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.