HALIDE AND AMINE INFLUENCE IN THE EQUILIBRIUM FORMATION OF PALLADIUM TRIS (O-TOLYL)PHOSPHINE MONO(AMINE) COMPLEXES FROM PALLADIUM ARYL HALIDE DIMERS

The relative binding constants (K-b) for the coordination of amines to the palladium fragment Pd[P(o-tol)(3)](p-C(6)H(4)Me)Cl were determine d by H-1 NMR spectroscopy and decrease in the order hexylamine > benzy lamine approximate to cyclohexylamine approximate to piperidine > dibu tylamine approximate to diethylamine approximate to N-benzylmethylamin e > morpholine > diisobutylamine > dibenzylamine approximate to ert-oc tylamine >> diisopropylamine > N-methylaniline. The palladium halide d imers {Pd[P(o-tol)(3)](p-C(6)H(4)Me)(mu-X)}(2) (X = Cl (1), Br (2), I (3)) react reversibly with dibenzylamine to generate the corresponding 1:1 palladium amine adducts Pd[P(o-tol)(3)](p-C(6)H(4)Me)(HNBn(2))X ( X = Cl (12), K = 6 +/- 1 x 10(3) M(-1); X = Br (18), K = 3.5 +/- 0.5 x 10(3) M(-1); X = I (22), K = 90 +/- 20 M(-1)), respectively. The rela ted reaction of dibenzylamine with the iodide dimer {Pd[P(o-tol)(3)](p -C(6)H(4)OMe)(mu-I)}(2) (21) to form Pd[P(o-tol)(3)](p-C(6)H(4)OMe)(HN Bn(2))I (24) provided the thermodynamic parameters Delta G(298 K) = -3 .1 +/- 0.1 kcal mol(-1), Delta H-298 K = -11.9 +/- 0.1 kcal mol(-1), a nd Delta S-298 K = 30 +/- 4 eu. Dimers 1-3 also react reversibly with diisopropylamine at 25 degrees C to form the amine adducts Pd[P(o-tol) (3)](p-C(6)H(4)Me)[HN(i-Pr-2)]X (X = Cl (17), K = 14 +/- 3 M(-1); X = Br (19), K = 2.8 +/- 0.5 M(-1); X = I (26), K = 6 +/- 2 x 10(-3) M(-1) ), respectively.