Hydride containing

A critical issue is the stabiUty of the hydride electrode in the cell environment. A number of hydride formulations have been developed. Table 5 shows hydride materials that are now the focus of attention. Most of these are Misch metal hydrides containing additions of cobalt, aluminum, or manganese. The hydrides are prepared by making melts of the formulations and then grinding to fine powers. The electrodes are prepared by pasting and or pressing the powders into metal screens or felt. The additives are reported to retard the formation of passive oxide films on the hydrides. 

For bicyclic structures the von Baeyer name consists of the prefix bicyclo-, followed in square brackets by the numbers of carbon atoms separating the bridgeheads on the three possible routes from one bridgehead to the other, followed in turn by the name of the alkane (or other homogeneous hydride, or repeating unit hydride) containing the same number of atoms in the chain as the whole bicyclic skeleton (examples 55-57). Replacement nomenclature can be applied to hydrocarbon names (example 58). 

Reactivity Hydrolysis products Arsenic acids and a hydride containing fewer hydrogen atoms than SA itself. 

Metal hydrides containing transition metal (TM)-hydrogen complexes, with the transition metal in a formally low oxidation state, are of fundamental interest for clarifying how an electron-rich metal atom can be stabilized without access to the conventional mechanism for relieving the electron density by back-donation to suitable ligand orbitals. By reacting electropositive alkali or alkaline earth metals ( -elements) with group 7, 8, 9, and 10 transition metals in... 

C. Helling, V. Imhof, L. Nielsen, and E. Jacobson Complex Alumino-Hydrides containing Nitrogen, Phosphorus and Arsenic. Inorg. Chem. 2, 504 (1963). 

Silicon hydrides containing more than two silicon atoms are unstable and decompose to produce SiH2, Si2Hs, and H2. These compounds are spontaneously flammable in air. 

Information published from several sources about 1970 presented details on both the halide-containing RhCl(CO)(PPh3)2- and the hydride-containing HRh(CO)(PPh3)3-catalyzed reactions. Brown and Wilkinson (25) reported the relative rates of gas uptake for a number of different olefinic substrates, including both a- and internal olefins. These relative rates are listed in Table XV. 1-Alkenes and nonconjugated dienes such as 1,5-hexadiene reacted rapidly, whereas internal olefins such as 2-pentene or 2-heptene reacted more slowly by a factor of about 25. It should also be noted that substitution on the 2 carbon of 1-alkene (2-methyl-l-pentene) drastically lowered the rate of reaction. Steric considerations are very important in phosphine-modified rhodium catalysis. 

There can be two kinds of chiral tin reagents tin chiral and C-chiral. Early reports of chiral tin hydride involved transfer of chirality via a chiral tin center [45-47]. These tin hydrides were prone to racemization. Thus, chiral carbon-based ligands attached to the tin center were synthesized to minimize racemization. The first chiral tin hydride containing a C2-symmetric binaphthyl substituent was reported by Nanni and Curran (Scheme 16) [48]. a-Bromoketone 58 was reduced by chiral tin hydride 59 (R3 = Me), where the reactivity and selectivity was dependent on the reaction conditions (entry 4). 

Metzger and co-workers have also described a reduction of a-bromoesters by chiral tin hydrides containing a diastereomeric mixture of 2-[(l-dimethyl-aminoalkyl)phenyl] (DAAP) ligands [51]. The observed enantioselectivities were dependent on the tin hydride used and on the substituents attached to the radical center. 

Isomerisation is also an important step in the DuPont process for making adiponitrile (Chapter 11) in which internal pentenenitriles must be converted to the terminal alkene. The catalyst is the same as that used for the hydrocyanation reaction, namely nickel(II) hydrides containing phosphite ligands. 

K Yvon, B. BertheviUe, Magnesium based ternary metal hydrides containing alkali and alkaline-earth elements, J. Alloys Compd. 425 (2006) 101-108. 

Scheme 8.4 Proposed propagation steps of the autoxidation of silicon hydrides containing at least two silyl substituents (R = Me or SiMe3)...

Calculated equilibrium geometries for hydrogen and main-group hydrides containing one and two heavy (non-hydrogen) atoms are provided in Appendix A5 (Tables A5-1 and A5-10 for molecular mechanics models, A5-2 and A5-11 for Hartree-Fock models, A5-3 and A5-12 for local density models, A5-4 to A5-7 and A5-13 to A5-16 for BP, BLYP, EDFl and B3LYP density functional models, A5-8 and A5-17 for MP2 models and A5-9 and A5-18 for MNDO, AMI and PM3 semi-empirical models). Mean absolute errors in bond lengths are provided in Tables 5-1 and 5-2 for one and two-heavy-atom systems, respectively. 

Calculated vibrational frequencies for main-group hydrides containing one first or second-row element are provided in Appendix A7 (Tables A7-1 to A7-8), and compared both with experimentally measured values and, where available, with harmonic experimental frequencies. The same theoretical models considered for diatomic molecules are also examined here. A summary of mean absolute errors for symmetric stretching frequencies (only) is provided in Table 7-2. 

CfQ 2 0 3 ft P 00 Assumes Assumes container is 25 of hydride weight 50 void space in hydride containers ... 

Whereas edge- and face-bridging hydrogen atoms are associated mainly with metal-metal orbitals already present in the tetrahedral skeleton (see last section) and therefore have limited steric requirements, terminal hydrides occupy a full coordination position. It is not surprising then that the only examples of tetrahedral species with terminal hydrides contain 11 and 10 carbonyls, [Ir4(CO)nH] and [Ir4(CO)ioH2]2 . (The assignment for [Ir4(CO)nH] is based on the structure determination of the analogous [Ir4(CO)nBr] and on the similarity of the ir spectra of the two species (11).)... 

Ruthenium and Rhodium Hydrides Containing Chiral Phosphine or Chiral Sulfoxide Ligands, and Catalytic Asymmetric Hydrogenation... 

Many metals react exothermally and reversibly with hydrogen according to Reaction 1. In many cases, the resulting metal hydrides contain more... 

Many of the intermediate metallathiabenzenes react with hydrogen gas at low temperatures to yield the fully saturated desulfurized hydrocarbon is high yield (4, 89, 98). Another important feature exhibited by these compounds is that many of them will add dihydrogen to the metal center and produce a stable hydride-containing product. This stable product can be destabilized by the addition of an external neutral ligand that forces the hydride to transfer to the carbon bonded to the metal, thus breaking the... 

Hydrides containing higher proportions of sulphur have been isolated (see p. 47), but such are unknown in the case of selenium and tellurium. 

All of the compounds discussed thus far (except diborane and decaborane) contain only two-center, two-electron bonds. A ample boron hydride containing three types of bonds is tetraborane, B4H 0 (Fig. 16.43). it is formed by the slow decomposition of diborane ... 

Ionic Hydrides. The ionic or saline hydrides contain metal cations and negatively charged hydrogen ions. They crystallize in the cubic lattice similar to the corresponding metal halide, and when pure, are white sulid.s. When dissolved in molten sales or hydroxides and electrolyzed, hydrogen gas is liberated al the anode. Their densities arc greater than those of the parent metal, and their rormalion is exothermic. All are strong bases. 

In the report that described the synthesis of 108 (777), Whitmire also observed that the reaction between NaBi03 and methanolic [Fe(CO)s] in the presence of hydroxide afforded the trianionic species [Bi Fe(CO)4 4]3, 110, which was subsequently characterized by X-ray crystallography (775). Cluster 110 contains a central bismuth atom tetrahedrally coordinated by four Fe(CO)4 fragments and is isoelectronic with the anionic tetracobalt-indium complex, 27, and the neutral tetracobalt-germanium, - tin, and -lead complexes, 68, 71, and 72. Oxidation of 110 affords 108 (777), while acidification (772) yields the hydride-containing cluster [BiFe3(CO)9(/i-H)3], 111, which also contains a tetrahedral BiFe3 core. Johnson and Lewis (114) have... 

---