Syntheses and structures of μ-[N,N′-bis(2-aminoethyl)-1,2-ethanediamine-N1,N1′,N2,N2′]-bis[N,N′-(bis(2-aminoethyl)-1,2-ethanediamine-N,N′,N″,N‴)]dinickel(II) perchlorate (1) and 4,4′-biphenyldisulfonate (2)

A pair of racemic (ΔΔ/ΛΛ) μ-[N,N′-bis(2-aminoethyl)-1,2-ethanediamine-N1,N1′,N2,N2′]-bis[N,N′-(bis(2-aminoethyl)-1,2-ethanediamine-N,N′,N″,N‴)]dinickel(II) compounds were prepared and structurally characterized by crystallography. The perchlorate salt (1) crystallizes in the space group Pbcn; while the 4,4′-biphenyldisulfonate (BPDS) salt (2) crystallizes in the chiral space group C2 with a pair of ΔΔ and ΛΛ enantiomers in the unit cell, which represents the first example of kryptoracemic crystallization documented for a binuclear coordination compound. The extensive hydrogen bonds between the SO3− groups of the BPDS anions and the amino hydrogens of the complex cations are accounted for the kryptoracemic crystallization pathway adopted by 2.