Synthesis and characterization of sterically expanded ansa-η1-fluorenyl-amido complexes

The octamethyloctahydrodibenzofluorenyl (Oct) ligand has been incorporated into twelve ansa -Oct-amido complexes having the general structures Me 2 Si(η 1 -C 29 H 36 )(η 1 -N- t Bu)MX 2 · L or Me 2 Si(η 5 -C 29 H 36 )(η 1 -N- t Bu)MX 2 (M = Zr or Hf): 2 (X = Cl, L = Et 2 O); 3 (X = Br, L = Et 2 O); 4 (X = Me, L = Et 2 O); 5 (X = Me, L = THF); 6 (X = CH 2 Ph); and 7 (X = CH 2 SiMe 3 ). The solid-state structures have been determined for seven of these complexes by X-ray crystallography, revealing η 5 -C 29 H 36 coordination for the ether-free, pseudotetrahedral species 6-Zr , 6-Hf , and 7-Zr , but η 1 -C 29 H 36 coordination for the ether-bound, trigonal bipyramidal species 2-Zr , 3-Zr , 3-Hf , and 5-Zr . The unusual η 1 -C 29 H 36 coordination was assigned because only one metal–carbon bond in each structure was in the range of 2.281–2.330 A; a second metal–carbon distance was found between 2.731 and 2.847 A; the remaining metal–carbon distances were found between 3.130 and 4.029 A. An increase in the hapticity of these and other Oct- and fluorenyl-containing compounds was correlated to a convergence in the carbon–carbon bond lengths within the relevant five-membered rings.