CONCERNING THE SILICON-GERMANIUM BOND - MASS-SPECTRAL FRAGMENTATIONS OF ISOMERIC SI-GE COMPOUNDS R(3)EE'R(3) (E=SI, E'=GE, R=PH, ME, (ETA(5)-C5H4)FE(C5H5), (ETA(5)-C5H5)FE(CO)(2) AND (ETA(5)-C9H7)FE(CO)(2))

Isomeric pairs of silicon-germanium compounds containing a Si-Ge bond (Me,SiGePh(3) (I) and Ph(3)SiGeMe(3) (II); FpSiMe(2)GeMe(3) (III) and FpGeMe(2)SiMe(3) (IV) (Fp=(eta(5)-C5H5)Fe(CO)(2)); IFpSiMe(2)GeMe(3) ( V) and IFpGeMe(2)SiMe(3) (VI) (IFp=(eta(5)-C9H7)Fe(CO)(2)); IFpSiMe(2) GePh(3) (VII) and IFpGeMe(2)SiPh(3) (VIII)) and the complex FcSiMe(2)G eMe(2)Fc (IX) (Fc=ferrocenyl) have been synthesized and examined by ma ss spectrometry. The R(3)SiGeR(3)' compounds I and II exhibit consider able exchange of R groups to produce [R(3-n)R(n)'Si](+) and [R(3-n)'R( n)Ge](+) ions in progressively lesser amounts as n = 1 --> 2 --> 3. Fo r the metal-substituted complexes containing the grouping Fe-Si-Ge fra gmentation occurs predominantly via Si-Ge bond cleavage with formation of ions containing the silylene ligand [Fe=SiR(2)](+). Complexes with the Fe-Ge-Si backbone undergo preferential scission of the Fe-Ge bond , illustrating the general bond strength trend Fe-Si > Si-Ge. Upon dir ect cleavage of the Si-Ge bond in R(3)SiGeR(3) compounds, the percenta ge of the charge carried by [R(3)Si](+) ions significantly exceeds tha t carried by [R(3)Ge](+) ions, reflecting the greater electronegativit y of Ge polarizing the Si-Ge bond.