Grinding and kneading, mechanochemical methods

As with the hydrothermal method, solid-solid grinding reactions, or mechanochemical reactions as they are also called, is a method with long tradition in solid state chemistry that has recently been applied also to molecular chemistry [56,57]. This method has several advantages  

The main disadvantage is that single crystals are not produced in these type of reactions. However, powder X-ray diffraction (also known as XRD) can be used to solve this problem, either by direct solution of the structure from the XRD-data, (sometimes possible although not quite a standard method) or by comparison to the XRD diffractogram of a known structure. If the product is a new compound it may be possible to grow single crystals from seeds using the powder material and in that way get the X-ray structure [58]. 

The examples of ID, 2D or 3D nets obtained in this way are still scarce, but recently the preparation of the coordination polymers [Ag(N(CH2CH2)3N)2 (CH3C00)]-5H20 and [Zn(N(CH2CH2)3N)Cl2] were reported [59]. 

Superconductors are for example conveniently made by grinding the starting materials, pressing them to a table, and finally prolonged heating at high temperatures. 

A small ( catalytic ) amount of solvent may also be added to the grindings in which case we call the method kneading. 

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