Correlations between the Structures of Binuclear Copper(II) Tetracarboxylates with 1,4-Dioxane and the Nature of Substituent R in the Carboxylate Anion

The dissolution of aqueous copper(II) acetate in coordinating bidentate 1,4-dioxane (reflux) affords anhydrous mononuclear complex Cu2(µ-OOCMe)4(dioxane)2 (I) (Cu…Cu 2.5781(3) Å). The crystal of complex I contains contacts of the α-H atom of the CH2 fragments of coordinated dioxane with the oxygen atom of the bridging anion with the formation of the 2D metal-organic framework (MOF). The anionic exchange reactions of the acetate bridges by pivalate or trifluoroacetate groups with the corresponding acids in boiling dioxane give 1D MOF {Cu2(µ-OOCR)4(dioxane)}n (R = tBu (II), Cu…Cu 2.5493(7) Å; CF3 (III), Cu…Cu 2.6391(12) Å) characterized by the step and linear geometry, respectively. A similar reaction of Cu2(µ-OOCMe)4(OH2)2 with HOOCCF3 but at room temperature in the presence of crude benzene affords mononuclear complex Cu(OOCCF3)2(OH2)3·2 dioxane (IV). Complexes I–IV are studied by elemental and X-ray diffraction analyses (CIF files CCDC nos. 2052618 (I), 2052619 (II), 2052620 (III), and 2052617 (IV)). The influence of the electronic and steric factors of substituents R on the compositions and structures of the mononuclear complexes and MOFs with 1,4-dioxane are discussed for the synthesized and known copper(II) tetracarboxylates.