Barium one-dimensional coordination polymers from barium β-diketonates and 2,2′-bipyrimidine derivatives

Abstract

Three unidimensional compounds were obtained by reacting the polymeric precursor [Ba(hfac)₂] (hfac⁻ = 1,1,1,5,5,5-hexafluoroacetylacetonate) either with 2,2′-bipyrimidine (bpm) or the bulkier 4,4′,6,6′-tetramethyl-2,2′-bipyrimidine (Me₄bpm). [Ba₂(hfac)₄(bpm)₃(CH₃OH)]·0.5 bpm (1) is composed of linear chains where the barium environments are alternatively tricapped trigonal primastic and tetradecahedral. Increasing the bpm-to-metal ratio leads to a unique tetradecahedral coordination environment for Ba(II) centres in [Ba(hfac)₂(bpm)₂] (2) zigzag chains. Finally in [Ba(hfac)₂(Me₄bpm)] (3) zigzag chains, the bulkiness of the Me₄bpm reduces the coordination number of the barium atom to eight leading to a distorted square prismatic coordination polyhedron. In 1 and 2, terminal bipyrimidine ligands govern the interchain interaction through π-stacking while, in 3, the crystal packing is dictated by the interaction between the perfluorinated moieties of the hfac⁻ ligands.