Synthesis and characterisation of 1-alkyl-2-imidazoline complexes of
noble metals; crystal structure of
trans-[PtCl2{![[upper bond 1 start]](https://www.rsc.org/images/entities/char_e010.gif)
N![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
C(H)N(Et)CH2C![[upper bond 1 end]](https://www.rsc.org/images/entities/char_e011.gif)
H2}(PEt3)]
Abstract
Treatment of a 1-alkyl-2-imidazoline
N(R)(CH
2
)
2
NCH with a
µ-dichloro-dirhodium(I) or -diplatinum(II)
complex [{Rh(µ-Cl)(cod)}
2
] or
[{Pt(µ-Cl)Cl(PEt
3
)}
2
] gave the
mononuclear 1-alkyl-2-imidazoline complex
[RhCl{NC(H)N(R)CH
2
CH
2
}(cod)] (R = Et 1a or CH
2
Ph
1b) or
trans-[PtCl
2
{NC(H)N(R)CH
2
CH
2
}(PEt
3
)]
(R = Et 2a or CH
2
Ph 2b)
(cod = cycloocta-1,5-diene). A single-crystal X-ray
diffraction study of 2a revealed it to have a square-planar
geometry about platinum, the imidazoline ring being coplanar with this
plane, and a Pt–N distance of 2.088(11) Å; the
Pt–P bond length of 2.231(4) Å indicates that the
imidazoline ligand has a marginally stronger trans influence
than analogues of its isomer such as
CN(R)(CH
2
)
2
NR. The rhodium complexes
1a and 1b have been shown to catalyse cyclopropanation
of styrene and ethyl diazoacetate in high yields.
N(R)(CH
2
)
2
NCH with a
µ-dichloro-dirhodium(I) or -diplatinum(II)
complex [{Rh(µ-Cl)(cod)}
2
] or
[{Pt(µ-Cl)Cl(PEt
3
)}
2
] gave the
mononuclear 1-alkyl-2-imidazoline complex
[RhCl{NC(H)N(R)CH
2
CH
2
}(cod)] (R = Et 1a or CH
2
Ph
1b) or
trans-[PtCl
2
{NC(H)N(R)CH
2
CH
2
}(PEt
3
)]
(R = Et 2a or CH
2
Ph 2b)
(cod = cycloocta-1,5-diene). A single-crystal X-ray
diffraction study of 2a revealed it to have a square-planar
geometry about platinum, the imidazoline ring being coplanar with this
plane, and a Pt–N distance of 2.088(11) Å; the
Pt–P bond length of 2.231(4) Å indicates that the
imidazoline ligand has a marginally stronger trans influence
than analogues of its isomer such as
CN(R)(CH
2
)
2
NR. The rhodium complexes
1a and 1b have been shown to catalyse cyclopropanation
of styrene and ethyl diazoacetate in high yields.
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![[upper bond 1 start]](https://www.rsc.org/images/entities/h2_char_e010.gif)
N![[double bond, length as m-dash]](https://www.rsc.org/images/entities/h2_char_e001.gif)
C(H)N(Et)CH2C![[upper bond 1 end]](https://www.rsc.org/images/entities/h2_char_e011.gif)
H2}(PEt3)]
