Syntheses and crystal structures of three novel oxalate coordination compounds: Rb2Co(C2O4)2·4H2O, Rb2CoCl2(C2O4) and K2Li2Cu(C2O4)3·2H2O.

Single crystals of three novel transition-metal oxalates, dirubidium di-aqua-dioxalatocobalt(II) dihydrate or dirubidium cobalt(II) bis-(oxalate) tetra-hydrate, Rb2[Co(C2O4)2(H2O)2]·2H2O, (I), catena-poly[dirubidium [[di-chlorido-cobalt(II)]-μ-oxalato]] or dirubidium cobalt(II) dichloride oxalate, {Rb2[CoCl2(C2O4)]} n , (II), and poly[dipotassium [tri-μ-oxalato-copper(II)dilithium] dihydrate] or dipotassium dilithium copper(II) tris-(oxalate) dihydrate, {K2[Li2Cu(C2O4)3]·2H2O} n , (III), have been grown under hydro-thermal conditions and their crystal structures determined using single-crystal X-ray diffraction. The structure of (I) exhibits isolated octa-hedral [Co(C2O4)2(H2O)2] units, whereas (II) consists of trans chains of Co2+ ions bridged by bidentate oxalato ligands and (III) displays a novel tri-periodic network of Li+ and Cu2+ ions linked by oxalato bridging ligands.