PAPER www.rsc.org/dalton | Dalton Transactions
Insertion reactions of alkynes and organic isocyanides into the
palladium–carbon bond of dimetallic Fe–Pd alkoxysilyl complexes†‡
Michael Knorr,*
a,b
Isabelle Jourdain,
a
Pierre Braunstein,*
b
Carsten Strohmann,
c
Antonio Tiripicchio
d
and
Franco Ugozzoli
d
Received 19th July 2006, Accepted 18th September 2006
First published as an Advance Article on the web 18th October 2006
DOI: 10.1039/b610324c
Insertion of MeO
2
C–C≡C–CO
2
Me (DMAD) into the Pd–C bond of the heterodimetallic complex
[(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd(dmba-C)] (2) (dppm = Ph
2
PCH
2
PPh
2
,
dmba-C = metallated dimethylbenzylamine) and [(OC)
3
{(MeO)
3
Si}F e(l-dppm)Pd(8-mq-C,N)] (3)
(8-mq-C,N = cyclometallated 8-methylquinoline) yielded the r-alkenyl complexes
[(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd{C(CO
2
Me)=C(CO
2
Me)(o-C
6
H
4
CH
2
NMe
2
)}](7) and
[(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd{C(CO
2
Me)=C(CO
2
Me)(CH
2
C
9
H
6
N)}](8), respectively.
The latter afforded the adduct [(OC)
3
{(MeO)
3
Si}F e(l-dppm)Pd{C(CO
2
Me)=C(CO
2
Me)-
(CH
2
C
9
H
6
N)}(CNBu
t
)] (9) upon reaction with 1 equiv. of Bu
t
NC. The heterodinuclear r-butadienyl
complexes [(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd{C(Ph)=C(Ph)C(CO
2
Me)=(CO
2
Me)(o-C
6
H
4
-
CH
2
NMe
2
)}](11) and [(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd{C(Ph)=C(CO
2
Et)C(Ph)=C(CO
2
Et)-
(CH
2
C
9
H
6
N)}](13) have been obtained by reaction of the metallate K[Fe{Si(OMe)
3
}(CO)
3
(dppm-P)]
(dppm = Ph
2
PCH
2
PPh
2
) with [P dCl{C(Ph)=C(Ph)C(CO
2
Me)=C(CO
2
Me)(o-C
6
H
4
CH
2
NMe
2
)}] or
[P dCl{C(Ph)=C(CO
2
Et)C(Ph)=(CO
2
Et)}(CH
2
C
9
H
6
N)], respectively. Monoinsertion of various organic
isocyanides RNC into the Pd–C bond of 2 and 3 afforded the corresponding heterometallic iminoacyl
complexes. In the case of complexes [(OC)
3
{(MeO)
3
Si} Fe(l-dppm)P d{C(=NR)(CH
2
C
9
H
6
N)}]
(15a R = Ph, 15b R = xylyl), a static six-membered C,N chelate is formed at the Pd centre, in contrast
to the situation in [(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd{C(=NR)(o-C
6
H
4
CH
2
NMe
2
)}](14a R =
o-anisyl, 14b R = 2,6-xylyl) where formation of a l-g
2
-Si–O bridge is preferred over NMe
2
coordination. The outcome of the reaction of the dimetallic alkyl complex
[(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)PdMe] with RNC depends both on the stoichiometry and the
electronic donor properties of the isocyanide employed for the migratory insertion process. In the case
of o-anisylisocyanide, the iminoacyl complex [(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd{C(=
N-o-anisyl)Me}](16) results from the reaction in a 1 : 1 ratio. Addition of three equiv. of
o-anisylisocyanide affords the tris(insertion) product [(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd-
{[C(=N-o-anisyl)]
3
Me}](18). After addition of a fourth equivalent of o-anisylNC, exclusive formation
of the isocyanide adduct [(OC)
3
{(MeO)
3
Si}F e(l-dppm)Pd{[C(=N-o-anisyl)]
3
Me}(CN-o-anisyl)] (19)
was spectroscopically evidenced. In the complex [(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)Pd{[C(=N-
o-C
6
H
4
COCH
2
)]
2
Me}](20), the r-bound diazabutadienyl unit is part of a 12-membered organic
macrocyle which results from bis(insertion) of 1,2-bis(2-isocyanophenoxy)ethane into the Pd–Me bond
of the precursor complex [(OC)
3
F e{l-Si(OMe)
2
(O Me)}(l-dppm)PdMe]. In contrast, addition of two
equivalents of tert-butylisocyanide to a solution of the latter afforded [(OC)
3
{(MeO)
3
Si}-
F e(l-dppm)Pd{C(=NBu
t
)Me}(CNBu
t
)] (21) in which both a terminal and an inserted isocyanide
ligand are coordinated to the Pd centre. In all cases, there was no evidence for competing CO
substitution at the Fe(CO)
3
fragment by RNC. The molecular structures of the insertion products
8·CH
2
Cl
2
and 16·CH
2
Cl
2
have been determined by X-ray diffraction.
a
Laboratoire de Chimie des Mat´ eriaux et Interfaces, Universit´ e de Franche-
Comt´ e, Facult´ e des Sciences et des Techniques, 16, Route de Gray, 25030,
Besanc ¸on Cedex, France. E-mail: michael.knorr@univ-fcomte.fr
b
Laboratoire de Chimie de Coordination (UMR 7177 CNRS), Universit´ e
Louis Pasteur, Institut Le Bel, 4 rue Blaise Pascal, F-67070, Strasbourg,
France. E-mail: braunst@chimie.u-strasbg.fr
c
Institut f¨ ur Anorganische Chemie der Universit¨ at W¨ urzburg, Am Hubland,
D-97074, W ¨ urzburg, Germany
d
Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chim-
ica Fisica, Universit` a di Parma, via G. P. Usberti 17/A, I-43100, Parma, Italy
Introduction
The insertion of small molecules such as CO, isocyanides, imines,
olefins, alkynes and SO
2
into palladium–carbon bonds represents
† Dedicated to Prof. Dr Ulrich Schubert on the occasion of his 60th
birthday.
‡Electronic supplementary information (ESI) available: IR spectrum
of [(OC)
3
{(MeO)
3
Si}F e(l-dppm)Pd(C≡NBu
t
){C(=NBu
t
)Me}] 21. See
DOI: 10.1039/b610324c
5248 | Dalton Trans., 2006, 5248–5258 This journal is © The Royal Society of Chemistry 2006