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Organometallics 2006, 25, 596-601
Novel Palladacycles Containing [C(sp2, ferrocene), N, O]- or
[C(sp2, ferrocene), N, O]2- Terdentate Ligands
Sonia Pe´rez,† Concepcio´n Lo´pez,*,† Amparo Caubet,† Xavier Solans,‡ Merce` Font-Bard´ıa,‡
Anna Roig,§ and Elies Molins§
Departament de Qu´ımica Inorga`nica, Facultat de Qu´ımica, UniVersitat de Barcelona,
Mart´ı i Franque`s 1-11, 08028-Barcelona, Spain, Departament de Cristal‚lografia, Mineralogia i Dipo`sits
Minerals, Facultat de Geologia, UniVersitat de Barcelona, Mart´ı i Franque`s s/n, 08028-Barcelona. Spain,
and Institut de Cie`ncia de Materials de Barcelona (ICMAB-CSIC), Campus de la UniVersitat Auto`noma
de Barcelona, 08193-Bellaterra, Spain
ReceiVed October 14, 2005
The synthesis, characterization, and study of the reactivity of the novel cyclopalladated complexes
[Pd{[(η5-C5H3)CHdN(C6H4-2-CH2OH)]Fe(η5-C5H5)}Cl] (2) and [Pd{[(η5-C5H3)CHdN(C6H4-2-CH2O)]-
Fe(η5-C5H5)}]2 (3) with PPh3 or MeO2CCtCCO2Me are described. Electrochemical and 57Fe Mo¨ssbauer
spectroscopic studies of the new palladacycles are also reported.
Palladium(II) compounds derived from ligands containing
modes than their analogues with an OR substituent.11b,14-17
Palladium(II) or platinum(II) complexes derived from organic
imino alcohols have been reported,14-17 and some of them (i.e.
[Pd{C6H4CHdN(C6H4-2-O)}]4) exhibit unusual structural fea-
tures.16
three donor atoms with different hardnesses1 have attracted great
interest due to their potential hemilability,2 which is especially
relevant in view of their use in homogeneous catalysis.3 Despite
of this and the prochiral nature of ferrocenyl ligands in the
cyclopalladation processes,4,5 palladium(II) compounds contain-
ing terdentate [C(sp2, ferrocene), N, X]q- (X ) N, S, O; q ) 1,
2) ligands are scarce.6-10 It is well-known that organometallic
complexes with a σ(Pd-O) bond are particularly interesting,
due to their applications in organic and/or organometallic
synthesis and in homogeneous catalysis.11,12 However, only two
palladacycles with a [C(sp2, ferrocene), N, O]q- ligand are
known,13 and in both cases, the palladium(II) is bound to the
oxygen of an ether group. Recent contributions have shown that
imino alcohols may exhibit greater versatility in the coordination
On the other hand, ring-chain tautomeric equilibria involving
1,3-O,N-heterocyclic systems have generated great interest in
the last few years,18-20 since this process may affect the
reactivity of the species involved. However, none of the articles
published so far have focused on the study of the effect produced
by transition metals upon the reactivity of the two tautomers.
We have recently reported the synthesis of 2-ferrocenyl-2,4-
dihydro-1H-benzo[d][1,3]oxazine (1a) and the tautomeric equi-
librium between 1a and the imino alcohol [(η5-C5H5)Fe{(η5-
C5H4)CHdN(C6H4-2-CH2OH)}] (1b).20 In view of this, 1b
appeared to be a good candidate to attempt the preparation of
palladacycles with terdentate [C(sp2, ferrocene), N, O]- or
[C(sp2, ferrocene), N, O]2- ligands. Here we describe the study
of the reactivity of 1a with palladium(II).
* To whom correspondence should be addressed. E-mail:
† Departament de Qu´ımica Inorga`nica, Universitat de Barcelona.
‡ Departament de Cristal‚lografia, Mineralogia i Dipo`sits Minerals,
Universitat de Barcelona.
§ Campus de la Universitat Auto`noma de Barcelona.
(11) For recent contributions in this area see for instance: (a) Lindsell,
W. E.; Palmer, D. D.; Preston, P. N.; Rosair, G. M.; Jones, R. V. H.;
Whitton, A. J. Organometallics 2005, 24, 1119. (b) Kang, M.; Sen, A.
Organometallics 2005, 24, 3508. (c) Vicente, J.; Abad, J. A.; Fo¨rtsch, W.;
Lo´pez-Saez, M. J.; Jones, P. G. Organometallics 2004, 23, 4414.
(12) Mun˜oz, M. P.; Mart´ın-Matute, B.; Ferna´ndez-Rivas, C.; Ca´rdenas,
D. J.; Echavarren, A. M. AdV. Synth. Catal. 2001, 343, 338 and references
therein.
(13) (a) Zhao, G.; Wang, Q. G.; Mak, T. C. W. Organometallics 1998,
17, 3437. (b) Zhao, G.; Wang, Q. G.; Mak, T. C. W. J. Chem. Soc., Dalton
Trans. 1998, 3785.
(14) Allen, T. H. Acta Crystallogr. 2002, B58, 360.
(15) Lo´pez, C.; Caubet, A.; Pe´rez, S.; Solans, X.; Font-Bard´ıa, M. Chem.
Commun. 2004, 540.
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(19) For the latest contributions in this field, see: (a) La´zar, L.; Fu¨lo¨p,
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10.1021/om050881o CCC: $33.50 © 2006 American Chemical Society
Publication on Web 01/06/2006