Reaction of octacarbonyldicobalt with organo-silanes, -germanes, and -stannanes: formation, properties, and vibrational spectra of trimethylgermyltetracarbonylcobalt and related complexes

Abstract

The hydrides R₃MH (R = Me, M = Si, Ge, or Sn; R = Et, M = Ge) react exothermically with Co₂(CO)₈ at 20 °C affording in high yield the complexes R₃MCo(CO)₄[R = Me, M = Si (I); M = Ge (II); M = Sn (III); and R = Et, M = Ge (IV)]. Conversion of (I) to (II) or (III) and of (II) to (III) occurs on reaction with Me₃MH (M = Ge or Sn), and (II) can also be prepared from (I) with Me₃GeBr. The Ge–Co bond in (II) is cleaved by HCl or HgCl₂; (II) with Et₃N or piperidine forms tetracarbonylcobaltate adducts. The vibrational spectra of (II)–(IV) are reported, with ν(M–Co) assigned to polarised Raman shifts respectively at 192,177, and 188 cm^–1. Variation with M of the vapour-phase i.r.-intensity of one of the two a₁ CO stretching fundamentals expected for C_3v symmetry points to a significant out-of-plane displacement of equatorial carbonyl groups in the direction of the silicon atom in (I), but with no analogous effect in (II) or (III). Deviations from C_3v selection rules observed in the solid state for (II) and (III) are also discussed.