Synthesis and structure of zirconium(IV) alkyl complexes with bi-, tri-, tetra- and penta-dentate amido ligands
Abstract
The reaction of
C
6
H
10
(NLiSiMe
3
)
2
-1,2
(Li
2
L
1
) with
[ZrCl
4
(thf
)
2
]
(thf = tetrahydrofuran) afforded the tetraamide
[ZrL
1
2
] 1. Similarly treatment of
(RHNSiMe
2
)
2
O (H
2
L
2
,
R = Bu
t
; H
2
L
3
,
R = cyclohexyl) with LiBu
n
followed by
[ZrCl
4
(thf)
2
] led to
[ZrL
2
2
] 2 and [ZrL
3
2
] 3,
respectively. Reaction of Zr(CH
2
Ph)
4
with
H
2
L
3
gave the pale yellow zirconium dibenzyl
compound [Zr(CH
2
Ph)
2
L
3
] 4, while the
analogous reaction with H
2
L
4
(R = quinolin-8-yl) led to ruby-red
[Zr(CH
2
Ph)
2
L
4
] 5. In addition the
bis(pyrrole)
[(2-C
4
H
3
NH)CH![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
NCH
2
]
2
(H
2
L
5
) reacted with
Zr(CH
2
Ph)
4
giving the complex
[Zr(CH
2
Ph)
2
L
5
] 6. The crystal
structures of 1, 4 and 5 have been determined. Compound 1 has a
distorted tetrahedral structure. In 4 and 5 all available donor atoms
co-ordinate to zirconium, including the silyl ether moiety, leading to a
distorted trigonal bipyramidal structure for 4 and an approximately
pentagonal bipyramidal geometry for 5. Although L
3
and
L
4
have flexible frameworks, in both 4 and 5 the heteroatom
donors and the metal form an essentially coplanar arrangement. The
zirconium–amido nitrogen distances proved to be highly variable,
depending on the degree of electron deficiency and the co-ordination of
the metal centres, and range from an average of 2.056 Å in 1 and
2.096 Å in 4 to 2.169 Å in 5. Complexes 1 and 4 activated
with methylaluminoxane gave high molecular weight polyethylene with
moderate activity.
)
2
]
(thf = tetrahydrofuran) afforded the tetraamide
[ZrL
1
2
] 1. Similarly treatment of
(RHNSiMe
2
)
2
O (H
2
L
2
,
R = Bu
t
; H
2
L
3
,
R = cyclohexyl) with LiBu
n
followed by
[ZrCl
4
(thf)
2
] led to
[ZrL
2
2
] 2 and [ZrL
3
2
] 3,
respectively. Reaction of Zr(CH
2
Ph)
4
with
H
2
L
3
gave the pale yellow zirconium dibenzyl
compound [Zr(CH
2
Ph)
2
L
3
] 4, while the
analogous reaction with H
2
L
4
(R = quinolin-8-yl) led to ruby-red
[Zr(CH
2
Ph)
2
L
4
] 5. In addition the
bis(pyrrole)
[(2-C
4
H
3
NH)CHNCH
2
]
2
(H
2
L
5
) reacted with
Zr(CH
2
Ph)
4
giving the complex
[Zr(CH
2
Ph)
2
L
5
] 6. The crystal
structures of 1, 4 and 5 have been determined. Compound 1 has a
distorted tetrahedral structure. In 4 and 5 all available donor atoms
co-ordinate to zirconium, including the silyl ether moiety, leading to a
distorted trigonal bipyramidal structure for 4 and an approximately
pentagonal bipyramidal geometry for 5. Although L
3
and
L
4
have flexible frameworks, in both 4 and 5 the heteroatom
donors and the metal form an essentially coplanar arrangement. The
zirconium–amido nitrogen distances proved to be highly variable,
depending on the degree of electron deficiency and the co-ordination of
the metal centres, and range from an average of 2.056 Å in 1 and
2.096 Å in 4 to 2.169 Å in 5. Complexes 1 and 4 activated
with methylaluminoxane gave high molecular weight polyethylene with
moderate activity.
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