Hg complex

Hg " complexes are common, but complexes of Na, Mg", or Al are rare. Chromium complexes are also common, but in such complexes the chromium is in a low or zero oxidation state (which softens it) or attached to other soft ligands. In another application, we may look at this reaction ... 

CiiHuOn 112-05-0) see Azelaic acid D-penicillamine Hg complex (CjH Cl2HgN02S 14062-65-8) see D-Penicillamine D-penicillamine hydrochloride (C5H12CINO2S 2219-30-9) see D-Penicillamine DL-penicillamine hydrochloride (CjH,2C1N02S 22572-05-0) see D-Penicillamine penicillin G... 

Experimental methods used for studies of Cd and Hg complexes in solution and in the solid state are reviewed briefly, with examples for the application of the method under discussion in recent work. In a separate section quantum-chemical studies, including consideration of relativistic effects, on existing and not-yet-existing species with Cd and/or Hg, are also surveyed. 

A survey of transition-metal polyazacycloalkane complexes in general, with data also for Cd and Hg species in particular, has been published.180 Structural, 3H and 13C NMR, UV/vis, and conductivity data of several transition-metal complexes, including Cd and Hg complexes, with derivatives of the 16-membered ligand l,9-dithia-5,13-diazacyclohexadecane have been compiled and compared. In particular, conversion between configurational isomers and exchange processes in solution have been discussed.181... 

Cd (and Hg) complexes with bis- and tris(l-pyrazolyl)methanes and -ethanes, as well as with bis(l-triazolyl)methane, have been prepared and studied by conductance measurements (H20, dmso, and dimethylformamide (dmf) solutions), IR, far-IR, H, and 13C NMR spectrometries.203 The Cd halides form complexes of the type [CdLX2] complexes of the types [CdL2](C104)2 and [CdL3](BF4)2 are obtained from the respective Cd salts. 

The elements of this group (zinc Zn, cadmium Cd, mercury Hg) all exhibit a II oxidation state in aqueous systems, and Hg also shows a I oxidation state as indicated by the unusual cation Hg2. None of the elements shows oxidation states greater than II, which indicates that the d electrons are not involved. Within the group Zn and Cd resemble each other more closely than Cd and Hg. This is especially evident in the nobility of Hg (E° positive for Zn and Cd, negative for Hg), the lack of an Hg hydroxide, the thermal instability of HgO, and the greater stabilities of many Hg complexes as compared to those of Zn and Cd. 

The free energy change (AG°) associated with this process is a measure of the relative stability of the HG complex. For a complex that forms spontaneously, that is, self-assembles in the solution phase, AG° < 0. The free energy is related to the association equilibrium constant by the well-known thermodynamic equation ... 

The complexes MX2L2 (M = Zn, X = Cl, Br or I M = Cd, X = Cl) and HgX2L (X = Q, Br, SCN, N03 or S04) have been isolated, where L is the sterically hindered ligand 2-imino-4-oxo-1,3-thiazolidine.880 All complexes are formulated as monomeric tetrahedral with Zn, ligand coordination is via the ring N atom, but in the Cd complexes coordination via sulfur is observed. The ligand is bound via both N and S in the Hg complexes. The SCN is unidentate and S-bonded nitrate is unidentate, whereas sulfate is bidentate. 

Equilibrium calculations suggested that Hg complexation varies greatly among redox and pH levels typical of the regions of lakes sampled during this study. In an oxic lake, pore water, and groundwater, Hg complexation with organic matter most likely dominates. Under anoxic conditions in the hypolimnion and pore waters, Hg most likely forms soluble bisulfide and polysulfide complexes. 

A recent comprehensive review, with references into 1980, outlines the main synthetic routes to and common properties of complexes of types B and C.1 Table 1 gives references to some of the more unusual species that have been described in the interim. New organic syntheses exploiting Pd— and Pt—Hg complexes have been summarized lately.14... 

Mercury(II) porphyrins seem to be rather irregular, since various types of Hg" complexes have been reported (Scheme 25).17"... 

Step (ID) leads to the decomposition of the HCI molecule in the encounter where the second molecule acts as a deactivator, while step (20) may be regarded as the decomposition of the HC-1 molecule, sensitized by the [HCI Hg ] complex. 

There are widespread reports concerning the thermal stability of various M—Sn bonds however, no systematic studies are apparent involving the effect on this stability of the metal component. A common decomposition pathway of triorganotin complexes involves the formation of ditin compounds as noted below for V and Hg complexes (equations 133323 and 134241,324). 

By reaction of /ram -[(NH3)2Ptri-MeCyH2,AY4j)2 2+ with Hg2+ ions a novel dinuclear Pt,Hg compound has been recently reported, where the bases are reversed with respect to the Pt,Hg complex described above. The heterometal is bound through the N(3) sites of the two cytosine rings (III, Fig. 5) [35],... 

Zn < Cd Hg. Complexes with Hg2+ are among the strongest known with any element. In addition to the [MI4] complexes, mercury can form linear [Hgl2] and sometimes [Hgl3], As in the solid compounds,... 

The processes (19.39)-(19.42) have not been studied so far. The CTSH calculations for the H- +H2 (X1A+ v) system [22,23] indicate that long-lived transient states of Hg complex are formed during the slow collision, particularly for the high initial vibrational states of v). Stabilization... 

Mercury(I) is assumed to be of minor importance as an environmental contaminant due to the instability of Hg complexes with common atmospheric ligands (e.g. OH and S03 , etc.). However, reliable trace analytical techniques for Hg in the gaseous or aqueous phase are unavailable. 

---