One way to reactive cations - stabilized by the weakly coordinating anions [Al(ORF)4]- - is the abstraction of a halide anion with the silver salt Ag[Al(ORF)4] from a halogene containing compound like CX4 or PX3. The driving force in these reactions is the big lattice energy of the precipitating AgX. In case of the tetrahalomethanes CX4 (X = Cl, Br, I) this leads directly to the trihalocarbenium cations [CX3]+. With the phosphorus trihalides PX3 (X = Br, I) an electrophilic carbene-analogous [PX2]+ intermediate (not isolable) is built, which can insert in different bonds like X-X, X2P-X (X = Br, I) or in a P-P bond of white phosphorus (P4) for example.
On this way the halocarbenium cations [CX3]+ (X = Cl, Br, I) and several reactive phosphorus cations were isolated as salts of the [Al(ORF)4]- anion and could be characterized in solution and in the solid state by X-Ray diffraction, vibrational (Raman and IR) and NMR spectroscopy (especially 13C and 31P).
[CCl3]+ und [CBr3]+:
A. J. Lehner, N. Trapp, H. Scherer, I. Krossing, Dalton Transactions 2010, 40, 1448.
I. Krossing, A. Bihlmeier, I. Raabe, N. Trapp, Angewandte Chemie 2003, 115, 1569.
I. Raabe, D. Himmel, S. Muller, N. Trapp, M. Kaupp, I. Krossing, Dalton Transactions 2008, 946.
[P5X2]+ (X = Br, I)
I. Krossing, I. Raabe, Angewandte Chemie 2001, 113, 4544.
[PX4]+, [P2X5]+ und [P5X2]+ (X = Br, I)
[P2I5]+ from P2I5[Al(OC(CF3)3)4]
M. Gonsior, I. Krossing, L. Müller, I. Raabe, M. Jansen, L. van Wüllen, Chemistry – A European Journal 2002, 8, 4475.
[P3I6]+ and [P5I2]+
[P5I2]+ calculated (RI-MP2/TZVPP)
I. Krossing, Journal of the Chemical Society, Dalton Transactions 2002, 500.