Max C Holthausen | Goethe-Universität Frankfurt am Main (original) (raw)
Papers by Max C Holthausen
Chemistry: A European Journal, Jun 1, 2012
The reaction of nido‐[1,2‐(Cp*RuH)2B3H7] (1 a, Cp*=η5‐C5Me5) with [Mo(CO)3(CH3CN)3] under mild co... more The reaction of nido‐[1,2‐(Cp*RuH)2B3H7] (1 a, Cp*=η5‐C5Me5) with [Mo(CO)3(CH3CN)3] under mild conditions yields the new metallaborane arachno‐[(Cp*RuCO)2B2H6] (2). Compound 2 catalyzes the cyclotrimerization of a variety of internal‐ and terminal alkynes to yield mixtures of 1,3,5‐ and 1,2,4‐substituted benzenes. The reactivities of nido‐1 a and arachno‐2 with alkynes demonstrates that a change in geometry from nido to arachno drives a change in the reaction from alkyne‐insertion to catalytic cyclotrimerization, respectively. Density functional calculations have been used to evaluate the reaction pathways of the cyclotrimerization of alkynes catalyzed by compound 2. The reaction involves the formation of a ruthenacyclic intermediate and the subsequent alkyne‐insertion step is initiated by a [2+2] cycloaddition between this intermediate and an alkyne. The experimental and quantum‐chemical results also show that the stability of the metallacyclic intermediate is strongly dependent on the nature of the substituents that are present on the alkyne.
Nucleation and Atmospheric Aerosols, 2022
In this work innovative additive printing methods for formation of polycrystalline silicon (poly-... more In this work innovative additive printing methods for formation of polycrystalline silicon (poly-Si) and polycrystalline silicon carbide (poly-SiC) layers of local tunnel oxide passivating contacts (TOPCon) is evaluated. Replacement of conventional vacuum processes and vapor-phase deposition by additive printing of Si in fabrication process of high efficiency solar cells reduces processing complexity, and, hence manufacturing costs. Reliable inkjet-and FlexTrail-printing processes are developed for liquid-phase polysilane and organic polysilazane inks that are precursors of Si and SiC, respectively. FlexTrail is introduced as a potential technology to print uniform closed thin films of polysilane free of ruptures. Moreover, from inkjet-printing of the developed polysilane ink, homogenous, closed and crack free thin films of poly-Si are obtained after high temperature annealing. The polysilane ink is formulated considering evaluation of several solvents and photoinduced polymerization conditions. Inkjet-printing process development and optimization according to high frequency rheological characterization of organic polysilazane (OPSZ) is presented. Printed thin films are characterized after high temperature annealing (T = 950 °C, t = 60 min) to be uniform and free of micro cracks.
Chemistry-an Asian Journal, May 17, 2023
Ferrocene‐based N‐heterocyclic plumbylenes fc[(NSiMe2R)2Pb:] (1; fc=1,1’‐ferrocenylene) are easil... more Ferrocene‐based N‐heterocyclic plumbylenes fc[(NSiMe2R)2Pb:] (1; fc=1,1’‐ferrocenylene) are easily accessible by transamination from [(Me3Si)2N]2Pb and the corresponding 1,1’‐diaminoferrocene derivatives fc(NHSiMe2R)2. They may form unconventional dimers 2 by a process, which causes the cleavage of a cyclopentadienyl C−H bond and the formation of a Pb−C and an N−H bond. The monomer‐dimer equilibrium (2 1⇆2) has been addressed experimentally and computationally. It critically depends on the steric demand of the N‐substituents SiMe2R, which has been varied systematically by using homologues with aliphatic (R=methyl, ethyl, isopropyl, tert‐butyl) and aromatic units (R=phenyl, mesityl, ferrocenyl). Even in the sterically least congested case (R=methyl), dimerization is only slightly exergonic. It eventually becomes prohibitively endergonic with increasingly larger substituents and is thus not observed for R=tert‐butyl, mesityl, and ferrocenyl. R=phenyl represents a borderline case, where the dimer is still detectable in the equilibrium mixture, albeit as a very minor component, in accord with the slightly endergonic Gibbs free energy change calculated for its formation. Addition of 4‐dimethylaminopyridine (DMAP) to the monomer‐dimer equilibrium mixtures cleanly affords the corresponding adducts [1(DMAP)], irrespective of the equilibrium composition.
Chemistry-an Asian Journal, May 17, 2023
Ferrocene‐based N‐heterocyclic plumbylenes fc[(NSiMe2R)2Pb:] (1; fc=1,1’‐ferrocenylene) are easil... more Ferrocene‐based N‐heterocyclic plumbylenes fc[(NSiMe2R)2Pb:] (1; fc=1,1’‐ferrocenylene) are easily accessible by transamination from [(Me3Si)2N]2Pb and the corresponding 1,1’‐diaminoferrocene derivatives fc(NHSiMe2R)2. They may form unconventional dimers 2 by a process, which causes the cleavage of a cyclopentadienyl C−H bond and the formation of a Pb−C and an N−H bond. The monomer‐dimer equilibrium (2 1⇆2) has been addressed experimentally and computationally. It critically depends on the steric demand of the N‐substituents SiMe2R, which has been varied systematically by using homologues with aliphatic (R=methyl, ethyl, isopropyl, tert‐butyl) and aromatic units (R=phenyl, mesityl, ferrocenyl). Even in the sterically least congested case (R=methyl), dimerization is only slightly exergonic. It eventually becomes prohibitively endergonic with increasingly larger substituents and is thus not observed for R=tert‐butyl, mesityl, and ferrocenyl. R=phenyl represents a borderline case, where the dimer is still detectable in the equilibrium mixture, albeit as a very minor component, in accord with the slightly endergonic Gibbs free energy change calculated for its formation. Addition of 4‐dimethylaminopyridine (DMAP) to the monomer‐dimer equilibrium mixtures cleanly affords the corresponding adducts [1(DMAP)], irrespective of the equilibrium composition.
Chemistry: A European Journal, Sep 4, 2018
Journal of the American Chemical Society, May 26, 2021
Two silylene molecules oxidatively react under formal [1 + 2 + 1]-cycloaddition to the C≡N bond o... more Two silylene molecules oxidatively react under formal [1 + 2 + 1]-cycloaddition to the C≡N bond of nitriles to yield 1-aza-2,4-disilabicyclo[1.1.0]butanes (L)(Cl)Si[μ-η1,2-NC(p-RC6H4)]Si(Cl)(L) (L = PhC(NtBu)2, R = CF3 (2), F (3), Cl (4), Br (5)). The strongly folded bicyclic SiCNSi cores in 2-5 feature inverted bridgehead carbon atoms and superelongated C-N bonds [1.745(12) to 1.801(2) Å], exceeding the lengths of C-N single bonds in known silaaziridines by up to 23%. Detailed bonding analysis discloses C-N bonding interactions, sharing far-reaching similarities with the central C-C bond in [1.1.1]propellane.
Chemistry: A European Journal, Aug 9, 2017
Ac ombined experimentala nd theoretical study of the high-temperature reactiono fS iCl 4 and elem... more Ac ombined experimentala nd theoretical study of the high-temperature reactiono fS iCl 4 and elemental silicon is presented. The nature and reactivity of the product formed upon rapid coolingo ft he gaseous reactionm ixture is investigated by comparison with the defined model compounds cyclo-Si 5 Cl 10 , n-Si 5 Cl 12 and n-Si 4 Cl 10 .ADFT assessment provides mechanistic insight into the oligosilane formation. Experimental 29 Si NMR investigations, supported by quantum-chemical 29 Si NMR calculations, consistently show that the reactionp roduct is composed of discrete molecular perchlorinated oligosilanes. Low-temperature chlorination is an unexpectedly selective means for the transformation of cyclosilanes to acyclic speciesb ye ndocyclic SiÀSi bond cleavage, and we provide am echanistic rationalization for this observation. In contrast to the raw material, the product obtained after low-temperature chlorination represents an efficient source of neo-Si 5 Cl 12 or the amine-stabilizedd isilene EtMe 2 N•SiCl 2 Si(SiCl 3) 2 through reactionwith aliphatic amines.
Chemistry: A European Journal, Aug 16, 2016
A detailed quantum-chemical study on the amine-induced disproportionation reaction of perchlorina... more A detailed quantum-chemical study on the amine-induced disproportionation reaction of perchlorinated silanes to neo-Si5 Cl12 is reported. The key intermediate in the resulting mechanistic scenario is a dichlorosilylene amine adduct, which is in tune with recent experimental findings. Yet, at variance with the generally accepted notion of silicon-chain growth by concerted silylene insertion into Si-Cl bonds of lower silanes, the formation of neo-Si5 Cl12 follows more complex pathways. The reactivity is dominated by the Lewis-base character of the dichlorosilylene amine adduct and characterized by three elementary steps that bear close resemblance to the key elementary steps identified earlier for the chloride-induced disproportionation of Si2 Cl6 . NBO and QTAIM analyses of the key reactive species SiCl2 ⋅NMe3 and SiCl3 (-) provide a rationale for these striking similarities.
ACS Catalysis, Oct 10, 2014
Acceptorless dehydrogenation of alcohols, an important organic transformation, was accomplished w... more Acceptorless dehydrogenation of alcohols, an important organic transformation, was accomplished with welldefined and inexpensive iron-based catalysts supported by a cooperating PNP pincer ligand. Benzylic and aliphatic secondary alcohols were dehydrogenated to the corresponding ketones in good isolated yields upon release of dihydrogen. Primary alcohols were dehydrogenated to esters and lactones, respectively. Mixed primary/secondary diols were oxidized at the secondary alcohol moiety with good chemoselectivity. The mechanism of the reaction was investigated using both experiment and DFT calculations, and the crucial role of metal−ligand cooperativity in the reaction was elucidated. The iron complexes are also excellent catalysts for the hydrogenation of challenging ketone substrates at ambient temperature under mild H 2 pressure, the reverse of secondary alcohol dehydrogenation.
Nature Chemistry, Dec 16, 2020
The authors feel that some relevant references were missing from the version of this Article orig... more The authors feel that some relevant references were missing from the version of this Article originally published; the newly added references 44-47 have been cited in a new paragraph, beginning 'Our approach can be contrasted to' , which precedes the 'Results and discussion' section. These changes have now been made.
Chemical Communications, 2021
The reaction of a stable silylene with Ph2CCO and OCCCO respectively afforded the first sil... more The reaction of a stable silylene with Ph2CCO and OCCCO respectively afforded the first silaallene oxide and a silylketene, whose hydrolysis furnished a stable methyleneketene.
Inorganic Chemistry, Jul 2, 2021
Herein, we report on a facile and selective one-pot synthetic route to silicon-boron radicals. Re... more Herein, we report on a facile and selective one-pot synthetic route to silicon-boron radicals. Reduction of Br2BTip (Tip = 2,4,6-iPrC6H2) with KC8 in the presence of LSi-R affords LSi(tBu)-B(Br)Tip (1) and LSi(N(TMS)2)-B(Br)Tip (2) [L = PhC(NtBu)2]. These first examples of silicon-boron isolated radical species feature spin density on the silicon and boron atoms. 1 and 2 exhibit extraordinary stability to high temperatures under inert conditions in solution and air stability in the solid state. Both radicals have been isolated and fully characterized by electron paramagnetic resonance spectroscopy, SQUID magnetometry, mass spectrometry, cyclic voltammetry, single-crystal X-ray structure analysis, and density functional theory calculations. Moreover, compound 1 exhibits one-electron transfer when treated with 1 equiv of AgSO3CF3 and [Ph3C]+[B(C6F5)4]-, respectively, resulting in the corresponding cations [LSi(tBu)-B(Br)Tip]+[CF3SO3]- (3) and [LSi(tBu)-B(Br)Tip]+[B(C6F5)4]- (4). Compounds 3 and 4 have been characterized with multinuclear NMR and mass spectrometry.
Journal of the American Chemical Society, Nov 21, 2022
Chemical Science, 2019
The one-electron reduction of (CAAC Me)BCl 3 (CAAC Me ¼ 1-(2,6-diisopropylphenyl)-3,3,5,5tetramet... more The one-electron reduction of (CAAC Me)BCl 3 (CAAC Me ¼ 1-(2,6-diisopropylphenyl)-3,3,5,5tetramethylpyrrolidin-2-ylidene) yields the dichloroboryl radical [(CAAC Me)BCl 2 ]c. Furthermore, the twofold reduction of (CAAC Me)BCl 3 in the presence of a range of Lewis bases (L ¼ CAAC Me , N-heterocyclic carbene, phosphine) yields a series of doubly base-supported (CAAC Me)LBCl chloroborylenes, all of which were structurally characterised. NMR and UV-vis spectroscopic and electrochemical data for (CAAC Me)LBCl show that the boron centre becomes more electron-rich and the HOMO-LUMO gap widens as L becomes less p-accepting. A [(CAAC Me)BCl 2 ] À boryl anion coordination polymer was isolated as a potential intermediate in these reductions. In most cases the reduction of the chloroborylenes resulted in the formation of the corresponding hydroborylenes or derivatives thereof, as well as ligand C-H activation products.
Science, Mar 22, 2019
Boron brings nitrogen together Whereas carbon is prone to making chains, nitrogen usually sticks ... more Boron brings nitrogen together Whereas carbon is prone to making chains, nitrogen usually sticks to itself just once in the particularly stable form of N 2 . Légaré et al. now show that boron can coax two N 2 molecules together under reductive conditions below room temperature. Two borylene units sandwiched the resulting N 4 chain between them. Science , this issue p. 1329
Angewandte Chemie, Jan 3, 2019
Leaded ferrocene: An unprecedented type of dimerization is shown by an N-heterocyclic plumbylene ... more Leaded ferrocene: An unprecedented type of dimerization is shown by an N-heterocyclic plumbylene with ferrocenylene backbone. The initially formed aggregational dimer undergoes an intramolecular electrophilic substitution by an endo attack of a Pb II atom, causing the cleavage of a CH bond and the formation of a PbC and an NH bond. The reaction affords a planar-chiral ferrocene derivative and is the first example of a CH activation with Pb II .
Nachrichten Aus Der Chemie, Nov 1, 2005
Journal of the American Chemical Society, Mar 28, 2023
Chem, Jul 1, 2021
Summary In contrast to its lighter congener N2, neutral diphosphorus with a P≡P triple bond is a ... more Summary In contrast to its lighter congener N2, neutral diphosphorus with a P≡P triple bond is a highly reactive species observable only in the gas phase and by matrix isolation. Previous stabilization efforts with Lewis bases (e.g., carbenes) or by transition-metal coordination led to charge transfer to highly electrophilic P2 and thus to significant reduction of the bond order. Here, we report the crystallographic, spectroscopic, and quantum chemical characterization of the redox series [(μ2,η1:η1-P2){Pt(PNP)}2] (PNP = N(CHCHPtBu2)2), which features (P2)2–, (P2)⋅–, and (P2)0 as bridging ligands. Although common for N2, the stabilization as a neutral, triply bonded P≡P ligand is unprecedented for the heavier homolog. It was enabled by coordination of the dipnictogen to redox-inactive Lewis-acidic metal fragments and gave rise to the controlled release of P2 in the condensed phase.
![Research paper thumbnail of ChemInform Abstract: One-Step Synthesis of a [20]Silafullerane with an Endohedral Chloride Ion](https://attachments.academia-assets.com/115174276/thumbnails/1.jpg)
](Chemistry: A European Journal, Jun 1, 2012
The reaction of nido‐[1,2‐(Cp*RuH)2B3H7] (1 a, Cp*=η5‐C5Me5) with [Mo(CO)3(CH3CN)3] under mild co... more The reaction of nido‐[1,2‐(Cp*RuH)2B3H7] (1 a, Cp*=η5‐C5Me5) with [Mo(CO)3(CH3CN)3] under mild conditions yields the new metallaborane arachno‐[(Cp*RuCO)2B2H6] (2). Compound 2 catalyzes the cyclotrimerization of a variety of internal‐ and terminal alkynes to yield mixtures of 1,3,5‐ and 1,2,4‐substituted benzenes. The reactivities of nido‐1 a and arachno‐2 with alkynes demonstrates that a change in geometry from nido to arachno drives a change in the reaction from alkyne‐insertion to catalytic cyclotrimerization, respectively. Density functional calculations have been used to evaluate the reaction pathways of the cyclotrimerization of alkynes catalyzed by compound 2. The reaction involves the formation of a ruthenacyclic intermediate and the subsequent alkyne‐insertion step is initiated by a [2+2] cycloaddition between this intermediate and an alkyne. The experimental and quantum‐chemical results also show that the stability of the metallacyclic intermediate is strongly dependent on the nature of the substituents that are present on the alkyne.
Nucleation and Atmospheric Aerosols, 2022
In this work innovative additive printing methods for formation of polycrystalline silicon (poly-... more In this work innovative additive printing methods for formation of polycrystalline silicon (poly-Si) and polycrystalline silicon carbide (poly-SiC) layers of local tunnel oxide passivating contacts (TOPCon) is evaluated. Replacement of conventional vacuum processes and vapor-phase deposition by additive printing of Si in fabrication process of high efficiency solar cells reduces processing complexity, and, hence manufacturing costs. Reliable inkjet-and FlexTrail-printing processes are developed for liquid-phase polysilane and organic polysilazane inks that are precursors of Si and SiC, respectively. FlexTrail is introduced as a potential technology to print uniform closed thin films of polysilane free of ruptures. Moreover, from inkjet-printing of the developed polysilane ink, homogenous, closed and crack free thin films of poly-Si are obtained after high temperature annealing. The polysilane ink is formulated considering evaluation of several solvents and photoinduced polymerization conditions. Inkjet-printing process development and optimization according to high frequency rheological characterization of organic polysilazane (OPSZ) is presented. Printed thin films are characterized after high temperature annealing (T = 950 °C, t = 60 min) to be uniform and free of micro cracks.
Chemistry-an Asian Journal, May 17, 2023
Ferrocene‐based N‐heterocyclic plumbylenes fc[(NSiMe2R)2Pb:] (1; fc=1,1’‐ferrocenylene) are easil... more Ferrocene‐based N‐heterocyclic plumbylenes fc[(NSiMe2R)2Pb:] (1; fc=1,1’‐ferrocenylene) are easily accessible by transamination from [(Me3Si)2N]2Pb and the corresponding 1,1’‐diaminoferrocene derivatives fc(NHSiMe2R)2. They may form unconventional dimers 2 by a process, which causes the cleavage of a cyclopentadienyl C−H bond and the formation of a Pb−C and an N−H bond. The monomer‐dimer equilibrium (2 1⇆2) has been addressed experimentally and computationally. It critically depends on the steric demand of the N‐substituents SiMe2R, which has been varied systematically by using homologues with aliphatic (R=methyl, ethyl, isopropyl, tert‐butyl) and aromatic units (R=phenyl, mesityl, ferrocenyl). Even in the sterically least congested case (R=methyl), dimerization is only slightly exergonic. It eventually becomes prohibitively endergonic with increasingly larger substituents and is thus not observed for R=tert‐butyl, mesityl, and ferrocenyl. R=phenyl represents a borderline case, where the dimer is still detectable in the equilibrium mixture, albeit as a very minor component, in accord with the slightly endergonic Gibbs free energy change calculated for its formation. Addition of 4‐dimethylaminopyridine (DMAP) to the monomer‐dimer equilibrium mixtures cleanly affords the corresponding adducts [1(DMAP)], irrespective of the equilibrium composition.
Chemistry-an Asian Journal, May 17, 2023
Ferrocene‐based N‐heterocyclic plumbylenes fc[(NSiMe2R)2Pb:] (1; fc=1,1’‐ferrocenylene) are easil... more Ferrocene‐based N‐heterocyclic plumbylenes fc[(NSiMe2R)2Pb:] (1; fc=1,1’‐ferrocenylene) are easily accessible by transamination from [(Me3Si)2N]2Pb and the corresponding 1,1’‐diaminoferrocene derivatives fc(NHSiMe2R)2. They may form unconventional dimers 2 by a process, which causes the cleavage of a cyclopentadienyl C−H bond and the formation of a Pb−C and an N−H bond. The monomer‐dimer equilibrium (2 1⇆2) has been addressed experimentally and computationally. It critically depends on the steric demand of the N‐substituents SiMe2R, which has been varied systematically by using homologues with aliphatic (R=methyl, ethyl, isopropyl, tert‐butyl) and aromatic units (R=phenyl, mesityl, ferrocenyl). Even in the sterically least congested case (R=methyl), dimerization is only slightly exergonic. It eventually becomes prohibitively endergonic with increasingly larger substituents and is thus not observed for R=tert‐butyl, mesityl, and ferrocenyl. R=phenyl represents a borderline case, where the dimer is still detectable in the equilibrium mixture, albeit as a very minor component, in accord with the slightly endergonic Gibbs free energy change calculated for its formation. Addition of 4‐dimethylaminopyridine (DMAP) to the monomer‐dimer equilibrium mixtures cleanly affords the corresponding adducts [1(DMAP)], irrespective of the equilibrium composition.
Chemistry: A European Journal, Sep 4, 2018
Journal of the American Chemical Society, May 26, 2021
Two silylene molecules oxidatively react under formal [1 + 2 + 1]-cycloaddition to the C≡N bond o... more Two silylene molecules oxidatively react under formal [1 + 2 + 1]-cycloaddition to the C≡N bond of nitriles to yield 1-aza-2,4-disilabicyclo[1.1.0]butanes (L)(Cl)Si[μ-η1,2-NC(p-RC6H4)]Si(Cl)(L) (L = PhC(NtBu)2, R = CF3 (2), F (3), Cl (4), Br (5)). The strongly folded bicyclic SiCNSi cores in 2-5 feature inverted bridgehead carbon atoms and superelongated C-N bonds [1.745(12) to 1.801(2) Å], exceeding the lengths of C-N single bonds in known silaaziridines by up to 23%. Detailed bonding analysis discloses C-N bonding interactions, sharing far-reaching similarities with the central C-C bond in [1.1.1]propellane.
Chemistry: A European Journal, Aug 9, 2017
Ac ombined experimentala nd theoretical study of the high-temperature reactiono fS iCl 4 and elem... more Ac ombined experimentala nd theoretical study of the high-temperature reactiono fS iCl 4 and elemental silicon is presented. The nature and reactivity of the product formed upon rapid coolingo ft he gaseous reactionm ixture is investigated by comparison with the defined model compounds cyclo-Si 5 Cl 10 , n-Si 5 Cl 12 and n-Si 4 Cl 10 .ADFT assessment provides mechanistic insight into the oligosilane formation. Experimental 29 Si NMR investigations, supported by quantum-chemical 29 Si NMR calculations, consistently show that the reactionp roduct is composed of discrete molecular perchlorinated oligosilanes. Low-temperature chlorination is an unexpectedly selective means for the transformation of cyclosilanes to acyclic speciesb ye ndocyclic SiÀSi bond cleavage, and we provide am echanistic rationalization for this observation. In contrast to the raw material, the product obtained after low-temperature chlorination represents an efficient source of neo-Si 5 Cl 12 or the amine-stabilizedd isilene EtMe 2 N•SiCl 2 Si(SiCl 3) 2 through reactionwith aliphatic amines.
Chemistry: A European Journal, Aug 16, 2016
A detailed quantum-chemical study on the amine-induced disproportionation reaction of perchlorina... more A detailed quantum-chemical study on the amine-induced disproportionation reaction of perchlorinated silanes to neo-Si5 Cl12 is reported. The key intermediate in the resulting mechanistic scenario is a dichlorosilylene amine adduct, which is in tune with recent experimental findings. Yet, at variance with the generally accepted notion of silicon-chain growth by concerted silylene insertion into Si-Cl bonds of lower silanes, the formation of neo-Si5 Cl12 follows more complex pathways. The reactivity is dominated by the Lewis-base character of the dichlorosilylene amine adduct and characterized by three elementary steps that bear close resemblance to the key elementary steps identified earlier for the chloride-induced disproportionation of Si2 Cl6 . NBO and QTAIM analyses of the key reactive species SiCl2 ⋅NMe3 and SiCl3 (-) provide a rationale for these striking similarities.
ACS Catalysis, Oct 10, 2014
Acceptorless dehydrogenation of alcohols, an important organic transformation, was accomplished w... more Acceptorless dehydrogenation of alcohols, an important organic transformation, was accomplished with welldefined and inexpensive iron-based catalysts supported by a cooperating PNP pincer ligand. Benzylic and aliphatic secondary alcohols were dehydrogenated to the corresponding ketones in good isolated yields upon release of dihydrogen. Primary alcohols were dehydrogenated to esters and lactones, respectively. Mixed primary/secondary diols were oxidized at the secondary alcohol moiety with good chemoselectivity. The mechanism of the reaction was investigated using both experiment and DFT calculations, and the crucial role of metal−ligand cooperativity in the reaction was elucidated. The iron complexes are also excellent catalysts for the hydrogenation of challenging ketone substrates at ambient temperature under mild H 2 pressure, the reverse of secondary alcohol dehydrogenation.
Nature Chemistry, Dec 16, 2020
The authors feel that some relevant references were missing from the version of this Article orig... more The authors feel that some relevant references were missing from the version of this Article originally published; the newly added references 44-47 have been cited in a new paragraph, beginning 'Our approach can be contrasted to' , which precedes the 'Results and discussion' section. These changes have now been made.
Chemical Communications, 2021
The reaction of a stable silylene with Ph2CCO and OCCCO respectively afforded the first sil... more The reaction of a stable silylene with Ph2CCO and OCCCO respectively afforded the first silaallene oxide and a silylketene, whose hydrolysis furnished a stable methyleneketene.
Inorganic Chemistry, Jul 2, 2021
Herein, we report on a facile and selective one-pot synthetic route to silicon-boron radicals. Re... more Herein, we report on a facile and selective one-pot synthetic route to silicon-boron radicals. Reduction of Br2BTip (Tip = 2,4,6-iPrC6H2) with KC8 in the presence of LSi-R affords LSi(tBu)-B(Br)Tip (1) and LSi(N(TMS)2)-B(Br)Tip (2) [L = PhC(NtBu)2]. These first examples of silicon-boron isolated radical species feature spin density on the silicon and boron atoms. 1 and 2 exhibit extraordinary stability to high temperatures under inert conditions in solution and air stability in the solid state. Both radicals have been isolated and fully characterized by electron paramagnetic resonance spectroscopy, SQUID magnetometry, mass spectrometry, cyclic voltammetry, single-crystal X-ray structure analysis, and density functional theory calculations. Moreover, compound 1 exhibits one-electron transfer when treated with 1 equiv of AgSO3CF3 and [Ph3C]+[B(C6F5)4]-, respectively, resulting in the corresponding cations [LSi(tBu)-B(Br)Tip]+[CF3SO3]- (3) and [LSi(tBu)-B(Br)Tip]+[B(C6F5)4]- (4). Compounds 3 and 4 have been characterized with multinuclear NMR and mass spectrometry.
Journal of the American Chemical Society, Nov 21, 2022
Chemical Science, 2019
The one-electron reduction of (CAAC Me)BCl 3 (CAAC Me ¼ 1-(2,6-diisopropylphenyl)-3,3,5,5tetramet... more The one-electron reduction of (CAAC Me)BCl 3 (CAAC Me ¼ 1-(2,6-diisopropylphenyl)-3,3,5,5tetramethylpyrrolidin-2-ylidene) yields the dichloroboryl radical [(CAAC Me)BCl 2 ]c. Furthermore, the twofold reduction of (CAAC Me)BCl 3 in the presence of a range of Lewis bases (L ¼ CAAC Me , N-heterocyclic carbene, phosphine) yields a series of doubly base-supported (CAAC Me)LBCl chloroborylenes, all of which were structurally characterised. NMR and UV-vis spectroscopic and electrochemical data for (CAAC Me)LBCl show that the boron centre becomes more electron-rich and the HOMO-LUMO gap widens as L becomes less p-accepting. A [(CAAC Me)BCl 2 ] À boryl anion coordination polymer was isolated as a potential intermediate in these reductions. In most cases the reduction of the chloroborylenes resulted in the formation of the corresponding hydroborylenes or derivatives thereof, as well as ligand C-H activation products.
Science, Mar 22, 2019
Boron brings nitrogen together Whereas carbon is prone to making chains, nitrogen usually sticks ... more Boron brings nitrogen together Whereas carbon is prone to making chains, nitrogen usually sticks to itself just once in the particularly stable form of N 2 . Légaré et al. now show that boron can coax two N 2 molecules together under reductive conditions below room temperature. Two borylene units sandwiched the resulting N 4 chain between them. Science , this issue p. 1329
Angewandte Chemie, Jan 3, 2019
Leaded ferrocene: An unprecedented type of dimerization is shown by an N-heterocyclic plumbylene ... more Leaded ferrocene: An unprecedented type of dimerization is shown by an N-heterocyclic plumbylene with ferrocenylene backbone. The initially formed aggregational dimer undergoes an intramolecular electrophilic substitution by an endo attack of a Pb II atom, causing the cleavage of a CH bond and the formation of a PbC and an NH bond. The reaction affords a planar-chiral ferrocene derivative and is the first example of a CH activation with Pb II .
Nachrichten Aus Der Chemie, Nov 1, 2005
Journal of the American Chemical Society, Mar 28, 2023
Chem, Jul 1, 2021
Summary In contrast to its lighter congener N2, neutral diphosphorus with a P≡P triple bond is a ... more Summary In contrast to its lighter congener N2, neutral diphosphorus with a P≡P triple bond is a highly reactive species observable only in the gas phase and by matrix isolation. Previous stabilization efforts with Lewis bases (e.g., carbenes) or by transition-metal coordination led to charge transfer to highly electrophilic P2 and thus to significant reduction of the bond order. Here, we report the crystallographic, spectroscopic, and quantum chemical characterization of the redox series [(μ2,η1:η1-P2){Pt(PNP)}2] (PNP = N(CHCHPtBu2)2), which features (P2)2–, (P2)⋅–, and (P2)0 as bridging ligands. Although common for N2, the stabilization as a neutral, triply bonded P≡P ligand is unprecedented for the heavier homolog. It was enabled by coordination of the dipnictogen to redox-inactive Lewis-acidic metal fragments and gave rise to the controlled release of P2 in the condensed phase.