PREPARATION, STRUCTURE, AND SOLID-STATE REACTIVITY OF LANTHANUM PROPYNOATES

A comparative study of the complexes La-2(O2CC=CH)(6)(H2O)(4) . 2H(2)O (1) and La-2(O2CC=CH)(6)(C10H8N2)(2)(H2O)(2) . 4H(2)O . 2C(10)H(8)N(2 ) (2) was undertaken to assess the effect of introducing bulky ligands on the solid-state reactivity of metal propynoates. A solid-state pol ymerization reaction occurred when 1 was exposed to Co-60 gamma-rays; complex 2 was found to be stable to Co-60 gamma-irradiation. Complexes 1 and 2 have closely-related molecular structures and, as expected, r ather different packing arrangements. The crystal structures of 1 (wit h infinite chains of short acetylene-acetylene contacts) and 2 (contai ning 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 P2(1)/c, a = 11.1 26(3), b = 14.174(4), c = 8.851(3) Angstrom; beta = 99.65(3)degrees; Z = 2; R = 0.027, R(w) = 0.037 for 3674 data for which I > 1.96 sigma(1 ). 2: triclinic, space group <P(1)over bar >, a = 10.393(3), b = 13.02 2(4), c = 13.413(4) Angstrom; alpha = 116.90(1); beta = 101.03(1); gam ma = 103.82(1)degrees; Z = 1; R = 0.025, R(w) = 0.024 for 4921 data fo r which F > 4 sigma(F).