Jahn-Teller effect observation

A minor success is also seen in complexes of d and d" ions, in which the distorted octahedral geometries observed may be rationalized (and indeed predicted) in terms of the Jahn-Teller effect, and ultimately in terms of the steric activity of the open d shell. This is a common feature in copper(n) chemistry, and you will... 

The Jahn-Teller effect is always to be expected when degenerate orbitals are unevenly occupied with electrons. In fact, it is observed for the following electronic configurations ... 

RhAr6]+ ions are octahedral. As shown in Fig. 5, these observations are a manifestation of the Jahn-Teller effect in the gas phase. It must be stressed that other donor molecules easily displace these weak ligands this will be discussed in Section III.C.l. 

As far as the trication [Ni(bipy)3]3+ is concerned, both EPR spectroscopy166 and the magnetic moment (2.10 8) 67 confirm its Ni(III) nature (d7-t6ge>). Contrary to what has been observed for the corresponding Ni(II) complex, for which all the Ni-N distances are identical, in this case the equatorial Ni-N distances (2.02 A) are about 0.1 A longer than the axial Ni-N distances.166 This has been attributed to the Jahn-Teller effect. 

As there are no other sodium compounds Na2MeF4 hitherto known it may well be presumed, that the existence of this type is closely connected with the Jahn-Teller effect, that may stabilize the structure. There is a conspicuous increase of the molecular volumes of about 2% as compared to the sum of the volumes, the component fluorides have in their binary compounds NaF, CrF2 and CuF2 resp. Generally a decrease of volumes is observed during formation of compounds. 

Cotton, F. A., and M. D. Meyers Magnetic and spectral properties of the spin-free 3d -systems FeFj" and CoF Probable observation of dynamic Jahn. Teller effects. J. Am. Chem. Soc. 82, 5023 (1960). 

The Cupric, Cu2+ or Cu(II) State, 3d9 The most important and stable oxidation state for copper is divalent. There is a well-defined aqueous chemistry of the Cu2+ ion, which generates the familiar blue solution when complexed with water. A large number of copper coordination compounds exist and these have been studied extensively. A strong Jahn-Teller distortion is associated with the 3d9 electronic configuration of this ion. This implies that a regular tetrahedron or octahedron about the Cu2+ ion is never observed, except in the rare occurrence of a dynamic Jahn-Teller effect. The tetragonal distortion about an octahedron can lead to a square-planar coordination which is often observed in Cu(II) oxides. 

The preceding three reduced molybdenum clusters indicate that rhomboidal cluster units are common among this kind of oxide, and the Mo-Mo distances in the cluster units are dependent on CVE assignable to the Mo4 units. MO calculations on Mo4 molecular cluster compounds containing 10 CVE and 8 CVE have shown that the 8-electron clusters distort from a second-order Jahn-Teller effect (116). Such a distortion has been observed in the 8-electron W4(OEt)16 (117). 

TL OEt) ]224 with distortions due to M—M bonding. Crystal structure analysis of [W4(OEt)i6] (Figure 22) reveals the presence of two short W—W bonds (2.645 and 2.76 A) and two long bonds of 2.93 A. In this structure, there is a total of five possible W—W interactions, and thus, to form five bonds of order one, ten electrons are required. Only eight metal electrons are available for metal-metal bonding, which leads to the observed distortions. It has been suggested that this distortion results from a novel second order Jahn-Teller effect.225... 

Two additional factors that can contribute to line breadth and shape are spin-orbil coupling, which is particularly prevalent in complexes of the heavier transition metals, and departures from cubic symmetry, such as through the Jahn-Teller effect. This latter effect, which will be discussed later in this chapter, is believed to be responsible for the low-frequency shoulder observed on the absorption line for [TKH30)6)2 (Fig. 11.8). 

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