Sulfato-bridged ECE-pincer palladium(II) complexes: structures in the solid-state and in solution, and catalytic properties

ECE-pincer sulfato palladium complexes (pincer = [C6H3(CH2E)(2)-2,6](-); E = SPh (1), SMe (2), (SBu)-Bu-i (3), NMe2 (4)) were synthesized and characterized. In the solid-state (X-ray determinations) 3 and 4 exist as neutral ECE-pincer palladium sulfato complexes with a mu(2)-O,O' bridging sulfato ligand. IR and Raman spectroscopic studies revealed that in the solid-state the complexes can be present as either solely neutral or as a mixture of neutral and ionic species, depending on the preparation and morphology of the solids. In water, ionic complexes with non-coordinating sulfate ions prevail. Preliminary studies of the catalytic activity of 2-4 in the Suzuki Miyaura C-C cross-coupling reaction of 3-iodobenzoic acid and sodium tetraphenylborate in water reveal that the C-C cross-coupling product is efficiently formed in good yields at room temperature.