Ball-milling Mechanochemical Synthesis of Coordination Bonds: Discrete Units, Polymers and Porous Materials - Ball Milling Towards Green Synthesis: Applications, Projects, Challenges - page 153

Figure 7.1 (a) Mechanochemical synthesis of metal-organic molecular squares and

cages. 8 (b) Milling ZnCl 2 and cnge in a 1 : 1 ratio produced the coordin-
ation polymer Zn(cnge)Cl 2 , while milling the same reactants in a 1 : 2
stoichiometric ratio selectively yields the discrete complex
Zn(cnge) 2 Cl 2 . 20 (c) Acceleration of the mechanochemical synthesis of
the coordination polymer AgCl(etu) 3 by switching from neat grinding to
LAG with a small amount of water. 21

attached to the metal ion via nitrile groups only, as well as the 1D co-
ordination polymer Zn(cnge)Cl 2 in which pairs of zinc ions are bridged by
cnge. In solution, ZnCl 2 and cnge typically yield a mixture of these two
products. In contrast, mechanochemistry provides almost perfect selectivity:
milling of ZnCl 2 and cnge in a 1 : 1 stoichiometric ratio yields exclusively the
polymer Zn(cnge)Cl 2 , while milling a mixture of ZnCl 2 and cnge in a re-
spective 1 : 2 ratio yields the monomeric complex as the sole product
(Figure 7.1b). Such excellent control over the stoichiometric composition of
the product in mechanochemical reactions was recognized and exploited by
the Bowmaker group for the discovery and synthesis of previously unknown
complexes of silver halides with ethylenethiourea (etu). 21 For example,
whereas solution synthesis is known to produce only the previously
known complex AgCl(etu) 1.5 , mechanochemical synthesis readily provided
either AgCl(etu) 1.5 or the previously unknown AgCl(etu) 3 depending on the