Halides of group

CHLORIDES AND OTHER IMPORTANT HALIDES OF GROUP IV ELEMENTS... 

Chalcogenide Halides of Group IIIB and Lanthanides Bibliography... 

Very little is known about chalcogenide halides of Group IVB elements. Although the existence of sulfide chlorides (45, 274, 329, 365) and of a selenide chloride (329) of titanium was claimed in early publications, their true composition, and even their existence, remains doubtful. They have usually been obtained by the reaction of titanium chlorides with sulfur and selenium, respectively, or with hydrogen sulfide. The synthesis of a pure compound, TiSClj, was published in 1959 (113). It is an intermediate of the reaction of TiCU with HjS. 

The [(CO)4Co] anion reacts with halides of group-IIIB elements, e.g. ... 

Carburization by Thermal Diffusion. Carburization of chemically processed metal or metal-compound powders is carried out through solid-state, thermal diffusion processes, either in protective gas or vacuum. Carbide solid solutions are prepared by the same methods. Most carbides are made by these processes, using loose or compacted mixtures of carbon and metal or metal-oxide powders. Halides of Group 5 (VB) metals recovered from ores by chlorination are similarly carburized. 

Decontamination of Waters Containing Dissolved Explosive Wastes. Accdg to McDonald (Ref), decontamination may be achieved by means of a quartern ary salt of a halide of Group V, nonmetal. The general formula of such salt is R.A.M.R .R1 .R11. X, in which ... 

Examples of neutral Lewis acids are halides of group 3A elements, such as BF3. Boron trifluoride, a colorless gas, is an excellent Lewis acid because the boron atom in the trigonal planar BF3 molecule is surrounded by only six valence electrons (Figure 15.12). The boron atom uses three sp2 hybrid orbitals to bond to the three F atoms and has a vacant 2p valence orbital that can accept a share in a pair of electrons from a Lewis base, such as NH3. The Lewis acid and base sites are evident in electrostatic potential maps, which show the electron poor B atom (blue) and the electron rich N atom (red). In the product, called an acid-base adduct, the boron atom has acquired a stable octet of electrons. 

Table 8-4 Tetravalent Hydrides and Halides of Group 14 Elements...

Some radical initiators decomposing by heat can also be decomposed by UV radiation. Photopolymerization of acrylonitrile in the presence of AIBN or hydrogen peroxide, or of other initiators [75-78] has been reported. The quantum yield of AIBN decomposition is 0.4 at 298 K and 0.6 at 318 K. Photopolymerization of methyl methacrylate, styrene, and vinyl acetate can be initiated by tetramethylsilane, methylchlorosilanes, and halides of Group IV metals [79]. We assume that the radicals are formed by homolytic splitting of the covalent bond... 

These are halides and alkyl halides of Group HI metals and of transition metals in which the d electron shells are incomplete. This is the most generally useful group of initiators and includes compounds like BF3, SnCU, AICI3, AIR2CI, SbCl.s, and so on. 

Fig. 284. Addition compounds with thioethers of metal halides of Group IIB.

Many reduced (metal-rich) halides of group 4 (especially Zr) and the rare earth metals have been prepared. Most of these compounds are stabilized, by the metals forming Mg octahedral or other clusters having strong metal-metal bonds. The reactions to form these clusters are slow. Other nonmetals, especially oxygen, are undesirable impurities that may form more stable phases. Therefore the reactions are carried out with stoichiometric mixtures of pure halide and metal in degassed Ta or Nb tubes that have been loaded in an inert atmosphere and arc-welded shut. The welded ampule is then sealed in a protective quartz tube and heated to a temperature adequate to achieve a reaction in a week or more ( >600°C) . Yields may be small in some cases individual single crystals are produced as evidence of synthesis of a new material with metal-metal bonds. 

Very little chemistry has been performed with the halides and oxide halides of Group 16, and that reported appears to largely parallel that of Group 15. Both SjClj and SCIj dissolve in phosgene without association [151]. 

Table 1 reveals that, for the halides of group IV and group V elements, agreement between A and Zip-values is reasonably good it is least satisfactory for the iodides, which have low enthalpies of formation. Agreement between zl and Zip is perfect for HF as well as for NFg, NHg, HCl and CIF, despite low enthalpies of formation because formation of these compounds from the elements under standard conditions proceeds as a gas phase reaction. 

For all halogen compounds, both Qa and Ip decrease from fluoride to iodide. For group IV halides, Qa values follow the series G Si > Ge < Sn corresponding to the variation of the AUred-Rochow electronegativities (5)3). For halides of group V elements, the order for both Ip and Qa is... 

The halides of group V elements comprise a series of inorganic compounds which have been studied systematically by combining electron diffraction and spectroscopic tech niques. The intemuclear distances and bond angles in MX3 and YPX3, where M is N, P,... 

This laek of diseussion does not mean that hypervalent bonding is uneommon. It oeeurs for nearly all of the p-block elements. " Noble gas compounds, of course, have 3e-4e bonds. The central atom in trihalide anions sueh as li" is hypervalent. Similar 3c-4e interactions occur for halides of group 13-17 elements examples include anions such as AIF, ... 

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