Metal-ligand distances

Rl — 2.02 A, the average change being here AR a 0.12 A. In ligand field theory, A depends inversely on the fifth power of the metal-ligand distance R [13] ... 

The description of states participating in a spin-state transition as electronic isomers with discrete nuclear configurations, in particular different metal-ligand distances, requires that separate electronic and vibrational spectra of the two spin states exist. Indeed, a superposition of the individual vibrational spectra of the two states is in general observed, the relative contribution of the states being a function of temperature [41, 139, 140, 141, 142]. This observation sets a lower limit for the spin-state lifetime longer than the nuclear vibrational period, i.e.,... 

Bray, M. R., Deeth, R. J., Paget, V. J., Sheen, P. D., 1996, The Relative Performance of the Local Density Approximation and Gradient Corrected Density Functional Theory for Computing Metal-Ligand Distances in Werner-Type and Organometallic Complexes , Int. J. Quant. Chem., 61, 85. 

The neutral Irv complex, cp Ir(H)2(SiEt3)2, has been studied by neutron diffraction and its structural characteristics compared to those of the isomorphous Rh analogue.6 The significant differences are longer metal-ligand distances and larger bond angles for the Ir species. 

In the REC model, the ligand is modelled through an effective point charge situated in the axis described by the lanthanide-coordinated atom axis, at a distance R, which is smaller than the real metal-ligand distance (Figure 2.6). To account for the effect of covalent electron sharing, a radial displacement vector (Dr) is defined, in which the polar coordinate R is varied. At the same time, the charge value (q) is scanned in order to achieve the minimum deviation between calculated and experimental data, whereas 9 and cp remain constant. 

Fourier transformation of Cu EXAFS data gathered on the Cu(MPG) complex reveals two separate peaks representing shells at distances of 1.9 and 2.3 A. When tested for Ns (coordination number), metal-ligand distance (R as), and Debye-Waller parameter difference (Aa2as) followed by comparison to known model compounds, results show that the presence of both a Cu-(N, O) and Cu-S shell is necessary to obtain an adequate fit to the EXAFS data. Therefore it was concluded that a Cu-S bond is present in the compound. 

Franck-Condon factors is 1(T (these estimates being based on the difference in metal-ligand distances). One cannot fit the 12-... 

The overall octahedral geometry is maintained, but the electron removal causes a significant shortening of either the equatorial or the axial metal-ligand distances. 

Scott, R. A. (1985) Measurement of metal-ligand distances by EXAFS. Meth. EnzymoL, 117, 414-59. 

Ac/ = the difference of the metal-ligand distance between oxidized and reduced complex. 

Table 5.5 Electron Transfer Rate Constants and Differences in Metal-Ligand Distances between the Oxidation States (L = bpy) ...

In all the tetranuclear aggregates described here the metal-ligand distances are normal and typical for high-spin complexes. 

The average metal-ligand distances, Pr—Cl =2.72 A and Pr—0=2.353 A, are shorter than those calculated by summing the ionic radii. The average P—0 bond length of 1.487 A is slightly shorter than that observed for other phosphor-triamide [1.501 for 0P(NH2)3]. The P—N (1.64 A) possesses partial -bond character. 

Fig. 37. The molecular arrangement of NTA around Pr(III) and the metal-ligand distances in nonacoordinated [Pr(NTA) (OH2)2] complex...

Table 11.1 Metal-ligand distances for selected metal-hydrocarbyl species.

Though the peripheral contribution is considerably enhanced by the antishielding, it is nevertheless small relative to the central contribution, except for very short metal-ligand distances (Coppens 1990). 

Metal—Ligand Distances Measured in Crystal Structures of Small Molecules... 

---