Germyl hydride

An independent and virtually simultaneous report by Eabom and coworkers described the preparation of germyl hydride (5), the ethyl analogue of 3, by an analogous route (equation l)3. However, only one of the diastereomeric menthyloxy derivatives (4) could be separated by crystallization the other was not readily purified. Assignment of absolute configuration was not made for 5 but, based on the sign of rotation, it is most likely R. 

The isopropyl homologue R-6 of the chiral germyl hydrides 3 and 5 was prepared by Carre and Corriu as outlined in equation 24. The route closely parallels that of the previous investigators. 

Lithiation of the germyl hydride S -3 with BuLi in ether and subsequent protonolysis led to recovered hydride of [a]o — 18.5 (86% retention)2. It is assumed that both steps proceed with predominant retention of configuration. Carboxylation of the lithio derivative afforded the carboxylic acid R-12, also with retention of configuration (Scheme 4). The corresponding methyl ester underwent decarbonylation upon heating to afford the methoxy derivative R-15, which was subsequently reduced with LiAlH4 to the (—)-hydride S-... 

The assignment of configuration to these products was made by analogy with the R = CH3 system9. In that case, the two methylated enantiomers were compared with an authentic sample prepared from the known germyl hydride R-5 via the chloro derivative as outlined in equation 5. 

The hydrogermylation of phenylacetylene has been shown to proceed with retention at germanium12. Addition of the germyl hydride 5-3 in the presence of a Pt or Rh catalyst led to the adduct 5-23 as the major product. The enantiomer 5-23 was prepared by addition of tran.s-/3-styryllithium to chlorogermane 5 -7 prepared as shown in Scheme 10. The isopropyl analogues of 5-23 and 5-23 were similarly prepared from hydride 5-612. 

Oxidative addition of germyl compounds to metal centers germyl hydrides, Ge-H... 

Germyl hydrides readily undergo oxidative addition to the low-valent coordinatively unsaturated transition-metal complexes. Optically active [Co(CO)4GeMe(l-Np)Ph] was... 

Germyl copper compounds, obtained in a very low yield by the salt-elimination method42, can be obtained efficiently from the reaction of germyl hydrides with alkoxy... 

The reaction between Pt(0) or Pt(II) hydride precursors and silane or germanes with E-H bonds (E = Si, Ge) can provide a variety of E-H bond activated products, for example, a series of silyl or germyl bridging diplatinum(I) compounds (Eigure 10.19) [130]. Further conversion of these compounds was possible including E-E bond coupling as well as the formation of Pt(II) silyl/germyl hydride. 

---