cis-trans Isomerization under hydrothermal conditions. Synthesis and structure of calcium and barium 4-cyclohexene-1,2-dicarboxylates

Reaction of cis-4-cyclohexene-1,2-dicarboxylic acid with Ca(OH)2 and with BaCO3, under hydrothermal conditions, afforded two new metal dicarboxylates: (cis-4-cyclohexene-1,2-dicarboxylato)calcium(II), [CaC8H8O4] (1) and diaquabis(trans-cyclohex-4-ene-1-carboxylic-2-carboxylato)barium(II), [Ba(C8H9O4)2(OH2)2] (2). Compound (1) is monoclinic, P21/c, with unit cell parameters a = 12.6670(14), b = 6.7548(7), c = 9.5943(10) Å, β = 104.108(3)°, V = 796.16(15) Å3, Z = 4. Compound (2) is orthorhombic, Cmc21, a = 28.633(8), b = 9.036(3), c = 7.438(2), V = 1924.4(10) Å3, Z = 4. It should be noted that a cis-trans isomerization occurred in the reaction with BaCO3, suggesting an influence of the metal atom in the reaction.