Properties of trifluoromethylgermanes. Adduct formation and substitution reactions of (CF 3) nGeX 4− n ( n = 2–4) with NH 3

Abstract

Crystalline adducts of compositions (CF 3) 4Ge· nRNH 2 (R = H: n = 2, 3; R = CH 3: n = 1, 2 with dissociation vapour pressures at 22°C of 70 (R = H) and 75 mbar (R = CH 3) have been isolated. From their Raman spectra both NH 3 adducts are judged to have a cis-configurated octahedral coordination at the germanium atom. Reaction of (CF 3) 3Gel with NH 3 yielded the digermazane [(CF 3) 3Ge] 2NH whereas the cyclic trimers [(CF 3) 2GeNR] 3 (R = H, CH 3) were obtained from (CF 3) 2GeI 2 and RNH 2. IR spectra show that NH 3 and [(CF 3) 3Ge] 2NH undergo equilibration to give (CF 3) 3GeNH 2 in the gas phase, with simultaneous formation of a solid phase with the composition (CF 3) 3GeNH 2·2NH 3. Addition of trimethyl- or triethyl-amine to [(CF 3) 3Ge] 2NH yields solid 1:1 adducts. The vibration spectra of [(CF 3) 3Ge] 2NH, (CF 3) 3GeNH 2 and of the NH 3 adducts of (CF 3) 4Ge and of their deuterated analogues have been analyzed. A GeNGe bond angle of 130° was deduced for [(CF 3) 3Ge] 2NH from model force constant calculations.