Boron crystallographic structures

Conde O, Slivestre A.J., OUveria J.C. Influence of Carbon Content on the Crystallographic Structure of Boron Carbide Films//Surf Coat. Teehnol. 2000. V. 125. No 1. P. 141-146. 

Boron nitride exists in many different structures due to the special bonding behaviors of boron and nitrogen. Although the most well-defined crystallographic structures are hexagonal BN (h-BN), cubic BN (c-BN), and wurtzitic BN (w-BN), other crystalline structures, such as explosion boron nitride (e-BN) and ion beam-deposited boron nitride (i-BN) [124—135] and amorphous BN (a-BN) [136,137] also exist. 

Phonons. The crystallographic structure of SmBg is of the CaBg type, where boron octahedra sit on the corners of a simple cubic cell with the metal in the body centered position (fig. 21). The crystal structure of YbBi2 on the other hand is of the UBi2 type, which is a face centered cubic cell surrounded by B12 icosahedra. The standard... 

Such properties are explained by the crystal structure of the material that shows a combination of covalent and metallic bonding. In the crystallographic structure of ZrB layers of hexagonally closed packed metal atoms and graphite-like boron... 

The X-ray structures of the boron bromide and boron chloride complexes confirm the tridentate coordination of the triacetylrhenato ligand to the boron atom. Both molecules have crystallographically imposed mirror symmetry. Although both compounds decompose appreciably during data... 

Few examples have been reported of metals coordinated to six-membered boron-sulfur heterocycles. Ashe et al. prepared 4-methyl-l,4-thiaborin (SC4H4BMe) which forms a stable molybdenum tricarbonyl sandwich complex 144.158 jn g etjert s laboratory, the reaction of the diborolyl complex 33 (Section 3.01.3.2) with COS afforded the dinuclear complex 145 whose structure was determined crystallographically.36 Other products, not involving boron-sulfur heterocycles and hence outside the scope of this discussion, were obtained via the treatment of 33 with different sulfur reagents such as CS2.36... 

Another type of ligand, capable of forming multi-hapto interactions with metals, are boron and boron-carbon cage compounds of which in particular the carboranes have been used extensively in organometallic chemistry . The structures in the solid state of a few magnesacarboranes have been determined by X-ray crystallographic studies. 

The variety of C2-bridged PBs was further extended by Muhoro via hydroboration of diphenyl(vinyl)phosphine with catechol- and pinacol-boranes (Scheme 29).56 To compensate for the low Lewis acidity of these boronates, the hydroboration reactions were carried out in the presence of 5 mol% of titanocene bis(catecholborane) as catalyst. The desired products 40g and 40h were obtained with complete anti-Markovnikov selectivity. The spectroscopic data and the crystallographic study performed on 40h showed the expected monomeric open structure. 

The structure of 73 was substantiated spectroscopically (5 nB = 82.5 ppm) and confirmed crystallographically. A centrosymmetric chloro-bridged dimeric structure with tricoordinate copper centers was observed. The pendant character of the borane is apparent from the rather long the B- Cu (3.05 A) and B- Cl (4.06 A) distances associated with a trigonal planar geometry around boron. Compared to related mononuclear palladium and rhodium complexes (see Section IV.B), the presence of the chloro-bridge disfavors the formation of Cl-B interactions (coordination mode F) in 73. 

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