Experimental and quantum-chemical studies of 1H, 13C and 15N NMR coordination shifts in Pd(II) and Pt(II) chloride complexes with quinoline, isloquinoline, and 2,2′-biquinoline

H-1, C-13, and N-15 NMR studies of platinide(II) (M = Pd, Pt) chloride complexes with quinolines (L = quinoline-quin, or isoquinoline-isoquin; LL = 2,2'-biquinoline-bquin), having the general formulae trans-/cis-[ML2Cl2] and [M(LL)Cl-2], were performed and the respective chemical shifts (delta(1H), delta(13C), delta(15N)) reported. H-1 coordination shifts of various signs and magnitudes (Delta(1H)(coord) = delta(1H)(complex) - delta(1H)(ligand)) are discussed in relation to the changes of diamagnetic contribution to the relevant H-1 shielding constants. The comparison to the literature data for similar complexes containing auxiliary ligands other than chlorides exhibited a large dependence of delta(1H) parameters on electron density variations and ring-current effects (inductive and anisotropic phenomena). The influence of deviations from planarity, concerning either MN2Cl2 chromophores or azine ring systems, revealed by the known X-ray structures of [Pd(bquin)Cl-2] and [Pt(bquin)Cl-2], is discussed in respect to H-1 NMR spectra. N-15 coordination shifts (Delta(15N)(coord) = delta(15N)(complex) - delta(15N)(ligand)) of ca. 78-100 ppm (to lower frequency) are attributed mainly to the decrease of the absolute value of paramagnetic contribution in the relevant N-15 shielding constants, this phenomenon being noticeably dependent on the type of a platinide metal and coordination sphere geometry. The absolute magnitude of Delta(15N)(coord) parameter increased by ca 15 ppm upon Pd(II) - Pt(II) replacement but decreased by ca. 15 ppm following trans -> cis transition. Experimental H-1, C-13, N-15 NMR chemical shifts are compared to those quantum-chemically calculated by B3LYP/LanL2DZ+6-31G**//B3LYP/LanL2DZ+6-31G*, both in vacuo and in CHCl3 or DMF solution. Copyright (c) 2007 John Wiley & Sons, Ltd.