Undecaborates M2[B11H11]: Facile Synthesis, Crystal Structure, and Reactions

✍ Scribed by O. Volkov; W. Dirk; U. Englert; P. Paetzold

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: German
• Weight: 228 KB
• Volume: 625
• Category: Article
• ISSN: 0372-7874
• DOI: 10.1002/(sici)1521-3749(199907)625:7<1193::aid-zaac1193>3.0.co;2-l

✦ Synopsis

closo-Undecaborates were synthesized by the deprotonation of B 11 H 13 (SMe 2 ) with LitBu in thp or K [BHEt 3 ] in thf, [Li(thp) 3 ] 2 [B 11 H 11 ] and K 2 [B 11 H 11 ] being obtained in 83 and 93% yield, respectively. K 2 [B 11 H 11 ] can be transformed into A 2 [B 11 H 11 ] with the corresponding ammonium chlorides in aqueous solution (A = [NMe 3 Ph], [NBzlEt 3 ], [N(PPh 3 ) 2 ]). The crystal structure analysis of [Li(thp) 3 ] 2 [B 11 H 11 ] (space group P2 1 /c) reveals a rather distorted octadecahedron for the [B 11 H 11 ] 2± anion, whereas the corresponding octadecahedron in [NBzlEt 3 ] 2 [B 11 H 11 ] (space group P2 1 2 1 2 1 ) exhibits a structure close to C 2v symmetry, expected for the free anion. The protonation of [B 11 H 11 ] 2± at low temperature gives [B 11 H 12 ] ± , whose structure could be elucidated by NMR methods; it is formed, apparently, by the opening of the B1±B4 edge of [B 11 H 11 ] 2± in the course of its known degenerate skeletal rearrangement, followed by the protonation of the B2±B4 edge. The reaction of [B 11 H 12 ] ± with a second molecule of the acid HX (X = CF 3 COO) gives nido-[B 11 H 13 X] ± . The addition of BH 3 to [B 11 H 11 ] 2± yields closo-[B 12 H 12 ] 2± under loss of H 2 . Two [B 11 H 11 ] 2± units are fused by the aid of FeCl 3 , with the known anion [B 22 H 22 ] 2± as the product, whose 11 B-NMR signals could completely be assigned on the basis of C s symmetry. The compound [NBzlEt 3 ][N(PPh 3 ) 2 ][B 22 H 22 ] crystallizes in the space group Pna2 1 .