AMINO-ACID COMPLEXES OF PALLADIUM(II) .1. NMR-STUDY OF THE REACTIONS OF THE DIAQUA(ETHYLENEDIAMINE)PALLADIUM(II) CATION WITH AMMONIA, BETAINE, AND THE AMINO-ACIDS (NH3)-N-+(CH2)(N)CO2-(N=1-3)(1)

N-15 NMR spectra were obtained for solutions of [Pd(en-N-15(2))(H2O)(2)](2+) (1) and the complexes formed from it on addition of alkali, [{Pd(en-N-15(2))(mu-OH)}(n)](n+) (n = 2, 3), and [Pd(en-N-15(2))(OH2)]. In the presence of weak donor anions, NO3-, SO42-, and ClO4- and dioxane, the N-15 NMR peak from 1 was broadened at 298 K, owing to exchange between H2O and these ligands. When betaine ((+)(CH3)(3)NCH2CO2-, bet) reached with 1, the major N-15 NMR peaks at 277 K were assigned to [Pd(en)(bet-O)(H2O)](2+) and [Pd(en)(bet-O)(2)](2+). At higher temperatures, the peaks broadened and coalesced, until by 353 K there was a broad singlet, indicating that intermolecular exchange of betaine between the free ligand and these complexes was rapid. The products of reactions of 1 with ammonia depended on pH. [Pd(en)(NH3)(H2O)](2+), [Pd(en)(NH3)(2)](2+), [Pd(en)(NH3)(OH)](+), and [{Pd(en)(NH3)}(2)(mu-OH)](3+) were characterized in solution by N-15 NMR. Reaction of 1 (in excess) with glycine (Hgly) gave [Pd-(en)(gly-N,O)](+) as the dominant complex over the pH range 4-10. Above pH 10, [Pd(en)(gly-N)(OH)] formed. With excess glycine, at high pH, [Pd(en)(gly-N)(2)] was the the dominant complex. Near pH 2, [Pd(en)(Hgly-O)-(H2O)](2+) was in equilibrium with the N,O-chelate complex, free glycine, and 1. cis-[Pd(NH3)(2)(H2O)(2)](2+) with glycine, without addition of acid or base to adjust pH, gave initially [Pd(NH3)(2)(gly-N,O)](+), but with standing reaction with the acid liberated gave the isomer of [Pd(NH3)(H2O)2(gly-N,O)](+) with ammine trans to glycinate O, as well as [Pd(H2O)(2)(gly-N,O)](+). Reactions of beta-alanine ((NH3)-N-+(CH2)(2)CO2-, H beta ala) with 1 were generally similar to those of glycine, except that the N,O-chelate complex was less stable relative to [Pd(en)(H beta ala-O)(H2O)](2+) at low pH. Reaction of 1 with gamma-aminobutyric acid ((NH3)-N-+(CH2)(3)CO2-, H gamma aba) gave a mixture over the pH range 4-8 of the chelate complex [Pd(en)(gamma aba-N,O)](+) with the isomers of [{Pd(en)(mu-gamma aba)}(2)](2+).