Structure and preparation of boron‐rich borides

摘要: The B12 icosahedral compounds may be classified into 8 types: 1. α‐rhombohedral boron type; 2. β‐rhombohedral 3. α‐tetragonal 4. β‐tetragonal 5. AlB10 (or AlC4B26) 6. NaB15 7. YB66 and 8. γ‐AlB12 type. Both α‐AlB12 consist of icosahedra B20 units, have a framework analogous to that in boron. Charge balance among the polyhedral units these phases was investigated by counting number contacts between metal atoms units. Precision X‐ray diffraction studies on B13 C2, LiAlB14 revealed difference electron densities, demonstrating three‐center two‐center bonds structures. A net charge (B12)1.2− observed for LiAlB14. single crystal growth some borides from solution is discussed.