Donor and acceptor properties of the solvents tetrahydrofuran and tetrahydrothiophene

The donor and acceptor properties of tetrahydrofuran and tetrahydro-thiophene were evaluated by means of electrochemical and spectroscopic methods. Polarographic and cyclovoltammetric data for LiClO₄, NaClO₄, KClO₄, RbClO₄, CsClO₄, Ba(ClO₄)₂, AgCF₃SO₃, TlClO₄, Zn(CF₃SO₃)₂, Cd(CF₃SO₃)₂, Cu(CF₃SO₃)₂, Pb(CF₃SO₃)₂, Mn(CF₃SO₃)₂, Co(CF₃SO₃)₂, Ni(ClO₄)₂·2H₂O, oxygen, perylene, ferrocene, and bis(biphenyl)chromium tetraphenylborate in tetrahydrofuran and of TlClO₄, CuCF₃SO₃, Pb(CF₃SO₃)₂, Cd(CF₃SO₃)₂, oxygen, ferrocene and bis(biphenyl)chromium tetraphenylborate in tetrahydrothiophene together with the potentials of the Ag/0.01 M Ag⁺-ion electrodes in these two solvents are given. Molar Gibbs (free) energies for the transfer from acetonitrile into tetrahydrofuran for Na⁺, K⁺, Rb⁺, Ag⁺, Tl⁺, Zn²⁺, Cd²⁺, and Pb²⁺, and for the transfer into tetrahydrothiophene for Ag⁺, Cu⁺, Tl⁺, Cd²⁺, and Pb²⁺ were calculated from these data. Visible spectra were obtained for the solvatochromic dyes acetylacetonato(N,N,N,N,-tetramethylethylenediamine) copper(II) perchlorate and for 2,6-diphenyl-4-(2,4,6-triphenyl-l-pyridinio)phenoxide, which served as secondary standards to obtain donor and acceptor numbers. The changes in half-wave potentials of the cations vs. bis(biphenyl)chromium(I)/(0) and the Gibbs energies of transfer are discussed on basis of hard and soft donor properties of these two solvents.