Jahn-Teller distortions synthesis

This method has also been successfully applied in the synthesis of Cu(II)-containing LDHs, although well crystallized materials are difficult to prepare as a consequence of the Jahn-Teller distortion found in the coordination shell of Cu(II) [70,71]. Incorporation of Ni(II) in the layers was found to improve the crystallinity and structural stability of such LDHs. For the synthesis of Cu/Ni/Al - CO3 and Cu/Ni/Mg/Al - CO3 LDHs [70] by the method with separate nucleation and aging steps, LDHs with both smaller particle size and narrower distribution of particle size were obtained compared with those prepared using a conventional coprecipitation method, similar to the case for Mg/Al-C03 LDHs [20]. Well crystallized Cu/Ni/Cr-COs LDHs [71] were obtained when the Cu/Ni/Cr atom ratio ranged from 1 2 1 to 1 3 1 in the reaction mixture with hydrothermal aging conditions at 180 °C for 4 h. 

The synthesis of a [Mn" 2Mn 204] cubane-like complex, [Mn404(02PPh2)6] (65), by Dismutes and co-workers has also been reported by adopting a dimerization strategy of two preformed [Mu202] units. The addition of diphenylphosphinate salts to a solution of [Mn202(bpy)4] ( 104)3 results in the formation of the cluster. No appreciable Jahn-Teller distortions are observed... 

In 1991 we reported on the synthesis of P-silyl and -phosphanyl substituted silylidenephosphanes (phosphasilenes) 2, i.e., compounds of type IIA and III, which are accessible by thermally induced elimination of LiF from corresponding / -lithium-(fluorosilyl)phosphanides IV [5, 6] and possess a remarkable thermal stability (up to 110°C). In 1993 the first crystalline phosphasilene 5 [7], a compound of type IV, had been prepared and its structure was established by X-ray diffraction [8], whereas the Si=P compounds of type V were merely characterized by means of NMR spectroscopy [9]. Compound 5 possesses a relatively long Si=P bond length and a non-planar geometry around the A, , a -Si atom, which can be explained in terms of steric hindrance or a second-order Jahn-Teller distortion [10, 11]. In comparison, the Si=P bond in 6 [12] is significantly shorter and the Si atom is trigonal planar coordinated. 

Hexachloroiridates(IV) may be prepared by (i) chlorinating a mixture of iridium powder and an alkali metal chloride (ii) in solution, by the addition of an alkali metal chloride to a suspension of hydrous Ir02 in aqueous HC1 or (iii) by the oxidation of [IrCl ] " by O2 in acidic media. Oxidation by Oj probably occurs via reaction (122), with = + 0.21 V. Fine" has suggested that the reverse of reaction (122) occurs in alkaline media. The black crystalline sodium salt Na2[IrCls] is water soluble, and is the usual starting material for the synthesis of other iridium(IV) coordination complexes. The resonance Raman spectrum of (NBu4)2[IrCle] reveals anomalous polarization of all bands this has been ascribed to Jahn-Teller distortions present in the excited electronic state. The single-crystal electronic spectra of various [IrCl ] " salts have also been reported." ... 

Attempts at C[4]-supported cluster synthesis with first row TM ions under ambient conditions gave rise to the formation of two new assembly types. The first of these was found to be a family of mixed valence [Mn 2Mn 2(C[4])2(p3-OH)2(dmf)6] clusters (1, Fig. 25.3a), the metallic skeleton of which has a planar diamond- or butterfly-like topology (Fig. 25.4a) [22, 23]. The (Jahn-Teller distorted) Mn and (distorted octahedral) Mn ions occupy the wing-tip and body positions respectively and these are bridged via the C[4] lower-rim oxygens and p3-hydroxides. This cluster motif is not unusual in Mn cluster chemistry but, in this case, the oxidation states are reversed relative to those previously reported [24]. A notable feature of 1 is that the [Mn (C[4])] moiety caps the cluster core, a feature observed in all clusters ccmtaining manganese ions. 

Identity of Cye as D2(l) isomer was unambiguously confirmed by NMR spectroscopy in the very early studies of the higher fullerenes (Ettl et al. 1991). According to DFT calculations, 02(1) is considerably more stable than the second IPR isomer. Tail). Moreover, the latter is subject to Jahn-Teller distortion (the actual symmetry is D2) and has a small HOMO-LUMO gap. Recently, it was shown that Cje-Tail) is probably also formed in the fullerene synthesis but remains insoluble however, it can be solubilized and characterized in the form of trifluoromethyl derivative (C76-T(j(2))(CF3)i2 (Shustova et al. 2006). 

The chemistry of heavier allenes, >E=E=E< (E = Si, Ge, Sn, Ph), has been a focus of much attention lately (1). The first silicon analog of an allene, a trisilaallene with formally sp-hyhridized silicon atom was reported hy Kira and coworkers in 2003 (2). In contrast to the linear C=C=C suhunit in allenes, the heavy allenes possess a hent and fluxional skeleton which is explained hy Jahn—Teller distortion associated with the effective mixing of the TT and a orhitals (3). The present method describes the direct synthesis of silyl-substituted Sis-allene by the reaction of the dili-thiosilane fBu2MeSi)2SiLi2 (4) with the NHC-stabilized dichlorosi-lylene (5) (Scheme 7.5.1). 

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