Contacted ion-pair lithium alkylamidoaluminates: intramolecular alumination (al-h exchange) traps for tmeda and pmdeta

Ben Conway, Joaquin Garcia-Alvarez, Eva Hevia, Alan R. Kennedy, Robert E. Mulvey, Stuart D. Robertson

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Exploring the reactivity of mixed-metal synergic bases, it is found that the lithium TMP aluminate iBu3Al(TMP)Li functions as a dual TMP/alkyl base, exhibiting 2-fold AMMAl (alkali-metal-mediated alumination) toward TMEDA to yield the heterobimetallic bis-(deprotonated TMEDA) derivative [Li{Me2NCH2CH2N(Me)CH2}2Al(iBu)2] (2). In contrast, the amide enriched aluminate iBu2Al(TMP)2Li acts as only a single-fold amido base toward TMEDA or PMDETA to afford the amine-deprotonated derivatives [Li{Me2NCH2CH2N(Me)CH2}(TMP)Al(iBu)2] (4) and [Li{Me2NCH2CH2N(Me)CH2CH2N(Me)CH2}(TMP)Al(iBu)2] (5), respectively. On their own, the aluminum compounds iBu3Al or iBu2Al(TMP) are not sufficiently strong bases to metalate TMEDA or PMDETA, so in 2, 4, and 5, the α-deprotonations of TMEDA and PMDETA are synergic in origin, as the intramolecular communication between Li and Al appears to activate the TMP and iBu bases. This special behavior can be attributed to intramolecular proximity effects between the active base component (TMP or iBu) and the ligating TMEDA or PMDETA molecule. X-ray crystallography studies reveal 2 is a contacted ion-pair ate containing two α-aluminated TMEDA ligands, which chelate the lithium cation which is linked to the distorted tetrahedral Al center by two N bridges from the metalated junction of the TMEDA molecules. In contrast, 4 and 5 have a mixed NCH2-TMP bridging ligand set, completed by two terminal iBu ligands on Al and a chelating metalated TMEDA or PMDETA ligand attached to Li, respectively. In addition, the 1H, 7Li, and 13C{1H} spectra of 2 (recorded in C6D6 solutions), 4, and 5 (recorded in cyclohexane solutions-d12) are disclosed.
LanguageEnglish
Pages6462-6468
Number of pages6
JournalOrganometallics
Volume28
Issue number22
DOIs
Publication statusPublished - 23 Nov 2009

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Thymidine Monophosphate
Lithium
lithium
traps
Ions
ligands
ions
aluminum compounds
Ligands
chelates
cyclohexane
alkali metals
amides
crystallography
molecules
amines
reactivity
communication
Aluminum Compounds
cations

Keywords

  • ion-pair lithium alkylamidoaluminates
  • intramolecular alumination
  • TMEDA
  • PMDETA

Cite this

@article{434d59b7b2ed48e4a2c8c7df80496d46,
title = "Contacted ion-pair lithium alkylamidoaluminates: intramolecular alumination (al-h exchange) traps for tmeda and pmdeta",
abstract = "Exploring the reactivity of mixed-metal synergic bases, it is found that the lithium TMP aluminate iBu3Al(TMP)Li functions as a dual TMP/alkyl base, exhibiting 2-fold AMMAl (alkali-metal-mediated alumination) toward TMEDA to yield the heterobimetallic bis-(deprotonated TMEDA) derivative [Li{Me2NCH2CH2N(Me)CH2}2Al(iBu)2] (2). In contrast, the amide enriched aluminate iBu2Al(TMP)2Li acts as only a single-fold amido base toward TMEDA or PMDETA to afford the amine-deprotonated derivatives [Li{Me2NCH2CH2N(Me)CH2}(TMP)Al(iBu)2] (4) and [Li{Me2NCH2CH2N(Me)CH2CH2N(Me)CH2}(TMP)Al(iBu)2] (5), respectively. On their own, the aluminum compounds iBu3Al or iBu2Al(TMP) are not sufficiently strong bases to metalate TMEDA or PMDETA, so in 2, 4, and 5, the α-deprotonations of TMEDA and PMDETA are synergic in origin, as the intramolecular communication between Li and Al appears to activate the TMP and iBu bases. This special behavior can be attributed to intramolecular proximity effects between the active base component (TMP or iBu) and the ligating TMEDA or PMDETA molecule. X-ray crystallography studies reveal 2 is a contacted ion-pair ate containing two α-aluminated TMEDA ligands, which chelate the lithium cation which is linked to the distorted tetrahedral Al center by two N bridges from the metalated junction of the TMEDA molecules. In contrast, 4 and 5 have a mixed NCH2-TMP bridging ligand set, completed by two terminal iBu ligands on Al and a chelating metalated TMEDA or PMDETA ligand attached to Li, respectively. In addition, the 1H, 7Li, and 13C{1H} spectra of 2 (recorded in C6D6 solutions), 4, and 5 (recorded in cyclohexane solutions-d12) are disclosed.",
keywords = "ion-pair lithium alkylamidoaluminates, intramolecular alumination, TMEDA, PMDETA",
author = "Ben Conway and Joaquin Garcia-Alvarez and Eva Hevia and Kennedy, {Alan R.} and Mulvey, {Robert E.} and Robertson, {Stuart D.}",
year = "2009",
month = "11",
day = "23",
doi = "10.1021/om900736a",
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Contacted ion-pair lithium alkylamidoaluminates: intramolecular alumination (al-h exchange) traps for tmeda and pmdeta. / Conway, Ben; Garcia-Alvarez, Joaquin; Hevia, Eva; Kennedy, Alan R.; Mulvey, Robert E.; Robertson, Stuart D.

In: Organometallics, Vol. 28, No. 22, 23.11.2009, p. 6462-6468.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Contacted ion-pair lithium alkylamidoaluminates: intramolecular alumination (al-h exchange) traps for tmeda and pmdeta

AU - Conway, Ben

AU - Garcia-Alvarez, Joaquin

AU - Hevia, Eva

AU - Kennedy, Alan R.

AU - Mulvey, Robert E.

AU - Robertson, Stuart D.

PY - 2009/11/23

Y1 - 2009/11/23

N2 - Exploring the reactivity of mixed-metal synergic bases, it is found that the lithium TMP aluminate iBu3Al(TMP)Li functions as a dual TMP/alkyl base, exhibiting 2-fold AMMAl (alkali-metal-mediated alumination) toward TMEDA to yield the heterobimetallic bis-(deprotonated TMEDA) derivative [Li{Me2NCH2CH2N(Me)CH2}2Al(iBu)2] (2). In contrast, the amide enriched aluminate iBu2Al(TMP)2Li acts as only a single-fold amido base toward TMEDA or PMDETA to afford the amine-deprotonated derivatives [Li{Me2NCH2CH2N(Me)CH2}(TMP)Al(iBu)2] (4) and [Li{Me2NCH2CH2N(Me)CH2CH2N(Me)CH2}(TMP)Al(iBu)2] (5), respectively. On their own, the aluminum compounds iBu3Al or iBu2Al(TMP) are not sufficiently strong bases to metalate TMEDA or PMDETA, so in 2, 4, and 5, the α-deprotonations of TMEDA and PMDETA are synergic in origin, as the intramolecular communication between Li and Al appears to activate the TMP and iBu bases. This special behavior can be attributed to intramolecular proximity effects between the active base component (TMP or iBu) and the ligating TMEDA or PMDETA molecule. X-ray crystallography studies reveal 2 is a contacted ion-pair ate containing two α-aluminated TMEDA ligands, which chelate the lithium cation which is linked to the distorted tetrahedral Al center by two N bridges from the metalated junction of the TMEDA molecules. In contrast, 4 and 5 have a mixed NCH2-TMP bridging ligand set, completed by two terminal iBu ligands on Al and a chelating metalated TMEDA or PMDETA ligand attached to Li, respectively. In addition, the 1H, 7Li, and 13C{1H} spectra of 2 (recorded in C6D6 solutions), 4, and 5 (recorded in cyclohexane solutions-d12) are disclosed.

AB - Exploring the reactivity of mixed-metal synergic bases, it is found that the lithium TMP aluminate iBu3Al(TMP)Li functions as a dual TMP/alkyl base, exhibiting 2-fold AMMAl (alkali-metal-mediated alumination) toward TMEDA to yield the heterobimetallic bis-(deprotonated TMEDA) derivative [Li{Me2NCH2CH2N(Me)CH2}2Al(iBu)2] (2). In contrast, the amide enriched aluminate iBu2Al(TMP)2Li acts as only a single-fold amido base toward TMEDA or PMDETA to afford the amine-deprotonated derivatives [Li{Me2NCH2CH2N(Me)CH2}(TMP)Al(iBu)2] (4) and [Li{Me2NCH2CH2N(Me)CH2CH2N(Me)CH2}(TMP)Al(iBu)2] (5), respectively. On their own, the aluminum compounds iBu3Al or iBu2Al(TMP) are not sufficiently strong bases to metalate TMEDA or PMDETA, so in 2, 4, and 5, the α-deprotonations of TMEDA and PMDETA are synergic in origin, as the intramolecular communication between Li and Al appears to activate the TMP and iBu bases. This special behavior can be attributed to intramolecular proximity effects between the active base component (TMP or iBu) and the ligating TMEDA or PMDETA molecule. X-ray crystallography studies reveal 2 is a contacted ion-pair ate containing two α-aluminated TMEDA ligands, which chelate the lithium cation which is linked to the distorted tetrahedral Al center by two N bridges from the metalated junction of the TMEDA molecules. In contrast, 4 and 5 have a mixed NCH2-TMP bridging ligand set, completed by two terminal iBu ligands on Al and a chelating metalated TMEDA or PMDETA ligand attached to Li, respectively. In addition, the 1H, 7Li, and 13C{1H} spectra of 2 (recorded in C6D6 solutions), 4, and 5 (recorded in cyclohexane solutions-d12) are disclosed.

KW - ion-pair lithium alkylamidoaluminates

KW - intramolecular alumination

KW - TMEDA

KW - PMDETA

U2 - 10.1021/om900736a

DO - 10.1021/om900736a

M3 - Article

VL - 28

SP - 6462

EP - 6468

JO - Organometallics

T2 - Organometallics

JF - Organometallics

SN - 0276-7333

IS - 22

ER -