Tris anion

Dialkylamino phthalic acids resulting from the chemiluminescence reaction of 4-dialkylamino-phthalic hydrazides cannot easily form a tris anion because deprotonation of the amino group is impossible. They should therefore not exhibit such a strong decrease in fluorescence efficiency at higher pH values. This can actually be concluded from the pH dependence of the chemiluminescence of the 4-dialkylamino-phthalic hydrazides and related compounds 97>. 

Interestingly, if the C50 fullerene doped by alkali metals is rapidly cooled down to the liquid nitrogen temperature, polymerization does not occur. Only monomeric anion-radical salts are obtained. Warming up these monomers to 80-160 K results in dimerization polymerization does not take place. The dimer (KCgo)2 is dielectric (Pekker et al. 1995). It has been shown that the tris(anion)-radical Cgo can polymerize too. Particularly, Na2CsCgo forms a polymer that maintains superconducting properties (Mizuki et al. 1994). 

A crystallographic and spectrometric study of mercury(II) dithiocarbamate showed tetrahedrally coordinated mercury with Hg—S distances of 249.9-262.9 pm.398 The compounds (Bu4N)Hg(R2dtc)3 (R = Me, Et) have been prepared. The tris anion is not completely dissociated in acetone solution.398 ... 

It has been shown that the tris(anion)-radical C o can polymerize too. In particular, Na2CsC6o forms a polymer that maintains superconducting properties (Mizuki et al. 1994). 

We discuss here two examples of vibronic effects in polynuclear highly symmetrical transition metal clusters. The existence of degenerate and quasi-degenerate molecular orbitals in their energy spectra results in the Jahn-Teller effect or in the vibronic mixing of different electronic states. We show that both quantum-chemical methods and model approaches can provide valuable information about these vibronic effects. In the case of the hexanuclear rhenium tri-anion, the Jahn-Teller effect is responsible for the experimentally observed tetragonal distortion of the cluster. The vibronic model of mixed-valence compounds allows to explain the nature of a transient in the photo-catalytic reaction of the decatungstate cluster. 

It seems natural to suppose that the tetragonal distortion of the tri-anion results from the Jahn-Teller effect. In order to study the problem more thoroughly we undertook recently the DFT calculations of this cluster as well as of several other hexanuclear rhenium chalcohalide clusters. The technical details of these calculations can be found in the original publication [8]. Here we only want to note that the introduction of relativistic corrections for Re atoms is crucial for the correct reproduction of the geometry of clusters. In our calculations, this was done by the zero order regular approximation (ZORA) Hamiltonian [9] within ADF 2000.02 package [10]. 

Synthesis of the closely related acyclic (19) and macrocyclic (20) polyradicals has recently been reported (Figure 5.1).1231 The -conjugated carbanions (e.g., the calix[4]-arene-based tetraanion and the related calix[3]arene-based trianion) were synthesized and studied.1241 Oxidation of these tetra- and tri-anions gave the corresponding tetra- and tri-radicals, respectively. It has been shown in closely related systems that it is not the shape or overall geometric symmetry of the molecules, but rather it is the juxtaposition of the carbenic centers within the jt-cross-conjugated structure, that is most important in determining the spin multiplicity of the alternant hydrocarbon molecule.1251... 

To broaden our understanding of the chemical behavior of these novel monomers, it would be appropriate to try anionic polymerizations of captodative monomers. Inasmuch as sulfur is able to stabilize adjacent carbanions, a-alkylthioacrylates and -acrylonitriles should respond well to anionic initiators. Cationic polymerization of certain captodative monomers may also be of interest as alkylthio- and cyano-substituents can stabilize a cationic propagating center. 

When the drug and the CD are both charged, electrostatic effects may be observed. Adverse electronic effects have been observed for the complexation between the anionic form of indomethacin and the dianion of carboxymethyl-p-CD, CM2-p-CD.At pH 6.6, indomethacin exists as an anion and under these conditions, the anionic carboxymethyl CD did not complex the drug at all, probably due to electrostatic repulsions. However, the tri-anion, CM3-p-CD l has been reported to complex the anionic forms of warfarin and indomethacin (Table 5) although only at 71 and 60% of the binding observed for the neutral p-CD. 

Under highly basic conditions, ascorbic acid may exhibit chemistry derived from ionization of the C4 hydrogen, presumably with the formation of a tri-anion, 4. Brenner et al. (12) reported the epimerization and racemization of ascorbic acid at high pH and elevated temperature. 

Scheme 23. Generation of mono- and tri-anions of the l-zircona-4-phosphaindene complex 103...

Finally, the ability to prepare 1,4-diphosphaindenylmono-and tri-anions and enantiomerically pure phosphorus ligands open new ways in organophospho-rus chemistry and in asymmetric catalysis. 

Interesting structural features are observed for triorganotin halides containing one quadridentate tris-anionic-, cf. 62, terdentate dianionic-, cf. 63,64, quadridentate dianionic-, cf. 70-72, terdentate monoanionic-, cf. 65-69, or two bidentate monoanionic ligands, cf. 73-75. The latter three types of ligands are potential candidates in enforcing hexacoordination in triorganotin halides. 

An X-ray crystal structure determination of the triptych compound 62 revealed the trigonal bipyramidal coordination geometry, which is schematically shown in Fig. 17, with the three carbon atoms at the equatorial sites and the coordinating nitrogen atom and the chlorine atom at the axial positions. As a result of the fixed geometry of the quadridentate tris-anionic ligand, the Sn—N coordination bond (2.37(3) A) is extremely short 125). 

Fig. 17. Pentacoordinate triorganotin chlorides containing either quadridentate tris-anionic 62 or terdentate-dianionic 63 or 64 ligands.

The NMR spectra of the oxyanions generated by the action of BuLi on p-allylcalix[4]arene in DM SO suggest that the conformations of the mono- and tetra-anions are cone, while those of the di- and tri-anions are less clear " " (see ref. 1, pp. 124-126). However, X-ray crystal structures of the monosodium and dilithium salts of 4 , generated by the action of NaH or BuLi on the calixarene followed by treatment with MeOH, show both to be in the cone conformation in the solid state. "" ... 

The remaining compounds collected in Table 3 share several features and will be discussed together. All these compounds are based on NiioE2 icosahedral cores, centered on an additional Ni atom and having the heteroatoms E in trans positions, as shown in Fig. 7a by the structure of the [NinBi2(CO)i8] paramagnetic tri-anion. The examples reported so far include species with E = Sb, Bi, ... 

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