Structure of alkali biphenyl ion pairs in solution and in the solid state

Abstract

NMR experiments on sodium biphenyl (NaBp), potassium biphenyl (KBp) and ribidium 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.

Mechanistic Elucidation of the Formation of the Inverse Ca(I) Sandwich Complex [(thf)3Ca(μ-C6H3-1,3,5-Ph3)Ca(thf)3] and Stability of Aryl-Substituted Phenylcalcium Complexes

“…Reactions of an excess of calcium metal (more than 2 equiv) with different substituted (di)halogenobiphenyl derivatives gave deep-green solutions. EPR measurements confirmed the formation of biphenyl dianions in accordance with Rieke’s method of metal activation as well as with studies of alkali-metal−biphenyl adducts …”

Effects of Intraligand Electron Delocalization, Steric Tuning, and Excited-State Vibronic Coupling on the Photophysics of Aryl-Substituted Bipyridyl Complexes of Ru(II)

“…To achieve delocalization in our system, we postulate that the excited state of [Ru(dpb) 3 ](PF 6 ) 2 is characterized by a ligand conformation in which the 4,4‘-phenyl substituents are coplanar with the bipyridyl fragment. This structural motif is directly analogous to what is observed in biphenyl upon one-electron reduction , and one that is also implicated in the reduced form of paraquat …”

“…To achieve delocalization in our system, we postulate that the excited state of [Ru(dpb) 3 ](PF 6 ) 2 is characterized by a ligand conformation in which the 4,4′-phenyl substituents are coplanar with the bipyridyl fragment. This structural motif is directly analogous to what is observed in biphenyl upon one-electron reduction 63,64 and one that is also implicated in the reduced form of paraquat. 65 Before leaving this section we wish to point out to the reader that application of the above model (eq 5) to emission spectra results only in a description of vibrational modes that are coupled to radiatiVe transitions from the excited state to the ground state.…”

Glymes as versatile solvents for chemical reactions and processes: from the laboratory to industry

“…Smid and Grotens 128 reported the crystalline 1:l complexes of NaBPh 4 with glyme-5, glyme-6 and glyme-7, as well as a 2:l complex with glyme-4. de Boer et al 129 studied the alkali biphenyl (NaBp, KBp and RbBp) in triglyme or tetraglyme solutions by NMR and the crystal structures of NaBp·(2 triglyme), KBp·(2 tetraglyme) and RbBp·(2 tetraglyme) by X-ray diffraction; these crystals consist of solvent-separated ion pairs in the solid state. Magnetic experiments were performed for single crystals of these three systems, and the susceptibility measurements suggested a ferromagnetic coupling in NaBp·(2 triglyme) and KBp·(2 tetraglyme) while an antiferromagnetic coupling in RbBp·(2 tetraglyme).…”