Oxygen distance, metal

The second arrangement of the metal atoms, with u =— 0.030, is such that satisfactory interatomic distances are obtained only when the oxygen atoms are in the general position with a -, / = , and Each oxygen atom is then at about 2 A from four metal atoms if it be assumed that these four metal-oxygen distances are equal, the parameters are found to have the values... 

It is probable that the various metal-oxygen distances are not exactly equal, but show variations of possibly zb 0.05 A. The predicted parameter values may correspondingly be assumed to be accurate to only about zb 0.005. 

The longer metal-oxygen distances of about 2.6 A observed by EXAFS spectroscopy for these and related supported metal clusters suggest weak interactions between the metal and surface oxygen atoms these EXAFS contributions are not determined with as much confidence as those characterized by the shorter distances, and the interactions are not well understood. 

Table VI Equilibrium Metal-Oxygen Distances and (for Fe) Breathing Frequencies in Aquo Complexes. ...

Table 4. Metal-oxygen distances, A, in macrocyclic ether complexes...

The synthetic compounds of para. VII contain multiple groups which form five-membered chelate rings. Although the metal-oxygen distances, Tables 4 and 5, vary by amounts large compared with the standard deviations, it is clear that sodium-water distances are shorter than sodium-ether oxygen distances, even for the most flexible ligand, (XVIII). 

Spodumen is a monoclinic pyroxene, space group C C2 c), with two not equivalent metal cation sites Ml and M2. The aluminum occupies the smaller Ml site, which is approximately octahedral (actual symmetry C2) with an average metal-oxygen distance of 1.92 A. The M2 site, occupied by Li, is also six-fold coordinated with an average metal-oxygen distance of 2.23 A. Both A1 and Li sites may be substitutionally replaced by ions of the transitional metals in various proportions. Both Mn " " and Cr " centers have been identified in luminescence spectra by steady-state spectroscopy (Tarashchan 1978 Walker et al. 1997). At room and lower temperatures only one emission band of Mn + occurs and the excitation spectra taken for the different wavelengths of the luminescence bands are always the same. So it is very probable that Mn + ions in the spodumen matrix present only in one site. The calculated values of 10D,j and B are consistent with the occupation of larger M2(Li) weak-field site. Mn + is mainly in Li-sites rather than Al-sites. 

Finally, the configuration of the water (D20) molecule with respect to the metal ion can be probed by neutron diffraction methods. These give metal-deuterium distances which, when compared with metal-oxygen distances, give the angle between the plane of the water (D20) and the M—O bond. This is 55° for Nd3+ 193 it is said to vary with concentration for Ni2+ in solution.189... 

Table 4 The Range of Normal Short and Long Metal-Oxygen Distances for the Transition Metal and Main Group Elements...

As unidentate ligands, carboxylates are expected to (i) lose the equivalence of the two carbon- oxygen bonds found in the anion and (ii) have one metal-oxygen distance considerably shorter than the next shortest M—O contact. Lithium acetate dihydrate exemplifies this14 with C—O distances of 133 and 122 pm and Li—O distances of 227 and 257 pm. Most examples of unidentate carboxylate complexes have this classical configuration of M(0—C) and C=0 respectively so certainly the presence of features (i) and (ii) unambiguously determine this mode of coordination. 

Crystallographic values of metal-hydrogen and metal-oxygen distances in hexaaqua complexes of divalent 3d metal ions compared with calculated effective distances... 

Figure 3. Average metal-oxygen distance plotted against isomer shift for Fe3+ ions in different coordination environments in minerals. The data for clintonite (CL), yoderite (YO) and Mg-sapphirine (SAM), which are highlighted by spikes, are each plotted in two regions because dual ferric site occupancies have been suggested for these minerals.

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