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Neutral palladium(ii) complexes [Pd(Rf)X(P-L)] (Rf = 3,5-C6Cl2F3, X = Cl, I, OTf) with P-P (dppe and dppf) and P-N (PPh2(bzN)) ligands have chelated structures in the solid-state, except for P-L = dppf and X = Cl, were chelated and dimeric bridged structures are found. The species present in solution in different solvents (CDCl3, THF, NMP and HMPA) have been characterised by 19F and 31P{1H} NMR and conductivity studies. Some [Pd(Rf)X(P-L)] complexes are involved in equilibria with [Pd(Rf)(solv)(P-L)]X, depending on the solvent and X. The ΔH° and ΔS° values of these equilibria explain the variations of ionic vs. neutral complexes in the range 183-293 K. Overall the order of coordination strength of solvents and anionic ligands is: HMPA ≫ NMP > THF and I-, Cl- > TfO-. This coordination preference is determining the complexes participating in the alkynyl transmetalation from PhC[triple bond, length as m-dash]CSnBu3 to [Pd(Rf)X(P-L)] (X = OTf, I) in THF and subsequent coupling. Very different reaction rates and stability of intermediates are observed for similar complexes, revealing neglected complexities that catalytic cycles have to deal with. Rich information on the evolution of these Stille systems after transmetalation has been obtained that leads to proposal of a common behaviour for complexes with dppe and PPh2(bzN), but a different evolution for the complexes with dppf: this difference leads the latter to produce PhC[triple bond, length as m-dash]CRf and black Pd, whereas the two former yield PhC[triple bond, length as m-dash]CRf and [Pd(C[triple bond, length as m-dash]CPh)(SnBu3)(dppe)] or [Pd(C[triple bond, length as m-dash]CPh)(SnBu3){PPh2(bzN)}].

A polymer [Pd(CH 2 SO 2 C 6 H 4 Me) 2 ] n is obtained by thermolysis of cis-[Pd(CH 2 SO 2 C 6 H 4 Me) 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(CH 2 SO 2 C 6 H 4 Me) 2 {OC(CD 3 ) 2 } 2 ], cis-[Pd(CH 2 SO 2 C 6 H 4 Me) 2 (OH 2 ) 2 ], and cis-[Pd(CH 2 SO 2 C 6 H 4 Me) 2 (OH 2 ){OC(CD 3 ) 2 }], and cyclic dimers [Pd(CH 2 SO 2 C 6 H 4 Me) 2 (OH 2 )] 2 with bridging methylsulphone groups are formed. The Pd : PPh 3  : OH 2 1 : 1 : 1 reaction of the polymer produces cis-[Pd(CH 2 SO 2 C 6 H 4 Me) 2 (OH 2 )(PPh 3 )], which isomerizes to trans-[Pd(CH 2 SO 2 C 6 H 4 Me) 2 (OH 2 )(PPh 3 )], with water O-coordinated to Pd and making hydrogen bonds to the two SO 2 groups as seen in its X-ray structure. A similar role is played by RNH 2 groups in the structures of trans-[Pd(CH 2 SO 2 C 6 H 4 Me) 2 (NH 3 )(PPh 3 )] and the dimer μ-(N 2 H 4 )(trans-[Pd(CH 2 SO 2 C 6 H 4 Me) 2 (PPh 3 )]) 2 . In addition to these interesting intramolecular hydrogen bonding properties provided by the SO 2 groups, the structural and 1 H NMR data available suggest that the CH 2 SO 2 C 6 H 4 Me 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.