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Dialkyl Effect on Enantioselectivity: p-Stacking as a Structural Feature in P,N Complexes of Palladium(II)

A phosphino,oxazoline P,N-bidentate ligand, 4, contg. 3,5-di-tert-butylphenyl groups was prepd. In the Heck arylation of dihydrofuran, 4 affords higher ee's than either 2 or 3, the unsubstituted and m-dimethylphenyl analogs, resp. Several Pd(0) complexes of 4 are reported. The exchange dynamics of Pd(4)(dba) involve an interconversion of diastereomers via an intramol. process. The x-ray structure for PdCl2(4), 8, was detd. by x-ray diffraction methods. Comparison of data with PdCl2(2), 9, and PdCl2(3), 10, suggests that differing amts. of p-p stacking influence the structures of these relatively simple Pd complexes, with 9 and 10 revealing the strongest p-p interactions. An estn. of the van der Waals energies involved in the interaction supports a .apprx. 4 kcal/mol stabilization via p-p stacking. [on SciFinder (R)]

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    Record created on 2006-02-27, modified on 2016-08-08

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