Halide dihydrides

The halide groups can be replaced by other substituents like hydride or alkyl [86]. When the naphthyl (np) RuHnp(dmpe)2 is heated, the ligand undergoes an internal metallation to afford a dimer [87] (it was originally believed to be a monomer), though Ru(dmpe)2 has been isolated by photolysis of its dihydride, in matrixes at 12K (Figure 1.29) [88],... 

The mixed halide-hydrides PhjSnHCl and PhjSnHBr have been prepared from the reaction of diphenyltin dihydride with the appropriate diphenyltin dihalides (274). 

The reversible hydrogenolysis of trfl -(Ph2MeSi)2Pt(PMe2Ph)2 has been discussed in Sections II,B,4 and II,B,7. A mechanism similar to that postulated for hydrogen halide reactions [e.g., Eq. (78)] has been suggested 71, 114) such a dihydride intermediate has not been detected, but some support comes from the identification of H2XSiPtl2(H)(PEt3)2 (X = Cl, I), as shown in Eq. (79) 27). Further discussion is in Section III. 

The occurrence of transition and rare earth metal hydrides is shown in Figure 1. Not shown are the alkali hydrides and alkaline earth dihydrides that bear a close resemblence to their halide counterparts. Also not shown are compounds formed from elements to the right that are the topic of much of the rest of this symposium volume. 

The absence of any derivatives of selenophene or tellurophene from the chemical catalogues makes their laboratory synthesis an unavoidable point of departure for any study of their chemistry or other properties. As the range of potential organic selenium or tellurium precursors is also extremely restricted, there has been particular emphasis on routes starting from simple inorganic species such as the elements themselves, the dioxides, the halides, the dihydrides and, in the case of selenium, the selenocyanate anion. 

The formation of Si-X bonds was confirmed by measurements of XPS spectra and flat band potentials. For (100) surface, back-bond oxidation occurs simultaneously with the Si-X formation under the same conditions, though it is negligible for Si fill). The mechanism of the surface reactions can be explained by hole injection by an oxidant, followed by the nucleophilic attack of halide ions or water molecules.32,33) For dihydride (=Si H2) bonds on H-Si (100), for example, the reactions at the initial stage can be expressed as follows ... 

Multimetallic complexes, molybdenocene dihydrides, 5, 570 Multimetallic nickel-alkynes, synthesis and reactivity, 8, 145 Multinuclear chromium(II) complexes, with halides, alkyls,... 

However, as also observed in germanium chemistry, a mixture of dihydride with an excess of lithiated reagent behaves as a stannyldianion in reactions with organic halides, polyformaldehyde or epoxides (Scheme 7)29, and it thus appears as an interesting synthetic reagent. 

Regeneratable polymeric organotin dihydride beads have been used to reduce halides selectively (e.g. 3-bromocamphor to camphor).52 /3-Unsubstituted cyclohex-enones undergo exclusive and almost quantitative 1,4-reduction by potassium tri-s-butylborohydride to the corresponding saturated ketone [e.g. (16)] 53 reductive alkylation of carvone proceeds similarly to (17 R = Me, X = H).53 In contrast,... 

Osmium pentacarbonyl is a convenient precursor to other osmium carbonyl complexes. Hydrogenation gives the dihydride OsH2(CO)4. This hydride is not acidic with a p/fa of 18.5 but it can be deprotonated by strong bases to give [OsH(CO)4] and reduced by sodium (Scheme 23). Substitution of CO on Os(CO)5 by trialkyl or triarylphosphines, arsines, or stibenes gives Os(CO)4L or Os(CO)3L2. Other carbonyl phosphine complexes result from the reduction of osmium halides by alcohols in the presence of the tertiary phosphine. 

The bis(cyclopentadienyl)dihydrides of Mo serve as precursors for the generation of neutral, low-valent, group-VI metallocenes. Reduction of the readily available dihydride with MeLi followed by reaction with RX gives metal alkyl halides ... 

Ruthenium bis (hydrogen dihydride), reacted with alkyl and aryl halides to form a five-coordinate complex ... 

By the action of LiAlH4 on the halide (or in the case of Be on the dialkyls) a number of other hydrides have been prepared, including the dihydrides of Be, Zn, Cd, and Hg, trihydrides of Ga, In, and Tl, and CuH. Some of these are extremely unstable, those of Cd and Hg decomposing at temperatures below 0°C. Pure crystalline BeH2 has not been prepared, but a crystalline amine complex has been made for which the bridged structure (a) has been suggested Be—H bridges have... 

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