Cationic Brønsted Acids for the Preparation of SnIV Salts: Synthesis and Characterisation of [Ph3Sn(OEt2)][H2N{B(C6F5)3}2],[Sn(NMe2)3(HNMe2)2][B(C6F5)4] and [Me3Sn(HNMe2)2][B(C6F5)4]

Ph3SnN(SiMe3)(2) (1) was prepared in good yields by reaction of [{NaN(SiMe3)(2)}(2)center dot THF] (2) with Ph3SnF. Treatment of 1 with [H(OEt2)(2)][H2N{B(C6F5)(3)}(2)] (4) in dichloromethane afforded the stannylium cation [Ph3Sn(OEt2)][H2N{B(C6F5)(3)}(2)] (5), which was characterised by H-1, C-13{H-1}, B-11, F-19 and Sn-119 NMR spectroscopy. The reaction of Sn(NMe2)(4) with [Ph2MeNH][B(C6F5)(4)] (3) gave the amidotin(IV) compound [Sn(NMe2)(3)(HNMe2)(2)][B(C6F5)4] (6) which proved very stable towards ligand substitution and resisted treatment with Et2O, THF, TMEDA and pyrazine. Two new Bronsted acid salts [H(NMe2H)(2)][B(C6F5)(4)] (7). and [(C4H4N2)H center dot OEt2]-[H2N{B(C6F5)(3)}(2)] (8) were synthesised. The reaction of 7 with Sn(NMe2)(4) in Et2O allowed the preparation of 6 in a much improved yield (83%). The treatment of 7 with Me-3-SnN(SiMe3)(2) in Et2O yielded [Me3Sn(HNMe2)(2)][B(C6F5)(4)] (9) nearly quantitatively. Compounds 1, 2, 6, 8 and 9 were characterised by single-crystal X-ray diffraction analyses; 6 is the first example of a structurally characterised amidotin(IV) cation.