Aggregation and Solvation of Chiral N,P-Amide Ligands in Coordinating Solvents: A Computational and NMR Spectroscopic Study

• The lithium amides of a series of chiral N,P ligands were studied in solution. This ligand class had been shown previously to give good selectivities in asymmetric alkylation of benzaldehyde. These lithium amides were found to aggregate into dimers with surprisingly strong coordination of phosphorus to lithium. The equilibrium between dimeric forms was found to depend strongly on non-bonded interactions within the solute and between solute and solvent. Only if dispersion and free-energy contributions were scaled to approximately 20?% of the gas-phase values was it possible to reproduce the experimentally observed aggregation preferences. NMR spectroscopic shieldings were calculated and found to correlate well with the experimentally observed shifts. Calculated Li,P couplings were shown to be a sensitive measure of the Li?P distance.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

aggregation

density functional calculations

lithium

NMR spectroscopy

N

P ligands

molecular-orbital methods

transition-metal-complexes

chemical-shift

calculations

gaussian-type basis

lithium amide

asymmetric addition

ab-initio

dispersive interactions

substitution energies

dft methods

garrity jf

1985

journal of the american chemical society

v107

p1810

att lm

1995

tetrahedron-asymmetry

v6

p2165

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