Regioselective reactions of isothiocyanates with the titanocene
vinylidene fragment
[Ti(![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
CCH2)(η-C5Me
5)2]. Crystal and molecular structure of
[![[upper bond 1 start]](https://www.rsc.org/images/entities/char_e010.gif)
Ti{SC(NC6H11)C![[upper bond 1 end]](https://www.rsc.org/images/entities/char_e011.gif)
CH2}(η-C5Me5
)2]
Abstract
The titanocene vinylidene intermediate
[Ti(CCH
2
)(η-C
5
Me
5
)
2
] 1 formed by ethane or methane elimination from
[Ti(CH
2
CH
2
CCH
2
)(η-C
5
Me
5
)
2
] 2 or
[Ti(CHCH
2
)Me(η-C
5
Me
5
)
2
] 3 respectively, reacted with isothiocyanates RNCS
(R = C
6
H
11
a, Ph b or Bu
t
c) by a [2 + 2] cycloaddition, to give the titanathietane
complexes
[Ti{SC(NR)CCH
2
}(
η-C
5
Me
5
)
2
]. The crystal structure
of the R = C
6
H
11
complex has been
determined. In all cases the regioisomer in which the sulfur atom is
bonded to titanium is observed as the primary product. Upon heating in
the presence of pyridine a rearrangement to the regioisomeric
titanacyclobutane derivative
[Ti{C(NR)SCCH
2
}(
η-C
5
Me
5
)
2
] was observed. The
regioselectivity of the formation of the complexes 5 and 7 is discussed
on the basis of ab initio calculations at the
Hartree–Fock level of theory, with an effective core potential
basis set.
CCH
2
)(η-C
5
Me
5
)
2
] 1 formed by ethane or methane elimination from
[Ti(CH
2
CH
2
CCH
2
)(η-C
5
Me
5
)
2
] 2 or
[Ti(CHCH
2
)Me(η-C
5
Me
5
)
2
] 3 respectively, reacted with isothiocyanates RNCS
(R = C
6
H
11
a, Ph b or Bu
t
c) by a [2 + 2] cycloaddition, to give the titanathietane
complexes
[Ti{SC(NR)CCH
2
}(
η-C
5
Me
5
)
2
]. The crystal structure
of the R = C
6
H
11
complex has been
determined. In all cases the regioisomer in which the sulfur atom is
bonded to titanium is observed as the primary product. Upon heating in
the presence of pyridine a rearrangement to the regioisomeric
titanacyclobutane derivative
[Ti{C(NR)SCCH
2
}(
η-C
5
Me
5
)
2
] was observed. The
regioselectivity of the formation of the complexes 5 and 7 is discussed
on the basis of ab initio calculations at the
Hartree–Fock level of theory, with an effective core potential
basis set.
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![[double bond, length as m-dash]](https://www.rsc.org/images/entities/h2_char_e001.gif)
C![[upper bond 1 start]](https://www.rsc.org/images/entities/h2_char_e010.gif)
Ti{SC(![[upper bond 1 end]](https://www.rsc.org/images/entities/h2_char_e011.gif)
