Methyl Displacements from Cyclopentadienyl Ring Planes in Sterically Crowded (C_5Me_5)_3M Complexes

摘要

The displacements of the methyl substituents away from the metal and out of the cyclopentadienyl ring plane are compared in sterically crowded (C_5Me_5)_3M complexes vs sterically normal f-element complexes in an attempt to evaluate the utility of this parameter in predicting unusual (C_5Me_5)~(1-) ring reactivity.The out-of-plane displacements of 16 sterically crowded tris(cyclopentadienyl) complexes of general formula (C_5Me_5)_3M,(Cs_5Me_4R)_3M (R=Et,'Pr,~tBu,SiMe_3),(C_5Me_5)_3MX (X=anion),and (C_5Me_5)_3ML (L=neutral ligand) are compared with [(C_5Me_5)_2U]_2(C_6H_6),(C_5Me_5)_2Sm(PC_4H_2~tBu_2),and 33 representative examples of f-element bis(cyclopentadienyl) complexes with normal cyclopentadienyl behavior and coordination numbers ranging from 6 to 10.In general,the methyl displacement values of sterically crowded complexes overlap with those in the other complexes,which demonstrates that the basis of the structural distortions is complex.However,if the most extreme out-of-plane displacement in each of the sterically crowded complexes is examined vs the analogous maximum out-of-plane displacement in less crowded systems,there appears to be a basis for predicting cyclopentadienyl reactivity.