded alkanes R1CH2CH2R2, and after removing hydrogen, 2 was formed in quantitative yields. For alkyne complexes containing bulkier substituent(s) R1 = Me or Ph, R2 = SiMe3, and R1 = R2 = Ph or SiMe3, successful hydrogenation required the application of increased temperatures (70-80 °C) and prolonged reaction times, in particular for bis(trimethylsilyl)acetylene. Under these conditions, no transient 1 was detected during the formation of 2. The bulkier auxiliary ligands η5-C5Me4tBu and η5-C5Me4SiMe3 did not hinder the addition of dihydrogen to the corresponding titanocenes [(η5-C5Me4tBu)2Ti] and [(η5-C5Me4SiMe3)2Ti] yielding [(η5-C5Me4tBu)2TiH2] (3) and [(η5-C5Me4SiMe3)2TiH2] (4), respectively. In contrast to 1, the dihydride 4 did not decay with the formation of titanocene monohydride, but dissociated to titanocene upon dihydrogen removal. The monohydrides [(η5-C5Me4tBu)2TiH] (5) and [(η5-C5Me4SiMe3)2TiH] (6) were obtained by insertion of dihydrogen into the intramolecular titanium-methylene σ-bond in compounds [(η5-C5Me4tBu)(η5:η1-C5Me4CMe2CH2)Ti] and [(η5-C5Me4SiMe3)(η5:η1-C5Me4SiMe2CH2)Ti], respectively. The steric influence of the auxiliary ligands became clear from the nature of the products obtained by reacting 5 and 6 with butadiene. They appeared to be the exclusively σ-bonded η1-but-2-enyl titanocenes (7) and (8), instead of the common π-bonded derivatives formed for the sterically less congested titanocenes, including [Cp?2Ti(η3-(1-methylallyl))] (9). The molecular structure optimized by DFT for compound 1 acquired a distinctly lower total energy than the analogously optimized complex with a coordinated dihydrogen [Cp?2Ti(η2-H2)]. The stabilization energies of binding the hydride ligands to the bent titanocenes were estimated from counterpoise computations; they showed a decrease in the order 1 (-132.70 kJ mol-1), 3 (-121.11 kJ mol-1), and 4 (-112.35 kJ mol-1), in accordance with the more facile dihydrogen dissociation.
