FULL PAPER
C–H vs. N–H Bond Activation in Aminophosphane Ligands: Reaction of
[Cp*Ru(MeCN)
2
(PR
1
2
NHR
2
)]
+
(R
1
= Ph, iPr; R
2
= Ph, C
6
F
5
) with Alkynes
Manuel Jiménez-Tenorio,
[a]
M. Carmen Puerta,
[a]
and Pedro Valerga*
[a]
Dedicated to the memory of Prof. Francisco González García (Universidad de Sevilla)
[‡]
Keywords: Alkyne ligands / C–H activation / Half-sandwich complexes / Phosphane ligands / Ruthenium
The reaction of the complexes [Cp*Ru(MeCN)
2
(PR
1
2
NHR
2
)]
+
(R
1
=R
2
= Ph 1;R
1
= iPr, R
2
=C
6
F
5
2;R
1
= iPr, R
2
= Ph 3) with
1-alkynes HCCR (R = H, nBu, SiMe
3
) or diynes
HCCCH
2
XCH
2
CCH (X = O, CH
2
, CH
2
CH
2
) yields dif-
ferent products depending on the nature of the aminophos-
phane ligand. In some cases, alkyne coupling involving mi-
gration of the phosphane and N–H activation occurs, yielding
amidobutadiene complexes of the type [Cp*Ru{η
4
-C
4
H
3
(R)
2
-
PR
1
2
NR
2
-κ
1
N}]
+
or [Cp*Ru{η
4
-C
4
H
3
(CH
2
XCH
2
)PR
1
2
NR
2
-
κ
1
N}]
+
. The complexes [Cp*Ru{η
4
-C
4
H
3
(CH
2
OCH
2
)-
PPh
2
NPh-κ
1
N}][PF
6
] (1a) and [Cp*Ru{η
4
-C
4
H
3
(CH
2
-
OCH
2
)PiPr
2
NC
6
F
5
-κ
1
N}][PF
6
] (2a) have been structurally
characterized by X-ray crystallography. In other cases, for ex-
ample the reaction of 3 with HCCR (R = nBu, SiMe
3
), C–H
Introduction
Complexes of the type [(C
5
R
5
)Ru(MeCN)
2
(L)]
+
(R = H,
Me; L = CO, PR
3
, AsPh
3
, SbPh
3
) are regarded as synthons
for the corresponding cationic 14-electron fragments
[(C
5
R
5
)Ru(L)]
+
due to the substitutionally labile character
of the acetonitrile ligands.
[1]
The reactivity of these systems
towards alkynes has been thoroughly studied both from the
experimental and theoretical points of view.
[1–5]
The deriva-
tives [(C
5
R
5
)Ru(MeCN)
2
(L)]
+
react with alkynes to yield
bis(π-alkyne) adducts which readily undergo oxidative al-
kyne coupling of the two alkyne ligands to form cationic
ruthenacyclopentatriene complexes.
Ruthenacyclopentatriene complexes are key intermedi-
ates in the overall process, and the final products of the
reaction are determined by the nature of L, the use of Cp
or Cp* as co-ligands, and the nature of the substituents
present in the alkyne.
[1]
When L is PR
3
, migration of the
phosphane from Ru to C occurs in most cases, generating
[a] Departamento de Ciencia de Materiales e Ingeniería Metalúrg-
ica y Química Inorgánica, Facultad de Ciencias, Universidad
de Cádiz,
Apartado 40, 11510 Puerto Real, Cádiz, Spain
Fax: +34-956-016288
E-mail: pedro.valerga@uca.es
[‡] For his contribution to the development of Inorganic Chemistry
in Spain.
Eur. J. Inorg. Chem. 2005, 2631–2640 DOI: 10.1002/ejic.200500034 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2631
bond activation at the ortho-position of the phenyl ring of
the phenylamino moiety and coupling to the alkyne fragment
takes place. This results in the formation of the novel π-al-
kene complexes [Cp*Ru(MeCN){η
2
-RCH=CH(C
6
H
4
)-
NHPiPr
2
-κ
1
P}]
+
(R = nBu 4, SiMe
3
5), formally derived from
the insertion of the alkyne into the ortho-C–H bond of the
phenyl ring. The derivative [Cp*Ru(MeCN){η
2
-
nBuCH=CH(C
6
H
4
)NHPiPr
2
-κ
1
P}][BPh
4
] has been structurally
characterized by X-ray crystallography. These compounds
are related to the also structurally characterized olefin com-
plex [Cp*Ru(MeCN)(η
2
-MeOOCCH=CH
2
)(PPh
2
NHPh)][PF
6
]
(6), generated by reaction of 1 with methyl acrylate.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
allyl carbene species.
[2–4]
These species behave as masked
coordinatively unsaturated complexes that are capable of
activating C–H bonds. In cyclopentadienyl complexes con-
taining tertiary phosphane ligands the C–H activation pro-
cess takes place at one of the aryl or alkyl substituents of
the phosphane.
[4,6]
At variance with this, in pentamethylcyclopentadienyl
derivatives the C–H activation occurs at one of the methyl