0000000001132246
AUTHOR
Warren E. Piers
showing 29 related works from this author
Direct observation of a borane-silane complex involved in frustrated Lewis-pair-mediated hydrosilylations.
2014
Perfluorarylborane Lewis acids catalyse the addition of silicon-hydrogen bonds across C=C, C=N and C=O double bonds. This 'metal-free' hydrosilylation has been proposed to occur via borane activation of the silane Si-H bond, rather than through classical Lewis acid/base adducts with the substrate. However, the key borane/silane adduct had not been observed experimentally. Here it is shown that the strongly Lewis acidic, antiaromatic 1,2,3-tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene forms an observable, isolable adduct with triethylsilane. The equilibrium for adduct formation was studied quantitatively through variable-temperature NMR spectroscopic investigations. The interactio…
Zirconocene-Based Methods for the Preparation of BN-Indenes : Application to the Synthesis of 1,5-Dibora-4a,8a-diaza-1,2,3,5,6,7-hexaaryl-4,8-dimethy…
2017
A method for the preparation of 3-bora-9aza-indene heterocycles based on zirconocene mediated functionalization of the ortho-CH bonds of pyridines has been developed and used to make two such compounds. Unlike other methods, the boron center in these heterocycles remains functionalized with a chloride ligand and so the compounds can be further elaborated through halide abstraction and reduction. The utility of the method was further demonstrated by applying it towards the preparation of 1,5- dibora-4a,8a-diaza BN analogues of the intriguing hydrocarbon s-indacene starting from 2,5-dimethylpyrazine. Gram quantities of one such compound was prepared and fully characterized, and both experimen…
Divergent reactivity of nucleophilic 1-bora-7a-azaindenide anions
2017
The reactions of 1-bora-7a-azaindenide anions, prepared in moderate to excellent yields by reduction of the appropriate 1-bora-7a-azaindenyl chlorides with KC8 in THF, with alkyl halides and carbon dioxide were studied. With alkyl halides (CH2Cl2, CH3I and BrCH(D)CH(D)tBu), the anions behave as boron anions, alkylating the boron centre via a classic SN2 mechanism. This was established with DFT methods and via experiments utilizing the neo-hexyl stereoprobe BrCH(D)CH(D)tBu. These reactions were in part driven by a re-aromatization of the six membered pyridyl ring upon formation of the product. Conversely, in the reaction of the 1-bora-7a-azaindenide anions with CO2, a novel carboxylation of …
Mechanistic Studies on the Metal-Free Activation of Dihydrogen by Antiaromatic Pentarylboroles
2012
The perfluoro- and perprotiopentaphenylboroles 1 and 2 react with dihydrogen to effect H-H bond cleavage and formation of boracyclopentene products. The mechanism of this reaction has been studied experimentally through evaluation of the kinetic properties of the slower reaction between 2 and H(2). The reaction is first-order in both [borole] and [H(2)] with activation parameters of ΔH(‡) = 34(8) kJ/mol and ΔS(‡) = -146(25) J mol(-1) K(-1). A minimal kinetic isotope effect of 1.10(5) was observed, suggesting an asynchronous geometry for H-H cleavage in the rate-limiting transition state. To explain the stereochemistry of the observed products, a ring-opening/ring-closing mechanism is propos…
Boron–nitrogen substituted dihydroindeno[1,2-b]fluorene derivatives as acceptors in organic solar cells
2019
The electrophilic borylation of 2,5-diarylpyrazines results in the formation of boron–nitrogen doped dihydroindeno[1,2-b]fluorene which can be synthesized using standard Schlenk techniques and worked up and handled readily under atmospheric conditions. Through transmetallation via diarylzinc reagents a series of derivatives were synthesized which show broad visible to near-IR light absorption profiles that highlight the versatility of this BN substituted core for use in optoelectronic devices. The synthesis is efficient, scalable and allows for tuning through changes in substituents on the planar heterocyclic core and at boron. Exploratory evaluation in organic solar cell devices as non-ful…
Hydrogen activation with perfluorinated organoboranes: 1,2,3-tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene
2013
The perfluorinated boraindene was synthesized and fully characterized. Both computational and crystallographic data show that is antiaromatic. Compound was shown to react reversibly with H2 and to catalyse the hydrogenation of cyclohexene. The mechanism of catalysis was probed experimentally and computationally.
Dihydrogen Activation by Antiaromatic Pentaarylboroles
2010
Facile metal-free splitting of molecular hydrogen (H(2)) is crucial for the utilization of H(2) without the need for toxic transition-metal-based catalysts. Frustrated Lewis pairs (FLPs) are a new class of hydrogen activators wherein interactions with both a Lewis acid and a Lewis base heterolytically disrupt the hydrogen-hydrogen bond. Here we describe the activation of hydrogen exclusively by a boron-based Lewis acid, perfluoropentaphenylborole. This antiaromatic compound reacts extremely rapidly with H(2) in both solution and the solid state to yield boracyclopent-3-ene products resulting from addition of hydrogen atoms to the carbons alpha to boron in the starting borole. The disruption…
Hydrogen activation with perfluorinated organoboranes: 1,2,3- tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene
2014
The perfluorinated boraindene 3 was synthesized and fully characterized. Both computational and crystallographic data show that 3 is antiaromatic. Compound 3 was shown to react reversibly with H2 and to catalyse the hydrogenation of cyclohexene. The mechanism of catalysis was probed experimentally and computationally. peerReviewed
CCDC 956380: Experimental Crystal Structure Determination
2013
Related Article: Adrian Y. Houghton, Virve A. Karttunen, Warren E. Piers, Heikki M. Tuononen|2014|Chem.Commun.|50|1295|doi:10.1039/C3CC48796B
CCDC 1575610: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 1584568: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, J. Mikko Rautiainen, Warren E. Piers, Heikki M. Tuononen, Chris Gendy|2018|Dalton Trans.|47|734|doi:10.1039/C7DT04350C
CCDC 1575611: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 956381: Experimental Crystal Structure Determination
2013
Related Article: Adrian Y. Houghton, Virve A. Karttunen, Warren E. Piers, Heikki M. Tuononen|2014|Chem.Commun.|50|1295|doi:10.1039/C3CC48796B
CCDC 956383: Experimental Crystal Structure Determination
2013
Related Article: Adrian Y. Houghton, Virve A. Karttunen, Warren E. Piers, Heikki M. Tuononen|2014|Chem.Commun.|50|1295|doi:10.1039/C3CC48796B
CCDC 956379: Experimental Crystal Structure Determination
2013
Related Article: Adrian Y. Houghton, Virve A. Karttunen, Warren E. Piers, Heikki M. Tuononen|2014|Chem.Commun.|50|1295|doi:10.1039/C3CC48796B
CCDC 1575616: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 1575614: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 1584567: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, J. Mikko Rautiainen, Warren E. Piers, Heikki M. Tuononen, Chris Gendy|2018|Dalton Trans.|47|734|doi:10.1039/C7DT04350C
CCDC 1010911: Experimental Crystal Structure Determination
2014
Related Article: Adrian Y. Houghton, Juha Hurmalainen, Akseli Mansikkamäki, Warren E. Piers, Heikki M. Tuononen|2014|Nature Chemistry|6|983|doi:10.1038/nchem.2063
CCDC 1937170: Experimental Crystal Structure Determination
2019
Related Article: Matthew M. Morgan, Maryam Nazari, Thomas Pickl, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Gregory C. Welch, Benjamin S. Gelfand|2019|Chem.Commun.|55|11095|doi:10.1039/C9CC05103A
CCDC 1575615: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 1575617: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 912008: Experimental Crystal Structure Determination
2014
Related Article: Adrian Y. Houghton , Virve A. Karttunen , Cheng Fan , Warren E. Piers , and Heikki M. Tuononen|2013|J.Am.Chem.Soc.|135|941|doi:10.1021/ja311842r
CCDC 1575612: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 1575609: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 1937169: Experimental Crystal Structure Determination
2019
Related Article: Matthew M. Morgan, Maryam Nazari, Thomas Pickl, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Gregory C. Welch, Benjamin S. Gelfand|2019|Chem.Commun.|55|11095|doi:10.1039/C9CC05103A
CCDC 956378: Experimental Crystal Structure Determination
2013
Related Article: Adrian Y. Houghton, Virve A. Karttunen, Warren E. Piers, Heikki M. Tuononen|2014|Chem.Commun.|50|1295|doi:10.1039/C3CC48796B
CCDC 1575613: Experimental Crystal Structure Determination
2017
Related Article: Matthew M. Morgan, Evan A. Patrick, J. Mikko Rautiainen, Heikki M. Tuononen, Warren E. Piers, Denis M. Spasyuk|2017|Organometallics|36|2541|doi:10.1021/acs.organomet.7b00051
CCDC 956382: Experimental Crystal Structure Determination
2013
Related Article: Adrian Y. Houghton, Virve A. Karttunen, Warren E. Piers, Heikki M. Tuononen|2014|Chem.Commun.|50|1295|doi:10.1039/C3CC48796B