Issue 7, 2005

Coordination complexes of bivalent ansa-ytterbocenes: synthesis, structure and comparison with related unbridged ytterbocenes and ansa-ferrocenes

Abstract

The dimethylsilyl bridged bis(cyclopentadienide) ligands, {[2,4-(Me3C)2C5H2]2SiMe2}2− and {[(Me3Si)2C5H2]2SiMe2}2−, have been prepared and used for the preparation of ansa-metallocene derivatives of iron and bivalent ytterbium metallocene adducts. The structures of two ansa-ferrocenes, as well as that of the free tetraene [2,4-(Me3C)2C5H3]2SiMe2, have been determined by X-ray crystallography; the lability of the Me3Si group leads to a different ring substitution pattern in the structure of ansa-{[3,4-(Me3Si)2C5H2]2SiMe2}Fe compared with that in ansa-{[2,4-(Me3C)2C5H2]2SiMe2}Fe. The structures of ansa-{[2,4-(Me3C)2C5H2]2SiMe2}Yb(OEt2) and an analogous ansa-ytterbocene isocyanide complex are also reported, and compared with those of non-bridged ytterbocene diethyl ether complexes. Short distances from the ytterbium atom to the diethyl ether β carbon atoms are observed in several structures, consistent with the tendency of ytterbium to maximise its coordination number. Spectroscopic properties for the ansa-ytterbocene etherates and the isocyanide complex are reported and compared with the corresponding adducts of non-bridged ytterbocenes. The reduced Cp(centroid)–metal–Cp(centroid) angle enforced by the ansa-bridge does not lead to significant changes in the optical spectra compared with unbridged metallocene diethyl ether and tetrahydrofuran adducts, but significant changes are observed in the isocyanide adducts; a model rationalising the red and blue shifts of λmax is proposed.

Graphical abstract: Coordination complexes of bivalent ansa-ytterbocenes: synthesis, structure and comparison with related unbridged ytterbocenes and ansa-ferrocenes

Supplementary files

Article information

Article type
Paper
Submitted
09 Dec 2004
Accepted
11 Mar 2005
First published
20 May 2005

New J. Chem., 2005,29, 919-927

Coordination complexes of bivalent ansa-ytterbocenes: synthesis, structure and comparison with related unbridged ytterbocenes and ansa-ferrocenes

M. Schultz, C. D. Sofield, M. D. Walter and R. A. Andersen, New J. Chem., 2005, 29, 919 DOI: 10.1039/B418550A

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