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Palladium acetate complexes bearing chelating N-heterocyclic carbene (NHC) ligands: Synthesis and catalytic oxidative homocoupling of terminal alkynes (Articolo in rivista)
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- Palladium acetate complexes bearing chelating N-heterocyclic carbene (NHC) ligands: Synthesis and catalytic oxidative homocoupling of terminal alkynes (Articolo in rivista) (literal)
- Anno
- 2009-01-01T00:00:00+01:00 (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
- 10.1016/j.jorganchem.2009.08.039 (literal)
- Alternative label
Hsiao, Tsun-Hung; Wu, Tzu-Liang; Chatterjee, Sandipan; Chiu, Chin-Yi; Lee, Hon Man; Bettucci, Lorenzo; Bianchini, Claudio; Oberhauser, Werner (2009)
Palladium acetate complexes bearing chelating N-heterocyclic carbene (NHC) ligands: Synthesis and catalytic oxidative homocoupling of terminal alkynes
in Journal of organometallic chemistry (Print)
(literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
- Hsiao, Tsun-Hung; Wu, Tzu-Liang; Chatterjee, Sandipan; Chiu, Chin-Yi; Lee, Hon Man; Bettucci, Lorenzo; Bianchini, Claudio; Oberhauser, Werner (literal)
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- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
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- ISI Web of Science (WOS) (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
- ICCOM-CNR
Department of Chemistry, National Changhua University of Education , Changhua 50058, Taiwan (literal)
- Titolo
- Palladium acetate complexes bearing chelating N-heterocyclic carbene (NHC) ligands: Synthesis and catalytic oxidative homocoupling of terminal alkynes (literal)
- Abstract
- The imidazolium salts 1,10-dibenzyl-3,30-propylenediimidazolium dichloride and 1,10-bis(1-naphthalenemethyl)-
3,30-propylenediimidazolium dichloride have been synthesized and transformed into the
corresponding bis(NHC) ligands 1,10-dibenzyl-3,30-propylenediimidazol-2-ylidene (L1) and 1,10-bis(1-
naphthalenemethyl)-3,30-propylenediimidazol-2-ylidene (L2) that have been employed to stabilize the
PdII complexes PdCl2(j2-C,C-L1) (2a) and PdCl2(j2-C,C-L2) (2b). Both latter complexes together with their
known homologous counterparts PdCl2(j2-C,C-L3) (1a) (L3 = 1,10-dibenzyl-3,30-ethylenediimidazol-2-ylidene)
and PdCl2(j2-C,C-L4) (1b) (L4 = 1,10-bis(1-naphthalenemethyl)-3,30-ethylenediimidazol-2-ylidene)
have been straightforwardly converted into the corresponding palladium acetate compounds
Pd(j1-O-OAc)2(j2-C,C-L3) (3a) (OAc = acetate), Pd(j1-O-OAc)2(j2-C,C-L4) (3b), Pd(j1-O-OAc)2(j2-C,C-L1)
(4a), and Pd(j1-O-OAc)2(j2-C,C-L2) (4b). In addition, the phosphanyl-NHC-modified palladium acetate
complex Pd(j1-O-OAc)2 (j2-P,C-L5) (6) (L5 = 1-((2-diphenylphosphanyl)methylphenyl)-3-methyl-imidazol-
2-ylidene) has been synthesized from corresponding palladium iodide complex PdI2(j2-P,C-L5) (5).
The reaction of the former complex with p-toluenesulfonic acid (p-TsOH) gave the corresponding bis-tosylate
complex Pd(OTs)2(j2-P,C-L5) (7). All new complexes have been characterized by multinuclear NMR
spectroscopy and elemental analyses. In addition the solid-state structures of 1b?DMF, 2b?2DMF, 3a,
3b?DMF, 4a, 4b, and 6?CHCl3?2H2O have been determined by single crystal X-ray structure analyses.
The palladium acetate complexes 3a/b, 4a/b, and 6 have been employed to catalyze the oxidative
homocoupling reaction of terminal alkynes in acetonitrile chemoselectively yielding the corresponding
1,4-di-substituted 1,3-diyne in the presence of p-benzoquinone (BQ). The highest catalytic activity in
the presence of BQ has been obtained with 6, while within the series of palladium-bis(NHC) complexes,
4b, featured with a n-propylene-bridge and the bulky N-1-naphthalenemethyl substituents, revealed as
the most active compound. Hence, this latter precursor has been employed for analogous coupling
reaction carried out in the presence of air pressure instead of BQ, yielding lower substrate conversion
when compared to reaction performed in the presence of BQ. The important role of the ancillary ligand
acetate in the course of the catalytic coupling reaction has been proved by variable-temperature NMR
studies carried out with 6 and 70 under catalytic reaction conditions. (literal)
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