RuII Complexes Incorporating Tetrathiamacrocycles: Synthesis and Conformational Analysis

• Published in: Chemistry : a European journal Vol. 11; no. 7; pp. 2031 - 2046
• Main Authors: Adams, Harry, Amado, A. M., Félix, Vitor, Mann, Brian E., Antelo-Martinez, Jorge, Newell, Mike, Ribeiro-Claro, Paulo J. A., Spey, Sharon E., Thomas, James A.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 18.03.2005; WILEY‐VCH Verlag
• Subjects: Crystallography, X-Ray; fluxionality; invertomers; Ligands; Macrocyclic Compounds - chemistry; macrocylic ligands; Magnetic Resonance Spectroscopy - methods; Models, Molecular; Molecular Conformation; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; Pyridines - chemistry; ruthenium; Ruthenium - chemistry; Sensitivity and Specificity; Stereoisomerism; sulfur; Sulfur Compounds - chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200400693

The synthesis of a series of RuII complexes incorporating thiacrown ligands ([12]ane‐S4, [14]ane‐S4, [16]ane‐S4), as well as 2,2′‐bipyridine (bpy) or pyridine, is reported. Structural studies on these complexes have been carried out using a variety of techniques. Detailed 1H NMR spectroscopic studies on the previously reported [Ru([12]ane‐S4)(bpy)]2+ (1) reveal that—contrary to earlier reports—the observed fluxional 1H NMR behavior is not due to chemical exchange involving cleavage of the bpy RuN bond but is, in fact, due to lone‐pair inversion of coordinated macrocyclic sulfur donor atoms. This phenomenon is also observed for the [14]ane‐S4 and [16]ane‐S4 analogues of 1. For the first time, using a combination of X‐ray crystallography, more detailed 1H NMR experiments, and computational methods, an in‐depth study on the energetics and dynamics of invertomer formation and conversion for macrocyclic coordination complexes has been carried out. These studies reveal that the steric constraints of assembling each sulfur macrocycle and bpy ligand around the octahedral RuII center lead to close intramolecular contacts. These contacts are largely dependent on the orientation of the electron lone pairs of equatorial sulfur donor atoms and correlate with the comparative stability of the different invertomeric forms. Thus, the conformational preferences of the three macrocyles in [Ru([n]ane‐S4)(bpy)]2+ complexes are determined by steric rather than electronic effects. Flipping macrocycles! The synthesis of a series of RuII complexes incorporating thiacrown ligands, as well as 2,2′‐bipyridine (bpy) or pyridine, is reported. It is revealed that the conformational preferences of the three sulfur macrocyles around the RuII center in [Ru([n]ane‐S4)(bpy)]2+ complexes are determined by steric rather than electronic effects. The figure shows the HOMO for an isomer of one of the complexes described in this study.