Binary Compounds and Related Species

Binary Compounds and Related Species.—Halides and Oxyhalides. The i.r. spectra of matrix-isolated ZrF2, ZrF3, and ZrF4 have been obtained.230 The crystal structure... 

Binary Compounds and Related Species.—Halides. The electronic spectra of VX2 (X = Cl, Br, or I) crystals have been studied at various temperatures and, whilst the gross features are consistent with isolated V centres, sharp fine structure and intense spin-forbidden bands are indicative of some antiferromagnetic exchange between these centres. ... 

This section deals principally with binary derivatives of the alkali metals ternary compounds are omitted since they are considered, as appropriate, either elsewhere in this Report or in that covering the inorganic chemistry of the transition metals. Included here are subdivisions relating to hydrides, oxides and related species, and halides. Compounds of Group IV and V non-metals are not discussed because of the paucity of data. A separate section, entitled Molten Salts , dealing with the chemistry of molten halides (and nitrates) as solvents, is also included. 

T. M. Klapotke, Binary Selenium-Nitrogen Species and Related Compounds, in R. Steudel (ed.) The Chemistry of Inorganic Ring Systems, Elsevier, pp. 409-427 (1992). 

It will be convenient to describe first the binary. sulfur nitrides SjN,. and then the related cationic and anionic species, S,Nv. The sulfur imides and other cyclic S-N compounds will then be discus.sed and this will be followed by sections on S-N-halogen and S-N-O compounds. Several compounds which feature i.solated S<—N, S-N, S = N and S=N bonds have already been mentioned in the. section on SF4 e.g. F4S NC,H, F5S-NF2. F2S = NCF3, and FiS=N (p. 687). Flowever. many SN compounds do not lend themselves to simple bond diagrams, - and formal oxidation states are often unhelpful or even misleading. 

In the Fe2P-type structure there are four different groups of equipoints. The distribution of P and Fe atoms in different groups of positions is reported. A number of isostructural binary compounds are known. To the same structure, however, ternary or even more complex phases may be related if different atomic species are distributed in the different sites. This structure can be considered as an example of more complex structures built up by linked triangular prisms of Fe atoms. 

Most coordination catalysts have been reported to be formed in binary or ternary component systems consisting of an alkylmetal compound and a protic compound. Catalysts formed in such systems contain associated multinuclear species with a metal (Mt)-heteroatom (X) active bond ( >Mt X Mt—X > or — Mt—X—Mt—X— Mt = Al, Zn, Cd and X = 0, S, N most frequently) or non-associated mononuclear species with an Mt X active bond (Mt = Al, Zn and X = C1, O, S most frequently). Metal alkyls, such as triethylaluminium, diethylzinc and diethylcadmium, without pretreatment with protic compounds, have also been reported as coordination polymerisation catalysts. In such a case, the metal heteroatom bond active in the propagation step is formed by the reaction of the metal-carbon bond with the coordinating monomer. Some coordination catalysts, such as those with metal alkoxide or phenoxide moieties, can be prepared in other ways, without using metal alkyls. There are also catalysts consisting of a metal alkoxide or related compound and a Lewis acid [1]. 

Binary compounds with metals are generally of low ionic character. Many those with transition metals have the NiAs and related structures and show metallic properties. Some compounds appear to contain polyanionic species (e.g., P24- isoelectronic with S22- in Sr2P2 and P73- in Na3P7), although the bonding is certainly not fully ionic. 

The syntheses cited in this section have all involved attainment of high oxidation states in transition metal fluoro-anions, and thence in binary fluorides and in cationic species, by oxidation with F2 or other fluoro-oxidants in HF of metals or of compounds in lower oxidation states. A couple of examples are offered of syntheses of new fluoro-oxo-compounds involving fluorination of oxides already in high oxidation states with rare gas fluorides in HF. The ratio of F 0 in the ligands of these new compounds is greater than in the related compounds already reported. 

Nitrogen forms more than 20 binary compounds with hydrogen of which ammonia (NH3, p. 420), hydrazine (N2H4, p. 427) and hydrogen azide (N3H, p. 432) are by far the most important. Hydroxylamine, NH2(OH), is closely related in structure and properties to both ammonia, NH2(H), and hydrazine, NH2(NH2) and it will be convenient to discuss this compound in the present section also (p. 431). Several protonated cationic species such as NH4+, N2H5+, etc, and deprotonated anionic species such as NH2, N2H3", etc. also exist but ammonium hydride, NH5, is unknown. Among... 

Exposing a binary compound to a chemical potential gradient of one of its components results in a flux of that component through the binary compound as a neutral species. The process, termed ambipolar diffusion, is characterized by a chemical diffusion coefficient Z)chem which is related to the defect and electronic diffusivities by... 

The second part Fluorine and Nitrogen deals with the binary fluorine-nitrogen compounds. They are subdivided on the basis of the number of nitrogen atoms per molecule. Thus, species such as NFJ, NF3, NF2, and NF are considered first followed by the dinitrogen and trinitrogen fluorides N2F4, N2F2, and N3F and related ions. 

Ae metal complexes have been involved in polymerization processes of C=C containing compounds to different extents and in different circumstances. In this chapter, C=C cOTitaining monomers include three main subclasses (a) ethylene and related a-olefins, (b) styrene and conjugated dienes, and (c) what is often referred to as poW olefins, namely acrylates and methacrylates. For these three classes of monomers, Ae compounds have shown valuable, sometimes unique, abilities either as discrete compounds or in binary or even more comphcated tertiary combinations with other main group or transition metal compounds. Another essential distinction to be highlighted is the actual role of the Ae compounds in these processes they may be, as simply anticipated, the real active polymerization species, but they may be also involved in binary or tertiary combinations, as a partner component , undergoing tiansmetallation reactions with another metallic species which is in charge of polymerizatiOTi. 

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