Synthesis, Characterization, and Crystal Structures of Monomeric and Dimeric Palladium(II) Amide Complexes

Abstract

Addition of KN(R)Ph to írans-CPMeskPdCR')! (R = H, Me; R' = Ph, Me) results in the formation of the monomeric anilide complexes ircms-CPMeghPdCRONCRiPh in good yield. A single-crystal X-ray diffraction study of #rans-(PMe3)2Pd(Ph)N(H)Ph (1) reveals that it crystallizes in the space group PI with a = 8.423(3) Á, h = 10.768(4) Á, c = 12.565 Á, a = 68.81(3)°, ß -71.90(3)°, y = 87.65(3)°, V -1006.7(7) Á3, and Z = 2. There is no evidence for significant interaction between the N lone pair and the metal center, though a shortened N-C distance (1.32(2) Á) may indicate interaction between the N lone pair and the phenyl ring. Thermolysis of 1 at 90 °C in the solid state results in loss of PMes and formation of the dimeric complex [(PMe3)Pd(Ph)(w-NHPh)]2 (9), which was also characterized with a singlecrystal X-ray structure study. Compound 9 crystallizes in the space group PI with a = 6.805(1) Á, b = 12.186(2) Á, c = 18.943(3) Á, a -89.56(1)°, ß = 85.17(1)°, y = 87.67(1)°, V -1564.0(4) Á3, and Z = 2. The PMes groups are anti with respect to the Pd-Pd vector, while the phenyl groups of the anilides are anti with respect to the Pd2N2P2C2 coordination plane. In solution at 25 °C, 9 undergoes an isomerization equilibrium to form two new isomers. Spectroscopic data suggest that these two new isomers are consistent with syn PMes groups and syn anilide groups. Prolonged heating (110 °C, 12 h) of 9 results in reductive elimination of diphenylamine. 1991, 10, 2969.

Synthesis and Structure of an Asymmetric Binuclear Phenylhydrazonato Anionic Complex of Palladium Containing a Pd−C(aryl) Bondcis to a Pd−N(amido) Bond

“…This fact has been reported as transphobia, [14,15] and is followed in trans-[PdAr(NHPh)(PMe 3 ) 2 ]. [8] In complex 1 the hard N(amido) ligand arranges cis to the PdϪC(aryl) bond, leaving the softer ligand chloro in trans position to the PdϪC(aryl) bond. The alternative trans isomer of 1 would contain a PdϪC(aryl) bond with the harder amido ligand in trans position, obeing transphobia arguments, but this isomer is not formed.…”

“…[6,7] Mononuclear complexes of general formula [PdAr(NHPh)(PMe 3 ) 2 ] with these two bonds in trans array have also been reported. [8] They were stabilized against the natural tendency of terminal PdϪN(amido) bonds to make bridges, by using P-donor ligands cis to the amido bond. The stabilization of palladium compounds containing PdϪC and PdϪN(amido) bonds in a cis disposition has been achieved introducing the P-donor nonlabile chelating ancillary ligand DPPF [1,1Ј-bis(diphenylphosphanyl)ferrocene].…”

Palladium‐Catalyzed Amination of Aryl Halides and Sulfonates

“…Both Boncella et al [66] and Hartwig et al [63,64,101] have observed these reactions with palladium amido aryl complexes. Hartwig's group has studied the mechanism of this process in detail [101,280].…”

Mechanistic Aspects of Metal‐Catalyzed C—C and C—X Bond‐Forming Reactions

“…Kinetic studies on stoichiometric reactions from isolated amido and alkoxo organopalladium complexes have shed 26 1 Mechanistic Aspects of Metal-Catalyzed C,C-and C,X-Bond-Forming Reactions light into the mechanism by identifying the actual species involved and the factors controlling this process. The most extensively studied of these reactions is the reductive elimination of C-N bonds from amido arylpalladium complexes [215,216]. Both monomeric and dimeric species have been studied.…”