Lithium Diisopropylamide:  Oligomer Structures at Low Ligand Concentrations

Abstract

One- and two-dimensional (6)Li and (15)N NMR spectroscopic studies of lithium diisopropylamide (LDA) solvated by substoichiometric concentrations of oxetane, THF, Et(2)O, and diisopropylamine are described. Partially solvated dimers and trimers are identified. Possible benefits of carrying out organolithium chemistry at low ligand concentrations are discussed.

Synthetically Important Alkali‐Metal Utility Amides: Lithium, Sodium, and Potassium Hexamethyldisilazides, Diisopropylamides, and Tetramethylpiperidides

“…This finding was in contrast with earlier cryoscopic measurements by Bauer and Seebach which suggested a monomer/dimer equilibrium, with the monomer being favored 84. Rutherford and Collum were also able to identify a mixture of mono‐ and disolvated cyclodimers and mono‐ and disolvated cyclotrimers when studying LiDA in pentane/toluene in the presence of substoichiometric quantities of THF 85. The trimeric species constitute the minor species in solution with the disolvated dimer only seen once the concentration of THF exceeds 1.0 molar equivalents 86 .…”

Aufklärung der donorbasenfreien Aggregation von Lithiumdiisopropylamid in Kohlenwasserstoffen mithilfe einer DOSY‐Methode

“…Dieses genaue Resultat belegt, dass DA keine Tendenz zeigt, mit den Oligomeren zu koordinieren. Dieses Resultat ist somit in guter Übereinstimmung mit früheren Untersuchungen, die ergeben haben, dass DA ein schlechter Ligand für LDA ist 3c…”

Solid‐State Isolation of Cyclic Alkyl(Amino) Carbene (cAAC)‐Supported Structurally Diverse Alkali Metal‐Phosphinidenides

“…[4a, 7c, 8, 10, 15] The P-atom of Cy-cAAC= P À possesses an ear trigonal planar geometry with the sum of the bond angle close to 3608.T he average NaÀPd istances in the cyclic-trimer are lying in the range of 2.757(2)-2.882(5) ( Table S1)w hich are shorter than those (2.9246(8)-3.0178(8) ) of the dimeric( (Dipp) 2 PNa(THF) 2 ) 2 complex. [6c] The averageN a- 10, P2ÀK1 3.2314 9, P1ÀK4 3.2761 10, P2À K4 3.3532 10 P-Na/P-Na-P bond angles in 5 are found in the range of 107.9(2)-123.14 (14)8/111.42(7)-121.7(2)8.…”