Synthesis and reactivity of [Pd2L2R2(mu-OH)(2)]-type complexes (L = PEt3 or PPh3; R = Me, PhCH2 or Ph). Crystal structure of [Pd-2(PPh3)(2)Ph-2(mu-OH)(mu-NHC6H4OMe-p)]

The metathesis of Cl- by OH- in [Pd-2(PEt3)(2)R-2(mu-Cl)(2)] gave the binuclear hydroxo complexes [Pd-2(PEt3)(2)R-2(mu-OH)(2)] (R = Me or PhCH2) which in CDCl3 solution exist as 1:1 mixtures of syn and anti isomers. They reacted with 3,5-dimethylpyrazole (Hdmpz) in 1:2 molar ratio to yield the corresponding azolate complexes anti-[Pd-2(PEt3)(2)R-2(mu-dmpz)(2)] and with oxalic acid (H(2)ox), in 1:1 molar ratio, to afford the corresponding oxalate complexes anti-[Pd-2(PEt3)(2)R-2(mu-ox)]. The cleavage of the OH bridges of the di-mu-hydroxo complexes yields the mononuclear [Pd(PEt3)(2)R(OH)] which in solution are present as 1:1 mixtures bf cis and trans isomers. Binuclear mu-hydroxo-mu-amido palladium complexes [Pd2L2R2(mu-OH)(mu-NHR '' 2())] (R= Me, L = PEt3; R = Ph, L = PPh3; R '' = Ph, C6H4Me-p, C6H4OMe-p, C6H4Cl-p or C6H4NO2-p) have been prepared by reaction of [Pd2L2R2(mu-OH)(2)] with the corresponding aromatic amine R '' NH2. The NMR data indicate that the isolated complexes are the anti isomers. The crystal structure of complex [Pd-2(PPh3)(2)Ph-2(mu-OH)(mu-NHC6H4OMe-p)] has been established; the Pd2ON ring is severely bent.