STRUCTURE OF ALKALI BIPHENYL ION-PAIRS IN SOLUTION AND IN THE SOLID-STATE

NMR experiments on sodium biphenyl (NaBp), potassium biphenyl (KBp) and rubidium biphenyl (RbBp), dissolved in various solvents are summarized with emphasis on the structural information which can be obtained from such experiments. The crystal structures of NaBp.2Tg (Tg triglyme), KBp.2Ttg and RbBp.2Ttg (Ttg = tetraglyme) are discussed, in relation to the NMR results obtained for these systems in solution. In the solid state these crystals may be considered to be built up of solvent separated ion pairs. Magnetic experiments are reported for single crystals of the three systems. Susceptibility measurements revealed a ferromagnetic coupling in NaBp.2Tg and KBp.2Ttg and an antiferromagnetic coupling in RbBp.2Ttg. All crystals exhibit an exchange narrowed ESR line, with an orientation dependent linewidth. From the resonance positions the molecular g tensor of the biphenyl anion could be derived. The orientation dependent linewidth is due to dipolar interactions between the spins. A quantitative explanation of it could not be given at present. and at a temperature of about -20°C. Magnetic measurements. © 1979, Walter de Gruyter. All rights reserved.