SYNTHESIS AND CHARACTERIZATION OF CHIRAL PALLADIUM(II) COMPLEXES CONTAINING A PD-C-ASTERISK(SP(3)) SIGMA-BOND

A series of cyclometalated palladium(II) complexes containing a Pd-C*(sp(3)) sigma-bond has been prepared. 2-Substituted 8-quinolinol derivatives possessing two- or three-carbon side chains were synthesized. The terminal ethyl acetoactate moiety was shown to exist predominantly in the keto form. When these ligands were treated with potassium tetrachloropalladate(II) in the presence of pyridine, the corresponding complexes were formed. Single-crystal X-ray structure analyses on both the hemibenzene and chloroform solvates revealed that these molecules were racemic. When the pyridine ligand was exchanged with L-(-)-1-phenylethylamine, an SS or RS diastereomeric mixture resulted. Separation of the diastereomers was accomplished by column chromatography, and the structure of one isomer was characterized by X-ray crystallography. Ligand exchange with pyridine of each diastereomer generated the chiral Pd(II) complexes possessing a Pd-C(sp(3)) sigma-bond. C-24-H26N2O4Pd: a = 9.9763(7)Angstrom b = 18.0736(14)Angstrom, c = 12.4876(8)Angstrom, beta 100.877(6)degrees, monoclinic, P2(1), Z = 4. C22H21N2O4Cl3Pd: a = 8.4858(9) Angstrom, b = 11.1272(7) Angstrom, c = 13.6216(8) Angstrom, a 71.736(5)degrees, beta = 76.393(7)degrees, gamma = 80.612(7)degrees, triclinic, P $($) over bar$$ 1, Z = 2. C24H23N2O4Pd: a = 8.4205-(7) Angstrom, b 11.2537(13) Angstrom, c = 12.599(2) Angstrom alpha = 69.539(10)degrees, beta = 82.987(9)degrees, gamma = 81.956(9)degrees, triclinic, P $($) over bar$$ 1, Z = 2.