Solid-State Polymerization of Aquabis(3-butenoato)calcium

Aquabis(3-butenoato)calcium, Ca(C4H5O2)2(H2O) (1), the monomeric precursor for a new
solid-state polymerization reaction, was synthesized from 3-butenoic acid and calcium
carbonate. Irradiation of solid 1 with 60Co γ-rays (305 kGy dose) leads to high molecular
weight calcium poly(3-butenoate), M̄w = 400 000, in 97% yield. Prior to this report, solid-state reactivity was unknown for metal salts of β, γ-unsaturated carboxylic acids. An X-ray
structure determination of 1 shows it to be a two-dimensional coordination polymer. The
most outstanding feature of the crystal packing is a bilayer arrangement, leading to nearly
parallel, reactive vinyl groups, with short −CC− ··· −CC− contacts of 3.73 and 3.90 Å
along the crystallographic b direction. Crystal data for 1:  monoclinic, space group P21/n, a
= 5.9083(13), b = 6.7877(18), c = 27.927(10) Å; β = 92.42(2)°; V = 1119.0(5) Å3; Z = 4; R =
0.091, Rw = 0.103 for 464 data for which I > 1.96σ(I).