Coordination modes of the novel bifunctional nitrogen ligands 8-(2-pyridyl)quinoline and 8-(6-methyl-2-pyridyl)quinoline towards palladium and platinum. X-ray crystal structures of (8-(2-pyridyl)quinoline)Pd(Me)Cl, (8-(2-pyridyl)quinoline)-Pd(C(O)Me)Cl and (8-(2-pyridyl)quinoline)Pd(PEt 3)Cl 2

Abstract

The coordination chemistry of the new bidentate nitrogen ligands 8-(2-pyridyl)quinoline (8-PQ) and 8-(6-methyl-2-pyridyl)quinoline (Me-8-PQ) towards palladium and platinum has been studied. Several (N⌢N)Pd(R)Cl and (N⌢N)Pd(alkene) complexes have been synthesized. The complex (8-PQ)Pd(Me)Cl has been characterised by a single crystal X-ray determination (crystal data triclinic space group P l with a=8.513(5), b=9.338(4), c=10.219(2) A ̊ , α=108.11(2), β=89.82(3), γ=116.81(4)°, V=680.1(6) A ̊ 3, R=0.033, Z=2 ). A fast CO insertion occurs into the palladium-carbon bond of the complexes (N⌢N)Pd(Me)Cl providing the (N⌢N)Pd(C(O)Me)Cl complexes. For (8-PQ)Pd(C(O)Me)Cl an X-ray structure determination has been carried out (crystal data: monoclinic space group P2 1/ c with a=9.084(4), b=10.179(3), c=16.400(3) A ̊ , β=95.59(2)°, V=1509.2(9) A ̊ 3, R=0.043, Z=4 ). Unexpected in both molecular structures is the large dihedral angle between the plane of the bidentate nitrogen ligand and the coordination plane of the palladium. Both bidentate coordinating ligands 8-PQ and Me-8-PQ show a relatively large bite angle. A monodentate coordination mode has been observed for the complexes (N⌢N)M(PEt 3)Cl 2 (M=Pd, Pt), as the pyridyl group of the ligand is coordinated to the metal while the quinoline group is dissociated from the metal, which is shown in the X-ray structure determination for the complex (8-PQ)Pd(PEt 3)Cl 2 (crystal data: monoclinic space group P2 1/a with a=15.736(2), b=7.782(1), c=18.255(3) A ̊ , β=102.98(1)°, V=2178.3(6) A ̊ 3, R=0.062, Z=4 ).