M. Moreno-Man˜as et al. / Journal of Organometallic Chemistry 689 (2004) 3669–3684
3683
8. Concluding remarks
Acknowledgements
A new family of 15-membered macrocycles is easily
prepared from commercially available trans-1,4-dib-
romo-2-butene and arenesulfonamides. The cyclization
step is performed in good yield without special difficul-
ties arising from the formation of polymers or higher
rings. However, in certain cases both polymers and 30-
membered rings have been detected or isolated [10].
Macrocycles of this family coordinate certain transition
metals, such as palladium(0), platinum(0), and silver(I).
The palladium and platinum complexes are planar trigo-
nal. Little is known on complexes with other transition
metals.
Continuous financial support has been obtained from
the Spanish Ministry of Science and Technology and
from Generalitat de Catalunya. The last financed pro-
jects are 2002BQU-04002 and 2001SGR00181. Collabo-
rations with the groups of Jacques Muzart and
´
Franc¸oise Henin in Reims, and of Sandro Cacchi in
Rome have been possible thanks to the COST program
(COST D12/0011/98, D12/0028/999, and D24/0013/02)
and to the Socrates-Erasmus program of the European
Union. One of us (R.M.S.) has been incorporated to
´
the research group through a ‘‘Ramon y Cajal’’ contract
(MCYT-FEDER/FSE).
Palladium complexes 4 are excellent catalysts or pre-
catalysts in carbon–carbon bond forming reactions: Su-
zuki-type cross-couplings [6], Heck reactions [11],
hydroarylation of alkynes [15], and telomerization of
butadiene [8,14]. The mechanisms of catalysis are differ-
ent, and in some cases even far from clear. For telomer-
izations, complexes 4 play the role of palladium source
before catalysis and harbor for palladium after catalysis,
preventing agglomeration and precipitation [14]. Recov-
ery and reuse of the catalysts is possible in all the cases
above mentioned, and even a polymeric version, recov-
erable by simple filtration, has been described [6]. These
facts permit us to believe that our phosphine-free palla-
dium complexes of 15-membered macrocycles can be ex-
cellent substitutes for the more classical sources of
palladium such as Pd2(dba)3 and Pd(PPh3)4.
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