Hg-X bonds

The broken bonds (boldface = dissociated BDEs (boldface = recommended data reference in parentheses) Methods (reference in  

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Conversion of the Hg—X-bonded products to those containing two transition-metal-Hg bonds can be accomplished by adding a second equivalent of the carbonyl anion. 

If only one reactive Hg—X bond is available in RHgX, only one Hg-transition-metal bond is formed ... 

For bromide and iodide, the nature of the countercation influences the structure of the anionic complex. In fact, when the [(18-C-6)-K]Br and [(18-G-6)-K]I salts are used, the anionic complexes ([ 163—X]—, X = Br, I) remain mononuclear and adopt a T-shaped structure (Figure 11). In both cases, the Hg-X bonds are shorter than those observed in the corresponding dinuclear complexes in agreement with the terminal location of the anion. The reaction of bis(pentafluoro)phenylmercury 164 with [(18-C-6)-K]Br and [(18-C-6)-K]I also afford T-shaped complexes [164-Br] and [164-1]. The Hg-Br (2.93 A) and Hg-I (3.12 A) bonds found in these complexes are longer than those observed in [163-Br] and [ 163—1] indicating that 164 is a weaker Lewis acid than 163.206... 

For example, A/fj is -24.7 kJ-mor for chloride, -42.2 kJ-mol" for bromide, and -75.3 kJ-mol" for iodide. Thus, the increasingly covalent character of the Hg-X bonds is reflected in the larger values measured as the ligands to Hg(II) become softer. The formation reactions and thermodynamics for inorganic ligands with Hg(II) have been thoroughly reviewed (89). 

Various Hg-X and Hg -X Bond Strengths A (kcal/mol) Obtained at the PCI-80 Level"... 

Studies of the effect of internal rotation on molecular correlation functions have been made by Woessner [411], Zeidler [62], Levine, Partington and Roberts [412] and Wallach [63]. The latter work considers internal rotation around several rotational axes in a mercury halide "label anchored to a macromolecule. The resulting effects are that when the rate of internal rotation (1/t ) is much faster than the over-all motion of the macromolecule (t << f the effective quadrupole interaction in the Hg-X bond is reduced by a factor of... 

Some vibrational and structural characteristics of the neutral complexes HgX2 are given in Table 8. As previously discussed for the thiocyanate complexes, as the donating power of the solvent increases, the Hg—X bonds weaken and the X—Hg—X angle bends, adopting a more pseudotetrahedral coordination in order to accommodate the solvating solvent molecules better. 

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