Halides pseudohalides

Chemistry of Halides, Pseudohalides and Azides, Parts 1 and 2, Patai S, ... 

This section deals with the binary compounds that nitrogen forms with metals, and then describes the extensive chemistry of the hydrides, halides, pseudohalides, oxides and oxoacids of the element. The chemistry of P-N compounds is deferred until Chapter 12 (p. 531) and S-N... 

Compounds in which the anomeric hydroxy group is replaced by a halogen atom are named as glycosyl halides. Pseudohalides (azides, thiocyanates etc.) are named similarly. 

Covalent Organotin Halide, Pseudohalide, Carboxylate, and Nitrate Complexes... 

The trivalent [P04] and [As04] ions react similarly. Examples of anions that give insoluble Hg(I) compounds in this way include halides, pseudohalides, halates, carboxylates and sulfate. A trace of HNO3 or HCIO4 is often added to the solution of the Hg(I) nitrate or perchlorate to prevent disproportionation induced by alkali. Table 1 lists common Hg(I) derivatives prepared in this way and includes values of the solubility products of the sparingly soluble Hg(I) compounds where these are measured. A similar reaction is used to prepare HgjCO, from a soluble bicarbonate ... 

Ligand A anionic (e.g., halides, pseudohalides, alkyl, aryl, thiolate, alkoxide) ligand N neutral (e.g., amines, imines, phosphines, carbenes, nitriles, isonitriles, NO, CO) ligand C cationic (e.g., NO+)... 

Syntheses of Organic Halides/Pseudohalides and Aromatic Amines... 

Donor-stabilized compounds with simple, non-functional alkyl substituents R are known mainly for gold in its standard oxidation states +1 and +3, that is, (L)AuR and (L)AuR3, respectively. For the latter, R may be replaced by halide, pseudohalide, or other anionic or neutral ligands leading to compounds of the general formula (L)AuR X3 x. 

E. Bacciochi in The Chemistry of Functional Groups, The Chemistry of Halides, Pseudohalides and Azides, Suppl. D, Part 1 (Eds. S. Patai, Z. Rapport), Wiley, New York, 1983, pp. 161-201. 

A major group of rhenium(II) complexes is characterized by two chelating bis-phosphines forming the equatorial plane of a distorted octahedron (263). The axial ligands can be varied and representatives with halides, pseudohalides, thiolates, and nitriles have been studied extensively. 

Lever has successfully predicted Mn"/ potentials of 24 Mn-carbonyl complexes containing halide, pseudohalide, isonitrile, and phosphine co-ligands, with additivity parameters derived from the potentials of Ru "/" couples [39]. An important consideration for heteroleptic complexes is the influence of isomerism on redox thermodynamics. For Mn(CO) (CNR)6- complexes, with n = 2 or 3, the Mn"/ potentials for cis/trans and fac/mer pairs differ by as much as 0.2 V [40]. The effect arises from the different a-donor and 7r-acceptor abilities of carbonyl (CO) and isocyanide and their influence on the energy of the highest energy occupied molecular orbital (HOMO). 

The pseudohalides are discussed in the halogen ligand section rather than in the nitrogen ligand section because in the majority of the examples studied the pseudohalide is the minor ligand, i.e. one among many—most studied are antimony halide pseudohalides. 

Besides the very stable tris chelates, numerous bis chelates with both bipy and phen have been reported.850,851 Most of them have general formulas [NiX2(N—N)2], [Ni(N—N)2-(H20)2]X2 and [NiX(N—N)2(H20)]X (X = halides, pseudohalides, C104, N02 N—N = phen, bipy).850 All of the complexes are six-coordinate with a cis structure. 

Macrocycles with 14-16-membered chelate rings all encircle both high-spin and low-spin nickel(II) in the solid compounds. With anions which have coordination tendency, e.g. halides, pseudohalides and in some cases NOJ, trans octahedral paramagnetic complexes are obtained which are often blue or violet. With anions such as C104, PF6 and BF4 (and I, in some cases) which show little tendency to coordinate, square planar diamagnetic complexes are obtained which are generally yellow. 

Tertiary phosphines form a wide range of complexes of the type PtX2(PR3)2 (X - halide, pseudohalide R = alkyl, aryl or mixed alkylaryl). Space limitations preclude this chapter becoming a compendium of known compounds, therefore for each individual complex the reader is directed to Chemical Abstracts, Gmelin or the book by McAuliffe which contains extensive tabulations of compounds.1225 In this chapter we outline the general methods of synthesis, the properties, and the structures and spectral features which we expect to be found with this class of compounds. 

Apart from halides, pseudohalides and acetates, FeCl3 is able to activate hydroxyl groups in a similar manner. Hence various substitutions of hydroxyl groups have been developed, e.g. the condensation of alcohols or phenols with diphenylmethanol to give DPM-protected alcohols [Equation (7.4), Scheme 7.11] [15] or the direct coupling of allylic or benzylic alcohols with C—H-acidic compounds [Equation (7.5)] [16]. 

Hydroxyl radicals react with many halide (pseudohalide) ions at close to diffusion-controlled rates thereby forming a three-electron-bonded adduct radical [e.g., reaction (1) k = 1.1 x 1010 dm3 mol-1 s 1 Zehavi and Rabani 1972], These adducts may decompose into OH" and the halide (pseudohalide) radical which then complexes with another halide (pseudohalide) ion yielding the dihalogen radical anion [reactions (2) and (3) k2 = 4.2 x 106 s"1 k3 1010 dm3 mol"1 s"1 for resonance Raman spectra of such intermediates, see Tripathi et al. 1985]. 

A number of different polar and nonpolar covalent bonds are capable of undergoing the oxidative addition to M( ). The widely known substrates are C—X (X = halogen and pseudohalogen). Most frequently observed is the oxidative addition of organic halides of sp2 carbons, and the rate of addition decreases in the order C—I > C—Br >> C—Cl >>> C—F. Alkenyl halides, aryl halides, pseudohalides, acyl halides and sulfonyl halides undergo oxidative addition (eq. 2.1). 

Aryl chlorides are more reluctant to participate in amination than most other aryl halides/pseudohalides. To tackle this problem, Caddick et al. examined the effect of palladium-N-heterocyclic carbenes as catalysts in rapid microwave-promoted reactions [87]. Para-tolyl and -anisyl chloride were reacted with aromatic and aliphatic amines in mostly good yields within 6 minutes of heating at 160 °C. Reactions using anisyl, tolyl or phenyl chlorides and aliphatic amines have also been reported by Maes et al. using a phosphine ligand and a strong base, which creates the desired products after 10 minutes of heating at 110-200 °C [88]. 

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