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, Rw = 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, Rw = 0.024 for 4921
data for which F
> 4σ(F).