Phosphorus pentachloride PCI

PHOSPHORUS PENTACHLORIDE PCI, None Wmer magpicsiam oxide chenucaBy acB e metals sodhmi, potanhim alhalics Not combustible ... 

Typical inorganic compounds include titanium tetrachloride (TiCl ), dinitrogen pentoxide (N O ), phosphorus pentachloride (PCI,), and aluminum trichloride (AlCl,). 

The Lewis structure of the PCI, molecule is shown in (22), and we see that it obeys the octet rule. However, when phosphorus trichloride reacts with more chlorine (Fig. 2.10), phosphorus pentachloride, a pale yellow crystalline solid, is produced ... 

Phosphorus trichloride, PCI, and phosphorus pentachloride, PC15, are the two most important halides of phosphorus. The former is prepared by direct chlorination... 

Phosphorus pentachloride is an ionic solid consisting of PC14+ cations and PC16 anions, and it sublimes at 160°C to a gas of PCI, molecules. The Lewis structures of the polyatomic ions and the molecule are shown in (33). Although the cation is a polyatomic ion in which the P atom does not need to expand its valence shell, in the anion the P atom has expanded its valence shell to 12 electrons, by making use of two of its 3d-orbitals. In PC15, the P atom has expanded its valence shell to 10 electrons by using one 3d-orbital. 

Action of Phosphorus Pentachloride on Carbonyl Compounds RCOCHjR + PCI, RCCljCHjR + POCl,... 

Many trigonal bipyramidal phosphorus molecules exist in equilibrium with tetrahedral phospho-nium cations and octahedral anions. In some instances all forms can be isolated and characterised. Phosphorus pentachloride, for example, exists as PCI5 in the vapour state, but as an assembly of PCI4 PCI in the solid state. Dimerisation also occurs to a small extent in some solvents (3.41). 

By the action of phosphorus pentachloride, phosphonic and phosphinic acids and their esters are converted to the corresponding chlorides. In the case of phenol or catechol, substituted phospho-ranes are obtained (Chapter 6.12). Some of the reactions of PCI, are summarised in Figure 4.20. 

The atomic parameters of phosphorus pentachloride in the solid state have been refined. The PCI4+ cation has 4 symmetry and a unique P-Cl bond length of 1.90 A. In the PCI - anion, which has a four-fold axis only, the equatorial bonds are 2.11(1) A and the axial 2.12(1) and 2.16(1) A. 

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