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Triphenylphosphine oxide (often abbreviated TPPO) is the organophosphorus compound with the formula OP(C 6 H 5) 3, also written as Ph 3 PO or PPh 3 O (Ph = C 6 H 5). It is one of the more common phosphine oxides. This colourless crystalline compound is a common but potentially useful waste product in reactions involving triphenylphosphine.
Triphenylphosphine undergoes slow oxidation by air to give triphenylphosphine oxide, Ph 3 PO: 2 PPh 3 + O 2 → 2 OPPh 3. This impurity can be removed by recrystallisation of PPh 3 from either hot ethanol or isopropanol. [8] This method capitalizes on the fact that OPPh 3 is more polar and hence more soluble in polar solvents than PPh 3.
The hydrolysis of phosphorus(V) dihalides also affords the oxide: [9] R 3 PCl 2 + H 2 O → R 3 PO + 2 HCl. A special nonoxidative route is applicable secondary phosphine oxides, which arise by the hydrolysis of the chlorophosphine. An example is the hydrolysis of chlorodiphenylphosphine to give diphenylphosphine oxide: Ph 2 PCl + H 2 O → Ph ...
The structure of the phosphine oxide is not strongly perturbed by coordination. The geometry at phosphorus remains tetrahedral. The P-O distance elongates by ca. 2%. In triphenylphosphine oxide, the P-O distance is 1.48 Å. [3] In NiCl 2 [OP(C 6 H 5) 3] 2, the distance is 1.51 Å (see figure).
Wilkinson's catalyst (chloridotris(triphenylphosphine)rhodium(I)) is a coordination complex of rhodium with the formula [RhCl(PPh 3)], where 'Ph' denotes a phenyl group. It is a red-brown colored solid that is soluble in hydrocarbon solvents such as benzene, and more so in tetrahydrofuran or chlorinated solvents such as dichloromethane .
Phosphine oxides (designation σ 4 λ 5) have the general structure R 3 P=O with formal oxidation state V. Phosphine oxides form hydrogen bonds and some are therefore soluble in water. The P=O bond is very polar with a dipole moment of 4.51 D for triphenylphosphine oxide.
The tables below provides information on the variation of solubility of different substances (mostly inorganic compounds) in water with temperature, at one atmosphere pressure. Units of solubility are given in grams of substance per 100 millilitres of water (g/(100 mL)), unless shown otherwise. The substances are listed in alphabetical order.
The order of addition of the reagents of the Mitsunobu reaction can be important. Typically, one dissolves the alcohol, the carboxylic acid, and triphenylphosphine in tetrahydrofuran or other suitable solvent (e.g. diethyl ether), cool to 0 °C using an ice-bath, slowly add the DEAD dissolved in THF, then stir at room temperature for several hours.