Alane-Centered Ring Expansion of N-Heterocyclic Carbenes

Mathew D. Anker, Annie L. Colebatch, Kalon Iverson, David J. D. Wilson, Jason Dutton, Lucia Garcia Rodriguez, Michael Hill, David Liptrot, Mary Mahon

Research output: Contribution to journalArticle

  • 9 Citations

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.
LanguageEnglish
Pages1173-1178
Number of pages6
JournalOrganometallics
Volume36
Issue number6
Early online date3 Mar 2017
DOIs
StatusPublished - 27 Mar 2017

Fingerprint

carbenes
methylidyne
Aluminum
imidazoles
expansion
rings
Substitution reactions
Bearings (structural)
substitutes
aluminum
dihydrides
Deprotonation
Discrete Fourier transforms
adducts
cleavage
Chemical activation
activation
Ligands
Derivatives
ligands

Cite this

Anker, M. D., Colebatch, A. L., Iverson, K., Wilson, D. J. D., Dutton, J., Garcia Rodriguez, L., ... Mahon, M. (2017). Alane-Centered Ring Expansion of N-Heterocyclic Carbenes. DOI: 10.1021/acs.organomet.7b00056

Alane-Centered Ring Expansion of N-Heterocyclic Carbenes. / Anker, Mathew D.; Colebatch, Annie L.; Iverson, Kalon ; Wilson, David J. D.; Dutton, Jason; Garcia Rodriguez, Lucia; Hill, Michael; Liptrot, David; Mahon, Mary.

In: Organometallics, Vol. 36, No. 6, 27.03.2017, p. 1173-1178.

Research output: Contribution to journalArticle

Anker, MD, Colebatch, AL, Iverson, K, Wilson, DJD, Dutton, J, Garcia Rodriguez, L, Hill, M, Liptrot, D & Mahon, M 2017, 'Alane-Centered Ring Expansion of N-Heterocyclic Carbenes' Organometallics, vol. 36, no. 6, pp. 1173-1178. DOI: 10.1021/acs.organomet.7b00056
Anker MD, Colebatch AL, Iverson K, Wilson DJD, Dutton J, Garcia Rodriguez L et al. Alane-Centered Ring Expansion of N-Heterocyclic Carbenes. Organometallics. 2017 Mar 27;36(6):1173-1178. Available from, DOI: 10.1021/acs.organomet.7b00056
Anker, Mathew D. ; Colebatch, Annie L. ; Iverson, Kalon ; Wilson, David J. D. ; Dutton, Jason ; Garcia Rodriguez, Lucia ; Hill, Michael ; Liptrot, David ; Mahon, Mary. / Alane-Centered Ring Expansion of N-Heterocyclic Carbenes. In: Organometallics. 2017 ; Vol. 36, No. 6. pp. 1173-1178
@article{9578a672b8bf436cac831b19cb21b6cd,
title = "Alane-Centered Ring Expansion of N-Heterocyclic Carbenes",
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.",
author = "Anker, {Mathew D.} and Colebatch, {Annie L.} and Kalon Iverson and Wilson, {David J. D.} and Jason Dutton and {Garcia Rodriguez}, Lucia and Michael Hill and David Liptrot and Mary Mahon",
year = "2017",
month = "3",
day = "27",
doi = "10.1021/acs.organomet.7b00056",
language = "English",
volume = "36",
pages = "1173--1178",
journal = "Organometallics",
issn = "0276-7333",
publisher = "American Chemical Society",
number = "6",

}

TY - JOUR

T1 - Alane-Centered Ring Expansion of N-Heterocyclic Carbenes

AU - Anker,Mathew D.

AU - Colebatch,Annie L.

AU - Iverson,Kalon

AU - Wilson,David J. D.

AU - Dutton,Jason

AU - Garcia Rodriguez,Lucia

AU - Hill,Michael

AU - Liptrot,David

AU - Mahon,Mary

PY - 2017/3/27

Y1 - 2017/3/27

N2 - 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.

AB - 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.

U2 - 10.1021/acs.organomet.7b00056

DO - 10.1021/acs.organomet.7b00056

M3 - Article

VL - 36

SP - 1173

EP - 1178

JO - Organometallics

T2 - Organometallics

JF - Organometallics

SN - 0276-7333

IS - 6

ER -