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Abstract
The beta-diketiminato aluminum dihydrides, [HC{(Me)-CNAr}(2)AlH2] [4: Ar = 2,6-di-isopropylphenyl (Dipp), 5: 2,4,6-trimethylphenyl (Mes)] react directly with N-aryl-substituted N-heterocyclic carbenes (NHCs) by C-N bond activation to afford aluminum amido-alkyl derivatives of the form [HC{(Me)-CNAr}(2)AlCH2(N(Ar')CH)(2)]. The more sterically congested alane (4), bearing N-Dipp substitution, does not react with either 1,3-bis(2,6-di-isopropylphenAimidazol-2-ylidene (IPr) or 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), even under forcing conditions. In contrast, in situ generation of 1,3-bis(phenyl)imidazol-2-ylidene through deprotonation of the corresponding imidazolium tetrafluoroborate by KN(SiMe3)(2) in the presence of compound 4 provides facile ring opening of the NHC at room temperature to yield [HC{(Me)CNDipp}(2)AlCH2(N(Ph)CH)(2)]. Although compound 5 also does not react with IPr, relaxation of the steric demands of the supporting beta-diketiminate ligand to N-mesityl substitution enables analogous ring opening of IMes, with the formation of [HC{(Me)CNMes}(2)AlCH2(N(Mes)CH)(2)] (7), when the reaction is heated to 80 degrees C. DFT calculations performed on model systems suggest that in comparison to the parent alane (AlH3) the enhanced propensity of these systems to induce NHC ring cleavage is a consequence of the relative stability of the initially formed five- and four-coordinate adducts as well as the augmented hydridic character of the Al-H bonds within the beta-diketiminate-supported molecules.
Original language | English |
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Pages (from-to) | 1173-1178 |
Number of pages | 6 |
Journal | Organometallics |
Volume | 36 |
Issue number | 6 |
Early online date | 3 Mar 2017 |
DOIs | |
Publication status | Published - 27 Mar 2017 |
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Dive into the research topics of 'Alane-Centered Ring Expansion of N-Heterocyclic Carbenes'. Together they form a unique fingerprint.Projects
- 1 Finished
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Augmentation of Alkaline Earth Reactivity: An FLP Analogy
Hill, M. (PI)
Engineering and Physical Sciences Research Council
8/02/16 → 6/02/20
Project: Research council
Equipment
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Dual source (Cu and Mo) Single Crystal Diffractometer (SuperNova)
Material and Chemical Characterisation (MC2)Facility/equipment: Equipment
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Propulse 500 MHz Nuclear Magnetic Resonance (NMR) Spectrometer (1South)
Material and Chemical Characterisation (MC2)Facility/equipment: Equipment
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Raman confocal microscope RENISHAM INVIA
Material and Chemical Characterisation (MC2)Facility/equipment: Equipment