Ge Compound

The occurrence of more than two v(CO) bands in the IR spectrum of Cl2MeSiFe(CO)2Cp has led to the suggestion that conformational or rotational isomers are present, and the simple NMR spectrum is explained by assuming rapid interconversion of the two species 148). Assignments of particular v(CO) bands to the corresponding conformers have been made on the basis of v CO) studies 93, 93a). A similar situation has been observed in the analogous Sn and Ge compounds, and, in the latter, two of the four CO bands disappear at —40° C in agreement with the postulate 193). 

Planar distannacyclobutene ring. The C=C bond 248 is shorter than expected and the C—Sn bond longer. This may explain the slow dissociation this compound undergoes in solution. In the analogous Ge compound this ring is twisted. 

Organometallic compounds containing metal-carbon bonds are formed by nearly all metals. Some analogous Si and Ge compounds are known. 

Experimentalists have been particularly well served by numerous reviews from some of the leading workers in the field. For example, Brook and Baines (76) have reviewed silenes, Wiberg (77) discussed M=C and M=N double bonds (M = Si and Ge), Cowley and Norman (78) have reviewed M=M (M, M = group 14 and 15 elements) double bonds, Raabe and Michl (79,80) have provided complementary reviews of multiple bonds to silicon, West (81) has reviewed disilene chemistry, Masamune (82) has reviewed the work of his group on Si=Si and Ge=Ge compounds, and most recently Barrau et al. (83) have summarized multiple bonds to germanium. Studies from the reactive intermediates era of this field are beautifully summarized by Gusel nikov and Nametkin (84). 

This article starts with a discussion of the parent hydrides, MH (M = C, Si, and Ge, n = 2-4), highlighting the major differences between the methane series and the silane and germane series. Some attention is paid to substituent effects on bond energies and geometries, and we introduce the important notion of the divalent state stabilization energy (DSSE). After laying this foundation, Si=C and Ge=C compounds are reviewed. This is followed by Si=Si, Ge=Ge, and Ge=Si doubly bonded structures and their isomers. Finally, triply bonded Si==C, Si=Si, and Ge=Ge compounds are briefly considered. 

---