Rotational tunneling of methyl groups in partially deuterated tetramethyltin compounds,(CH3) x Sn (CD3) 4− x with x= 1 and 3, and in various isotopic mixtures,[(CH3) 4Sn] x [Sn (CD3) 4] 1− x, x= 0.027, 0.20, and 0.50, and [CH3Sn (CD3) 3] x [Sn (CD3) 4] 1− x, x= 0.10, respectively, has been studied using the inelastic neutron??scattering (INS) technique. Compared with the INS spectrum of fully protonated tetramethyltin,(CH3) 4Sn, ...