[Se(CH(2)C(O)CH(3))(3)][B(12)F(11)NH(3)]: The first selenium cation with three β-ketone substituents.

The reaction of [Se(8)][B(12)F(11)NH(3)](2) with acetone and subsequent crystallization from acetone/diethyl ether yielded the selenium cation [Se(CH(2)C(O)CH(3))(3)](+) as a by-product, which is stabilized by the weakly coordinating undeca-fluorinated anion [B(12)F(11)NH(3)](-). While attempting to crystallize pure [Se(8)][B(12)F(11)NH(3)](2), the structure of the isolated product, namely, tris-(2-oxoprop-yl)selenium 1-ammonio-undeca-fluoro-dodeca-borate, was surprising. The cation [Se(CH(2)C(O)CH(3))(3)](+) represents the first example for a cationic selenium compound with three ketone functional groups located in the β-position with respect to the selenium atom. The cation possesses almost trigonal-pyramidal C (3) symmetry and forms hydrogen bonds to the ammonio group of the anion.