Dihydride anion

The complex OsHCl(CO)(P Pr3)2 reacts with n-BuLi in hexane at room temperature to give the dihydride OsH2(CO)(r 2-CH2=CHEt)(P,Pr3)2, which is isolated as a colorless oil in quantitative yield. The reaction most probably involves the replacement of the CP anion by a butyl group to give OsH( -Bu)(CO)(P Pr3)2, which evolves into the dihydride derivative by a hydrogen (3-elimination reaction (Scheme 19).57 Treatment of OsHCl(CO)(P Pr3)2 with C3H5MgBr affords OsH( n3-C3H5)(CO)(P,Pr3)2.58... 

Acidification of the anion leads progressively to [HOs6(CO)18] and H2Os6(CO)i8. These two compounds may be compared with the related ruthenium complexes. The dihydride, H2Ru (CO)x8, was initially prepared by interaction of [Mn(CO)5] with Ru3(CO)12 (222). However, a... 

When a large excess of base is used, the anion Ru CO) 8 may be isolated in good yields by the use of large cations. Acidification of the anion yields the dihydride H2Ru6(CO),8. 

DR. WILLIAM TROGLER (Northwestern University) You looked at exchange between the monohydride anion of osmium and the neutral dihydride. Have you ever studied the bimolecular self-exchange for a neutral dihydride This could be followed by mixing one sample labelled with deuterium and one with hydrogen. 

The methods described here are based on the thermal stability of such clusters under CO pressure.4 In the case of Co2Fe(CO)9S, the complex itself is stable under hydroformylation conditions (130-180 °C, 50-150 bar CO and H2) and is formed under such conditions from almost every sulfur-containing substance, iron, cobalt, and carbon monoxide.1 Ethanethiol is used in the procedure as the sulfur source because of its reactivity. The dihydride cluster Fe3H2(CO)9S is not directly accessible by this method because it is a thermally much less stable species but the anion Fe3H(CO)9S" can be prepared in this way and its acidification yields the desired complex. 

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 foregoing remarks do not hold, of course, for the dihydrides of the triva-lent lanthanides. They exhibit metallic conduction (10), as would be expected, since their conduction band is only somewhat depleted. One would expect them to display a tendency to order at low temperatures, but it seems not unreasonable to expect that this tendency would be weaker than the corresponding element, in view of the decreased electron concentration, and the ordering would hence occur at lower temperatures. This was in fact observed for HoH2, which exhibits (6) a Neel point at 8° K., as coippared to 135° K. for Ho. It is also observed in the present work for the terbium dihydrides, whose Neel points are 40° to 50° K., whereas that for the element is 241° K. These properties are compatible with the notion that hydrogen in all the lanthanide hydrides is anionic. On this basis the dihydrides appear as an intermediate form between the truly metallic elements on the one hand and the truly ionic or saline trihydrides on the other. 

There are relatively few examples of anionic ruthenium hydrido complexes. Thus, several papers have discussed the preparation of the [RuH6]4 ion from Ru, H2 and various lanthanide dihydrides at 800°C.2490,2491 The 99Ru Mossbauer spectra at 4.2 K for various M2[RuH6] (M = Ca, Sr, Eu, Y) are consistent with diamagnetic Ru11 centres.2492... 

Addition of protons to anionic clusters to generate hydrides leaves the cluster electron count unaffected, yet the process is sometimes accompanied by structural changes. For example, both [Os6(CO)i8] (87) and [Os6(CO)igH] (88) have octahedral arrangements of metal atoms as predicted by Wade s rules. In the dihydride Osg(CO)i8H2, however, the metal atoms describe a capped square-based pyramid (87). 

This is the best method for preparing Zn dihydride, because using equimol ratios of NaH and ZnCl or LiH and ZnBrj gives Zn dihydride free from anionic species. Sodium hydride and Znl in a 2 1 ratio also give ZnHj, but if the ratio of alkali-metal hydride to ZnX, is increased, then the ZnH, is contaminated with complex hydrides . ... 

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