Tl5[NO3]3[CB11H12]2: A novel carbadodecaborate double salt with an unprecedented crystal structure

The novel compound Tl 5 [NO 3 ] 3 [CB 11 H 12 ] 2 was prepared by the aqueous reaction of (HNEt 3 )[CB 11 H 12 ] with Tl 2 [CO 3 ] after the treatment of the resulting product with diluted nitric acid. Tl 5 [NO 3 ] 3 [CB 11 H 12 ] 2 crystallizes as colorless platelets in the hexagonal space group P 6 3 / m with the lattice parameters a = 767.52(4) pm and c = 3026.75(17) pm ( c / a = 3.944) for Z = 6. Unlike other double salts of closo -(carba)borates, Tl 5 [NO 3 ] 3 [CB 11 H 12 ] 2 does not crystallize in a well-known structure type, but with a completely new structure, which contains electroneutral layers held together only by van-der-Waals interactions. These layers consist of [NO 3 ] − -centered (Tl + ) 6 octahedra, which are linked to their four neighbors via faces. The connecting faces and the non-connecting faces occur opposite to each other, creating a layer with a hexagonal recess, in which the closo -carbaborate anions find their place attached via Tl + ‧‧‧H δ− bonds. In the Raman spectrum of Tl 5 [NO 3 ] 3 [CB 11 H 12 ] 2 , the most prominent vibration bands are the respiratory vibration of the closo -carbaborate skeleton at 762 cm −1 and the valence vibrations of the B−H bonds in the range between 2470 and 2620 cm −1 . • Synthesis and crystal structure of Tl 5 [NO 3 ] 3 [CB 11 H 12 ] 2 • Kagome net formed by the nitrate anions • Electroneutral layers held together only by van-der-Waals interactions