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 (FcCtriple bond; length of mdashC)nPh3−nPdouble bond; length as m-dashSe (2a, n = 1; 2b, n = 2; 2c, n = 3; Fc = ferrocenyl, (η5-C5H4)(η5-C5H5)Fe) from (FcCtriple bond; length of mdashC)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 [((FcCtriple bond; length of mdashC)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.