catena-Poly[[cadmium-bis(μ-triethylenetetramine-κ4 N,N′:N′′,N′′′)-cadmium-(μ-triethylenetetramine-κ4 N,N′:N′′,N′′′)] hexafluoridogermanate]

The title fluoridogermanate, {[Cd2(C6H18N4)3][GeF6]}n, was synthesized hydrothermally. The crystal structure comprises undulated cationic [Cd2(TETA)3]4+ chains (TETA is triethylenetetramine) propagating parallel to [101]. The central CdII atom is six-coordinated in a CdN6 set by three TETA ligands. The isolated [GeF6]2− units, serving as counter-anions, occupy the inter-chain spaces and simultaneously link adjacent chains into a three-dimensional network through extensive N—H⋯F hydrogen-bonding interactions. One of the ethylene bridges of one TETA ligand is disordered around a twofold rotation axis.

The title fluoridogermanate, {[Cd 2 (C 6 H 18 N 4 ) 3 ][GeF 6 ]} n , was synthesized hydrothermally. The crystal structure comprises undulated cationic [Cd 2 (TETA) 3 ] 4+ chains (TETA is triethylenetetramine) propagating parallel to [101]. The central Cd II atom is six-coordinated in a CdN 6 set by three TETA ligands. The isolated [GeF 6 ] 2À units, serving as counter-anions, occupy the inter-chain spaces and simultaneously link adjacent chains into a three-dimensional network through extensive N-HÁ Á ÁF hydrogen-bonding interactions. One of the ethylene bridges of one TETA ligand is disordered around a twofold rotation axis.

Comment
Much interest has been focused on the rational design and construction of microporous materials with intriguing topological architectures and promising applications (Cheetham et al., 1999;Zheng et al., 2003;Zou et al., 2005;Liang et al., 2006;Su et al., 2009). Compared to the rapid development of silicate and phosphate open-framework structures, the progress in the field of fluorides remains moderate. With the exception of some fluoridosilicates, fluoridoaluminates and fluoridotitanates, only a few fluoridogermanates (Brauer et al., 1980(Brauer et al., , 1986Lukevics et al., 1997;Wang et al., 2004;Zhang et al., 2003) have been reported. In this structure family, the central Ge(IV) ions are octahedrally coordinated by fluorine atoms. In addition, various organic amines or metal-complex cations have frequently been employed in the synthesis of such fluorides. The main purpose of our work is to explore the construction of novel microporous germanates with Cd II complexes as counter anions.
Unexpectedly, the title compound, (I), was obtained, which represents a new fluoridogermanate with one-dimensional Cd II complex cations.
As shown in Fig. 1, the asymmetric unit of (I) contains one unique germanium(IV) atom, one cadmium(II) atom, six fluoride anions, as well as one and a half TETA molecules (TETE = triethylenetetramine, C 6 H 18 N 4 ), the latter being completed by a twofold rotation axis. The cadmium atom is six-coordinated in a distorted octahedral geometry by six amine N atoms from three TETA ligands. The Cd-N bond lengths span the range 2.313 (3)-2.444 (3) Å, which are comparable with those observed in other related compounds, e.g. (Bartoszak-Adamska et al., 2002;Ma et al., 2005;Bose et al., 2006).
The crystal structure of (I) features an undulated cationic chain [Cd 2 (TETA) 3 ] 4+ , with discrete [GeF 6 ] 2groups serving as the counter anions and occupying the inter-chain spaces. As shown in Fig. 2, two neighboring cadmium atoms are linked by two bridging TETA ligands to form a dimeric Cd 2 fragment, with Cd···Cd contacts of 6.311 (2) Å. Such dimeric Cd 2 motifs, which can be considered as secondary building units (SBUs), are interconnected by the third TETA linker to generate one-dimensional corrugated chains parallel the [101] directions (Fig. 3). Adjacent uniform chains are further interlinked and packed together through the [GeF 6 ] 2groups into a three-dimensional supramolecular framework (Fig. 4). There are extensive N-H···F hydrogen-bonding interactions between the [GeF 6 ] 2ions and amine groups within each of the chains (Table 2).