Topologically different infinite co-ordination structures of [CdNi(CN)4]·2H2N(CH2)nNH2·mH2O complexes (n= 2–7 and 9, m= 0–2) caused by the catenation behaviour of the diamine and the –NC–Ni(CN)2–CN–moieties

Abstract

The single-crystal structures have been determined for a tris(en)-chelated complex [Cd(en)3][Ni(CN)4]2a and a series of [CdNi(CN)4]·2H2N(CH2)nNH2·mH2O complexes with n= 2–7 and 9 and m= 0–2: [Cd(en)2Ni(CN)4]2b(monoclinic) and 2c(orthorhombic)(n= 2), [Cd(tn)2Ni(CN)4](n= 3)3, [Cd(dabtn)2Ni(CN)4]·2H2O 4(n= 4), [Cd(daptn)2Ni(CN)4]·H2O 5(n= 5), [Cd(H2O)2(dahxn)2][Ni(CN)4]6(n= 6), [Cd(dahpn)2Ni(CN)4]·H2O 7(n= 7) and [Cd(danon)2Ni(CN)4]9(n= 9). Only 2a comprises discrete [Cd(en)3]2+ and [Ni(CN)4]2–; the other structures are constructed by the catenation of either H2N(CH2)nNH2 or [Ni(CN)4]2–, or both, linking octahedral Cd atoms successively. In 2b and 2c the bis(en)-chelated Cd atoms are spanned by cis-[–NC–Ni(CN)2–CN–] moieties to form a one-dimensional chain (cis-one-dimensional). Each single span of the tn and danon in 3 and 9 links Cd atoms to form a two-dimensional network as a single two-dimensional network builder; a cis-one-dimensional Ni(CN)4 moiety reinforces one of the single tn spans in 3, whereas it bridges the single two-dimensional networks in 9 to build up a three-dimensional framework. Two diamine ligands span the Cd atoms in 4–6 to form a doubly bridged one-dimensional chain. The chains are spanned by trans-[–NC–Ni(CN)2–CN–] moieties to form a two-dimensional network in 4, whereas the double one-dimensional chain in 5 is additionally reinforced by a cis-one-dimensional Ni(CN)4 moiety to form a triple-span chain. The Cd atom in the double one-dimensional dahxn chain in 6 is co-ordinated by two trans related H2O molecules, among whose chains discrete [Ni(CN)4]2– anions are accommodated. Complex 7 shows a complicated structure constructed of a four-fold interpenetrating diamondoid three-dimensional sub-lattice framed by Cd–dahpn–Cd spans which has interconnections through the catenation of cis-one-dimensional Ni(CN)4 at every Cd. The H2O molecules in 4, 5 and 7 are accommodated in the void spaces formed in the respective multidimensional structures. These crystal structures are additionally stabilised by hydrogen bonds involving the NH2 group of the diamine, the nitrogen end of the Ni(CN)4 moiety and H2O molecules. The variations of the multidimensional structures are discussed in terms of the number of methylene units n in the diamines.