Aluminium complexes of bidentate N,O- and N,N-ligands derived from oxidative functionalization of amido phosphines

Synthesis, structure and reactivity

Lan Chang Liang, Feng Yi Chen, Mei Hui Huang, Liang Chien Cheng, Chun Wei Li, Hon Man Lee

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

A series of amido phosphinoxide and amido phosphinimine ligands that are electronic variations of monoanionic N,O- and N,N-ketiminates have been prepared and employed to examine the coordination chemistry of aluminium. Oxidation of the previously established N-(2-diphenylphosphinophenyl)-2,6-dialkylaniline in the presence of H2O2 or organic azides RN3 (R = 2,6-C6H3iPr2, SiMe3) led to phosphinoxides (H[NO] 1a-b) and phosphinimines (H[NN] 1c-d), respectively. Alkane elimination reactions of these protio-ligand precursors with trialkylaluminium in toluene or pentane solutions afforded cleanly the corresponding organoaluminium complexes, including dimethyl 2a-d, diethyl 3a-d and diisobutyl derivatives 4a-b and 4d. Solution NMR studies revealed Cs symmetry for these organoaluminium species, in which the α-hydrogen atoms are all diastereotopic. The correlation between the steric congestion of these molecules and the degree of resolution of the multiplet signals corresponding to the diastereotopic α-hydrogen atoms observed by the 1H NMR spectroscopy is of particular interest. Dichloroaluminium complexes 5c-d were prepared in high yields by protonolysis of MeAlCl2 with 1c-d. Single-crystal X-ray diffraction analyses of 2c-d, 3a, 3d, 4a, and 4d elucidated a mononuclear, distorted tetrahedral core for all of these aluminium species. Interestingly, complexes 2c-d are active initiators for catalytic ring-opening oligomerization of ε-caprolactone, whereas 2a-b are rather inactive, highlighting the significance of the steric hindrance imposed by the amido phosphinimine ligands, as compared to that imposed by the phosphinoxide counterparts.

Original languageEnglish
Pages (from-to)9941-9951
Number of pages11
JournalDalton Transactions
Volume39
Issue number41
DOIs
Publication statusPublished - 2010 Nov 7

Fingerprint

Phosphines
Aluminum
Ligands
Hydrogen
Atoms
Oligomerization
Alkanes
Azides
Toluene
Nuclear magnetic resonance spectroscopy
Nuclear magnetic resonance
Single crystals
Derivatives
X ray diffraction
Oxidation
Molecules

All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

Cite this

Liang, Lan Chang ; Chen, Feng Yi ; Huang, Mei Hui ; Cheng, Liang Chien ; Li, Chun Wei ; Lee, Hon Man. / Aluminium complexes of bidentate N,O- and N,N-ligands derived from oxidative functionalization of amido phosphines : Synthesis, structure and reactivity. In: Dalton Transactions. 2010 ; Vol. 39, No. 41. pp. 9941-9951.
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abstract = "A series of amido phosphinoxide and amido phosphinimine ligands that are electronic variations of monoanionic N,O- and N,N-ketiminates have been prepared and employed to examine the coordination chemistry of aluminium. Oxidation of the previously established N-(2-diphenylphosphinophenyl)-2,6-dialkylaniline in the presence of H2O2 or organic azides RN3 (R = 2,6-C6H3iPr2, SiMe3) led to phosphinoxides (H[NO] 1a-b) and phosphinimines (H[NN] 1c-d), respectively. Alkane elimination reactions of these protio-ligand precursors with trialkylaluminium in toluene or pentane solutions afforded cleanly the corresponding organoaluminium complexes, including dimethyl 2a-d, diethyl 3a-d and diisobutyl derivatives 4a-b and 4d. Solution NMR studies revealed Cs symmetry for these organoaluminium species, in which the α-hydrogen atoms are all diastereotopic. The correlation between the steric congestion of these molecules and the degree of resolution of the multiplet signals corresponding to the diastereotopic α-hydrogen atoms observed by the 1H NMR spectroscopy is of particular interest. Dichloroaluminium complexes 5c-d were prepared in high yields by protonolysis of MeAlCl2 with 1c-d. Single-crystal X-ray diffraction analyses of 2c-d, 3a, 3d, 4a, and 4d elucidated a mononuclear, distorted tetrahedral core for all of these aluminium species. Interestingly, complexes 2c-d are active initiators for catalytic ring-opening oligomerization of ε-caprolactone, whereas 2a-b are rather inactive, highlighting the significance of the steric hindrance imposed by the amido phosphinimine ligands, as compared to that imposed by the phosphinoxide counterparts.",
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Aluminium complexes of bidentate N,O- and N,N-ligands derived from oxidative functionalization of amido phosphines : Synthesis, structure and reactivity. / Liang, Lan Chang; Chen, Feng Yi; Huang, Mei Hui; Cheng, Liang Chien; Li, Chun Wei; Lee, Hon Man.

In: Dalton Transactions, Vol. 39, No. 41, 07.11.2010, p. 9941-9951.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Aluminium complexes of bidentate N,O- and N,N-ligands derived from oxidative functionalization of amido phosphines

T2 - Synthesis, structure and reactivity

AU - Liang, Lan Chang

AU - Chen, Feng Yi

AU - Huang, Mei Hui

AU - Cheng, Liang Chien

AU - Li, Chun Wei

AU - Lee, Hon Man

PY - 2010/11/7

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N2 - A series of amido phosphinoxide and amido phosphinimine ligands that are electronic variations of monoanionic N,O- and N,N-ketiminates have been prepared and employed to examine the coordination chemistry of aluminium. Oxidation of the previously established N-(2-diphenylphosphinophenyl)-2,6-dialkylaniline in the presence of H2O2 or organic azides RN3 (R = 2,6-C6H3iPr2, SiMe3) led to phosphinoxides (H[NO] 1a-b) and phosphinimines (H[NN] 1c-d), respectively. Alkane elimination reactions of these protio-ligand precursors with trialkylaluminium in toluene or pentane solutions afforded cleanly the corresponding organoaluminium complexes, including dimethyl 2a-d, diethyl 3a-d and diisobutyl derivatives 4a-b and 4d. Solution NMR studies revealed Cs symmetry for these organoaluminium species, in which the α-hydrogen atoms are all diastereotopic. The correlation between the steric congestion of these molecules and the degree of resolution of the multiplet signals corresponding to the diastereotopic α-hydrogen atoms observed by the 1H NMR spectroscopy is of particular interest. Dichloroaluminium complexes 5c-d were prepared in high yields by protonolysis of MeAlCl2 with 1c-d. Single-crystal X-ray diffraction analyses of 2c-d, 3a, 3d, 4a, and 4d elucidated a mononuclear, distorted tetrahedral core for all of these aluminium species. Interestingly, complexes 2c-d are active initiators for catalytic ring-opening oligomerization of ε-caprolactone, whereas 2a-b are rather inactive, highlighting the significance of the steric hindrance imposed by the amido phosphinimine ligands, as compared to that imposed by the phosphinoxide counterparts.

AB - A series of amido phosphinoxide and amido phosphinimine ligands that are electronic variations of monoanionic N,O- and N,N-ketiminates have been prepared and employed to examine the coordination chemistry of aluminium. Oxidation of the previously established N-(2-diphenylphosphinophenyl)-2,6-dialkylaniline in the presence of H2O2 or organic azides RN3 (R = 2,6-C6H3iPr2, SiMe3) led to phosphinoxides (H[NO] 1a-b) and phosphinimines (H[NN] 1c-d), respectively. Alkane elimination reactions of these protio-ligand precursors with trialkylaluminium in toluene or pentane solutions afforded cleanly the corresponding organoaluminium complexes, including dimethyl 2a-d, diethyl 3a-d and diisobutyl derivatives 4a-b and 4d. Solution NMR studies revealed Cs symmetry for these organoaluminium species, in which the α-hydrogen atoms are all diastereotopic. The correlation between the steric congestion of these molecules and the degree of resolution of the multiplet signals corresponding to the diastereotopic α-hydrogen atoms observed by the 1H NMR spectroscopy is of particular interest. Dichloroaluminium complexes 5c-d were prepared in high yields by protonolysis of MeAlCl2 with 1c-d. Single-crystal X-ray diffraction analyses of 2c-d, 3a, 3d, 4a, and 4d elucidated a mononuclear, distorted tetrahedral core for all of these aluminium species. Interestingly, complexes 2c-d are active initiators for catalytic ring-opening oligomerization of ε-caprolactone, whereas 2a-b are rather inactive, highlighting the significance of the steric hindrance imposed by the amido phosphinimine ligands, as compared to that imposed by the phosphinoxide counterparts.

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