Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Boron hydrides metal complexes

The structural complexity of borate minerals (p. 205) is surpassed only by that of silicate minerals (p. 347). Even more complex are the structures of the metal borides and the various allotropic modifications of boron itself. These factors, together with the unique structural and bonding problems of the boron hydrides, dictate that boron should be treated in a separate chapter. [Pg.139]

Boron is unique among the elements in the structural complexity of its allotropic modifications this reflects the variety of ways in which boron seeks to solve the problem of having fewer electrons than atomic orbitals available for bonding. Elements in this situation usually adopt metallic bonding, but the small size and high ionization energies of B (p. 222) result in covalent rather than metallic bonding. The structural unit which dominates the various allotropes of B is the B 2 icosahedron (Fig. 6.1), and this also occurs in several metal boride structures and in certain boron hydride derivatives. Because of the fivefold rotation symmetry at the individual B atoms, the B)2 icosahedra pack rather inefficiently and there... [Pg.141]

Boron hydrides are reducing agents and reduce many metal cations to the metal. However, it is also known that noble metal complexes, particularly those of rho-... [Pg.50]

Boron absorbs hydrogen and forms hydrides. There are two classes of hydrides metallic hydrides and complex hydrides, with the main difference being the transition of metals to ionic or covalent componnds for the complex hydrides upon absorbing hydrogen. [Pg.142]

Lippard, S.J., Ucko, D.A. 1968. Transition metal borohydride complexes. II. Th reaction of copper(I) compounds with boron hydride anions. Inorg Chem 7 1051-1058. [Pg.157]

Complex aluminum and boron hydrides can contain other cations. The following compounds are prepared by metathetical reactions of lithium aluminum hydride or sodium borohydride with the appropriate salts of other metals sodium aluminum hydride [55], magnesium aluminum hydride [59], lithium borohydride [90], potassium borohydride [9i], calcium borohydride [92] and tetrabutylammonium borohydride [95]. [Pg.14]

Hunt s group (50, 51) have pioneered the application of the Cl source to organometallics such as the iron tricarbonyl complex of heptafulvene, whose electron impact spectrum shows (M—CO)+ as the heaviest ion, in contrast to the methane Cl spectrum with the ion as base peak. Boron hydrides (52) and borazine (53) have also been studied. The methane Cl spectrum of arenechromium and -molybdenum (54) show protonation at the metal giving a protonated parent or molecular ion. Risby et al. have studied the isobutane Cl mass spectra of lanthanide 2,2,6,6-tetramethylheptane-3,5-dionates[Ln(thd)3] (55) and 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-oetanedione [H(fod)] lanthanide complexes (56). These latter complexes have been suggested as a means of analysis for the lanthanide elements. [Pg.233]

To unlock its full potential, C-H activation has to be coupled with a functionalization event (e.g., 3—>4). For instance, a hydride elimination occurring after the formation of metal complexes such as 3 furnishes olefins, versatile intermediates for further modification reactions. Transition metal-catalyzed atom- or atom group-transfer reactions that permit the introduction of oxygen-, carbon-, and boron-containing groups are also presented. [Pg.37]

In addition, for metal complexes of the larger boron hydrides, more complicated types of bonding (where M-H-B linkages are augmented by M-B, M-M or B-B bonds) are found. As mentioned earlier in this article, metalloborane complexes are generally unsuitable for neutron diffraction because of the very large absorption cross... [Pg.18]

Fig. 22. The structure of the unusual mixed metal boron hydride complex Fe(CO)3(BsH8)Cu-(PPh3)2, whose FeBs cage is based on BgHio (Ref. 113)... Fig. 22. The structure of the unusual mixed metal boron hydride complex Fe(CO)3(BsH8)Cu-(PPh3)2, whose FeBs cage is based on BgHio (Ref. 113)...
It should be clear from the discussion of Section 2 that all of these clusters can be unstable with respect to cluster degradation in the presence of Lewis bases with the formation of saturated fragment species (see Boron Hydrides and Polynuclear Organometallic Cluster Complexes). Thus, in the presence of an excess of phosphine, the reaction of [HFe3(CO)9(/u-H)2BH] changes from that shown in equation (10) to that shown in equation (12). The mononuclear boron and iron products demonstrate that both transition metal and main group element vertices are removed by base and the cluster is degraded. ... [Pg.1760]


See other pages where Boron hydrides metal complexes is mentioned: [Pg.1867]    [Pg.1866]    [Pg.145]    [Pg.40]    [Pg.300]    [Pg.48]    [Pg.4]    [Pg.842]    [Pg.138]    [Pg.143]    [Pg.87]    [Pg.122]    [Pg.227]    [Pg.113]    [Pg.397]    [Pg.147]    [Pg.335]    [Pg.147]    [Pg.106]    [Pg.87]    [Pg.11]    [Pg.23]    [Pg.51]    [Pg.153]    [Pg.46]    [Pg.231]    [Pg.198]    [Pg.418]    [Pg.953]    [Pg.1622]    [Pg.1758]    [Pg.1761]    [Pg.4113]    [Pg.5782]    [Pg.442]    [Pg.670]    [Pg.94]   
See also in sourсe #XX -- [ Pg.2 , Pg.5 , Pg.5 , Pg.9 , Pg.9 ]




SEARCH



Boron complexes

Boron metals

Metal hydrides, complex

Metalation-boronation

© 2024 chempedia.info