4045-44-7Relevant academic research and scientific papers
Synthesis and characterization of cyclopentadienylgallium amide compounds as potential single source precursors to GaN
Perrotin,Kennon, Bretni S.,Twamley, Brendan,Miller, Joel S.,Shapiro, Pamela J.
, p. 216 - 222 (2014)
The synthesis, spectroscopic characterization, and single crystal X-ray structures of [(η5-C5Me4H)2Ga(μ2-NH2)] (1), [(η5-C5Me5)2Ga(μ2-
Enzyme-like control of carbocation deprotonation regioselectivity in supramolecular catalysis of the nazarov cyclization
Hastings, Courtney J.,Backlund, Mikael P.,Bergman, Robert G.,Raymond, Kenneth N.
, p. 10570 - 10573 (2011)
The kinetically controlled, regioselective deprotonation of cyclopentenyl cations is mediated by encapsulation within a metal-ligand assembly. The regiochemistry of the deprotonation step determines which one of two possible products is formed. Moreover, subtle differences in the stereochemistry of the encapsulated cation switch the selectivity of this process (see scheme). Copyright
Reactions of hydrogen sulfide with singly and doubly tucked-in titanocenes
Pinkas, Jiri,Cisarova, Ivana,Horacek, Michal,Kubista, Jiri,MacH, Karel
, p. 1034 - 1045 (2011)
Hydrogen sulfide reacts with tucked-in titanocene complexes [Ti(III){η5:η1-C5Me4(CH 2)}Cp*] (Cp* = η5-C5Me 5) (2) and [Ti{η4:η3-C 5Me3(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-C5Me4SiMe2CHCH 2SiMe2C5Me4)] (5) and ansa-[Ti II(η2:η5:η5-C 5Me4SiMe2CH=CHSiMe2C 5Me4)] (6), affording hydrosulfides ansa- [(η5-CH2Me2SiC5Me 4)2Ti(SH)] (7) and ansa-[(η5-CH 2Me2SiC5Me4)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-CH2Me2SiC5Me 4)2TiIII}2S] (12), respectively. Combination of 7 with 2a gave rise to the mixed titanocene sulfide [ansa-{(η5-CH2SiMe2C5Me 4)2Ti}S(TiCp*2)] (13). The titanium(III) d1 electrons in 11-13 form an electronic triplet state well observable by EPR spectra in toluene glass. All the hydrosulfides were decomposed by sunlight. Compound 1 eliminated Cp*H and H2S, while 4 mainly Cp*H. Apparently formed transient [Cp*TiS] species probably gave rise to the serendipitously isolated cluster [{Cp*Ti(S)} 4] (14). Crystal structures of the all complexes were determined by X-ray diffraction analysis.
Reactivity of Cp*Al towards Silanols: Formation and Hydrolysis of Alumosiloxanes
Wittwer, Philipp,Stelzer, Adrian,Braun, Thomas
, p. 3187 - 3194 (2018)
Treatment of [Cp*Al]4 (1) (Cp* = pentamethylcyclopentadienyl) with various silanols gave access to the compounds [Al{OSi(OtBu)3}3(DMAP)] (3) (DMAP = 4-dimethylaminopyridine), [HNEt3][Al(OSiPh3)4
Enzymelike catalysis of the nazarov cyclization by supramolecular encapsulation
Hastings, Courtney J.,Pluth, Michael D.,Bergman, Robert G.,Raymond, Kenneth N.
, p. 6938 - 6940 (2010)
The water-soluble, self-assembled, tetrahedral assembly K 12Ga4L6 (L = 1,5-biscatecholamidenaphthalene) catalyzes the Nazarov cyclization of 1,3-pentadienols with extremely high levels of efficiency. The catalyzed reaction proceeds over a million times faster than the background reaction, an increase comparable to those observed in some enzymatic systems. This catalysis operates under aqueous conditions at mild temperatures and pH, and the reaction is halted by the addition of an appropriate inhibitor. This unprecedented rate enhancement is attributed to both the stabilization of protonated reaction intermediates and the effect of constrictive binding on the bound guest.
Ytterbium(III) Complexes Coordinated by Dianionic 1,4-Diazabutadiene Ligands
Shestakov, Boris G.,Mahrova, Tatyana V.,Larionova, Joulia,Long, Jêrome,Cherkasov, Anton V.,Fukin, Georgy K.,Lyssenko, Konstantin A.,Scherer, Wolfgang,Hauf, Christoph,Magdesieva, Tatiana V.,Levitskiy, Oleg A.,Trifonov, Alexander A.
, p. 1177 - 1185 (2015)
A series of new Yb(III) complexes XYb(DAD)2-(L) (X = C5Me5, C5Me4H, N(SiMe3)2, tBuO; DAD = 2,6-R″2C6H3N=C(R′)-C(R′)=NC6H3R″2-2,6, R′ = H, Me, R″ = Me, iPr; L = thf, dme) coordinated by redox-active diazabutadiene ligands in dianionic form were synthesized and characterized. The half-sandwich complexes Cp#Yb(DAD)2-(THF) (Cp# = C5Me5, C5Me4H) were synthesized by the reactions of the ytterbocenes Cp#2Yb(THF)2 with the corresponding DADs in a 1:1 molar ratio. These reactions are accompanied by oxidation of the Yb(II) to Yb(III), cleavage of one Cp#-Yb bond, oxidation of cyclopentadienyl anion, and reduction of the diazabutadiene to dianionic form. It was found that the substituents by the DAD nitrogens (2,6-iPr2C6H3 vs 2,6-Me2C6H3) and imino carbons (H vs Me) do not affect the reaction outcome and afford Cp#Yb(DAD)2-(thf). The amido and alkoxo derivatives XYb(DAD)2-(dme) (X = N(SiMe3)2, tBuO) were obtained by the salt metathesis reactions of the in situ generated species [XYbCl2(thf)n] and Na2(thf)n[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6]. If the reaction was carried out in the presence of Li ions, it afforded an ate-complex {Li(thf)3}{Yb[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6]2-[N(SiMe3)2](μ-Cl)}. The X-ray studies of complexes XYbIII(DAD)2-(L) revealed that they feature the 2σ:η2-type of coordination of dianionic DAD ligands. Introduction of Me-substituents by the imino carbons of DADs leads to some elongation of Yb-Cp# bonds compared to the NCHCHN-analogues. The Yb-CNCCN bonds and the dihedral YbNN-NCCN angles were found to be the most sensitive to replacing H by Me. Unlike the formerly reported complex Cp?Yb[2,6-iPr2C6H3NCHCHNC6H3iPr2-2,6]2-(thf), the variable-temperature magnetic measurements (1.8-300 K) of complexes 3-5 and 7-9 did not reveal thermally induced redox isomeric transformations for these compounds. However, for complex (C5Me4H)Yb[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6](thf) at 9 K, the structural phase transition accompanied by changes of the coordination behavior of the DAD ligand was detected, which might hint for an onset of a temperature-induced redox isomerism. These results clearly indicate high sensitivity of redox isomeric transformations of XYbIII(DAD)2-L to the smallest changes of the structural and electronic properties of the DAD ligands. (Chemical Equation Presented).
Pentamethyl cyclopentadiene preparation method
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Paragraph 0013-0015, (2019/08/07)
The invention relates to a pentamethyl cyclopentadiene preparation method which is characterized in that a Grignard reagent is prepared from chloromethane and magnesium in ether solvents under low-temperature conditions, temperature is reduced, tetramethyl cyclopentanone is dropwise added, temperature reaction is performed, and hydrochloric acid is added after reaction to perform dehydration alkene forming reaction. Post-treatment and rectification under vacuum are performed to obtain qualified products. The preparation method has the advantages that raw materials are inexpensive and easy to obtain, yield is high, production cost can be controlled, process steps are short, conditions are mild, and the preparation method is safe, reliable and suitable for industrial production.
Hemilability of the 1,2-Bis(dimethylphosphino)ethane (dmpe) Ligand in Cp?Mo(NO)(κ2-dmpe)
Holmes, Aaron S.,Patrick, Brian O.,Levesque, Taleah M.,Legzdins, Peter
, p. 11299 - 11309 (2017/09/25)
Reaction of Cp?Mo(NO)Cl2 with 1 equiv of 1,2-bis(dimethylphosphino)ethane (dmpe) in THF at ambient temperature forms [Cp?Mo(NO)(Cl)(κ2-dmpe)]Cl (1), which is isolable as an analytically pure yellow powder in 65% yield. Further addition of 2 equiv of Cp2Co to 1 in CH2Cl2 affords dark red Cp?Mo(NO)(κ2-dmpe) (2), which was isolated in 36% yield by recrystallization from Et2O at -30 °C. Reaction of a benzene solution of 2 with an equimolar amount of elemental sulfur results in the immediate production of dark blue (μ-S)[Cp?Mo(NO)(κ1-dmpeS)]2 (3), which is a rare example of a bimetallic transition-metal complex bridged by only a single sulfur atom and involving Mo=S=Mo bonding. In contrast, reaction of 2 with an excess of sulfur in benzene results in the formation of Cp?Mo(NO)(η2-S2)(κ1-dmpeS) (4). Complex 4 can also be formed by the addition of elemental sulfur to 3, thereby indicating that 3 is a precursor to 4. Cp?Mo(NO)(κ2-dmpe) (2) also undergoes interesting transformations when treated with organic bromides. For instance, reaction of 2 with 5 equiv benzyl bromide in THF produces the bimetallic complex (μ-dmpe)[ Cp?Mo(NO)Br2]2 (5) and bibenzyl after 4 d at 70 °C probably via radical intermediates. In contrast to its reaction with benzyl bromide, complex 2 forms [Mo(NO)Br2(κ2-dmpe)]2 (6), olefin, alkane, and Cp?H when treated with 5 equiv of 1-bromopropane or 1-bromooctane in THF at 70 °C for 72 h. Interestingly, complex 2 does not display any reactivity with bromobenzene or 1-bromoadamantane even after being heated for several days at 70 °C. All new complexes were characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them were established by single-crystal X-ray crystallographic analyses.
Reactivity Study of Pyridyl-Substituted 1-Metalla-2,5-diaza-cyclopenta-2,4-dienes of Group 4 Metallocenes
Becker, Lisanne,Rei?, Fabian,Altenburger, Kai,Spannenberg, Anke,Arndt, Perdita,Jiao, Haijun,Rosenthal, Uwe
supporting information, p. 10826 - 10838 (2016/07/27)
In this work the reactivity of 1-metalla-2,5-diaza-cyclopenta-2,4-dienes of group 4 metallocenes, especially of the pyridyl-substituted examples, towards small molecules is investigated. The addition of H2, CO2, Ph?C≡N, 2-py?C≡N, 1,3-dicyanobenzene or 2,6-dicyanopyridine results in exchange reactions, which are accompanied by the elimination of a nitrile. For CO2, a coordination to the five-membered cycle occurs in case of Cp*2Zr(N=C(2-py)?C(2-py)=N). A 1,4-diaza-buta-1,3-diene complex is formed by H-transfer in the conversion of the analogous titanocene compound with CH3?C≡N, PhCH2?C≡N or acetone. For CH3?C≡N a coupling product of three acetonitrile molecules is established additionally. In order to split off the metallocene from the coupled nitriles, we examined reactions with HCl, PhPCl2, PhPSCl2and SOCl2. In the last case, the respective thiadiazole oxides and the metallocene dichlorides were obtained. A subsequent reaction produced thiadiazoles.
Facile C-H, C-F, C-Cl, and C-C Activation by Oxatitanacyclobutene Complexes
Nguyen, Trang T.,Bertke, Jeffery A.,Gray, Danielle L.,Hull, Kami L.
supporting information, p. 4190 - 4193 (2015/09/22)
Aryl ketones react readily with oxatitanacyclobutenes bearing pentamethylcyclopentadienyl ligands to form unique titanocene complexes resulting from Cp modification and C-H activation. An intermediate in this reaction is intercepted with various functional groups to form carbonyl insertion, C-F activation, and cyclopropane ring-opening products.
