Английская Википедия:Bis(triphenylphosphine)iminium chloride
Шаблон:Chembox Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula Шаблон:Chem2, often abbreviated Шаблон:Chem2, where Ph is phenyl Шаблон:Chem2, or even abbreviated [PPN]Cl or [PNP]Cl or PPNCl or PNPCl, where PPN or PNP stands for Шаблон:Chem2. This colorless salt is a source of the Шаблон:Chem2 cation (abbreviated Шаблон:Chem2 or Шаблон:Chem2), which is used as an unreactive and weakly coordinating cation to isolate reactive anions. Шаблон:Chem2 is a phosphazene.
Synthesis and structure
Шаблон:Chem2 is prepared in two steps from triphenylphosphine Шаблон:Chem2:[1]
This triphenylphosphine dichloride Шаблон:Chem2 is related to phosphorus pentachloride Шаблон:Chem2. Treatment of this species with hydroxylamine in the presence of Шаблон:Chem2 results in replacement of the two single P–Cl bonds in Шаблон:Chem2 by one double P=N bond:
Triphenylphosphine oxide Шаблон:Chem2 is a by-product.
Bis(triphenylphosphine)iminium chloride is described as Шаблон:Chem2. The structure of the bis(triphenylphosphine)iminium cation Шаблон:Chem2 is Шаблон:Chem2. The P=N=P angle in the cation is flexible, ranging from ~130 to 180° depending on the salt. Bent and linear forms of the P=N=P connections have been observed in the same unit cell.[2] The same shallow potential well for bending is observed in the isoelectronic species bis(triphenylphosphoranylidene)methane, Шаблон:Chem2, as well as the more distantly related molecule carbon suboxide, Шаблон:Chem2. For the solvent-free chloride salt Шаблон:Chem2, the P=N=P bond angle was determined to be 133°.[3] The two P=N bonds are equivalent, and their length is 1.597(2) Å.
Use as reagent
In the laboratory, Шаблон:Chem2 is the main precursor to Шаблон:Chem2 salts. Using salt metathesis reactions, nitrite, azide, and other small inorganic anions can be obtained with Шаблон:Chem2 cations. The resulting salts Шаблон:Chem2, Шаблон:Chem2, etc. are soluble in polar organic solvents.
Шаблон:Chem2 forms crystalline salts with a range of anions that are otherwise difficult to crystallize. Its effectiveness is partially attributable to its rigidity, reflecting the presence of six phenyl rings. Often Шаблон:Chem2 forms salts that are more air-stable than salts with smaller cations such as those containing quaternary ammonium cation Шаблон:Chem2, or alkali metal cations. This effect is attributed to the steric shielding provided by this voluminous cation. Illustrative Шаблон:Chem2 salts of reactive anions include Шаблон:Chem2, Шаблон:Chem2, Шаблон:Chem2 (M = Cr, Mo, W), and Шаблон:Chem2.[1] The role of ion pairing in chemical reactions is often clarified by examination of the related salt derived from Шаблон:Chem2.
Related cations
A phosphazenium cation related to Шаблон:Chem2 is Шаблон:Chem2.[4]
References
