Crystal Engineering towards Design of Macrocyclic Coordination Compounds: Crystal Structure of Rubidium Tetrachloro-and Tetracyanoaurate(III) Complexes with 18-Crown-6

Abstract

Abstract The new macrocyclic complexes of composition Rb(18-crown-6)AuX4 (X = Cl (1) and CN (2)) have been prepared and characterized by X-ray crystallography (1: monoclinic, space group P21/n, with a = 8.747(1), b = 8.366(1), c = 15.404(1) Å; β = 104.37(1)°, V = 1092.0(3) Å3 , Z = 2; final R1 =0.025 for 2030 independent reflections used; 2: monoclinic, space group P21/c, with a = 14.765(3), 6 = 17.134(3), c = 8.855(2) Å; β = 90.20(1)°, V = 2240.2(8) Å3, Z = 4; final R1 = 0.080 for 2034 independent reflections used). Both structures consist of Rb(18-crown-6)+ cations (A) and complex aurate(III) anions AuX4 - (B). Complex 1 has a linear polymeric array -A-B-A-B-(Rb-Cl 3.604(3), 3.654(3) Å) with the rubidium ions disordered 0.276(2) Å above and below the crown ether plane (Rb-O 2.819(5)-2.884(5) Å, av. 2.846(5) Å). The positioning of the rubidium atom away from the center of the 18-crown-6 is effected by the packing of the Rb(18-crown-6)+ and AuCl4 - moieties, and by the resemblance in the charge and symmetry of the cationic and anionic parts of the structure. Complex 2 has a zig-zag polymeric array -A-B-A-B-(Rb-N 2.92(2), 2.94(1) Å) with orthogonal disposition of Rb(18-crown-6)+ and Au(CN)4 - planes. The rubidium atom is situated 0.90(2) Å above the mean plane of the macrocyclic oxygen atoms (Rb-O 2.93(5)-3.15(4) Å) and adopts a typical “sunrise coordination”.