PMDTA (N,N,N′,N′′,N′′-pentamethyldiethylenetriamine) is an organic compound with the formula [(CH3)2NCH2CH2]2NCH3. PMDTA is a basic, bulky, and flexible, tridentate ligand that is a used in organolithium chemistry. It is a colorless liquid, although impure samples appear yellowish.
Unlike diethylenetriamine, all three amines in PMDTA are tertiary. Both PMDTA and diethylenetriamine are tridentate ligands that form two five-membered chelate rings. The σ-donating properties of the amino groups of diethylenetriamine are greater than that of PMDTA in copper(II) complexes.[2] Both ligands can coordinate metal complexes in arrangements where the three nitrogen centers are co-planar or mutually cis.
Organolithium compounds and PMDTAedit
PMDTA is used to modify the reactivity of organolithium compounds, which deaggregate in the presence of Lewis bases to enhance their reactivity.[3] Commonly, the ditertiary amine TMEDA is used in these applications; it binds to the lithium center as a bidentate ligand. PMDTA behaves analogously, but since it is tridentate, it binds more strongly to lithium. In contrast to TMEDA, PMDTA forms monomeric complexes with organolithium compounds. Both amines affect the regiochemistry of metalation.[3][4]
In the PMDTA/n-BuLi adducts, the Li-C bonds are highly polarized, thus increasing the basicity of the butyl group.[5]
The effect of PMDTA on lithium anilide is illustrative of PMDTA's complexing power. The complex, [{PhN(H)Li}3·2PMDTA], is trinuclear, featuring approximately colinear Li+ centers that are three-, four-, and five-coordinate. The central three-coordinate lithium atom is not bonded to PMDTA. One of the terminal Li centers is pseudo-tetrahedral in an N4 coordination sphere. The other terminal lithium atom is five-coordinate and binds to two anilino N centers and the PMDTA.[6]
Transition metal and aluminium complexesedit
PMDTA often forms five-coordinate complexes due to steric bulk of the methyl groups. PMDTA stabilize unusual cations. The first cationic derivative of alane, [H2Al(PMDTA)]+[AlH4]− was prepared by treating H3AlNMe3 with PMDTA.[5]
Referencesedit
^Marxer, A.; Miescher, K. (1951). "Über die stufenweise Quaternisierung von aliphatischen Polyaminen. Neue Verbindungen mit ganglienblockierender Wirkung". Helvetica Chimica Acta. 34 (3): 924–931. doi:10.1002/hlca.19510340327.
^Angelici, R. J.; Allison, J. W. (1971). "Stability Constants for Amino Acid Coordination by Substituted Diethylenetriamine Complexes of Copper(II) and the Kinetics of Amino Acid Ester Hydrolysis". Inorganic Chemistry. 10 (10): 2238–2243. doi:10.1021/ic50104a030.
^ abStrohmann, C.; Gessner, V. H. (2007). "From the Alkyllitium Aggregate (nBuLi)2·PMDTA2 to Lithiated PMDTA". Angewandte Chemie International Edition. 46 (24): 4566–4569. doi:10.1002/anie.200605105.
^Fraenkel, G. (2002). "PMDTA". Encyclopedia of Reagents for Organic Synthesis. Weinheim: Wiley-VCH. pp. 806–813. doi:10.1002/047084289X.rp028. ISBN0-471-93623-5.
^ abElschenbroich, C. (2006). Organometallics. Weinheim: Wiley-VCH. pp. 45–46. ISBN978-3-527-29390-2.
^Barr, D.; Clegg, W.; Cowton, L.; Horsburgh, L.; Mackenzie, F. M.; Mulvey, R. (1995). "Lithium Anilide Complexed by pmdeta: Expectations of a simple monomer, but in Reality an Odd Trinuclear Composition Combining Three-, Four-, and Five-coordinate Lithium". Journal of the Chemical Society, Chemical Communications. 1995 (8): 891–892. doi:10.1039/C39950000891.
December 14, 2023
pmdta, pentamethyldiethylenetriamine, organic, compound, with, formula, 2nch2ch2, 2nch3, basic, bulky, flexible, tridentate, ligand, that, used, organolithium, chemistry, colorless, liquid, although, impure, samples, appear, yellowish, namespreferred, iupac, n. PMDTA N N N N N pentamethyldiethylenetriamine is an organic compound with the formula CH3 2NCH2CH2 2NCH3 PMDTA is a basic bulky and flexible tridentate ligand that is a used in organolithium chemistry It is a colorless liquid although impure samples appear yellowish PMDTA NamesPreferred IUPAC name N1 2 Dimethylamino ethyl N1 N2 N2 trimethylethane 1 2 diamineIdentifiersCAS Number 3030 47 5 Y3D model JSmol Interactive imageBeilstein Reference 1741396ChEBI CHEBI 39475 NChemSpider 17187 NECHA InfoCard 100 019 275EC Number 221 201 1Gmelin Reference 27747PubChem CID 18196RTECS number IE2100000UNII 3274UTY3HL YUN number 2734CompTox Dashboard EPA DTXSID7029249InChI InChI 1S C9H23N3 c1 10 2 6 8 12 5 9 7 11 3 4 h6 9H2 1 5H3 NKey UKODFQOELJFMII UHFFFAOYSA N NSMILES CN C CCN C CCN C CPropertiesChemical formula C 9H 23N 3Molar mass 173 304 g mol 1Appearance Colorless liquidOdor Fishy ammoniacalDensity 830 mg mL 1Melting point 20 C 4 F 253 K Boiling point 198 C 388 F 471 K Vapor pressure 31 Pa at 20 C Refractive index nD 1 442HazardsGHS labelling PictogramsSignal word DangerHazard statements H302 H311 H314Precautionary statements P280 P305 P351 P338 P310Flash point 53 C 127 F 326 K Autoignitiontemperature 155 C 311 F 428 K Explosive limits 1 1 5 6 Lethal dose or concentration LD LC LD50 median dose 232 mg kg 1 dermal rabbit 1 351 g kg 1 oral rat Safety data sheet SDS sigmaaldrich comRelated compoundsRelated amines triethylenetetraminetmedadiethylenetriaminetriazacyclononaneExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox references Contents 1 Synthesis 2 Comparison with diethylenetriamine 3 Organolithium compounds and PMDTA 4 Transition metal and aluminium complexes 5 ReferencesSynthesis editPMDTA is prepared from diethylenetriamine by the Eschweiler Clarke reaction involving the use of formaldehyde and formic acid 1 H2N CH2 2 2NH 5 CH2O 5 HCO2H Me2N CH2 2 2NMe 5 CO2 5 H2OComparison with diethylenetriamine editUnlike diethylenetriamine all three amines in PMDTA are tertiary Both PMDTA and diethylenetriamine are tridentate ligands that form two five membered chelate rings The s donating properties of the amino groups of diethylenetriamine are greater than that of PMDTA in copper II complexes 2 Both ligands can coordinate metal complexes in arrangements where the three nitrogen centers are co planar or mutually cis Organolithium compounds and PMDTA editPMDTA is used to modify the reactivity of organolithium compounds which deaggregate in the presence of Lewis bases to enhance their reactivity 3 Commonly the ditertiary amine TMEDA is used in these applications it binds to the lithium center as a bidentate ligand PMDTA behaves analogously but since it is tridentate it binds more strongly to lithium In contrast to TMEDA PMDTA forms monomeric complexes with organolithium compounds Both amines affect the regiochemistry of metalation 3 4 In the PMDTA n BuLi adducts the Li C bonds are highly polarized thus increasing the basicity of the butyl group 5 The effect of PMDTA on lithium anilide is illustrative of PMDTA s complexing power The complex PhN H Li 3 2PMDTA is trinuclear featuring approximately colinear Li centers that are three four and five coordinate The central three coordinate lithium atom is not bonded to PMDTA One of the terminal Li centers is pseudo tetrahedral in an N4 coordination sphere The other terminal lithium atom is five coordinate and binds to two anilino N centers and the PMDTA 6 Transition metal and aluminium complexes editPMDTA often forms five coordinate complexes due to steric bulk of the methyl groups PMDTA stabilize unusual cations The first cationic derivative of alane H2Al PMDTA AlH4 was prepared by treating H3AlNMe3 with PMDTA 5 References edit Marxer A Miescher K 1951 Uber die stufenweise Quaternisierung von aliphatischen Polyaminen Neue Verbindungen mit ganglienblockierender Wirkung Helvetica Chimica Acta 34 3 924 931 doi 10 1002 hlca 19510340327 Angelici R J Allison J W 1971 Stability Constants for Amino Acid Coordination by Substituted Diethylenetriamine Complexes of Copper II and the Kinetics of Amino Acid Ester Hydrolysis Inorganic Chemistry 10 10 2238 2243 doi 10 1021 ic50104a030 a b Strohmann C Gessner V H 2007 From the Alkyllitium Aggregate nBuLi 2 PMDTA2 to Lithiated PMDTA Angewandte Chemie International Edition 46 24 4566 4569 doi 10 1002 anie 200605105 Fraenkel G 2002 PMDTA Encyclopedia of Reagents for Organic Synthesis Weinheim Wiley VCH pp 806 813 doi 10 1002 047084289X rp028 ISBN 0 471 93623 5 a b Elschenbroich C 2006 Organometallics Weinheim Wiley VCH pp 45 46 ISBN 978 3 527 29390 2 Barr D Clegg W Cowton L Horsburgh L Mackenzie F M Mulvey R 1995 Lithium Anilide Complexed by pmdeta Expectations of a simple monomer but in Reality an Odd Trinuclear Composition Combining Three Four and Five coordinate Lithium Journal of the Chemical Society Chemical Communications 1995 8 891 892 doi 10 1039 C39950000891 Retrieved from https en wikipedia org w index php title PMDTA amp oldid 1162386551, wikipedia, wiki, book, books, library,
