Conformational analysis of a helically distorted gold(I) macrocycle derived from xantphos: Evidence for the aurophilic Au⋯Au interaction from NMR

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Abstract

Variable-temperature solution 1H- and 31P-NMR experiments are reported for [Au2(xantphos)2](NO 3)2 gold(I) complex incorporating a 16-membered Au 2P4C8O2 macrocycle derived from the 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (xantphos) ligand. These NMR studies provide detailed structural information about its solution structure in comparison to the solid-state structure available from single crystal X-ray diffraction. Two-dimensional 1H-NOESY spectroscopy at low temperatures allowed the full assignment of proton resonances, which are severely exchange-broadened at room temperature. The 1H-1H spatial connectivities of the large number of non-equivalent protons unravel the complete stereochemistry of the gold(I) macrocycle in its symmetrically twisted conformation. Chemical exchange between particular proton pairs has allowed understanding the molecular dynamics and ruled out formation of coordination oligomers. Spectral analysis of the unique phosphorous AA′BB′ spin system has revealed three-bond 31P- 31P scalar couplings mediated through the Au⋯Au bond, and has confirmed the existence of the aurophilic contact in low-temperature solutions. The solution 13C and 31P spectra are compared to the solid state 31P-MAS and 13C-CP/MAS spectra, where signal doubling effects due to the crystal packing have been discovered.

Original languageEnglish
Pages (from-to)917-924
Number of pages8
JournalMagnetic Resonance in Chemistry
Volume45
Issue number11
DOIs
Publication statusPublished - Nov 1 2007

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Keywords

  • AA′BB′
  • Aurophilic contact
  • C
  • CP/MAS
  • Helical conformation
  • NMR
  • Nuclear overhauser effect
  • P
  • Signal doubling
  • Solid state
  • Spin

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)

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