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

✍ Scribed by Leszek Pazderski; Jaromír Toušek; Jerzy Sitkowski; Lech Kozerski; Edward Szłyk

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 330 KB
• Volume: 45
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2105

✦ Synopsis

Abstract

^1^H, ^13^C, and ^15^N 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‐[ML~2~Cl~2~] and [M(LL)Cl~2~], were performed and the respective chemical shifts (δ^1H^, δ^13C^, δ^15N^) reported. ^1^H coordination shifts of various signs and magnitudes (Δ^1H^~coord~ = δ^1H^~complex~ − δ^1H^~ligand~) are discussed in relation to the changes of diamagnetic contribution to the relevant ^1^H shielding constants. The comparison to the literature data for similar complexes containing auxiliary ligands other than chlorides exhibited a large dependence of δ^1H^ parameters on electron density variations and ring‐current effects (inductive and anisotropic phenomena). The influence of deviations from planarity, concerning either MN~2~Cl~2~ 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 ^1^H NMR spectra. ^15^N coordination shifts (Δ^15N^~coord~ = δ^15N^~complex~ − δ^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 ^15^N shielding constants, this phenomenon being noticeably dependent on the type of a platinide metal and coordination sphere geometry. The absolute magnitude of Δ^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 ^1^H, ^13^C, ^15^N NMR chemical shifts are compared to those quantum‐chemically calculated by B3LYP/LanL2DZ + 6–31G**//B3LYP/LanL2DZ + 6–31G*, both in vacuo and in CHCl~3~ or DMF solution. Copyright © 2007 John Wiley & Sons, Ltd.