Outer-Sphere Macrochelation in [Pd(en)(5′-GMP-N7)2]-9H20 and [Pt(en)(5′-GMP-N7)2] 9H20: X-ray Crystallography and NMR Spectroscopy in Solution

Abstract

X-ray crystallography shows that [Pd(en)(5′-GMP-AN7)2]-9H20 and [Pt(en)(5′-GMP-N7)2]-9H20 are isostructural square-planar complexes with the bases coordinated head-to-tail in the A configuration. The sugar conformations are C3′-endo (N-type), anti (χ = ‒155.6 and −155.5°, Pd and Pt), gauche+. Macrochelate rings are formed via intramolecular H-bonding between the monoanionic 5′-phosphate groups and coordinated ethylenediamine NH (N ••• OP 2.92 Å). Electrostatically-bonded axial water molecules (Pd-0 = 3.365 Å, Pt-O = 3.493 Å) play key roles in a network of H-bonding involving the phosphate oxygens, ethylenediamine NH, and C60. 1H{15N} NMR shifts together with 31P{1H} NOE’s show that macrochel..