Sulfur—nitrogen bonds phosphorus halides

Acid anhydrides Carbon-carbon bonds Halide bonds Phosphorus-nitrogen Sulfur-nitrogen bonds... 

The chemistry of phosphorus and the heavier congeners is dominated by element to element (E-E) single bonds and, particularly in the case of phosphorus, the availability of l>d orbitals to form dir—pir double bonds with a variety of other atoms such as oxygen, nitrogen, and even sulfur. Orbital participation results in expanded octets as found in compounds such as PF5, SbCl5, X3P=0 (where X=F, Cl, Br, I), the phosphorus oxoadds and oxoanions, and a class of compounds called the phosphazenes. We will take up many of these cases as we encounter them in the appropriate sections under our usual survey of the hydrides, oxides and oxoacids, and halides. For now, however, let s take a quick look at the phosphazenes, formerly called the phosphonitriles, that contain both N and P atoms in the same molecule. 

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