Lithium cyclopentadienide adds to a variety of
isocyanates [R−NCO, R = tert-butyl
(a), n-butyl (b), cyclohexyl
(c), phenyl (d), 3-pyridyl (e),
2-tetrahydropyranyl (f), adamantyl
(g)] to yield the monocarbamoyl-substituted
cyclopentadienides
C5H4CONHR-
3
admixed
with varying amounts of the respective 1,2-dicarbamoyl-substituted
C5H3(CONHR)2
-
systems
4 and a corresponding quantity of the
C5H5
- starting material.
Subsequent treatment of
these reaction mixtures with anhydrous FeCl2 gave the
1,1‘-dicarbamoylferrocenes 6 and
the corresponding monocarbamoylferrocenes 5, which were
easily separated by chromatography. The carbamoylferrocenes 5b, 5c, and
6d were characterized by X-ray crystal
structure
analyses. The (N-phenyl- and
(N-adamantylcarbamoyl)cyclopentadienides were treated
with
CpTiCl3 to give the carboxamide-substituted titanocene
dichloride complexes
[Cp(C5H4CONHR)TiCl2] 8a (R = Ph) and
8b (R = adamantyl), respectively. Complex
8b was also
characterized by X-ray diffraction. The valine ester-derived
isocyanate reacts with lithium
cyclopentadienide to give the N-valinyl-substituted
carbamoylcyclopentadienide 3h. Subsequent treatment with FeCl2 or FeCl2/CpLi,
respectively, produces the 1,1‘-difunctionalized
ferrocene 6h or the monofunctionalized ferrocene
5h. Both complexes were characterized
by X-ray crystal structure analyses.