Transition metal complexes containing the S(NtBu)42− tetraimidosulfate dianion

Abstract

Three novel metal complexes [(acac)₂Cu₂(NtBu)₄S] (3), [Li(thf)₄]₂[I₄Cd₂(NtBu)₄S] (4) and [(thf)₂Li{(SiMe₃)₂N}Zn(NtBu)₄S] (5) are prepared from the intended transmetalation of the dilithium complex of N,N′,N′′,N′′′-tetrakis(tert-butyl)tetraimidosulfate [(thf)₄Li₂(NtBu)₄S] (1). The two lithium cations are replaced by either the cationic (acac)Cu(II) moiety, the neutral I₂Cd(II) residue or only a single lithium cation is substituted by the cationic (Me₃Si)₂NZn(II) fragment. The complexes show two main results: first the S(NtBu)₄²⁻ tetrahedron can serve as a ligand to transition metals from the soft Cu(II) to the harder Zn(II) at opposite sides and second the S–N bond distances vary only marginally in response to the various metals and the four distances constantly sum up to 6.38(2) Å. Hence the electropositive sulfur atom responds by internal shift to the metal-polarized negative charge at the outside of the S(NR)₄²⁻ tetrahedron.