Making a 16-electron bromo (or iodo) complex of ruthenium(II) and a C—F bond in one pot

Abstract

The 16e– bromo or iodo complexes [RuX(dppp)2]+ (dppp = 1,3-bis(diphenylphosphino)propane, X = Br (1c), I (1d)) and [RuX(dppe)2]+ (dppe = 1,2-bis(diphenylphosphino)ethane, X = Br (2c), I (2d)) have been prepared exploiting the reaction of the fluoro complexes [RuF(dppp)2]+ (1a) and [Tl(µ-F)2Ru(dppe)2]+ (3) with activated alkyl bromides or iodides. The X-ray structures of 1c, 1d, 2c, and 2d suggest that the distortion of the Y-shaped trigonal-bipyramidal structure of [MX(P∩P)2]+ is possibly related to the formation of intramolecular hydrogen bonds between the halide ligand and the ortho-hydrogen atoms of the neighbouring phenyl rings. The five-coordinate species 1c, 1d, 2c, and 2d react with H2 to form the dihydrogen complexes [RuX(η2-H2)(P∩P)2]+. The reaction of the dppp derivatives 1c and 1d with H2 (P = 1 atm, 1 atm = 101.322 kPa) is an equilibrium. Quantitative formation of [RuBr(η2-H2)(dppp)2] (4c) is obtained under H2 pressure (100 bar, 1 bar = 100 kPa), whereas the iodo analogue is not stable under analogous conditions. The less crowded dppe derivatives 2c and 2d react quantitatively with H2 under ambient pressure. The iodo and bromo derivatives [RuX(η2-H2)(P∩P)2]+ contain elongated dihydrogen ligands, as indicated by their transverse relaxation times T1 (min). The present data suggest that Cl, Br, and I have similar donor properties in these dihydrogen complexes, and that the different chemical behaviour in the Cl, Br, I series is mainly a result of steric effects.Key words: 16e– complexes, ruthenium, fluoro complexes, bromo complexes, iodo complexes, dihydrogen complexes.