Metal-directed self-assembly of transition metal heterometallascorpionates

Abstract

The heterobimetallic complexes [Co(L^tzE)₃K(THF)₂] [L^tzE = [{4,5-(P(E)Ph₂)₂}tz]⁻; tz = 1,2,3-triazole; E = S(3), Se(4)] featuring high-spin cobalt centres, and [Ni(L^tzE)₃K(THF)₂] [E = S(5), Se(6)] were synthesized through the self-assembly reaction of HL^tzE [E = S(1), Se(2)], KOH or K⁰ and MCl₂ (M = Co, Ni). Compounds 3–6 exhibit an unusual metallascorpionate-type anion formed by the coordination of three triazole units via a κ²-N,E mode to the transition-metal atom, and this anion further coordinates to a potassium cation through a κ³-N′,N′′,N′′′ fashion. Compounds 3 and 5 were used in the synthesis of 3d-metal heterometallascorpionates [M(L^tzS)₃Cu(PPh₃)] [M = Co, (7), M = Ni (8)] and the bimetallic complex [Ni(L^tzE)₃Ni(NO₃)(THF)] (9) through metathesis reactions, pointing to stable metallascorpionate anions in solution. The solution behavior of 3–9 was investigated by UV-visible spectroscopy, high-resolution mass spectrometry, electrochemical methods and by magnetic-susceptibility measurements. The molecular structures of 3–6, 8 and 9 were determined by single-crystal X-ray diffraction studies and exhibit M⋯M′ distances ranging from 3.52 to 3.88 Å.