Hexachloro-metallates: infrared, nuclear quadrupole resonance spectra, and X-ray structural studies

Abstract

A solid-state study of tervalent hexachloro-complexes R₃MCl₆(M= Rh or Ir) and quadrivalent hexachlorocomplexes R₂MCl₆(M= Mn, Tc, Ru, and Rh) has been carried out by use of X-ray, n.q.r., and i.r. techniques. The ³⁵Cl n.q.r. spectra of the complexes K₃RhCl₆,H₂O, K₃lrCl₆,H₂O, K₃lrCl₆, and (NH₄)₃lrCl₆,H₂O are complex and suggest a low site-symmetry for the anion. This is verified from the low-frequency i.r. spectra of the compounds and a full single-crystal X-ray analysis of K₃RhCl₆,H₂O. The latter complex is orthorhombic and has space-group Pbcn with 8 molecules Z= 8 in a unit cell of dimensions a= 1·2368(9), b= 1·5655(6), and c= 1·2041 (10) nm. The structure was solved from diffractometer data and refined R 0·07 for 920 independent reflexions. The octahedral RhCl₆^3– anions contain six crystallographically independent Rh–Cl bonds ranging in length from 230·2(4) to 236·6(4) pm. The lack of symmetry in the anion appears to be influenced by the neighbouring molecule of water of crystallisation. The n.q.r. spectra of the cubic octahedral quadrivalent complexes R₂MCl₆(M= Mn, Tc, Ru, or Rh) have been measured and display the same trends as observed previously for the metal hexachloro-complexes of the third transition-series.