Ladder-type frameworks

Crystals of Ni(N03)2 with 4,4 -bipyridine produce a ladder type framework polymer, which can be desolvated to yield a stable porous solid. The adsorption of methanol has then been studied and shown to cause a guest-driven solid-to-solid transformation. Fascinatingly, this material is able to accept... 

Subtle structural differences have been observed in some dimers of lithiated 1,3-bis[(dimethylamino)alkyl]benzenes [14]. Direct lithiation of l,3-bis[(dimethylami-no)ethyl]henzens with H-butyllithium produced a symmetric dimer, in which the coordination sphere of lithium was saturated by coordination of the chelating amino substituents. An analogous lithiation reaction performed between 1,3-bis[(dimethylamino)/ ro 7y/]benzene and n-butyllithium yielded a mixed dimeric aggregate comprising the expected phenyllithium derivative and nBuLi in a 1 1 molar ratio. In the molecular structure four lithium ions and four bridging carbon atoms form a ladder-type framework. 

The "unfolded-drum" or "ladder" compound 2 has crystallographic symmetry. This corresponds to the idealized molecular symmetry and, therefore, there are three chemically inequivalent types of Sn atoms in the molecule, although all are hexacoordinated. The oxygen atoms in the open form can be subdivided into two types, as in the case of the drum molecule tricoordinate framework oxygen atoms and the dicoordinate oxygen atoms of the bridging carboxylate ligands. 

The presence of triethylenetetramine in the hydrothermal synthesis of open-framework zinc phosphates results in a number of frameworks with one- to three-dimensional structures. The structures include one-dimensional ladders, two-dimensional layer structures, and one structure where the tetramine is bound to the zinc center. The structural type was highly sensitive to the relative concentration of the amine and phosphoric acid.411 Piperazine and 2-methylpiperazine can be used as templating molecules in solvothermal syntheses of zinc phosphates. The crystallization processes of the zinc compounds were investigated by real time in situ measurements of synchrotron X-ray powder diffraction patterns.412... 

Scheme 1. Various Types of Transformations in Open-Framework Zinc Phosphates (a) Transformations of One-Dimensional Ladder and 20 Layer Compounds and (b) Transformations of 0D Monomer1...

Among the inorganic open-framework compounds, the family of phosphates is a large one [3]. A large variety of open-framework metal phosphates of different architectures have been synthesized in the last few years. They include one-dimensional (ID) linear chain and ladder structures, two-dimensional (2D) layer structures and three-dimensional (3D) channel structures [4]. In the linear chain and ladder structures, four-membered metal phosphate units of the type M2P2O4 share comers and edges respectively. Zero-dimensional four-membered zinc phosphates have been synthesised and characterized recently [5]. Several open-framework metal carboxylates have also been reported [6] and the presence of a hierarchy of zinc oxalates covering the monomer, dimer, chain, honeycomb-layer and 3D structures has indeed been established [7]. 

Figure 8. Chart showing various types of low D - high D transformations in open-framework zinc phosphates. Primacy of the 1D ladder structure can be seen.

Figure 5.25 The one-dimensional chain in [ Ce(H20)7 2Mn4Si2 Vi806s(H20)2] [73], (Reproduced with permission from W.L. Chen, et al, An inorganic aggregate based on a sandwich-type polyoxomet-alate with lanthanide and potassium cations from ID chiral ladder-like chains to a 3D open framework, European Journal of Inorganic Chemistry, 2007, no. 15, 2216-2220 (Figure 2). Wiley-VCH Verlag GmbH Co. KGaA.)...

It has been made from the rare ladder or tube silicate litidionite using a Lentz-type extraction-substitution process. The constituent fibers of this polymer have very small diameters, often 40-60 X, and are flexible and inert. They are believed to have frameworks closely related to that of the parent silicate ion. A polymer which appears to be the same as this one has been made from the syn-... 

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