Synthesis and structural elucidation of solvent-free and solvated lithium dimethyl (HMDS) zincates

D.R. Armstrong, E. Herd, D.V. Graham, E. Hevia, A.R. Kennedy, W. Clegg, L. Russo

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Using a co-complexation methodology the unsolvated lithium zincate [LiZn(HMDS)Me2] (4, HMDS = 1,1,1,3,3,3-hexamethyldisilazide) was prepared by reaction of an equimolar amount of LiHMDS with Me2Zn in a non-polar toluene-hexane solvent mixture. X-Ray crystallographic studies reveal that the asymmetric unit of 4 has a dinuclear arrangement, based on a planar LiNZnC four-membered ring. As a result of intermolecular interactions between the lithium centre of one asymmetric unit and a terminal methyl group of another, 4 presents a polymeric chain array in the solid state. DFT calculations revealed that the formation of the polymer is the driving force for the success of co-complexation of LiHMDS and Me2Zn to yield the unsolvated zincate 4. The reaction of 4 with PMDETA (N,N,N′,N″,N″-pentamethyldiethylenetriamine) afforded the new solvated zincate [(PMDETA)Li(µ-Me)Zn(HMDS)Me] (5). X-Ray crystallographic studies show that the asymmetric unit of 5 consists of an open, dinuclear LiCZnC arrangement rather than a closed cyclic one, in which the HMDS ligand unusually occupies a terminal position on Zn. DFT computational studies showed that the structure found for 5 was energetically preferred to the expected HMDS-bridging isomer due to the steric hindrance imposed by the tridentate PMDETA ligand. The reaction of 4 with the neutral nitrogen donors 4-tert-butylpyridine and tert-butylcyanide afforded the homometallic compounds [(tBu-pyr)Li(HMDS)] (6) and [(tBuCN)Li(HMDS)] (7) respectively as a result of disproportionation reactions. Compounds 6 and 7 were characterized by NMR (1H, 13C and 7Li) spectroscopy. (Abstract from: http://www.swetswise.com/eAccess/viewAbstract.do?articleID=35973847)
LanguageEnglish
Pages1323-1330
Number of pages7
JournalDalton Transactions
Issue number10
Publication statusPublished - 2008

Fingerprint

Complexation
Lithium
Discrete Fourier transforms
Ligands
X rays
Toluene
Hexanes
Isomers
Polymers
Nitrogen
Nuclear magnetic resonance
Spectroscopy
4-tert-butylpyridine

Keywords

  • synthesis
  • structural elucidation
  • solvent-free
  • solvated lithium dimethyl (HMDS) zincates

Cite this

Armstrong, D.R. ; Herd, E. ; Graham, D.V. ; Hevia, E. ; Kennedy, A.R. ; Clegg, W. ; Russo, L. / Synthesis and structural elucidation of solvent-free and solvated lithium dimethyl (HMDS) zincates. In: Dalton Transactions. 2008 ; No. 10. pp. 1323-1330.
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Synthesis and structural elucidation of solvent-free and solvated lithium dimethyl (HMDS) zincates. / Armstrong, D.R.; Herd, E.; Graham, D.V.; Hevia, E.; Kennedy, A.R.; Clegg, W.; Russo, L.

In: Dalton Transactions, No. 10, 2008, p. 1323-1330.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Synthesis and structural elucidation of solvent-free and solvated lithium dimethyl (HMDS) zincates

AU - Armstrong, D.R.

AU - Herd, E.

AU - Graham, D.V.

AU - Hevia, E.

AU - Kennedy, A.R.

AU - Clegg, W.

AU - Russo, L.

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PY - 2008

Y1 - 2008

N2 - Using a co-complexation methodology the unsolvated lithium zincate [LiZn(HMDS)Me2] (4, HMDS = 1,1,1,3,3,3-hexamethyldisilazide) was prepared by reaction of an equimolar amount of LiHMDS with Me2Zn in a non-polar toluene-hexane solvent mixture. X-Ray crystallographic studies reveal that the asymmetric unit of 4 has a dinuclear arrangement, based on a planar LiNZnC four-membered ring. As a result of intermolecular interactions between the lithium centre of one asymmetric unit and a terminal methyl group of another, 4 presents a polymeric chain array in the solid state. DFT calculations revealed that the formation of the polymer is the driving force for the success of co-complexation of LiHMDS and Me2Zn to yield the unsolvated zincate 4. The reaction of 4 with PMDETA (N,N,N′,N″,N″-pentamethyldiethylenetriamine) afforded the new solvated zincate [(PMDETA)Li(µ-Me)Zn(HMDS)Me] (5). X-Ray crystallographic studies show that the asymmetric unit of 5 consists of an open, dinuclear LiCZnC arrangement rather than a closed cyclic one, in which the HMDS ligand unusually occupies a terminal position on Zn. DFT computational studies showed that the structure found for 5 was energetically preferred to the expected HMDS-bridging isomer due to the steric hindrance imposed by the tridentate PMDETA ligand. The reaction of 4 with the neutral nitrogen donors 4-tert-butylpyridine and tert-butylcyanide afforded the homometallic compounds [(tBu-pyr)Li(HMDS)] (6) and [(tBuCN)Li(HMDS)] (7) respectively as a result of disproportionation reactions. Compounds 6 and 7 were characterized by NMR (1H, 13C and 7Li) spectroscopy. (Abstract from: http://www.swetswise.com/eAccess/viewAbstract.do?articleID=35973847)

AB - Using a co-complexation methodology the unsolvated lithium zincate [LiZn(HMDS)Me2] (4, HMDS = 1,1,1,3,3,3-hexamethyldisilazide) was prepared by reaction of an equimolar amount of LiHMDS with Me2Zn in a non-polar toluene-hexane solvent mixture. X-Ray crystallographic studies reveal that the asymmetric unit of 4 has a dinuclear arrangement, based on a planar LiNZnC four-membered ring. As a result of intermolecular interactions between the lithium centre of one asymmetric unit and a terminal methyl group of another, 4 presents a polymeric chain array in the solid state. DFT calculations revealed that the formation of the polymer is the driving force for the success of co-complexation of LiHMDS and Me2Zn to yield the unsolvated zincate 4. The reaction of 4 with PMDETA (N,N,N′,N″,N″-pentamethyldiethylenetriamine) afforded the new solvated zincate [(PMDETA)Li(µ-Me)Zn(HMDS)Me] (5). X-Ray crystallographic studies show that the asymmetric unit of 5 consists of an open, dinuclear LiCZnC arrangement rather than a closed cyclic one, in which the HMDS ligand unusually occupies a terminal position on Zn. DFT computational studies showed that the structure found for 5 was energetically preferred to the expected HMDS-bridging isomer due to the steric hindrance imposed by the tridentate PMDETA ligand. The reaction of 4 with the neutral nitrogen donors 4-tert-butylpyridine and tert-butylcyanide afforded the homometallic compounds [(tBu-pyr)Li(HMDS)] (6) and [(tBuCN)Li(HMDS)] (7) respectively as a result of disproportionation reactions. Compounds 6 and 7 were characterized by NMR (1H, 13C and 7Li) spectroscopy. (Abstract from: http://www.swetswise.com/eAccess/viewAbstract.do?articleID=35973847)

KW - synthesis

KW - structural elucidation

KW - solvent-free

KW - solvated lithium dimethyl (HMDS) zincates

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UR - http://dx.doi.org/10.1039/b716494g

M3 - Article

SP - 1323

EP - 1330

JO - Dalton Transactions

T2 - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

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