Experimental and quantum-chemical studies of 1H, 13C and 15N NMR coordination shifts in Pd(II) and Pt(II) chloride complexes with methyl and phenyl derivatives of 2,2′-bipyridine and 1,10-phenanthroline

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

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 272 KB
• Volume: 45
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2104

✦ Synopsis

Abstract

^1^H, ^13^C and ^15^N NMR studies of platinide(II) (M = Pd, Pt) chloride complexes with methyl and phenyl derivatives of 2,2′‐bipyridine and 1,10‐phenanthroline [LL = 4,4′‐dimethyl‐2,2′‐bipyridine (dmbpy); 4,4′‐diphenyl‐2,2′‐bipyridine (dpbpy); 4,7‐dimethyl‐1,10‐phenanthroline (dmphen); 4,7‐diphenyl‐1,10‐phenanthroline (dpphen)] having a general [M(LL)Cl~2~] formula were performed and the respective chemical shifts (δ^1H^, δ^13C^, δ^15N^) reported. ^1^H high‐frequency coordination shifts (Δ^1H^~coord~ = δ^1H^~complex~ − δ^1H^~ligand~) were discussed in relation to the changes of diamagnetic contribution in the relevant ^1^H shielding constants. The comparison to literature data for similar [M(LL)(XX)], [M(LL)X~2~] and [M(LL)XY] coordination or organometallic compounds containing various auxiliary ligands revealed a large dependence of δ^1H^ parameters on inductive and anisotropic effects. ^15^N low‐frequency coordination shifts (Δ^15N^~coord~ = δ^15N^~complex~ − δ^15N^~ligand~) of ca 88–96 ppm for M = Pd and ca 103–111 ppm for M = Pt were attributed to both the decrease of the absolute value of paramagnetic contribution and the increase of the diamagnetic term in the expression for ^15^N shielding constants. The absolute magnitude of Δ^15N^~coord~ parameter increased by ca 15 ppm upon Pd(II) → Pt(II) transition and by ca 6–7 ppm following dmbpy → dmphen or dpbpy → dpphen ligand replacement; variations between analogous complexes containing methyl and phenyl ligands (dmbpy vs dpbpy; dmphen vs dpphen) did not exceed ± 1.5 ppm. Experimental ^1^H, ^13^C, ^15^N NMR chemical shifts were compared to those quantum‐chemically calculated by B3LYP/LanL2DZ + 6–31G**//B3LYP/LanL2DZ + 6–31G*, both in vacuo and in DMSO or DMF solution. Copyright © 2007 John Wiley & Sons, Ltd.