Site-selective substitution and vinylidene–alkylidyne–vinylidene interconversion in dimolybdenum–ruthenium clusters
Abstract
The thermal reaction of the dimolybdenum–ruthenium vinylidene
clusters
[Mo
2
Ru(µ
3
-C![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
CHR)(CO)
7
(η-C
5
H
5
)
2
]
(R = H 1a, Me 1b, Ph 1c or CO
2
Me 1d) with the
tertiary phosphine PPh
2
Me afforded the monosubstituted
complexes
[Mo
2
Ru(µ
3
-CCHR)(CO)
6
(PPh
2
Me)(η-C
5
H
5
)
2
]
2a–2d in excellent yields. The products exist as single isomers in
which site-selective substitution of a CO ligand has occurred
exclusively at the ruthenium atom. The crystal structure of 2b has been
determined by X-ray diffraction; the geometry of the vinylidene ligand
is identical to that previously found in the parent compound 1b, but a
slightly different pattern of semi-bridging carbonyls is present. The
reactions of 1a and 1b with diphenylphosphine are more complex.
Depending on the stoichiometry and conditions employed, three different
types of cluster have been isolated: the substitution product
[Mo
2
Ru(µ
3
-CCH
2
)(CO)
6
(PPh
2
H)(η-C
5
H
5
)
2
] 2e; the 46-electron monophosphido compounds
[Mo
2
Ru(µ
3
-CCH
2
R)(
µ-PPh
2
)(CO)
5
(η-C
5
H
5
)
2
] 3a, 3b and the saturated bis(phosphido) species
[Mo
2
Ru(µ
3
-CCHR)(µ-
PPh
2
)
2
(CO)
4
(η-C
5
H
5
)
2
] 4a, 4b. Separate experiments have established that
these products are formed sequentially, thus demonstrating the
conversion of the initial vinylidene into an alkylidyne ligand and then
back to a vinylidene. The structures of 3b and 4a have been confirmed by
X-ray diffraction, showing that the phosphido groups bridge one or both
of the Mo–Ru edges respectively.
CHR)(CO)
7
(η-C
5
H
5
)
2
]
(R = H 1a, Me 1b, Ph 1c or CO
2
Me 1d) with the
tertiary phosphine PPh
2
Me afforded the monosubstituted
complexes
[Mo
2
Ru(µ
3
-CCHR)(CO)
6
(PPh
2
Me)(η-C
5
H
5
)
2
]
2a–2d in excellent yields. The products exist as single isomers in
which site-selective substitution of a CO ligand has occurred
exclusively at the ruthenium atom. The crystal structure of 2b has been
determined by X-ray diffraction; the geometry of the vinylidene ligand
is identical to that previously found in the parent compound 1b, but a
slightly different pattern of semi-bridging carbonyls is present. The
reactions of 1a and 1b with diphenylphosphine are more complex.
Depending on the stoichiometry and conditions employed, three different
types of cluster have been isolated: the substitution product
[Mo
2
Ru(µ
3
-CCH
2
)(CO)
6
(PPh
2
H)(η-C
5
H
5
)
2
] 2e; the 46-electron monophosphido compounds
[Mo
2
Ru(µ
3
-CCH
2
R)(
µ-PPh
2
)(CO)
5
(η-C
5
H
5
)
2
] 3a, 3b and the saturated bis(phosphido) species
[Mo
2
Ru(µ
3
-CCHR)(µ-
PPh
2
)
2
(CO)
4
(η-C
5
H
5
)
2
] 4a, 4b. Separate experiments have established that
these products are formed sequentially, thus demonstrating the
conversion of the initial vinylidene into an alkylidyne ligand and then
back to a vinylidene. The structures of 3b and 4a have been confirmed by
X-ray diffraction, showing that the phosphido groups bridge one or both
of the Mo–Ru edges respectively.
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