Spin mercury compounds

While the mercury compound shows localized N—Hg bonds, the TADB-system (which is isoelectronic with cyclopentadiene) forms a low-spin complex with iron. This was the first identified example of a sandwich-compounds of a boron-nitrogen ring. The complex is prepared by adding an etheric solution of TADBLi to a suspension of FeCl2 in tetra-hydrofuran. 

Table t.1-181 Spin-orbit splitting energies 4so of mercury compounds... 

The electron spin resonance spectra were run in nitrogen-saturated solutions of aromatic compound ca. 10" m) and nucleophile (0-05-0-1 M) in the solvent(s) indicated. Irradiation in the cavity was effected with a high pressure mercury arc. Electrolysis was performed with the platinum cathode in the cavity, tetraethyl-ammonium perchlorate as electrolyte and electric currents of 10-250 /lA. 

A selective membrane for chloride was obtained by spin coating onto glass a PVC membrane containing a novel mercury-containing carborand, a compound which displayed strong Lewis acid activity [ 123]. This membrane,which also contained a pH-sensitive dye to give an optical response, exhibited strong... 

Table 3. Vertical ionization energies / (in eV) of gaseous zinc(II), cadmium(II) and mercury (II) compounds. The lowest / corresponds to a M.O. with symmetry type (and oj = 3/2 in spin-orbit coupling) mainly consisting of halide n pn orbitals (carbon a in the case of dimethylmercury). Further on, the d-like components at high / are given in two groups (separated by a semi-colon) with 2Ds/2 at lower and 2D3/2 at higher /.

However, the potential range within which the spin trap is electro-inactive is considerably reduced. This, the commonly used trap nitroso-t.-butane is reduced at a potential -0.98 V (vs. Ag/AgI) at mercury in dimethyl-formamide. The range may be extended by substitution of appropriate aryl groups for butane [114]. Nitroso compounds also present a problem in that some compounds have been shown to undergo a monomer/dimer equilibrium in solution in which only the monomeric form acts as a radical trap. Hence, for nitroso compounds, it is necessary to understand this equilibrium, as well as the electrochemical properties of the trap, before it may be used in the investigation of electrode reactions. 

The separation of solvent effects on reactivities into constituent initial-state and transition-state effects by the use of appropriate kinetic and thermodynamic data has been successfully carried out for several organic reactions. Thus, for example, the solvolysis of t-butyl chloride and the Menschutkin reaction were treated in this manner some time ago a recent organic example is afforded by the solvolysis of isopropyl bromide in aqueous ethanol. For inorganic reactions, this approach was early used for reactions of tetra-alkyltin(iv) compounds with mercury(ii) halides. A more recent analysis of reactions of low-spin iron(n) complexes with hydroxide and with cyanide in binary aqueous mixtures was complicated by the need to make assumptions about single-ion values in such ion+ion reactions. Recent estimates of thermodynamic parameters for solvation of complexes of the [Fe(phen)3] + type are helpful in this connection. However, it is more satisfactory to work with uncharged reactants when trying to undertake this type of analysis of reactivity trends. A suitable system is provided by the reaction of [PtClaCbipy)] with thiourea. In dioxan-and tetrahydrofuran-water solvent mixtures, reactivity is controlled almost entirely... 

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