Si-N-P compounds

The structural and chemical diversity of compounds containing the Si-N-P linkage is a result of both the variety of coordination numbers which phosphorus may assume and the reactivity of the Si-N bond. The combination of these features gives Si-N-P compounds very promising synthetic utility, particularly in the area of inorganic polymer synthesis. 

Regardless of which N-silylphosphinimine products are formed they all are potential precursors to phosphazenes via elimination of Me3SiCl. Preliminary evidence indicates that the thermal elimination does indeed occur in some cases. The N-silyIphosphinimines are also potential precursors to another type of novel Si-N-P compound, i.e. three-coordinate phosphoranes ... 

The poly(alky1/arylphosphazenes) are a special type of phosphazene polymer in which all substituents are attached to the backbone phosphorus by direct P-C linkages. Unlike the majority of polyphosphazenes, which are usually prepared by ring opening of fully (3 - 5) or partially (6 -8) halogenated cyclic phosphazenes followed by nucleophilic substitution of the halogens, the poly(alkyl/arylphosphazene) homopolymers and simple copolymers are made by the condensation polymerization (9, 10) of Si-N-P compounds known as N-silylphosphoranimines (eg 1 and 2). 

Acetylene-substituted Si-N-P compounds, synthesis, 236-237 Activated aluminas, description, 165 Aerogels, definition, 127 Aggregation of fractals, 104,106 Alcohol-substituted polymers from aldehydes and ketones, deprotonation-substitution reactions, 249-250 Alkenylborazine copolymers, quantitative reactivity studies of copolymerization reactions, 394... 

Typically, the most common precursors to new Si-N-P systems are simple silylaminophosphines (eq 1). The difunctional character of these compounds, which is due to the nucleophilic site at phosphorus and a complementary electrophilic site at silicon, makes them very versatile reagents. They have been used in a new synthesis of alkyl and/or phenyl substituted phospha-zenes (R2PN)jj ( ) and have led to the preparation of promising precursors to potentially electrically conducting polymer systems of general formula (RPN)n>... 

Compounds containing the Si-N-P linkage combine the structural and stereochemical diversity of phosphorus with the reactivity of the silicon-nitrogen bond. Indeed, much of the derivative chemistry and synthetic potential of these compounds, especially the (silylamino)phosphines such as (Me3Si)2NPMe2, is based on this difunctional character. We report here a general, "one-pot" synthesis of (silylamino)phos-phines and describe their use in the preparation of several types of phosphorus-containing materials. 

Compounds of the type R2SnX2, where X = H, Si, N, P, O, S or a substituted carbon, are listed in Table 12. Cyclic compounds of this type are summarized in Table 13. 

The addition reactions of H2O and MeOH (or EtOH) to azametaUenes and phosphametallenes are completely regioselective with the formation of >M(OR)-E(H)-(M = Si, Ge, E = N, P) compounds, indicating their ylidic character of M +=e 5- Similarly, the addition of hydrogen halides is also regioselective, giving the corresponding halometallanes. 

Amino, alkoxy, and aryloxy polyphosphazenes are typically prepared by nucleophilic displacement reactions of poly(dihalophosphazenes). Analogous reactions with organometallic reagents, however, result in chain degradation and cross linking rather than in linear, alkyl, or aryl substituted poly(phosphazenes). The thermolysis of appropriate silicon-nitrogen-phosphorus compounds can be used to prepare fully P—C bonded poly(organophosphazenes). The synthesis of two of these materials and their Si—N—P precursors is described here. 

S and N are cycled by life and by atmospheric photochemistry through many oxidation states. Natural Si and P compounds are involatile and less mobile in the environment. Environmental problems include acid rain, and pollution by soluble phosphates and organochlorine compounds. 

Several reviews encompassing a number of aspects of the inorganic chemistry of Group V elements have appeared. These include surveys of X-ray diffraction studies of a number of N, P, As, Sb, and Bi compounds, the stereochemistry of compounds containing Si—N, P—N, S—N, and Cl—N bonds, and ESCA-derived group shifts for a substantial number of nitrogen, phosphorus, and arsenic compounds. The latter describe the experimental shifts to within 0.5 eV, and facilitate the predictive and analytical use of ESCA. ... 

Other Binary Compounds. Direct reaction of uranium with B, C, Si, N, P, As, Sb, Se, S, Te, etc., leads to semimetallic compounds that are often non-stoichiometric, resembling the oxides. Some of them, for example, the silicides, are chemically inert, and the sulfides,35 notably US, can be used as refractories. 

The Ultraviolet and Photoelectron Spectra of Some Unsaturated Fluorocarbon Derivatives . The compounds studied include derivatives of Si, N, P, and As. 

Sihcon nitride is one of the few nonmetaUic nitrides that is able to form alloys with other refractory compounds. Numerous soHd solutions of P-Si N and AI2O2 have gained technical interest. Many companies have begun to mass produce reaction-sintered and hot-pressed Si N parts. 

The binary compounds of the Group 13 metals with the elements of Group 15 (N, P, As, Sb, Bi) are stmcturally less diverse than the chalcogenides just considered but they have achieved considerable technological application as III-V semiconductors isoelectronic with Si and Ge (cf. BN isoelectronic with C, p. 207). Their stmctures are summarized in Table 7.10 all adopt the cubic ZnS stmcture except the nitrides of Al, Ga and In which are probably more ionic (less covalent or metallic) than the others. Thallium does not form simple compounds... 

The physicochemical properties of carbon are highly dependent on its surface structure and chemical composition [66—68], The type and content of surface species, particle shape and size, pore-size distribution, BET surface area and pore-opening are of critical importance in the use of carbons as anode material. These properties have a major influence on (9IR, reversible capacity <2R, and the rate capability and safety of the battery. The surface chemical composition depends on the raw materials (carbon precursors), the production process, and the history of the carbon. Surface groups containing H, O, S, N, P, halogens, and other elements have been identified on carbon blacks [66, 67]. There is also ash on the surface of carbon and this typically contains Ca, Si, Fe, Al, and V. Ash and acidic oxides enhance the adsorption of the more polar compounds and electrolytes [66]. 

This fundamental discovery dramatically affected the whole chemistry of main-group elements. Subsequently, a series of new compounds with silicon element multiple bonds has been introduced. Within only a few years, stable silenes (silaethenes with a Si = C double bond) [8-11], silaimines Si = N [12-14], and silaphosphenes Si = P [15] were synthesized. As a pacemaker, silicon chemistry has exerted a strong influence on further areas of main-group chemistry a variety of stable molecules with Ge = Ge [16], P = P [17], As = As [18], P = C and P = C [19-22] bonds were subsequently isolated, and systems with cumulated double bonds P = C = P [23-25] are also known today. 

The chemistry of unsaturated silicon compounds, i.e. silylenes and molecules having (p-p)ic-sili-con element multiple bonds >Si=E (E = C, Si, Ge, Sn, N, P, As, O, S), is an interesting field of research for the theoretician as well as for the preparative chemist because of the unexpected and fascinating results which can be obtained. Yet 30 years ago, such compounds were considered "non existent" because of the classical "double bond rule", established by Pitzer and Mulliken in the early fifties. Since then, the chemistry of unsaturated silicon compounds proceeded from the investigation of small" species in the gas phase to the synthesis and isolation of stable species with bulky substituents at the > Si =E moiety, and to the determination of their structural features. 

The small atoms at the center of the first row of the Periodic Table (B, C, N, O, and to a lesser extent Al, Si, and P) can fit into the interstices of aggregates of larger transition metal atoms to form boride, carbide, and nitride compounds. These compounds are both hard and moderately good electronic conductors. Therefore, they are commonly known as hard metals (Schwarzkopf and Kieffer, 1953). 

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