Palladiumdichloride (ferrocenylethynyl)phosphanes and their use in Pd-catalyzed Heck–Mizoroki- and Suzuki–Miyaura carbon–carbon cross-coupling reactions

In this work the synthesis of phosphane selenides (FcCC)nPh3−nPSe (2a, n = 1; 2b, n = 2; 2c, n = 3; Fc = ferrocenyl, (η5-C5H4)(η5-C5H5)Fe) from (FcCC)nPh3−nP (1a, n = 1; 1b, n = 2; 1c, n = 3) and selenium is described to estimate the σ-donor properties of these systems by 31P{1H} NMR spectroscopy. Progressive replacement of phenyl by ferrocenylethynyl causes a shielding of the phosphorus atom with increasing of the 1J(31P–77Se) coupling constants.The palladiumdichloride metal-organic complexes [((FcCC)nPh3−nP)2PdCl2] (3a, n = 1; 3b, n = 2; 3c, n = 3) have been used as (pre)catalysts in the Suzuki–Miyaura (reaction of 2-bromo-toluene (4a) and 4-bromo-acetophenone (4b), respectively, with phenyl boronic acid (5) to give 2-methyl biphenyl (6a) and 4-acetyl biphenyl (6b)) and in the Heck–Mizoroki reaction (treatment of iodobenzene (7) with tert-butyl acrylate (8) to give E-tert-butyl cinnamate (9)).The structures of molecules 1a, 1c, 2c, and 3c in the solid state were determined by single X-ray structure analysis showing that the structural parameters of these systems are unexceptional and correspond to those of related phosphanes, seleno phosphanes, and palladium dichloride complexes.

The synthesis of phosphane selenides (FcCC)nPh3−nPSe (n = 1, 2, 3) and the appropriate (ferrocenylethynyl)phosphane palladium dichlorides is described. The use of the latter complexes as (pre)catalysts in the Suzuki–Miyaura and Heck–Mizoroki carbon–carbon cross-coupling reactions is reported. Electronic (J31P–77Se) and steric effects (Tolman cone angle) are discussed.Figure optionsDownload as PowerPoint slide