Bis halides

As previously mentioned, the catalyst precursors in aprotic solvents generally contain a Pd-alkyl moiety for immediate insertion of CO without the need of activators. In some cases, bis-halide Pd" precursors have been employed in conjunction with activators such as methyl aluminoxane (MAO), which is able to replace one halide ligand with a methyl group and to create a free coordination site at the metal [17]. 

Readily available N-(diethoxyphosphoryl)-benzylhydroxyamine (124) with primary and secondary halides as well as with bis-halides under basic conditions lead to N-alkylated derivatives (125). Eacile dephosphorylation afforded appropriate N-substituted O-benzylhydroamines (126) (Scheme 35). ... 

The Bi halides are quite different. The ionic (YFa) structure of BiFa is noted on p. 357. 

Bianchini G, Giambastiani IG, Rios A et al (2007) Synthesis of a new polydentate ligand obtained by coupling 2,6-bis(amino)pyridine and (imino)pyridine moieties and its use in ethylene oligomerisation in conjunction with iron(II) and cobalt(II) bis-halides. Organometallics 26 5066-5078... 

The gold cyano complexes M[Au(CN)2], where M = alkali metal [33,34], and bis(halide)gold(I) ions [35] have also been used as precursors for gold(I) mercaptides, but these routes have not been utilized by the decorative industry. 

Mercuric halides, silver nitrate, and copper nitrates form stable complexes with bis-2.2 -thiazolylazo compounds (1591). for which the X-ray structure is not yet known. 

The formation of ethyl cyano(pentafluorophenyl)acetate illustrates the intermolecular nucleophilic displacement of fluoride ion from an aromatic ring by a stabilized carbanion. The reaction proceeds readily as a result of the activation imparted by the electron-withdrawing fluorine atoms. The selective hydrolysis of a cyano ester to a nitrile has been described. (Pentafluorophenyl)acetonitrile has also been prepared by cyanide displacement on (pentafluorophenyl)methyl halides. However, this direct displacement is always aecompanied by an undesirable side reaetion to yield 15-20% of 2,3-bis(pentafluoro-phenyl)propionitrile. 

Lehn s approach is slightly more complex than that illustrated above in that the diol is chloromethylated and then treated with cyanide. Hydrolysis then affords the diacid which may be carried through as shown. It should also be noted that once the bis-acyl halide is in hand, it may be treated directly with an open-chained amine to yield a lipophilic diazacrown, after reduction ... 

The ligand exchange reaction of tin halides with bis(trifliioroinethyl)iner-cury has been used to prepare trifluoromethyltin halides [6 7] (equation 5)... 

Dialkylcadmium reagents are often useful alternatives to the more reactive Gngnard reagents in the preparation of ketones from acyl halides However, bis(trifluotomethyl)cadmium glyme is decomposed by acyl halides and does not give trifluoromethyl ketones [, 124] Nevertheless, this reaction can be used as a low-temperature source of difluorocarbene [S, 124] (equation 102)... 

Aryl bromides were also perfluoroethylated under these conditions [205] The key to improved yields was the azeotropic removal of water from the sodium perfluoroalkylcarboxylate [205] Partial success was achieved with sodium hepta-fluorobutyrate [204] Related work with halonaphthalene and anthracenes has been reported [206 207] The main limitation of this sodium perfluoroalkylcarboxylate methodology is the need for 2 to 4 equivalents of the salt to achieve reasonable yields A trifluoromethylcopper solution can be prepared by the reaction of bis(tri-fluoromethyl)mercury with copper powder in /V-methylpyrrolidone (NMP) at 140 °C [208] (equation 138) or by the reaction of N-trifluoromethyl-A-nitro-sotnfluoromethane sulfonamide with activated copper in dipolar aprotic solvents [209] This trifluoromethylcopper solution can be used to trifluoromethylate aro matic [209], benzylic [209], and heterocyclic halides [209]... 

Codeposition of silver vapor with perfluoroalkyl iodides at -196 °C provides an alternative route to nonsolvated primary perfluoroalkylsilvers [272] Phosphine complexes of trifluaromethylsilver are formed from the reaction of trimethyl-phosphme, silver acetate, and bis(trifluoromethyl)cadmium glyme [755] The per-fluoroalkylsilver compounds react with halogens [270], carbon dioxide [274], allyl halides [270, 274], mineral acids and water [275], and nitrosyl chloride [276] to give the expected products Oxidation with dioxygen gives ketones [270] or acyl halides [270] Sulfur reacts via insertion of sulfur into the carbon-silver bond [270] (equation 188)... 

The lower halides of Bi are rather different. The diatomic species BiX (X = Cl, Br, I) occur in the equilibrium vapour above heated Bi-BiX3 mixtures. A black crystalline lower chloride of composition BiCli.iev is obtained by heating Bi-BiCls mixtures to 325° and cooling them during 1-2 weeks to 270° before removing excess BiC by sublimation or extraction into... 

The trihalides of As, Sb and Bi are strong halide-ion acceptors and numerous complexes have been isolated with a wide variety of compositions. They are usually prepared by direct reaction of the trihalide with the appropriate... 

No completely general and quantitative theory of the stereochemical activity of the lone-pair of electrons in complex halides of tervalent As, Sb and Bi has been developed but certain trends are discernible. The lone-pair becomes less decisive in modifying the stereochemistry (a) with increase in the coordination number of the central atom from 4 through 5 to 6, (b) with increase in the atomic weight of the central atom (As > Sb > Bi), and (c) with increa.se in the atomic weight of the halogen (F > Cl > Br > 1). The relative energies of the various valence-Ievel orbitals may also be an important factor the F(a) orbital of F lies well below both the s and the p valence... 

The stable molecular nitrosyl halides NOX (p. 442) and phosphoryl halides POX3 (p. 501) find few counterparts in the chemistry of As, Sb and Bi. AsOF has been reported as a product of the reaction of AS4O6 with ASF3 in a sealed tube at 320° but has not been fully characterized. ASOF3 is known only as a polymer. Again, just as AsClj eluded preparation for over 140 y after Liebig s first attempt to make it in 1834, so... 

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