FORMATION OF PALLADIUM BIS(AMINE) COMPLEXES FROM REACTION OF AMINE WITH PALLADIUM TRIS(O-TOLYL)PHOSPHINE MONO(AMINE) COMPLEXES

Palladium mono(benzylamine) complexes Pd[P(o-tolyl)(3)](p-C(6)H(4)CMe( 3))[H(2)NBn]X (X = Cl (7), Br (8), I (14)) react reversibly with benzy lamine in CDCl3 at 25 degrees C via P(o-tolyl)(3) displacement to gene rate the corresponding bis(amine) derivatives trans-Pd(p-C(6)H(4)CMe(3 )[H-2-NBn](2)X (X = Cl(17), K-eq = 0.18 +/- 0.02; Br (16), K-eq = 0.14 +/- 0.01; I (18), K-eq = 0.10 +/- 0.01). Complexes 16-18 were isolate d from reaction of the palladium aryl halide dimers {Pd[P(o-tolyl)(3)] (p-C(6)H(4)CMe(3))(mu-X)}(2) (X = Cl (4), Br (5), I (6)) and excess be nzylamine as the corresponding mono(benzylamine) solvate Pd(p-C(6)H(4) CMe(3))[H(2)NBn](2)X . H(2)NBn (X = Br (16 . H(2)NBn), Cl (17 . H(2)NB n), I (18 . H(2)NBn)). IR and H-1 NMR spectroscopy of 16 . H(2)NBn ind icated the presence of N-H ... X (X = N, Br, Pd) hydrogen bonds in bot h the solid state and solution. The equilibrium constant for the forma tion of 16 and P(o-tolyl)(3) from 8 and benzylamine ranged from 0.066 +/- 0.005 in CD2Cl2 to 3.6 +/- 0.3 in THF-d(8) and in C6D6 ranged from 0.90 +/- 0.07 at 25 degrees C to 0.44 +/- 0.04 at 77 degrees C (Delta G degrees(298K) = 0.06 +/- 0.01 kcal mol(-1); Delta H degrees(298K) - 2.8 +/- 0.1 kcal mol(1); Delta S degrees(298K) = -9 +/- 1 eu). The equ ilibrium constants for the formation of the bis(amine) complexes Pd(p- C(6)H(4)CMe(3))[amine]Br-2 from the reaction of Pd[P(o-tolyl)(3)]-(p-C (6)H(4)CMe(3))\amine\Br and amine decreased in the order phenethylamin e approximate to cyclohexylamine approximate to benzylamine approximat e to (4-methylbenzyl)amine >> piperidine >> N-methylbenzylamine.