Borides and Silicides of the Platinum Metals

Aronsson, B.; Åselius, J.; Stenberg, E.

doi:10.1038/1831318b0

Cited by 26 publications

(13 citation statements)

References 3 publications

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“…As to the nature of the passivating boron layer on the surface of the Rh colloid, the formation of rhodium boride may be a distinct possibility. For example, the structure of rhodium boride (RhB) has been determined and metal borides are well-known materials . This boride layer may be formed from a catalyzed decomposition of “BH 3 ”, similar to a reaction that has been previously reported involving Co particles and B 2 H 6 in which elemental boron and H 2 are formed .…”

Section: Resultsmentioning

confidence: 99%

Poisoning of Heterogeneous, Late Transition Metal Dehydrocoupling Catalysts by Boranes and Other Group 13 Hydrides

et al. 2005

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Borane reagents are widely used as reductants for the generation of colloidal metals. When treated with a variety of heterogeneous catalysts such as colloidal Rh, Rh/Al2O3, and Rh(0) black, BH3.THF (THF = tetrahydrofuran) was found to generate H2 gas with the concomitant formation of a passivating boron layer on the surface of the Rh metal, thereby acting as a poison and rendering the catalyst inactive toward the dehydrocoupling of Me2NH.BH3. Analogous poisoning effects were also detected for (i) colloidal Rh treated with other species containing B-H bonds such as [HB-NH]3, or Ga-H bonds such as those present in GaH3.OEt2, (ii) colloidal Rh that was generated from Rh(I) and Rh(III) salts using borane or borohydrides as reductants, and (iii) for other metals such as Ru and Pd. In contrast, analogous poisoning effects were not detected for the catalytic hydrogenation of cyclohexene using Rh/Al2O3 or the Pd-catalyzed Suzuki cross-coupling of PhB(OH)2 and PhI. These results suggest that although this poisoning behavior is not a universal phenomenon, the observation that such boron layers are formed and surface passivation may exist needs to be carefully considered when borane reagents are used for the generation of metal colloids for catalytic or materials science applications.

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Section: Resultsmentioning

confidence: 99%

Poisoning of Heterogeneous, Late Transition Metal Dehydrocoupling Catalysts by Boranes and Other Group 13 Hydrides

et al. 2005

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“…Borides are usually classified according to the linking of the boron atoms (Kiessling, 1950;Aronsson, 1961). In boron-rich compounds the boron atoms form threedimensional frameworks.…”

Section: Discussionmentioning

confidence: 99%

The crystal structure of MoCoB and related compounds

Jeitschko¹

1968

Acta Crystallogr Sect B

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MoCoB crystallizes with an orthorhombic unit cell, space group Pnma, having the lattice constants a=5.741+0.003, b=3.232+0.001, c=6.634+0"001 A. The structure is of the ordered PbC12 type (TiNiSi type, E-phase). The positional parameters have been refined by the least-squares method with (limited) three-dimensional single-crystal data, giving a final R value of 0.103 (including the unobserved reflections). The compounds WCoB and WFeB are isotypic with MoCoB. A survey on the known PbClz type compounds is given.

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“…The Rh-B system contains hP20-Rh 7 B 3 (SG#186) 198 , oP12-Rh 2 B (SG#62) 199 , hP18-Rh 5 B 4 (SG#194) 200 , and hP4-RhB 1.1 (SG#194) 198,201 . The first two match our calculated ground states.…”

Section: Rh-bmentioning

confidence: 99%

Stability of 41 metal–boron systems at 0GPa and 30GPa from first principles

Geest

Kolmogorov

2014

Calphad

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A multitude of observed boron-based materials have outstanding superconducting, mechanical, and refractory properties. Yet, the structure, the composition, and the very existence of some reported metal boride (M-B) compounds have been a subject of extensive debate. This density functional theory work seeks to set a baseline for current understanding of known metal boride phases as well as to identify new synthesizable candidates. We have generated a database of over 12,000 binary M-B entries for pressures of 0 and 30 GPa producing the largest scan of compositions and systems in this materials class. The 175 selected crystal structures include both observed prototypes and new ones found with our evolutionary ground state search. The metals considered are: Al, and Zr. Based on the formation energy calculated at zero pressure and temperature 4 new M-B phases or structures have been predicted, while a number of previously reported compounds have been shown to be unstable. At 30 GPa, changes in the convex hulls are expected to occur in 18 out of 41 M-B systems, which is used to indicate regions of the periodic table (for metal borides) that require further investigation from the community. Analysis of the collected information has revealed a nearly linear relationship between the magnetic moment per atom and the metal content for all the Fe-B, Co-B, and Ni-B structures within 0.15 eV/atom of the stability tie line. Both GGA-PBE and LDA-PW functionals were used to provide an understanding of the systematic error introduced by the choice of the exchange-correlation functional.arXiv:1310.4157v2 [cond-mat.mtrl-sci]

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Borides and Silicides of the Platinum Metals

Cited by 26 publications

References 3 publications

Poisoning of Heterogeneous, Late Transition Metal Dehydrocoupling Catalysts by Boranes and Other Group 13 Hydrides

Poisoning of Heterogeneous, Late Transition Metal Dehydrocoupling Catalysts by Boranes and Other Group 13 Hydrides

The crystal structure of MoCoB and related compounds

Stability of 41 metal–boron systems at 0GPa and 30GPa from first principles

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