Preparation, characterization, and X-ray crystal structures of helical and syndiotactic zinc-based coordination polymers

The reactions of (facac)(2)Zn.2H(2)O (facac = 1,1,1,5,5,5-hexafluoroacetylacetonate) with 2,5-bis(4-ethynylpyridyl)-furan (1) and 1,2-bis(4-ethynylpyridyl)benzene (2) yield upon crystallization, coordination polymers. The former polymer, {(facac)(2)Zn.1}(n), has an isotactic, helical structure in the solid state [monoclinic space group P2(1)/n; a 11.0374(3) Angstrom, b = 24.2179(10) Angstrom, c = 14.3970(3) Angstrom, beta = 92.880(2)degrees; Z = 4]. The latter polymer, {(facac)(2)Zn.2}(n), adopts a syndiotactic structure in the solid state [monoclinic space group P2(1)/n; a = 9.1344(1) Angstrom, b = 21.7985(5) Angstrom, c = 16.0322(4) Angstrom, beta = 99.6680(11)degrees; Z = 4]. The solution structures of the corresponding oligomers have been studied by low-temperature H-1 and F-19 NMR spectroscopy. Chiral polymers were prepared using the fragment [(+)-tfc](2)Zn ((+)-tfc = 3-((trifluoromethyl)hydroxymethylene)-(+)-camphorate. A linear, zigzag structure was found for {[(+)-tfc](2)Zn.1}(n) [triclinic space group P1; a 7.4833(2) Angstrom, b = 14.1563(5) Angstrom, c = 21.21230(5) Angstrom, alpha = 78.4440(15)degrees, beta = 81.5634(15)degrees, gamma = 76.4976(13)degrees; Z = 1]. Reaction with tris(4-pyridyl)methanol (3) yielded a homochiral, helical polymer, ([(+)-tfc]2Zn 3), [monoclinic space group C2; a = 25.0633(12) Angstrom, b = 11.8768(7) Angstrom, c = 17.1205(9) Angstrom, alpha = 900, beta = 117.954(3)degrees, gamma = 90 degrees; Z = 4].