Crystal Structure and Thermodynamic Stability of the [Hg(Pyridine)4(NO3)2] � 2(Pyridine) Inclusion Compound

Fluorescence and Metal-Binding Properties of the Highly Preorganized Tetradentate Ligand 2,2′-Bi-1,10-phenanthroline and Its Remarkable Affinity for Cadmium(II)

“…This type of effect may be attributed to the typical distorted geometry observed most strongly in complexes of heavy d 10 metal ions such as Ag I and Hg II . − There is a preference for two more covalently bound donor atoms to occupy sites corresponding to the linear coordination geometry, with short M–L bonds, while the remaining donor atoms form long M–L bonds at right angles to the quasi-linear geometry of the two covalently bound donor atoms. Such an effect is shown particularly well for the [Hg­(pyridine) 4 NO 3 ) 2 ] complex, where there are two short Hg–N bonds of about 2.19 Å at close to 180° to each other, with the other two long Hg–N bonds of 2.58 Å and long Hg–O bonds of about 2.68 Å to the two nitrates, all at roughly right angles to the two short Hg–N bonds. Cd II is much less prone to this type of distorted geometry, but it is possible that the very high log K 1 for Cd II with DPP, compared to the shorter TPY or QPY, is due to the two terminal nitrogen donors of the ligand occupying the favored quasi-linear coordination sites on the metal ion.…”

Structural characterization of the nickel(II) formate complex, Ni(py)4(O2CH)2·2py, and re-evaluation of the nitrate counterpart, Ni(py)4(ONO2)2·2py: Evidence for non-linear nitrate coordination

“…A large variety of compounds of composition M(py) 4 X 2 •2py have been previously investigated with respect to their clathrate nature, the ability to maintain a structural similarity upon varying the M(py) 4 X 2 host molecules, and the ability to introduce guest molecules other than pyridine. [7][8][9][10][11][12][13] Our particular interest in this class of compounds, however, pertains to the nickel formate derivative, Ni(py) 4 It is also pertinent to point out that the formate ligand adopts a proximal conformation in which the uncoordinated oxygen resides with a cis-like disposition relative to the metal, rather than a distal conformation in which the uncoordinated oxygen atom and metal adopt a trans-like disposition (Figure 3). 5) and (ii) the R values are significantly higher (Table 3).…”