Rotational tunnelling and librations of the methyl groups in (CH3)2SnC12 measured by inelastic neutron scattering are explained on the basic of coupled pairs of CH 3 groups. The self and the interaction part of the rotational potential are determined to be (V3, W3)=(17.5 meV, 10.9 meV). Thus, in agreement with our expectation from the crystallographic structure, the frustrated coupling is realized in (CH3)2SnC12 where the interaction W 3 counteracts the single particle potential V 3.