The hindered inversion of the seven-membered ring in N-(chlorodimethylgermylmethyl)- and N-(chlorodimethylstannylmethyl)hexahydroazepin-2-ones

The stereochemical flexibility of N-(chlorodimethylgermylmethyl)- and N-(ch lorodimethylstannylmethyl) hexahydroazepin-2-ones was studied by dynamic NM R spectroscopy. Protons of the NCH2M and MMe2 groups (M = Ge, Sn) were show n to be anisochronic at low temperatures (<-70 degrees C). The free activat ion energy of the process resulting in chemical equivalence of the protons indicated was determined. The anisochronicity of signals observed is due to the restricted inversion of the seven-membered cycle.