Premium
Bisguanidines with Biphenyl, Binaphthyl, and Bipyridyl Cores: Proton‐Sponge Properties and Coordination Chemistry
Author(s) -
Maronna Astrid,
Hübner Olaf,
Enders Markus,
Kaifer Elisabeth,
Himmel HansJörg
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201204294
Subject(s) - protonation , chemistry , delocalized electron , paramagnetism , ligand (biochemistry) , crystallography , coordination complex , metal , chemical shift , pyridine , proton , medicinal chemistry , organic chemistry , ion , biochemistry , physics , receptor , quantum mechanics
Herein, we report on the synthesis, protonation, and coordination chemistry of chelating guanidine ligands with biphenyl, binaphthyl, and bipyridyl backbones. The ligands are shown to be proton sponges, and this protonation was studied experimentally and by using quantum‐chemical calculations. Group 10 metal (Ni, Pd, and Pt) complexes with different metal/ligand ratios were synthesized. In the case of the bipyridyl systems, coordination occurs exclusively at the pyridine N atoms, as opposed to protonation. The spin‐density distribution and the magnetism were evaluated for a series of paramagnetic Ni II complexes with the aid of paramagnetic NMR spectroscopic studies in alliance with quantum‐chemical calculations and magnetic (SQUID) measurements. Through direct delocalization from the singly occupied molecular orbitals (SOMOs), a significant amount of spin density is placed on the guanidinyl groups, and spin polarization also transports spin density onto the aromatic backbone.