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New Pyridazine‐Bridged NHC/Pyrazole Ligands and Their Sequential Silver(I) Coordination
Author(s) -
Wimberg Jan,
Scheele Ulrich J.,
Dechert Sebastian,
Meyer Franc
Publication year - 2011
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201100264
Subject(s) - pyridazine , chemistry , pyrazole , ligand (biochemistry) , medicinal chemistry , stereochemistry , coordination complex , carbene , metal , crystallography , organic chemistry , catalysis , receptor , biochemistry
A family of new pyridazine‐bridged NHC/pyrazole ligand precursors HL 1–5 were prepared and fully characterized including analysis by XRD {HL 1 = 3‐[3‐(2,6‐diisopropylphenyl)‐3 H ‐imidazolium‐1‐yl]‐6‐(3‐pyridin‐2‐yl‐pyrazol‐1‐yl)‐pyridazine, HL 2 = 3‐[3‐(2,4,6‐trimethylphenyl)‐3 H ‐imidazolium‐1‐yl]‐6‐(3‐pyridin‐2‐yl‐pyrazol‐1‐yl)‐pyridazine, HL 3 = 3‐[3‐(2,4,6‐trimethylphenyl)‐3 H ‐imidazolium‐1‐yl]‐6‐(3,5‐dimethylpyrazol‐1‐yl)‐pyridazine, HL 4 = 3‐(3‐ tert ‐butyl‐3 H ‐imidazolium‐1‐yl)‐6‐(3,5‐dimethylpyrazol‐1‐yl)‐pyridazine, HL 5 = 3‐[3‐(2,4,6‐trimethylphenyl)‐3 H ‐imidazolium‐1‐yl]‐6‐(3‐methyl‐5‐phenylpyrazol‐1‐yl)‐pyridazine, X = PF 6 – or BF 4 – }. Reaction of the ligand precursors with Ag 2 O yielded various silver(I) complexes whose structures have been elucidated crystallographically. In complexes [(L 3 ) 2 Ag](PF 6 ) ( 4 ) and[(L 4 ) 2 Ag](PF 6 ) ( 4′ ) the single silver(I) ion is coordinated in a linear fashion by the NHC moieties of the two ligand strands. An NMR titration with AgBF 4 reveals that 4 can bind two more silver(I) ions. The complex [(L 5 ) 2 Ag 2 ](PF 6 ) 2 ( 5′ ) features an additional silver(I) centre bound to the two pyrazole rings, whereas in [(L 3 ) 2 Ag 2 ](BF 4 ) 2 ( 6 ) ligand reshuffling has occurred to give antiparallel ligand strands with {C NHC N pyrazole } coordination of each metal ion. Secondary interactions with the pyridazine N‐atom are observed in some cases. An additional third silver(I) ion can be accommodated between the central pyridazine bridges, as shown in [(L 3 ) 2 Ag 3 ](PF 6 ) 2 (BF 4 ) ( 7 ). The sequence of binding events and the identity of the species in solution have been investigated by NMR spectroscopy and ESI mass spectrometry.