Layered-type inclusion compounds

We shall be discussing other types of inclusion compounds formed by layered graphite and Ta 2 as well as other varieties of hosts in Chapter 8, which deals with intercalation chemistry. 

Another type of inclusion compd is the layer or sandwich compound. This includes certain hydrated clays (such as halloysite and montmoril-lonite) which form layer-or sandwich-inclusion compds with polar organic molecules (such as alcohols, glycols, some hydrocarbons, etc) which replace the water, loosely bound in clays (Ref 10, pp445-7)... 

A new class of compounds in which hydrogen bonding is important is that of the molecular intercalates. These are a special type of inclusion compound, formed by the insertion of molecules into empty sites between layers of a layered structure. All intercalation reactions are characterized by an expansion of the crystal lattice along the c direction perpendicular to the layers to an extent that may be correlated... 

Layer Inclusion-compounds In this type of complex formation, the layer structure of the host is made use of. Certain clays, such as montmorillonite and halloysite, have a sandwich or layer structure that will readily include organic compounds of a polar nature. Alcohols, ethers, nitriles and amines are among the guests included by these clays. The layer width may vary, depending upon the compound included. Ionic attraction and van der Waals forces are involved in this type of inclusion. 

Other subsidiary descriptive terms used to illustrate the spatial relationships between host and guest refer to the designations "layer-type" (two-dimensionally open), "channel-type" (one-dimensionally open), and cage-type" (totally enclosed) inclusion compound, also termed "intercalates." "tubulates." and "cryptates," respectively, which makes further coinbinations of descriptive hybrid terms possible, e.g., tubulatoclathrate indicating a channel-type clathrate and so Even more precise... 

Host inolecules may be broadly classified into two main types those that form molecular complexes by fitting convex guests into the concave cavity of the host (examples include cyclodextrins, cyclophanes. calixar-enes, cycloveratrylenes, and various carcerands ) and those that form lattice inclusion compounds by packing in such a manner as to leave cavities, channels, or layers in the crystal structure so as to accommodate various guest... 

Intercalation compounds (inclusion complexes) are formed by VO PO4 2H2O and structurally related layer-type compounds MO PO4 H20 (M = Mo, W, Nb, Ta, Ti). Foreign metal cations can sometimes be incorporated with the water molecules between the layers, particularly if the V or M has been partially reduced. 

The important group of inclusion compounds based on the early transition metal layer and channel type chalcogenides has been investigated. The problems of the formation of Li intercalates by interacting n-bytyllithium hexene solutions with Nb, Mo, W and Re chalcogenides have been considered. 

---