An improved procedure for the preparation of vinylcyclopentadienyllithium (1) from 6-methylfulvene and lithium diisopropylamide in THF solution has been developed. Reaction of 1 with thallium ethoxide in THF has produced vinylcyclopentadienylthallium (3). Compounds 1 and 3 have been used in the synthesis of vinyl- (4) and 1,1′-divinyltitanocene dichloride (5). Treatment of 1,2,3,4,6-pentamethylfulvene with lithium diisopropylamide in THF solution has afforded vinyltetramethylcyclopentadienyllithium (2) in high yield. Reactions of 2 with FeCl2 or TiCl4 have led to bis(η5-vinyltetramethylcyclopentadienyl)iron (7) and (η5-vinyltetramethylcyclopentadienyl)titanium trichloride (8), respectively. Compound 8 reacts with (η5-C5H5)T1 to produce 1-vinyl-2,3,4,5-tetramethyltitanocene dichloride (9) in high yield. The crystal structure of 5 has been determined. 5 is monoclinic, C21/c, with a = 14.420(3), b = 6.610(2), c = 14.111(3) Å, β = 102.18(2)° and Dcalc = 1.52 g cm-3 for Z = 4. The Ti atom resides on a crystallographic two-fold axis. The η5-vinylcyclopentadienyl groups are slightly staggered with the carbons bonded to the vinyl groups next to one another and between the ClTiCl bond. The TiC(η5) separations range from 2.343(4) to 2.450(3) Å, the latter values for the carbon atoms bonded to the vinyl group.
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Acknowledgement is made to the donors to the Petroleum Research Fund, administered by the American Chemical Society, and to Sekisui Chemical Company for support of this research program. We also wish to thank Prof. Helmut Alt for assistance in obtaining the mass spectra. The National Science Foundation Chemical Instrumentation Program provide4 funds used to purchase the diffractometer (N.I.U.).