om701133e_si_001.pdf (1.03 MB)

Octa- and Nonamethylfluorenyl Complexes of Zr(II), Zr(IV), and Hf(IV). Investigation of Steric and Electronic Effects

Download (1.03 MB)
journal contribution
posted on 24.03.2008 by Patrick Bazinet, T. Don Tilley
The lithium salts of 1,2,3,4,5,6,7,8-octamethylfluorenyl (Flu′′) and 1,2,3,4,5,6,7,8,9-nonamethylfluorenyl (Flu*) were reacted with Zr and Hf half-sandwich complexes to generate mixed-ligand-metallocenes Cp′′Flu′′ZrCl2 (1), Cp′′Flu*ZrCl2 (2), and Cp*Flu*HfCl2 (3) (Cp′′ = 1,3-(SiMe3)2C5H3, Cp* = C5Me5). Reaction of the metallocene dichlorides with MeLi yielded the dimethyl derivatives Cp′′Flu*ZrMe2 (4) and Cp*Flu*HfMe2 (5). Reduction of the zirconocene dichlorides in the presence of CO gas yielded the dicarbonyl derivatives Cp′′Flu′′Zr(CO)2 (6) and Cp′′Flu*Zr(CO)2 (7), which represent the first examples of zirconocene dicarbonyls containing a fluorenyl ligand derivative. Structural characterization of the zirconocene dichloride 2 and the dicarbonyls 6 and 7 revealed that the methylated fluorenyl ligands adopt an η5-coordination and display a twisted tricyclic core in each case. A spectroscopic study of a small series of zirconocene dicarbonyl analogues indicates that the methylated fluorenyl ligands are strong electron donors and similar in this regard to heptamethylindenyl (Ind*) and Cp*.