Zirconium Oxalates: Zr(OH)₂(C₂O₄), (H₁₁O₅)₂[Zr₂(C₂O₄)₅(H₂O)₄], and MM′[Zr(C₂O₄)₃]·xH₂O with M and M′ = Ammonium, Alkali Metal, and Hydroxonium Ion H_2n+1O_n⁺ (n = 2, 3, 4)

Abstract

Crystallized powder of dihydroxide zirconium oxalate Zr(OH) 2 (C 2 O 4 ) ( ZrOx ) was obtained by precipitation and the structure determined from powder X-ray data. The three-dimensional (3D) framework observed in ( ZrOx ) results from the interconnection of zirconium hydroxide chains 1 ∞ [Zr(OH) 2 ] 2+ and zirconium oxalate chains 1 ∞ [{Zr(C 2 O 4 )} 2+ ]. Single crystals of (H 11 O 5 ) 2 [Zr 2 (C 2 O 4 ) 5 (H 2 O) 4 ] ( H2Zr2O5 ) were obtained by evaporation. The structure contains dimeric anions [Zr 2 (C 2 O 4 ) 5 (H 2 O) 4 ] 2– connected through hydrogen bonds to hydroxonium ions (H 11 O 5 ) + to create a 3D supramolecular framework. The addition of ammonium or alkali nitrate led to the formation of single crystals of Na 2 [Zr(C 2 O 4 ) 3 ]·2H 2 O ( Na2ZrOx3 ), M(H 7 O 3 )[Zr(C 2 O 4 ) 3 ]·H 2 O, M = K ( KHZrOx3 ), M = NH 4 ( NH4HZrOx3 ), M(H 5 O 2 ) 0.5 (H 9 O 4 ) 0.5 [Zr(C 2 O 4 ) 3 ], M = Rb ( RbHZrOx3 ), and M = Cs ( CsHZrOx3 ). For the five compounds, the structure contains ribbons 1 ∞ [{ZrOx 3 } 2– ] formed by entities Zr(C 2 O 4 ) 4 sharing two oxalates. In ( Na2ZrOx3 ), the shared oxalates are in cis positions and the chain 1 ∞ [Zr–Ox] is stepped with a Zr–Zr–Zr angle of 98.27(1)°. In the other compounds, the shared oxalates are in trans positions and the chains 1 ∞ [Zr–Ox] are corrugated with Zr–Zr–Zr angles in the range 140.34(1)–141.07(1)°. In the compounds ( MHZrOx3 ), the cohesion between t...