Zr[(SiMe2tBu)2(H)-ABA]Cl3 (6c), was also analysed by X-ray diffraction and shown to exhibit analogous structural characteristics. Low-temperature NMR studies revealed all these complexes to be fluxional and permitted an insight into the molecular structures in solution. The ABA framework undergoes a rocking motion about the corresponding ZrN2 plane, whose activation energy is between 37 and 43 kJ mol−1. Compounds