SYNTHESIS, CHARACTERIZATION, AND CRYSTAL-STRUCTURES OF MONOMERIC AND DIMERIC PALLADIUM(II) AMIDE COMPLEXES

Addition of KN(R)Ph to trans-(PMe3)2Pd(R')I (R = H, Me; R' = Ph, Me) r esults in the formation of the monomeric anilide complexes trans-(PMe3 )2Pd(R')N(R)Ph in good yield. A single-crystal X-ray diffraction study of trans-(PMe3)2Pd(Ph)N(H)Ph (1) reveals that it crystallizes in the space group P1BAR with a = 8.423(3) angstrom, b = 10.768(4) angstrom, c = 12.565 angstrom, alpha = 68.81(3)-degrees, beta = 71.90(3)-degrees , gamma = 87.65(3)-degrees, V = 1006.7(7) angstrom 3, and Z = 2. There is no evidence for significant interaction between the N lone pair an d the metal center, though a shortened N-C distance (1.32(2) angstrom) may indicate interaction between the N lone pair and the phenyl ring. Thermolysis of 1 at 90-degrees-C in the solid state results in loss o f PMe3 and formation of the dimeric complex [(PMe3)Pd(Ph)(mu-NHPh)]2 ( 9), which was also characterized with a single-crystal X-ray structure study. Compound 9 crystallizes in the space group P1BAR with a = 6.80 5(1) angstrom, b = 12.186(2) angstrom, c = 18.943(3) angstrom, alpha = 89.56(1)-degrees, beta = 85.17(1)-degrees gamma = 85.17(1)-degrees, g amma = 87.67(1)-degrees, V = 1564.0(4) angstrom 3, and Z = 2. The PMe3 groups are anti with respect to the Pd-Pd vector, while the phenyl gr oups of the anilides are anti with respect to the Pd2N2P2C2 coordinati on plane. In solution at 25-degrees-C, 9 undergoes an isomerization eq uilibrium to form two new isomers. Spectroscopic data suggest that the se two new isomers are consistent with syn PMe3 groups and syn anilide groups. Prolonged heating (110-degrees-C, 12 h) of 9 results in reduc tive elimination of diphenylamine.