Chiral cyclometalated platinum(II) and palladium(II) complexes with derivatives of thienylpyridine as ligands: Helical distortion of the square planar (SP-4) geometry

Four cis-bis-cyclometalated complexes of platinum(II) and palladium(II) have been synthesized with chiral substituted thienylpyridine ligands. These ligands are (5aR,6aS)-5,5a,6a,7-tetrahydro-6,6-dimethyl-3-(2'-thienyl)-cyclopropa[g]isoquinoline (th4,5capy) (1), (6aR,7aS)-5,6,6a,7a-tetrahydro-7,7-dimethyl-2-(2'-thienyl)cyclopropa[h]quinoline (th5,6capy) (2), (6R,8R)-5,6,7,8-tetrahydro-9,9-dimethyl-2-(2'thienyl)-6,8-methanoquinoline (th5,6 beta ppy) (3), and (6R,8R)-5,6,7,8-tetrahydro-9,9-dimethyl-(th4,5ppy) (5). Two complexes have a well-defined chirality at the metal center, due to the sterical interaction of the ligands. These complexes are Delta-Pt(th5,6capy)(2) (8) and Lambda-Pt(th5,6 beta ppy)(thpy) (9). The crystal structure of 8 shows a strong distortion from the ideal square planar geometry. Crystals of Delta-Pt(th5,6capy)(2) (8) are tetragonal, space group P4(3)2(1)2, a = 13.407(1) Angstrom, b = 13.407(1) Angstrom, c = 14.860(2) Angstrom, alpha = beta = gamma = 90 degrees, and Z = 4. Final R = 0.0237 and R-w = 0.0450 for 2353 observed reflections. Compound 8 possesses a crystallographic C-2 symmetry.