Tetraphenyl metals

Figure 7.6 (a) Arrhenius plot from the muon spin relaxation rates shown in Figure 7.5 for Pb(C6H5)4. (b) The correlation of activation energies calculated with muon spin relaxation with the size of the central atom for the tetraphenyl metallates [15]. 

Binuclear complexes of Ni and Pd containing oxamidinate (OXAM) ligands have been successfully employed in the synthesis of tetramethyl and tetraphenyl metallate complexes (Scheme The methyl derivative 10 has a... 

At 100°C the tetraphenyl compound decomposes to triphenylbismuthine and metallic bismuth (68). 

Samsonova and Nikiforov, 1984), and porphyrin and phthalocyanine metal complexes (Becker et al., 1985a, 1986b Becker and Grossmann, 1990) were tested. That a series of relatively simple anions such as the oxalate monoanion, tetraphenyl bor-anate (Ph4B ), bromide, chloride, and even tetrafluoroborate can act as donors is, at least for the last mentioned anion, surprising, but Becker et al. (1985 b) were able to trap aryl radicals and in some cases also donor radicals (Cl, COO ) by spin trapping with nitrosodurene and phenyl-tert-butylnitrone. The photochemical effect is postulated to be due to ion pairs ArNJ X-. 

Disiloxane, tetramesityl-, 3,206 Disproportionation iridium catalysts, 4,1159 Dissolution nuclear fuels, 6, 927 Distannene, 3,217 Distannoxane, 1,3-dichloro-, 3,207 Distibine, tetraphenyl-, 2,1008 Distibines, 2,1008 Disulfido ligands metal complexes, 2,531-540, 553 bonding, 2, 539 electron transfer, 2, 537 intramolecular redox reactions, 2,537 reactions, 2, 537... 

Porphyrin, tetrahydro-metal complexes geochemistry. 6, 862 Porphyrin, tetraphenyl-indium complexes radiopharmacology, 6, 971 iron complexes, 4, 260,1266 zinc complexes spectra, 6, 617... 

Although the copolymerization of propylene oxide with C02 takes place effectively with organozinc additives or the (tetraphenyl) porphyrin-AlCl system [61], the copolymerization of epichlorohydrin with C02 seldom occurs with these catalysts. Shen et al. [62] showed that a rare earth metal catalyst such as the Nd(2-EP)3/AliBu3 (Al/Nd = 8) system was very effective for the copolymerization of epichlorohydrin with C02 (30-40 atm) at 60 °C (Scheme 16). The content of C02 in the copolymer reached 23-24 mol % when 1,4-dioxane was used as solvent. 

It needs to be noted that when the ligand system contains extensive unsaturation, then oxidation of the corresponding complex may yield a product containing a stabilized cation radical (rather than one in which the metal oxidation state has been altered). For example, such a situation has a tendency to occur on oxidation of divalent metal complexes [including Ni(n)] of the tetraphenyl-substituted porphyrin macrocycle. 

Fig. 10 Electrochemical energy level model for orbital mediated tunneling. Ap and Ac are the gas-and crystalline-phase electron affinities, 1/2(SCE) is the electrochemical potential referenced to the saturated calomel electrode, and provides the solution-phase electron affinity. Ev, is the Fermi level of the substrate (Au here). The corresponding positions in the OMT spectrum are shown by Ar and A0 and correspond to the electron affinity and ionization potential of the adsorbate film modified by interaction with the supporting metal, At. The spectrum is that of nickel(II) tetraphenyl-porphyrin on Au (111). (Reprinted with permission from [26])...

Thirty years ago Bacci and Sacconi [15] reported on five coordinate metal complexes of the tetradentate ligand l,4,7,10-tetraphenyl-l,4,7,10-tetraphos-phadecane (pppp) (3). 

Unlike the metal atoms in the chalcogenides discussed in the previous section, the iron atoms in iron(II) tetraphenyl porphyrins and the related iron(II) phthalocyanine generally occupy crystallographic sites with symmetry T or 1 only. The exception is the iron site in iron(II) tetraphenyl porphyrin (FeTPP), space group I42d, which has 4 symmetry. 

Irngartinger et al. 1977), and the hydro-bis(squarate) anion (Lin et al. 1994). Even in the deformation density maps of the five-membered pyrrole rings in transition metal tetraphenyl porphyrins (chapter 10), bond bending is visible. 

A number of syntheses of substituted 2,3 -bipyridines are worthy of note. Tetracyclone heated at 215°C with nicotinonitrile affords 3,4,5,6-tetraphenyl-2,3 -bipyridine, whereas 3,4-di(2-pyridyl)pyridine is obtained by an oxidative degradation of the corresponding 6,7-disubstituted thiazolo[3,2-a]-pyridinium salt. Nicotinic acid on UV irradiation in aqueous solution at pH 4-6 gives 2,3 -bipyridine-5-carboxylic acid, whereas irradiation of picolinic acid in the same pH range in the absence of metal ions gives some 2,3 -bipyridine. 6,6 -Diphenyl-2,3 -bipyridine is thought to be formed from... 

Both the radical ion (40) and the alkali metal salts (41) react unusually with trityl perchlorate, giving 2,2, 5,5 -tetraphenyl-l,l -diarsolyl (44) as a deep red crystalline solid (m.p. 209-212 °C). This reforms the lithium or potassium salt (41) on reaction with the metal in an inert solvent (74TL303). These reactions are shown in Scheme 9. 

Bis(dithiobenzil)nickel decomposes on being heated at 292° to give (exclusively) 2-phenylbenzo[ ]thiophene(95%).263a,263b Related metal complexes (e.g., those of Pd and Pt) behave similarly. In some cases (e.g., Pd) a mixture of 2-phenylbenzo[6]thiophene and tetraphenyl-thiophene is obtained. 

---