Linear-chain complexes

The trinuclear complexes [Au3(/7-MeC6H4N = OEt)3] and [Au3(Bzim)3] (Bzim= 1-benzylimida-zolate), which are colorless, can produce brightly colored materials by sandwiching naked Ag+ or Tl+ ions form linear-chain complexes (Figure 27) with luminescence properties as luminescence thermochromism.3173,3174... 

The physical properties of low dimensional magnetic materials have attracted the attention of many researchers.3015 Several nickel(II) linear chain complexes have been synthesized and... 

Also linear chain complexes such as Pt(etn)4Cl3 which is known colloquially as Wolf-fram s red (etn being an abbreviation for ethylamine) have been studied successfully by resonance Raman spectroscopy (Clark, 1984). As example, we show in Fig. 6.1-12 the resonance Raman spectrum of a related halogen-bridged linear-chain species, [Pt(pn)2] [Pt(pn)2Br2] [Cu3Br5]2 (Clark et al., 1980). Although this species contains a complicated copper bromine chain, the resonance Raman spectrum (Fig. 6.1-12) is completely dominated by bands attributed to the v fundamental and its overtones n U[ of the platinum-bromine chain. 

Results on a large number of linear-chain complexes of platinum are summarised in Table 11. Harmonic wavenumbers and anharmonicity constants have been determined in all cases. The normal coordinate seems to be related to the halogen movements involved in the proposed hopping process for the conductivity of these linear-chain mixed-valence complexes (95). The chain halogen atoms would need to move, on average, 0.54,0.38 and 0.22 A for chlorides, bromides and iodides, respectively, in order to reach the point midway between the two platinum atoms, i.e. to the situation of a platinum (III) chain. These values only differ by a factor of about two from the root-mean-square amplitudes of vibration of Vi in the Vj = 16 states these are calculated (91) to be 0.22 A for X = Cl (wi = 319.5 cm-i) and 0.20 A for X = Br (cji = 179.6 cm ). These distance changes are related to the shift in the equilibrium... 

Mixed-valence linear-chain complexes of palladium display very similar features to those of platinum (97). Indeed, the great intensity of the t j progression in all these cases means that resonance Raman spectroscopy provides a sensitive and rapid means for detecting the formation of new linear-chain complexes of this sort. 

Table 11. Resonance Raman data on mixed-valence linear-chain complexes of platinum...

Macrocyclic ligands with extended 7i-delocalisation were studied in order to improve the conductivity of linear-chain complexes, because extended n delocalisation may reduce the on-site coulombic repulsion. The metal dibenzotetraazaannulene complexes, [M(taa)j (taa = dibenzo-tetraazaannulene M = H2, Ni, Pd, Co, Cu) and [M(tmtaa)] (tmtaa = tetramethyl dibenzotetraazaannulene M = H2, Ni, Pd) (Figure4.13), are... 

Figure 2.4.2 Views of (a) a simple linear chain complex [Ag(4-pytz)]PF6 °° that contrasts with the helical staircase structure formed by [Ag(4-pytz)]N03 °° [29].

It is now reasonably well established that the organic linear chain complexes... 

ONE-DIMENSIONAL LINEAR-CHAIN COMPLEXES OF PLATINUM, PALLADIUM AND NICKEL... 

A summary of the types of linear-chain complexes of the +2,+2 charge type... 

Fig. 3 Summary of known M°/M linear-chain complexes of the type [ML4][ML4XJY4, [M(LL)J[M(LL)2XJY4 and [M(LLLL)][M(LLLL)4XJY4.

Fig. 4 ORTEP drawings of X-ray crystallographic structures of linear chain complexes of the open-ring isomer (50% probability), a (4-py2-DTEf)2Zn(hfac)2. b (4-py2-DTEf)Mn(hfac)2.

At 295 K the [N(CD3)4]+ cations in the infinite linear chain complex, [N(CD3)4]MnCl3, are disordered. However, upon cooling [N(CD3)4]MnCl3 to 126 K it undergoes a first-order phase... 

Using the resonance Raman effect, Hester and Nour have assigned the Fe(II) -> Co(III) intervalence transitions in the complexes [(NC)5Fe(II)CNCo(III)(CN)5] and [(NC)5Fe(II)CNCo(III)(edta)f . Detailed analysis of the CN stretching modes also confirms the ground state valency assignments as shown. In the linear chain complexes [Pt(LL)2][Pt(LL)2X2]X4 (LL = diamine, X = Br or l ) the Pt(II)-Pt-Pt(IV) intervalence band is coupled to the symmetrical stretch, X-Pt-X of the Pt(IV) units, as in other complexes of this type. 

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