Polymer [Pd(CH₂SO₂C₆H₄Me)₂]_n, a precursor to remarkably stable Pd organometallics

A polymer [Pd(CH₂SO₂C₆H₄Me)₂]_n is obtained by thermolysis of cis-[Pd(CH₂SO₂C₆H₄Me)₂(NCMe)₂] to release the MeCN ligands. The corresponding coordination sites are then occupied by weak Pd-O bonds, easier to break than the previous Pd-N bonds. This allows us to produce from the polymer cis complexes containing ligands weaker than NCMe, such as acetone or water. The complexes cis-[Pd(CH₂SO₂C₆H₄Me)₂{OC(CD₃)₂}₂], cis-[Pd(CH₂SO₂C₆H₄Me)₂(OH₂)₂], and cis-[Pd(CH₂SO₂C₆H₄Me)₂(OH₂){OC(CD₃)₂}], and cyclic dimers [Pd(CH₂SO₂C₆H₄Me)₂(OH₂)]₂ with bridging methylsulphone groups are formed. The Pd : PPh₃ : OH₂ 1 : 1 : 1 reaction of the polymer produces cis-[Pd(CH₂SO₂C₆H₄Me)₂(OH₂)(PPh₃)], which isomerizes to trans-[Pd(CH₂SO₂C₆H₄Me)₂(OH₂)(PPh₃)], with water O-coordinated to Pd and making hydrogen bonds to the two SO₂ groups as seen in its X-ray structure. A similar role is played by RNH₂ groups in the structures of trans-[Pd(CH₂SO₂C₆H₄Me)₂(NH₃)(PPh₃)] and the dimer μ-(N₂H₄)(trans-[Pd(CH₂SO₂C₆H₄Me)₂(PPh₃)])₂. In addition to these interesting intramolecular hydrogen bonding properties provided by the SO₂ groups, the structural and ¹H NMR data available suggest that the CH₂SO₂C₆H₄Me group is an interesting kind of strong alkyl σ donor, with high trans influence, and forms very stable Pd complexes extraordinarily resistant to reductive elimination and to hydrolysis by water at room temperature.