Halogen complexes Halogens

In TT-complexes formed from aromatic compounds and halogens, the halogen is not bound to any single carbon atom but to the 7r-electron structure of the aromatic, though the precise geometry of the complexes is uncertain. The complexes with silver ions also do not have the silver associated with a particular carbon atom of the aromatic ring, as is shown by the structure of the complex from benzene and silver perchlorate. ... 

Constituents. Complex halogenated organic compounds have been widely used in commerce in the last fifty years. A few representative examples are shown in Eigure 9 pentachlorophenol has been widely used as a wood preservative, and also for termite control. 

The hexafluorophosphates are among the most stable halogen complexes known. The highly symmetrical PF ion is stable to boiling aqueous alkaH and is decomposed only slowly in acidic solutions at ambient temperatures. It does hydrolyze rapidly at elevated temperatures in acid (85). The stabiHty of the PF 3 ion can be compared to the isoelectronic SF. The hexafluorophosphates can be decomposed yielding PF although in many cases only at temperatures where the PF reacts with the metal containers. Benzenediazonium hexafluorophosphate can be decomposed to PF, N2, and fluorobenzene at 120°C (86) and is a convenient source for laboratory amounts of PF as well as a frequently used catalyst. 

Direct halogenation of sucrose has also been achieved using a combination of DMF—methanesulfonyl chloride (88), sulfuryl chloride—pyridine (89), carbon tetrachloride—triphenylphosphine—pyridine (90), and thionyl chloride—pyridine—1,1,2-trichloroethane (91). Treatment of sucrose with carbon tetrachloride—triphenylphosphine—pyridine at 70°C for 2 h gave 6,6 -dichloro-6,6 -dideoxysucrose in 92% yield. The greater reactivity of the 6 and 6 primary hydroxyl groups has been associated with a bulky halogenating complex formed from triphenylphosphine dihaUde ((CgH )2P=CX2) and pyridine (90). 

Diazo compounds Diazoniiim sulfides and derivatives, Xanthates 1,2-epoxides Halo-aryl metals Haloarenemetal TC-complexes Halogen oxides Hydraziniiim salts Hyjiohalites... 

The PdXg (X = halogen) complexes are described in section 3.3.1. A limited range of complexes have been made by oxidation of palladium(II) species [188] ... 

The X-ray photoelectron spectroscopy of metal halides and their complexes halogen binding energies and their correlation with structure. R. A. Walton, Coord. Chem. Rev., 1976,21, 63-91 (112). 

X-ray Structures and Electronic Spectra of the Jt-Halogen Complexes between Halogen Donors and Acceptors with jr-Receptors... 

Roewer G, Herzog U, Trommer K, Muller E, Friihauf S (2002) Silicon Carbide - A Survey of Synthetic Approaches, Properties and Applications 101 59-136 Rosa A, Ricciardi G, Gritsenko O, Baerends EJ (2004) Excitation Energies of Metal Complexes with Time-dependent Density Functional Theory 112 49-116 Rosokha SV, Kochi JK (2007) X-ray Structures and Electronic Spectra of the n-Halogen Complexes between Halogen Donors and Acceptors with jc-Receptors. 126 137-160 Rudolf P, see Golden MS (2004) 109 201-229... 

This is a widely used preparation route towards metal chalcogenolates since the alkali compounds, mainly lithium and sodium derivatives, react with halogen complexes of almost any metal. The chalcogenols in the presence of a base can be used to scavenge the hydrogen halide. 

RhX(CO)(PPh3)2 [X=halogen] complexes with hydrogen. The reaction for X=C1 is shown in Figure 11.3. 

The nitrosonium cation bears a formal relationship to the well-studied halogens (i.e. X2 = I2, Br2, and Cl2), with both classes of structurally simple diatomic electron acceptors forming an extensive series of intermolecular electron donor-acceptor (EDA) complexes that show well-defined charge-transfer absorption bands in the UV-visible spectral region. Mulliken (1952a,b 1964 Mulliken and Person, 1969) originally identified the three possible nonbonded structures of the halogen complexes as in Chart 7, and the subsequent X-ray studies established the axial form II to be extant in the crystals of the benzene complexes with Cl2 and Br2 (Hassel and Stromme, 1958, 1959). In these 1 1 molecular complexes, the closest approach of the... 

These results have been rationalized74 by Heasley and coworkers by assuming that the primary function of the complexes is to limit the concentration of free halogen. In the reaction of free bromine where the reaction is second order in bromine, two or more molecules of halogen participate in the transition state while the halogen complexes with pyridine or amines impose a first-order mechanism by limiting the availability of free halogen (equation 40). 

Halogenation of conjugated dienes proceeds chiefly by 1,4-addition with molecular halogens (equation 3). 1,2-Addition is favored in the presence of pyridine-halogen complexes and amine tribromide salts (equation 4)9. The stereochemistry of 1,4-bromine addition with 2,4-hexadienes and cyclopentadiene is primarily anti in the presence of amine, but syn with molecular halogen in the absence of amine. 

Iridiuin(iv).—Group VII Donors. All reported studies of Ir concerned halogen complexes. Pure IrF4 has been prepared for the first time via reduction of IrFg on a hot filament of Ir or W. X-Ray powder pattern studies of this volatile, red-brown compound showed it to be different from IrFj or IrFs. A simple melt synthesis of K2lrFg has been developed involving the reaction ... 

Condensed ring systems, in polysulfidemetal complexes, 31 101-102 Conductance measurements, of halogen complexes, 3 104... 

Methylbenzene halogen complex of, 3 122 iodine monochloridecomplese, 3 109 Methylchlorosilanes hydrolysis, 42 149-150, 157 pyrolysis products of, 7 356-363 Methylcobalamin, 19 151, 152 Methyl-coenzyme M reductase, 32 323-325 EPR spectra, 32 323, 325 F43 and, 32 323-324 function, 32 324-325 Methyl-CoM reductase, 32 329 Methyl cyanide, osmium carbonyl complexes, reaction, 30 198-201 Methylcyclophosphazene salts, 21 70 synthesis, 21 109... 

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