FULL PAPER DOI: 10.1002/ejic.200600397 Cationic Brønsted Acids for the Preparation of Sn IV Salts: Synthesis and Characterisation of [Ph 3 Sn(OEt 2 )][H 2 N{B(C 6 F 5 ) 3 } 2 ], [Sn(NMe 2 ) 3 (HNMe 2 ) 2 ][B(C 6 F 5 ) 4 ] and [Me 3 Sn(HNMe 2 ) 2 ][B(C 6 F 5 ) 4 ] Yann Sarazin, [a] Simon J. Coles, [b] David L. Hughes, [a] Michael B. Hursthouse, [b] and Manfred Bochmann* [a] Keywords: Tin / Cations / N ligands / Anions Ph 3 SnN(SiMe 3 ) 2 (1) was prepared in good yields by reaction of [{NaN(SiMe 3 ) 2 } 2 ·THF] (2) with Ph 3 SnF. Treatment of 1 with [H(OEt 2 ) 2 ][H 2 N{B(C 6 F 5 ) 3 } 2 ](4) in dichloromethane afforded the stannylium cation [Ph 3 Sn(OEt 2 )][H 2 N{B(C 6 F 5 ) 3 } 2 ] (5), which was characterised by 1 H, 13 C{ 1 H}, 11 B, 19 F and 119 Sn NMR spectroscopy. The reaction of Sn(NMe 2 ) 4 with [Ph 2 MeNH][B(C 6 F 5 ) 4 ](3) gave the amidotin(IV) compound [Sn(NMe 2 ) 3 (HNMe 2 ) 2 ][B(C 6 F 5 ) 4 ] (6) which proved very stable towards ligand substitution and resisted treatment with Et 2 O, THF, TMEDA and pyrazine. Two new Brønsted acid salts [H(NMe 2 H) 2 ][B(C 6 F 5 ) 4 ](7) and [(C 4 H 4 N 2 )H·OEt 2 ]- Introduction Organotin(IV) compounds have long attracted interest due to their reactivity, their industrial applications and their intriguing biological activity. [1,2] In particular, organo- tin(IV) cations are thought to play an essential part in the cytotoxicity of organotin compounds [3] or in their catalytic activity for esterification reactions, [4] and the search for stable examples of Sn IV cations was initiated over half a century ago. [5–19] However, to this date only few cationic complexes of tin have been isolated. Even though in the past decade or so fundamental breakthroughs have been achieved where tin cations free of donor atoms have been Scheme 1. Involvement of Me 3 Sn + in the formation of a tin-stabilised carbocation. [a] Wolfson Materials and Catalysis Centre, School of Chemical Sciences and Pharmacy, University of East Anglia, University Plain, Norwich NR4 7TJ, UK Fax: +44-01603-592044 E-mail: m.bochmann@uea.ac.uk [b] School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK Eur. J. Inorg. Chem. 2006, 3211–3220 © 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 3211 [H 2 N{B(C 6 F 5 ) 3 } 2 ](8) were synthesised. The reaction of 7 with Sn(NMe 2 ) 4 in Et 2 O allowed the preparation of 6 in a much improved yield (83 %). The treatment of 7 with Me 3 - SnN(SiMe 3 ) 2 in Et 2 O yielded [Me 3 Sn(HNMe 2 ) 2 ][B(C 6 F 5 ) 4 ](9) nearly quantitatively. Compounds 1, 2, 6, 8 and 9 were char- acterised by single-crystal X-ray diffraction analyses; 6 is the first example of a structurally characterised amidotin(IV) cation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) characterised in the solid state, [20–25] stannylium cations sta- bilised by donor heteroatoms appear to be more readily ac- cessible. [2] For instance, cationic tin species stabilised by a Y,C,Y-chelating pincer-type ligand (where Y is an hetero- atom such as oxygen or nitrogen) have been prepared very successfully in the past 15 years. [26–32] The utilisation of N,C,N-coordinating ligands has even enabled the prepara- tion of air-stable organotin cations. [33,34] Our interest in the chemistry of cationic tin species is based on our recent iso- lation of a thermally remarkably stable sec-alkyl carbo- cation that was generated by the attack of a Me 3 Sn + inter- mediate on a suitably substituted propene (Scheme 1). [35,36] This prompted us to investigate the chemistry of cationic tin species in more detail. We report here the reactions of a number of tin amideswith cation-generating agents. To the best of our knowledge, simple Sn IV -amide precursors have never been employed efficiently for this purpose. A convenient way of generating cationic metal species is the reaction of protolysis-sensitive metal complexes with