Binary sulfur nitrides

It wilt be convenient to describe first the binary sulfur nitrides SiN, and then the related cationic and anionic species, S,Ny . The. sulfur imides and other cyclic S-N compounds will then be di.scussed and this will be followed by sections on S-N-halogen and S-N-0 compounds. Several compounds which feature isolated S —N, S-N, S=N and S=N bonds have already been mentioned in the section on SF4 e.g. F4S-(-NC5H, F5S-NF2. F2S=NCF3, and F SsN (p. 687). However, many SN compounds do not lend themselves to simple bond diagrams, - and formal oxidation states are often unhelpful or even misleading. 

Nitrogen and sulfur are diagonally related in the periodic table and might therefore be expected to have similar electronic charge densities for 

Disulfur dichloride was added to an aqueou.s. solution of ammonia to give a yellow precipitate of sulfur contaminated with S4N4 J. Phann. Chim. 21, 31.S (183.S). 

The compound also results from the reversible equilibrium reaction of sulfur with anhydrous liquid ammonia  

The H2S, of course, reacts with further ammonia to form ammonium sulfides but the reaction can be made to proceed in the forward direction as written by addition of (soluble) Agl to precipitate AgS and form NH4I. 

It is not possible to write down a single, satisfactory, classical bonding diagram for S4N4 and, in valence-bond theory, numerous resonance hybrids must be considered of which the following are typical  

---

The oxidative addition of one equivalent of X2 (X=C1, F) to S4N4 under mild conditions produces 1,5-S4N4X2.106 The structure of 1,5-S4N4C12 (32) consists of a folded eight-membered ring [d(S- -S) = 2.45 A] with the exocyclic substituents in exo,endo positions. The reaction of 32 with (Me3SiN)2S is the best route to the binary sulfur nitride S5N6 (11).42... 

In spite of the hazardous nature of Sc4N4, this binary selenium nitride has been used for the synthesis of other Se-N compounds, all of which have sulfur analogues (Scheme 5.2). " However, safer alternatives to the use of Sc4N4, e.g., selenium-nitrogen halides and silicon-nitrogen-selenium reagents, are available for the development of Se-N chemistry. ... 

Structurally characterized since 1970 and the structure of the eighth (S4N3 ) has been redetermined recently b) the first binary sulfur-nitrogen anion, S N " was isolated in 1975 and its structure was reported a year later c) the novel sulfur nitride, SjNg, was first identified in 1978 and d) although tetrasulfur dinitride, S N, has been known since 1897, the structure was not unequivocally determined until 1981... 

Hydrides of variable composition are not only formed with pure metals as solvents. A large number of the binary metal hydrides are non-stoichiometric compounds. Non-stoichiometric compounds are in general common for d,f and some p block metals in combination with soft anions such as sulfur, selenium and hydrogen, and also for somewhat harder anions like oxygen. Hard anions such as the halides, sulfates and nitrides form few non-stoichiometric compounds. Two factors are important the crystal structures must allow changes in composition, and the transition metal must have accessible oxidation states. These factors are partly related. FeO,... 

The metal reacts with halogens above 200°C forming its trihalides. It combines with nitrogen above 1,000°C producing a nitride, YN. It combines at elevated temperatures forming binary compounds with most nonmetals and some metalloid elements such as hydrogen, sulfur, carbon, phosphorus, silicon, and selenium. 

Solution The first two ions are single atom anions and are called sulfide and nitride. The next two are binary ionic compounds, calcium fluoride and potassium sulfide. The polyatomic ions hydroxide and sulfate are present in sodium hydroxide and sodium sulfate. Finally, the last two compounds are covalently bonded and are called sulfur trioxide and carbon tetrachloride. 

In Chapters 20 and 21 we shall look at individual elements of the c -block in detail. However, a few general points are given here as an overview. In general, the metals are moderately reactive and combine to give binary compounds when heated with dioxygen, sulfur or the halogens (e.g. reactions 19.1-19.3), product stoichiometry depending, in part, on the available oxidation states (see below). Combination with H2, B, C or N2 may lead to interstitial hydrides Section 9.7), borides Section 12.10), carbides Section 13.7) or nitrides Section 14.6). 

Iron is reactive and, if sufficiently finely divided, is pyrophoric in air. It forms binary compounds by direct reaction with many elements, and some of these are described in more detail later. It reacts with oxygen, sulfur, halogens, phosphorus, and even forms a nitride with dinitrogen. With... 

The study of binary compounds of sulfur and nitrogen has been spurred both by the problems they pose to simple bonding theory and by the observation that polysulfur nitride is metallic in its properties. 

The author considered it best not to include in the reference book the properties of certain little-studied compounds rarely used in practice. Thus, in the presentation of the information on carbides, borides, nitrides, and other classes of metal-like compounds, no data are given on the refractory compounds of metals of the platinum group for the sulfides, data are given only for the class of sulfides of the rare-earth metals and actinides, in most of which the properties of refractory compounds in the wide sense are most clearly expressed, the proportion of ionic bond, in particular, being small. It was, however, found e qpedient to consider also the properties of oxysulfides of the rare-earth metals and actinides, which are very similar to the properties of sulfides and are obtained simply by replacement of two atoms of sulfur in a sesquisulfide by two atoms of oxygen. This is one of the few exceptions where the tables of the reference book give the properties of ternary and not binary compounds. 

---