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Lyubov DM, Zakaria H, Nelyubina YV, Aysin RR, Bukalov SS, Trifonov AA. Ca(II) and Yb(II) complexes featuring M(C≡C) 4 structural motif: enforced proximity or genuine η 2 -bonding? Chemistry 2024; 30:e202303533. [PMID: 38070175 DOI: 10.1002/chem.202303533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Indexed: 01/12/2024]
Abstract
Bis(carbazolide) complexes M[3,6-tBu2 -1,8-(RC≡C)2 Carb]2 (THF)n (R=SiMe3 , n=0, M=Ca, Yb; R=Ph, n=1, M=Ca, Yb; n=0, M=Yb) were synthesized through transamination reaction of M[N(SiMe3 )2 ]2 (THF)2 with two molar equivalents of carbazoles. The complexes feature M(η2 -C≡C)4 structural motif composed of M(II) ions encapsulated by four acetylene fragments due to atypical for alkaline- and rare-earth metals η2 -interactions with triple C≡C bond. This interaction is evidenced experimentally by X-ray diffraction, Raman spectroscopy in the solid state and by NMR-spectroscopy in the solution. According to QTAIM analysis there are 4 bond critical points (3;-1) between the metal atom and each of the triple bonds, which are connected by a strongly curved, almost T-shaped bond pathway.
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Affiliation(s)
- Dmitry M Lyubov
- G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Russia, 49 Tropinina str., GSP-445, 603950, Nizhny Novgorod
| | - Hamza Zakaria
- G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Russia, 49 Tropinina str., GSP-445, 603950, Nizhny Novgorod
- N. I. Lobachevsky State University of Nizhny Novgorod, Gagarina Avenue 23, 603950, Nizhny Novgorod, Russia
| | - Yulia V Nelyubina
- A. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Gagarina Avenue 23, 603950, Nizhny Novgorod, Russia
- 28 Vavilova str., 119334, Moscow, Russia
| | - Rinat R Aysin
- A. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Gagarina Avenue 23, 603950, Nizhny Novgorod, Russia
- 28 Vavilova str., 119334, Moscow, Russia
| | - Sergey S Bukalov
- A. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Gagarina Avenue 23, 603950, Nizhny Novgorod, Russia
- 28 Vavilova str., 119334, Moscow, Russia
| | - Alexander A Trifonov
- G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Russia, 49 Tropinina str., GSP-445, 603950, Nizhny Novgorod
- A. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Gagarina Avenue 23, 603950, Nizhny Novgorod, Russia
- 28 Vavilova str., 119334, Moscow, Russia
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2
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Reactions of a Bis(pentalene)dititanium complex with alkenes; the molecular structure of the butadiene complex [Ti2(µ: η5,η5-Pn††)2(μ: η2,η2-s-trans-C4H6)] (Pn†† = 1,4-(Si Pr3)2-C8H4). Polyhedron 2022. [DOI: 10.1016/j.poly.2021.115574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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3
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Fortier S, Gomez-Torres A. Redox chemistry of discrete low-valent titanium complexes and low-valent titanium synthons. Chem Commun (Camb) 2021; 57:10292-10316. [PMID: 34533140 DOI: 10.1039/d1cc02772g] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Titanium is a versatile metal that has important applications in practical synthesis, though this is typically limited to stoichiometric reactions or Lewis acid catalysis. Recently, interest has grown in using titanium and other early-metals for redox catalysis; however, notable limitations exist due to the thermodynamic preference of these metals to adopt high oxidation states. Nonetheless, discrete low-valent titanium (LVT) complexes and their synthons (titanium complexes which chemically behave as LVT sources) are known. Here, we detail the various ligand platforms that are capable of stabilizing LVT compounds and present the redox chemistry of these systems. This includes a discussion of recent developments in the use of LVT synthons for accessing fully reversible oxidative-addition/reductive-elimination reactions.
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Affiliation(s)
- Skye Fortier
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, TX 79968, USA.
| | - Alejandra Gomez-Torres
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, TX 79968, USA.
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4
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Gyepes R, Pinkas J, Kubišta J, Mach K, Horáček M. Sunlight-induced dehydrogenation rearrangement of the dititanium complex [Ti(η5-C5HMe4)(μ-η1: η5-C5Me4)]2. J Organomet Chem 2021. [DOI: 10.1016/j.jorganchem.2020.121663] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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5
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Lindenau K, Jannsen N, Rippke M, Al Hamwi H, Selle C, Drexler HJ, Spannenberg A, Sawall M, Neymeyr K, Heller D, Reiß F, Beweries T. Mechanistic insights into dehydrocoupling of amine boranes using dinuclear zirconocene complexes. Catal Sci Technol 2021. [DOI: 10.1039/d1cy00531f] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Catalytic dehydrocoupling of H3B·NMe2H using Cp2Zr(Cl)(μ-Me3SiC3SiMe3)Zr(Cl)Cp2 (1)/MeLi was studied. Spectroscopic monitoring and stoichiometric experiments show the formation and interconversion of several catalytically active Zr species.
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Affiliation(s)
| | - Nora Jannsen
- Leibniz-Institut für Katalyse e.V
- 18059 Rostock
- Germany
| | - Mirko Rippke
- Leibniz-Institut für Katalyse e.V
- 18059 Rostock
- Germany
| | | | - Carmen Selle
- Leibniz-Institut für Katalyse e.V
- 18059 Rostock
- Germany
| | | | | | - Mathias Sawall
- Institut für Mathematik
- Universität Rostock
- 18055 Rostock
- Germany
| | - Klaus Neymeyr
- Leibniz-Institut für Katalyse e.V
- 18059 Rostock
- Germany
- Institut für Mathematik
- Universität Rostock
| | - Detlef Heller
- Leibniz-Institut für Katalyse e.V
- 18059 Rostock
- Germany
| | - Fabian Reiß
- Leibniz-Institut für Katalyse e.V
- 18059 Rostock
- Germany
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6
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Reinholdt A, Pividori D, Laughlin AL, DiMucci IM, MacMillan SN, Jafari MG, Gau MR, Carroll PJ, Krzystek J, Ozarowski A, Telser J, Lancaster KM, Meyer K, Mindiola DJ. A Mononuclear and High-Spin Tetrahedral Ti II Complex. Inorg Chem 2020; 59:17834-17850. [PMID: 33258366 PMCID: PMC7928263 DOI: 10.1021/acs.inorgchem.0c02586] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Indexed: 12/31/2022]
Abstract
A high-spin, mononuclear TiII complex, [(TptBu,Me)TiCl] [TptBu,Me- = hydridotris(3-tert-butyl-5-methylpyrazol-1-yl)borate], confined to a tetrahedral ligand-field environment, has been prepared by reduction of the precursor [(TptBu,Me)TiCl2] with KC8. Complex [(TptBu,Me)TiCl] has a 3A2 ground state (assuming C3v symmetry based on structural studies), established via a combination of high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy, solution and solid-state magnetic studies, Ti K-edge X-ray absorption spectroscopy (XAS), and both density functional theory and ab initio (complete-active-space self-consistent-field, CASSCF) calculations. The formally and physically defined TiII complex readily binds tetrahydrofuran (THF) to form the paramagnetic adduct [(TptBu,Me)TiCl(THF)], which is impervious to N2 binding. However, in the absence of THF, the TiII complex captures N2 to produce the diamagnetic complex [(TptBu,Me)TiCl]2(η1,η1;μ2-N2), with a linear Ti═N═N═Ti topology, established by single-crystal X-ray diffraction. The N2 complex was characterized using XAS as well as IR and Raman spectroscopies, thus establishing this complex to possess two TiIII centers covalently bridged by an N22- unit. A π acid such as CNAd (Ad = 1-adamantyl) coordinates to [(TptBu,Me)TiCl] without inducing spin pairing of the d electrons, thereby forming a unique high-spin and five-coordinate TiII complex, namely, [(TptBu,Me)TiCl(CNAd)]. The reducing power of the coordinatively unsaturated TiII-containing [(ΤptBu,Me)TiCl] species, quantified by electrochemistry, provides access to a family of mononuclear TiIV complexes of the type [(TptBu,Me)Ti═E(Cl)] (with E2- = NSiMe3, N2CPh2, O, and NH) by virtue of atom- or group-transfer reactions using various small molecules such as N3SiMe3, N2CPh2, N2O, and the bicyclic amine 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene.
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Affiliation(s)
- Anders Reinholdt
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Daniel Pividori
- Inorganic
Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander University (FAU) Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Alexander L. Laughlin
- Baker
Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Ida M. DiMucci
- Baker
Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Samantha N. MacMillan
- Baker
Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Mehrafshan G. Jafari
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Michael R. Gau
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Patrick J. Carroll
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - J. Krzystek
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
| | - Andrew Ozarowski
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
| | - Joshua Telser
- Department
of Biological, Physical and Health Sciences, Roosevelt University, Chicago, Illinois 60605, United States
| | - Kyle M. Lancaster
- Baker
Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Karsten Meyer
- Inorganic
Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander University (FAU) Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Daniel J. Mindiola
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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7
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Rosenthal U. A Ghost Trapped: Realization of the 1‐Titanacyclobuta‐2,3‐diene as the First Four‐Membered Group 4 Metallacycloallene. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201900661] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- U. Rosenthal
- Leibniz Institute for Catalysis at the University of Rostock Albert‐Einstein‐Str. 29A 18059 Rostock Germany
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8
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Low-valent ansa-dimethylsilylene-, dimethylmethylene-bis(cyclopentadienyl) titanium compounds and ansa-titanium–magnesium complexes. J Organomet Chem 2019. [DOI: 10.1016/j.jorganchem.2019.03.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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9
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Rosenthal U. Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201801484] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Uwe Rosenthal
- Leibniz Institute for Catalysis at the University of Rostock Albert‐Einstein‐Str. 29A 18059 Rostock Germany
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10
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Pinkas J, Mach K, Kubišta J, Horáček M, Szarka K, Gyepes R. Insertion of 1-t-butylpropyne into singly tucked-in permethyltitanocene. Synthesis, crystal structure of product and transition-state geometry. J Mol Struct 2018. [DOI: 10.1016/j.molstruc.2018.04.071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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11
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Reiß F, Reiß M, Spannenberg A, Jiao H, Hollmann D, Arndt P, Rosenthal U, Beweries T. Titanocene Silylpropyne Complexes: Promising Intermediates en route to a Four-Membered 1-Metallacyclobuta-2,3-diene? Chemistry 2017; 23:14158-14162. [PMID: 28846172 DOI: 10.1002/chem.201703444] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Indexed: 11/10/2022]
Abstract
Coordination of the alkyl-substituted alkynes Me3 SiC2 CH2 R (1: R=SiMe3 ; 2: R=N(SiMe3 )2 ) to titanocene centres [Cp'2 Ti] (Cp'=Cp, Cp*) yields stable alkyne complexes of the type Cp'2 Ti(η2 -Me3 SiC2 CH2 R) (3: Cp'=Cp, R=SiMe3 ; 5: Cp'=Cp, R=N(SiMe3 )2 ; 6: Cp'=Cp*, R=SiMe3 ) that are not prone to alkyne/allene isomerisation. When reacting alkyne 2 with Cp*2 TiCl2 and Mg formation of the complex Cp*2 Ti(III)(η3 -Me3 SiC2 CH2 ) (7) which displays a propargylic unit coordinated to the TiIII centre takes place. All complexes were fully characterised, the molecular structures for 5, 6, and 7 are discussed.
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Affiliation(s)
- Fabian Reiß
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059, Rostock, Germany
| | - Melanie Reiß
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059, Rostock, Germany
| | - Anke Spannenberg
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059, Rostock, Germany
| | - Haijun Jiao
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059, Rostock, Germany
| | - Dirk Hollmann
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059, Rostock, Germany
| | - Perdita Arndt
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059, Rostock, Germany
| | - Uwe Rosenthal
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059, Rostock, Germany
| | - Torsten Beweries
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059, Rostock, Germany
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12
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Pinkas J, Gyepes R, Císařová I, Kubišta J, Horáček M, Mach K. Decamethyltitanocene hydride intermediates in the hydrogenation of the corresponding titanocene-(η 2-ethene) or (η 2-alkyne) complexes and the effects of bulkier auxiliary ligands. Dalton Trans 2017; 46:8229-8244. [PMID: 28617500 DOI: 10.1039/c7dt01545c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
1H NMR studies of reactions of titanocene [Cp*2Ti] (Cp* = η5-C5Me5) and its derivatives [Cp*(η5:η1-C5Me4CH2)TiMe] and [Cp*2Ti(η2-CH2[double bond, length as m-dash]CH2)] 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-R1C[triple bond, length as m-dash]CR2)] (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.
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Affiliation(s)
- Jiří Pinkas
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic.
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13
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Gyepes R, Pinkas J, Císařová I, Kubišta J, Horáček M, Mach K. Synthesis, molecular and electronic structure of a stacked half-sandwich dititanium complex incorporating a cyclic π-faced bridging ligand. RSC Adv 2016. [DOI: 10.1039/c6ra14940e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The thermally robust ground singlet state complex [bis(η5-pentamethylcyclopentadienyltitanium)-μ-(η4:η4-1,2,4,5-tetrakis(trimethylsilyl)cyclohexa-1-4-diene-3,6-diyl)] (3) arises from thermolysis of Cp*TiMe3.
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Affiliation(s)
- Róbert Gyepes
- J. Selye University
- Department of Chemistry
- Faculty of Education
- 945 01 Komárno
- Slovak Republic
| | - Jiří Pinkas
- J. Heyrovský Institute of Physical Chemistry
- Academy of Sciences of the Czech Republic, v.v.i
- 182 23 Prague 8
- Czech Republic
| | - Ivana Císařová
- Department of Inorganic Chemistry
- Faculty of Science
- Charles University in Prague
- 128 40 Prague 2
- Czech Republic
| | - Jiří Kubišta
- J. Heyrovský Institute of Physical Chemistry
- Academy of Sciences of the Czech Republic, v.v.i
- 182 23 Prague 8
- Czech Republic
| | - Michal Horáček
- J. Heyrovský Institute of Physical Chemistry
- Academy of Sciences of the Czech Republic, v.v.i
- 182 23 Prague 8
- Czech Republic
| | - Karel Mach
- J. Heyrovský Institute of Physical Chemistry
- Academy of Sciences of the Czech Republic, v.v.i
- 182 23 Prague 8
- Czech Republic
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14
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Pinkas J, Císařová I, Gyepes R, Kubišta J, Mach K, Horáček M. Substituent effects in reduction-induced synthesis of ansa-titanocenes. TRANSIT METAL CHEM 2015. [DOI: 10.1007/s11243-015-0006-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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15
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Phadke N, Findlater M. Isomerization of Internal Alkynes to Iridium(III) Allene Complexes via C-H Bond Activation: Expanded Substrate Scope, and Progress towards a Catalytic Methodology. Molecules 2015; 20:20195-205. [PMID: 26569203 PMCID: PMC6332053 DOI: 10.3390/molecules201119686] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 10/29/2015] [Accepted: 11/02/2015] [Indexed: 11/17/2022] Open
Abstract
The synthesis of a series of allene complexes (POCOP)Ir(η²-RC=(.)=CR') 1b-4b (POCOP = 2,6-bis(di-tert-butylphosphonito)benzene) via isomerization of internal alkynes is reported. We have demonstrated that the application of this methodology is viable for the isomerization of a wide variety of alkyne substrates. Deuterium labeling experiments support our proposed mechanism. The structures of the allene complexes 1b-4b were determined using spectroscopic data analysis. Additionally, the solid-state molecular structure of complex 2b was determined using single crystal X-ray diffraction studies and it confirmed the assignment of an iridium-bound allene isomerization product. The rates of isomerization were measured using NMR techniques over a range of temperatures to allow determination of thermodynamic parameters. Finally, we report a preliminary step towards developing a catalytic methodology; the allene may be liberated from the metal center by exposure of the complex to an atmosphere of carbon monoxide.
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Affiliation(s)
- Neha Phadke
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
| | - Michael Findlater
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
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