Iodo-complexes

Solid cadmium(II) iodide Cdlj has a layer lattice —a structure intermediate between one containing Cd " and P ions and one containing Cdl2 molecules—and this on vaporisation gives linear, covalent I—Cd—I molecules. In solution, iodo-complexes exist, for example... 

E values. Nitric acid attacks mercury, oxidising it to Hg (aq) when the acid is concentrated and in excess, and to Hgf (aq) when mercury is in excess and the acid dilute. Hydriodic acid Hl(aq) attacks mercury, because mercury(Il) readily forms iodo-complexes (see below, p. 438). 

Picolylphenylketone S-benzyldithiocarbazate, 48, yielded paramagnetic [ Ni(48-H)A 2] (A = Cl, Br) and diamagnetic [Ni(48-H)I] [207]. All three compounds are non-electrolytes and the iodo complex is planar while the other two complexes involve sulfur bridging atoms and five-coordinate nickel(II) centers. All three complexes can be converted to monomeric, octahedral complexes by addition of pyridine, 2-picoline or quinoline. 

The P-N chelate (91) (dapdmp) exhibits a variety of coordination geometries in complexes with divalent Co. Pseudotetrahedral Co(dapdmp)X2 (X = C1, Br, I, NCS), low-spin five-coordinate [Co(dapdmp)2X]+ (X = C1, Br, I), planar [Co(dapdmp)2]2+ and pseudo-octahedral Co(dapdmp) (N03)2 were all identified.390 The tetradentate P2N2 Schiff base complex (92) is formed by reacting the free ligand with CoI2. The iodo complex is low spin and square pyramidal.391... 

The compounds [Au3Ira(MeN=COMe)3] ( = 2, 4, 6) obtained by stepwise addition of iodine to the cyclic tetranuclear gold(I) complexes [Au3(MeN=COMe)3] have been revisited. The structure of [Au3I6(MeN=COMe)3] (338) consists of columns of the molecular units united by weak iodine- iodine interactions which range in length from 3.636(2) A to 3.716(2) A. The solid-state molecular packing of the di-iodo and tetra-iodo complexes reveal no unusual features.1971... 

Tetrachlorooxotechnetate(V) results from action of cone. HC1 on perteeh-netate at ambient temperatures and is preferably isolated as the tetrabutyl-ammonium salt [19]. Tetrabromooxotechnetate(V) was similarly obtained with hydrobromic add at 0 °C [8]. The molecular structures of both compounds are reported in [20,21]. The analogous iodo complex, tetraiodooxotechnetate(V), was synthesized by ligand exchange of the chloro compound with sodium iodide in acetone [22]. However, it suffers from considerable decomposition during isolation. 

I wish to point out that these reactions were studied in either neutral or acidic solutions where the cyanide cobalt system is really unstable thermodynamically. I raise the question about oxidation-reduction in the iodo complex. This wasn t mentioned in the paper. It seems to me it would provide an alternate path which might increase the reaction rates in the case of the iodide complex. 

Complexes with the simplest alkoxyphenylisocyanide and several halides are prepared by metathetical reactions of [AuCl(CNR)] with KX salts (Figure 7.19) [17]. The chloro-derivatives (n > 4) andthebromo-complexes (n > 6) display SmA phases. However, the ligands and the iodo-complexes are not liquid crystals. The transition temperatures decrease in the order Cl > Br > I, according to the decrease in polarity of the Au—X bond. It is important to note that the coordination of a very simple non-mesomorphic isocyanide (only one alkoxy chain and one aromatic ring) to Au—Cl allows the formation of a quite ordered and stable smectic mesophase. 

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