First optically active PC-palladacycle bearing a phosphorus atom in an axially chiral environmentстатья
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Дата последнего поиска статьи во внешних источниках: 27 мая 2015 г.
Аннотация:Direct aromatic C-H bond activation in the (S-a)-BINOL-derived phosphite (S-a)-HL afforded the dimeric cyclopalladated complex (S-a,S-a)-{Pd(eta(2)-L)(mu-Cl)}(2) (2) which is the first optically active PC-palladacycle bearing a phosphorus atom in an axially chiral environment. ortho-Palladated structure of dimer 2 was confirmed by spectral (H-1 and P-31 NMR) examination of its mononuclear derivatives and by X-ray diffraction analysis of the phosphine adduct (eta(2)-L)PdCl(PPh3) (4). The enantiomeric purity of the starting ligand remained unchanged in the PC-palladacycle under the thermal conditions used for the cyclopalladation (similar to 110 degrees C); this fact was confirmed by the P-31 NMR spectroscopy after chiral derivatization in situ of dimer (S-a,S-a)-2 with the (R-C)-valinate chiral auxiliary (Val). trans(N,C)-Configuration of the valinate complex (eta(2)-L)Pd(Val) (5) was established by H-1 NMR and supported by DFT calculations. The chirality transfer in the new PC-palladacycle was discussed on the basis of X-ray diffraction data for the phosphine adduct rac-4 and DFT calculations performed for both phosphine and valinate mononuclear derivatives.