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A comparative study of the complexes La 2 (O 2 CCtCH) 6 (H 2 O) 4 ‚2H 2 O (1) and La 2 (O 2 CCtCH) 6 -(C 10 H 8 N 2 ) 2 (H 2 O) 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 polymerization reaction occurred when 1 was exposed to 60 Co γ-rays; complex 2 was found to be stable to 60 Co 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 P2 1 /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 P1 h, a ) 10.393(3), b ) 13.022(4), c ) 13.413(4) Å; R ) 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).

Eight anhydrous metal carboxylate complexes have been studied in the solid state by 13C crosspolarization magic-angle-spinning n.m.r. spectroscopy. A general assignment of the 13C n.m.r. spectra can be made by comparing the data obtained with definitive structural data previously reported in single-crystal X-ray crystallographic studies. Although a complete assignment of all n.m.r. peaks has not been achieved, the results highlight the important parameters involved and demonstrate that in many cases definitive structural data can be deduced for these complexes in the solid state using n.m.r. spectroscopy. Metal carboxylates are excellent compounds for a comparative study because of the very high quality of the solid-state spectra produced. A crystallographic splitting of 8 Hz can be seen clearly in some spectra. The chemical shift is very

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