Complexes Jahn-Teller distortions

Octahedral complexes (Jahn-teller distorted) d z-elongated d z-compressed d z-elongated... 

Copper(II) salts (blue in aqueous solution) are typical M(II) salts but generally have a distorted co-ordination (Jahn-Teller distortion, 4 near plus 2 far neighbours). Extensive ranges of complexes are known, particularly with /V-ligands. 

Complexes of the divalent metals [M(ttcn)2]2+ undergo electrochemical oxidation to paramagnetic [M(ttcn)2]3+. Red [Pd(ttcn)2]3+ has a tetragonally distorted octahedral structure (d7, Jahn-Teller distortion) with Pd—S 2.356-2.369 A (equatorial) and 2.545 A (axial) in keeping with the ESR spectrum (gj = 2.049, gy = 2.009) which also displays 105Pd hfs. Similarly, electrochemical oxidation of the palladium(II) tacn complex (at a rather lower... 

Jahn-Teller distortions cobalt and copper complexes, 2, 91 hydrates, 2, 308 Jahn-Teller effect, 5, 535 Jahn-Teller theorem, 1, 247 Jarosites... 

The driving force for Jahn-Teller distortions in transition-metal complexes is the open d shell. It is likely that explanations for them along the lines given above would have come about even if the theorem of Jahn and Teller had not been discovered. We make this remark not to denigrate that powerful piece of work, but as an attempt to defuse any mystery that might otherwise attach to OrgeTs application of that group-theoretical construction. 

The data for the 1,2-diaminoethane complexes now parallels the trends in ionic radius and LFSE rather closely, except for the iron case, to which we return shortly. What is happening Copper(ii) ions possess a configuration, and you will recall that we expect such a configuration to exhibit a Jahn-Teller distortion - the six metal-ligand bonds in octahedral copper(ii) complexes are not all of equal strength. The typical pattern of Jahn-Teller distortions observed in copper(ii) complexes involves the formation of four short and two long metal-ligand bonds. 

Barakat, K., Cundari, T. and Omary M. (2003) Jahn-Teller Distortion in the Phosphorescent Exdted State of Three-Coordinate Au(I) Phosphine Complexes. Journal of the American Chemical Society, 125, 14228-14229. 

The series of 3d elements from scandium to iron as well as nickel preferably form octahedral complexes in the oxidation states I, II, III, and IV. Octahedra and tetrahe-dra are known for cobalt, and tetrahedra for zinc and copper . Copper(II) (d9) forms Jahn-Teller distorted octahedra and tetrahedra. With higher oxidation states (= smaller ionic radii) and larger ligands the tendency to form tetrahedra increases. For vanadium(V), chromium(VI) and manganese(VII) almost only tetrahedral coordination is known (VF5 is an exception). Nickel(II) low-spin complexes (d8) can be either octahedral or square. 

State which of the following octahedral high-spin complexes should be Jahn-Teller distorted. 

The versatile binding modes of the Cu2+ ion with coordination number from four to six due to Jahn-Teller distortion is one of the important reasons for the diverse structures of the Cu-Ln amino acid complexes. In contrast, other transition metal ions prefer the octahedral mode. For the divalent ions Co2+, Ni2+, and Zn2+, only two distinct structures were observed one is a heptanuclear octahedral [LnM6] cluster compound, and the other is also heptanuclear but with a trigonal-prismatic structure. 

Which of the following complexes would undergo Jahn-Teller distortion ... 

Would Jahn-Teller distortion be as significant for tetrahedral complexes as it is for octahedral complexes For which of the electron configurations would Jahn-Teller distortion occur ... 

It was proposed that mono-protonation of [CuL]2+ to yield [Cu(HL)]2+ occurs initially at the axial nitrogen atom since this Cu-N bond is expected to be weaker as a result of Jahn-Teller distortion. With respect to this, it should be noted that species such as [Cu(HL)]3+ are commonly observed during potentiometric studies of the formation of Cu(n) polyamine complexes. From the proposed mechanism, the following rate law can be deduced ... 

Trans- complex is obtained only with Cu11 which is coordinated to four oxygen atoms of two hfac ions and two nitrogen atoms of two TTF—CH=CH py ligands. Cu11 lies on inversion center and therefore the TTF—CH=CH py ligands are in trans- conformation. The copper ion adopts a Jahn-Teller distorted octahedral... 

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