Polyhedral C2@Agn cages distorted by ancillary pyridine N-oxideligands in silver–acetylenediide complexes

Abstract

Reactions of the pyridine N-oxide ligands L, L² and L³ with the silver acetylenediide-containing system under hydrothermal conditions gave rise to four silver–acetylenediide complexes bearing interesting C₂@Ag_n motifs: (Ag₂C₂)₂(AgCF₃CO₂)₈(L¹)_3.5 (1), (Ag₂C₂)₂(AgCF₃CO₂)₈(L²)₂ (2), (Ag₂C₂)(AgCF₃CO₂)₄(L³) (3) and [(Ag₇(C₂)(CF₃SO₃)₃(L³)₂(H₂O)₂]·2CF₃SO₃ (4) (L = nicotinic acid N-oxide, L¹ = pyridine N-oxide, L² = 1,2-bis(4-pyridyl)ethane N,N′-dioxide, L³ = 1,3-bis(4-pyridyl)propane N,N′-dioxide), which exhibit new distorted polyhedral C₂@Ag_n cage motifs. Complex 1 has a pair of acetylenediide dianions encapsulated in a Ag₁₄ aggregate composed of three polyhedral parts, whereas 2 contains an irregular (C₂)₂@Ag₁₃ double cage. In 3, the basic building unit is a centrosymmetric (C₂)₂@Ag₁₂ double cage with each component single cage taking the shape of a highly distorted triangulated dodecahedron with one missing vertex. As to complex 4, the core is a C₂@Ag₇ single cage in the form of a slightly distorted monocapped trigonal prism with four cleaved edges that include all three vertical sides. Furthermore, in the silver-rich environment, the pyO-type ligands are induced to exhibit unprecedented coordination modes, such as the µ₅-O,O,O,O′,O′ ligation mode of L² in 2 and the µ₄-O,O,O′,O′ mode of L³ in 3 and 4.