SQUARE-PLANAR (SP-4) AND OCTAHEDRAL (OC-6) COMPLEXES OF PLATINUM(II) AND PLATINUM(IV) WITH PREDETERMINED CHIRALITY AT THE METAL CENTER

cis-Bis-homoleptic platinum(II) complexes, with predetermined helical chirality at the metal center, can be obtained by using strongly steri cally interacting ligands. With this aim, two new ligands, (8R,10R)-2- (2'-thienyl)-4,5-pinenopyridine, th4,5ppy (2), and (8R,10R)-2-(2'-thie nyl)-5,6-pinenopyridine, th5,6ppy (4), were synthesized and coordinate d to platinum. The structures of the resulting complexes, Pt(th4,5ppy) (2) (5) and Pt(th5,6ppy)(2) (6), were determined by X-ray diffraction, and it was found that they both crystallize with a Delta-cis configur ation. Thermal oxidative additions (TOA) of alkyl halides were perform ed with both complexes leading, in the case of 5, to a mixture of isom ers and, in the case of 6, to isomerically pure products. The predeter mination of chirality at the metal center is therefore preserved in th e octahedral (OC-6) platinum(IV) complexes. Crystals of Pt(th4,5ppy)(2 ) (5) are orthorhombic, of space group P2(1)2(1)2(1), with a = 12.973( 1) Angstrom, b = 13.619(2) Angstrom, c = 17.665(2) Angstrom, alpha = b eta = gamma = 90 degrees, and Z = 4. Final R = 0.0268 and R(w) 0.0424 for 3101 observed reflections. Crystals of Pt(th5,6ppy)(2) (6) are hex agonal, of space group P6(1), with a = 11.5465(4) Angstrom, b = 11.546 5(4) Angstrom, c = 35.356(3) Angstrom, alpha = beta = 90 degrees, gamm a = 120 degrees, and Z = 6. Final R = 0.0424 and R(w) = 0.0845 for 266 0 observed reflections. Neither molecule possesses a crystallographic C-2 symmetry.