Crystal and mol-ecular structures of di-chlorido-palladium(II) containing 2-methyl- or...

The crystal structures of di-chlorido-palladium(II) complexes bearing 2-methyl- and 2-phenyl-8-(di-phenyl-phosphan-yl)quinoline, namely, di-chlorido-[8-(di-phenyl-phosphan-yl)-2-methyl-quinoline-κ² N,P]palladium(II), [PdCl₂(C₂₂H₁₈NP)] (1) and di-chlorido-[8-(di-phenyl-phosphan-yl)-2-phenyl-quinoline-κ² N,P]palladium(II), [PdCl₂(C₂₇H₂₀NP)] (2), were analyzed and compared to that of the 8-(di-phenyl-phosphan-yl)quinoline (PQ^H) analogue (3). In all three complexes, the phosphanyl-quinoline moiety acts as a bidentate P,N-donating chelate ligand. In the PQ^H complex (3), the Pd^II center has a typical planar coordination environment; however, both the methyl- and phenyl-substituted phosphanyl-quinoline (PQ^Me and PQ^Ph, respectively) complexes (1) and (2) exhibit a considerable tetra-hedral distortion around the Pd^II center, as parameterized by the τ₄ values of 0.1555 (4) and 0.1438 (4) for (1) and (2), respectively. The steric inter-action from the substituted group introduced at the 2-position of the quinoline ring enforces the cis-positioned Cl ligand to be displaced from the ideal coordination plane. Also, the ideally planar phosphanyl-quinoline five-membered chelate ring shows a large bending deformation by the displacement of the Pd^II center from the quinoline plane. In addition, in the phenyl-substituted complex (3), the coordinating quinolyl and the substituted phenyl rings are not co-planar to each other, having a dihedral angle of 33.08 (7)°. This twist conformation prohibits any inter-molecular π-π stacking inter-action between the quinoline planes, which is observed in the crystals of complexes (1) and (2).