Mercury complexes pseudohalides

There is little evidence for the formation of soluble complexes in aqueous solutions of Hg1 halide and pseudohalide systems,12,32 but the mercury(I) halides themselves are well-known substances. X-ray studies on the dimercury(I) dihalides show that all these compounds possess... 

Addition of excess iodide to the insoluble Hgl2 results in the formation of soluble mercury iodo complex [Hgl3] , with a trigonal planar structure. The ion is solvated in water and converts to a tetrahedral structure. Further, addition of H leads to tetrahedral [Hg ] ". Reaction of iodide salts with Hg can be used to produce mercury iodo complexes. Other halide and pseudohalides also form [HgXj] and [HgX4] . The tetrahalo anions see Anion) are usually tetrahedral, while the trihalo ions readily add solvent molecules to form distorted tetrahedral or Trigonal Bipyramidal structures. 

Mercury (II) is known to accelerate Ligand Substitution reactions of complexes of formula ML5X (M = Rh, Cr, Co, Ru L = H2O or NH3 X = bridging halide or pseudohalide), probably by forming an intermediate with a halide bridge between Hg and M. 

As observed previously for soft donor ligands such as thioethers and phosphines, mercury(II) reacts with selenoethers and telluroethers to form complexes of the general type HgLX2, where X is a halide or pseudohalide. In addition, mercury (II) forms complexes with various Se-donor ligands such as diethylselenocarbamate and selenourea. 

Stability constant measurements for the aqueous Zn -azide system indicate that four mononuclear complexes of moderate stability are formed, whereas for mercury, maximum coordination of only two azide ligands is observed. Complexation of Cd " in aqueous NOJ-NJ yields the mixed species [Cd(N03)(N3) ] ( = 1-4). Crystallographic structural determinations of A2Zn(Ns)4 (A = K or Cs) have been reported the former exhibits isolated Zn(Ns)4 tetrahedra with linear azide (N—N = 1.18 A). Thermal decomposition of the above compounds yields nitrogen and ZnsN2 as the main products. A new a modification of Zn(Na)2 has been obtained by the use of an ethereal solution of The compounds and ZnLC (M = Zn or Cd X = halide or pseudohalide L =... 

Mercury(n) is also an effective catalyst for pseudohalide leaving groups, for example thiocyanate. In this connection, recently determined equilibrium data for complex formation between cobalt(ra)-thiocyanate complexes and mercury(n) are of relevance. ... 

Mercury(II) salts have been employed as reagents for the abstraction of halides and pseudohalide ligands from complexes of transition metals,26 Eq. 3.4 ... 

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