Preparation, Structure, and Solid-State Reactivity of Lanthanum Propynoates

A comparative study of the complexes La2(O2CC⋮CH)6(H2O)4·2H2O (1) and La2(O2CC⋮CH)6(C10H8N2)2(H2O)2·4H2O·2C10H8N2 (2) was undertaken to assess the effect of introducing bulky ligands on the solid-state reactivity of metal propynoates. A solid-state polymerization reaction occurred when 1 was exposed to 60Co γ-rays; complex 2 was found to be stable to 60Co γ-irradiation. Complexes 1 and 2 have closely-related molecular structures and, as expected, rather different packing arrangements. The crystal structures of 1 (with infinite chains of short acetylene−acetylene contacts) and 2 (containing only a chain of only five short acetylene−acetylene contacts) are consistent with the observed reactivity patterns. The results provide useful insight into the planning of syntheses for radiation-sensitive materials. Crystal data: 1: monoclinic, space group P21/c, a = 11.126(3), b = 14.174(4), c = 8.851(3) Å; β = 99.65(3)°; Z = 2; R = 0.027, R w = 0.037 for 3674 data for which I > 1.96σ(I). 2: triclinic, space group P1̄, a = 10.393(3), b = 13.022(4), c = 13.413(4) Å; α = 116.90(1); β = 101.03(1); γ = 103.82(1)°; Z = 1; R = 0.025, R w = 0.024 for 4921 data for which F > 4σ(F).