Ruthenium complexes of diphenylphosphino derivatives of carboxylic amides: Synthesis and characterization of bidentate P,N- and P,O-chelate ligands and their reactivity towards [RuCl2(PPh3)3]

The carboxylic amides N-methylbenzamide (HLa), phthalimidine (HLb) and pyridine-2-one (HLc) were diphenylphosphino-functionalized (with ClPPh2 and a base, n-BuLi for HLa, triethylamine for HLb and HLc) to yield the N-PPh2 derivatives of N-methylbenzamide (1a) and of phthalimidine (1b) as well as the O-PPh2 derivative 2-diphenylphosphinoxypyridine (1c). Thus, 1a and 1b represent P,O-chelate ligands, whereas 1c is a P,N-chelate ligand. Both P,O-ligands (1a, 1b) react with [RuCl2(PPh3)(3)] in a two-step fashion to form mono-chelates with trans-situated Cl atoms (2a, 2b) upon using a 1:1 stoichiometric ratio or Cl-trans bis-chelates (3a(II), 3b(II)) upon using two equivalents of the chelator. In contrast, reaction of [RuCl2(PPh3)(3)] and the P,N-chelator 1c in 1:1 molar ratio immediately produced a bis-chelate (3c(I)) with an all-cis orientation of the ligands (while 50% of the [RuCl2(PPh3)(3)] starting material remained unreacted). Compound 3c(I) slowly isomerizes to the Cl-trans isomer (3c(II)). All isolated compounds were characterized with multi-nuclear NMR spectroscopy, single-crystal X-ray diffraction and elemental analysis. (C) 2016 Elsevier Ltd. All rights reserved.