Determining the electron-donating properties of bidentate ligands by13C NMR spectroscopy

Abstract

(Chemical Equation Presented) A series of 15 mononuclear complexes [PdBr-(iPr2-bimy)(L2)]PF6 (1-15) (iPr2-bimy = 1,3-diisopropylben-zimidazolin- 2-ylidene, L2 = aromatic 1,2-diimines, diazabutadienes, or methylene-, ethylene- and propylene-bridged di-Nheterocyclic carbenes) and two dicarbene-bridged, dinuclear complexes [Pd2Br4(iPr2-bimy)2(diNHC)] ( 16 and 17) were synthesized and characterized by multinuclear NMR spectroscopy, electrospray ionization mass spectrometry, and in some cases X-ray diffraction analysis. The influence of the 15 bidentate ligands L2 on the 13Ccarbene signals of the iPr2-bimy reporter ligand in the chelate complexes was studied, on the basis of which a facile methodology for the donor strength determination of bidentate ligands was developed.