Calcium complexes with imino-phosphinanilido chalcogenide ligands for heterofunctionalisation catalysis
Résumé
The syntheses, characterisation and utilisation of the calcium complexes [L-xCaN(SiMe3)(2)center dot(THF)] supported by monoanionic, tridentate imino-phosphinanilido chalcogenide ligands Ph2P(E)-N-C6H4-CH] N(Dipp)(-) (E = S, L-2(-); E = Se, L-3(-); Dipp = 2,6-diisopropylphenyl) as molecular precatalysts for the heterofunctionalisation of styrene are reported. The protio-ligand L-1H (for E = O) was obtained upon reaction of the aniline-iminophosphane Ph2PHN-C6H4-CH] N(Dipp) (L-0H) and hydrogen peroxide at room temperature. The related sulphide and selenide compounds L-2H and L-3H were prepared by treatment of L0 H with elemental sulphur and selenium. Beside, reaction of L-0H with Me2S center dot BH3 yielded the corresponding imino-phosphinanilido borane protio-ligand Ph2P(BH3)N-C6H4-CH=N(Dipp)H (L-4 H). The heteroleptic calcium complexes [L-xCaN(SiMe3)(2)center dot(THF)] (E = S, 2; E = Se, 3) were synthesised by one-pot reaction of L-2H and L-3H with 2 equiv of [KN(SiMe3)(2)] and Cal(2) at room temperature. The reaction of L-2H with [KN(SiMe3)(2)] and Cal(2) in 2 : 2 : 1 proportions yielded the homoleptic complex [Ca L-2(2)] (5). The molecular structures of the protio-ligand L-3H and complexes 3 and 5 were established by single crystal X-ray analysis. The heteroleptic complexes 2 and 3 constitute moderately efficient precatalysts for the intermolecular hydrophosphination and hydroamination of styrene with diphenylphosphine or pyrrolidine, respectively, to mediate the formation of C-P and C-N sigma-bonds.