Further studies of the reactivity of cyclopentadienyl, substituted
cyclopentadienyl and indenyl ligands with
M2Cl2(NMe2)4
(M = Mo or W). Crystal and molecular structures
of
Mo2(C9H7)2(NMe2)
4 and
W2(C5H4Me)2(NMe2
)4
Abstract
Metathetic reactions employing
1,2-M
2
Cl
2
(NMe
2
)
4
compounds
(M = Mo or W) and the sodium or lithium salts of
cyclopentadienyl (Cp), methylcyclopentadienyl, indenyl
(C
9
H
7
) and bis(methyl)bis(cyclopentadienyl)silyl,
Me
2
Si(C
5
H
4
)
2
2-
, anions carried out in hydrocarbon or ether solvents have led to
the isolation of orange, hydrocarbon-soluble, air-sensitive crystalline
solids of formula
1,2-M
2
R
2
(NMe
2
)
4
. In solution
the NMR data are consistent with C
2
symmetry and
restricted rotation about the M–N bonds. The complexes where
R = C
5
H
5
show only one CH resonance
in their
1
H NMR spectra consistent with ring whizzing. The
solid-state and molecular structures of
Mo
2
(C
9
H
7
)
2
(NMe
2
)
4
and
W
2
(C
5
H
4
Me)
2
(NMe
2
)
4
reveal that the indenyl and C
5
H
4
Me
ligands are η
3
-bonded to the M![[triple bond, length as m-dash]](https://www.rsc.org/images/entities/char_e002.gif)
M
6+
moiety with three M–C distances within the range 2.35 to 2.52
Å and two distinctly larger, ca. 2.75–2.80 Å.
The M–M distances, 2.252(1) Å (M = Mo) and
2.345(1) Å (M = W) and M–N distances, 1.96 to
1.99 Å, are similar to those for
1,2-M
2
R
2
(NMe
2
)
4
compounds,
where R = alkyl or aryl. The linked Cp complex
W
2
[(C
5
H
4
)
2
SiMe
2
]
(NMe
2
)
4
was found to show similar structural
features although the molecular structure suffered from disorder. The
data reported, together with previous results, show that
cyclopentadienyl ligands compete favorably with the NMe
2
ligand as σ
2
π
2
donors,
η
3
-C
5
. The η
5
-C
5
mode is not favoured (on electronic grounds) because this would require
disruption of the M–M triple bond in the presence of four
Me
2
N σ
2
π
2
donors.
M
6+
moiety with three M–C distances within the range 2.35 to 2.52
Å and two distinctly larger, ca. 2.75–2.80 Å.
The M–M distances, 2.252(1) Å (M = Mo) and
2.345(1) Å (M = W) and M–N distances, 1.96 to
1.99 Å, are similar to those for
1,2-M
2
R
2
(NMe
2
)
4
compounds,
where R = alkyl or aryl. The linked Cp complex
W
2
[(C
5
H
4
)
2
SiMe
2
]
(NMe
2
)
4
was found to show similar structural
features although the molecular structure suffered from disorder. The
data reported, together with previous results, show that
cyclopentadienyl ligands compete favorably with the NMe
2
ligand as σ
2
π
2
donors,
η
3
-C
5
. The η
5
-C
5
mode is not favoured (on electronic grounds) because this would require
disruption of the M–M triple bond in the presence of four
Me
2
N σ
2
π
2
donors.
Please wait while we load your content...
