PREPARATION, VIA DOUBLE OXIDATIVE ADDITION, AND CHARACTERIZATION OF BIMETALLIC PLATINUM AND PALLADIUM COMPLEXES - UNIQUE BUILDING-BLOCKS FOR SUPRAMOLECULAR MACROCYCLES - C-13 NMR ANALYSIS OF THE NATURE OF THE PALLADIUM-CARBON BOND
J. Manna et al., PREPARATION, VIA DOUBLE OXIDATIVE ADDITION, AND CHARACTERIZATION OF BIMETALLIC PLATINUM AND PALLADIUM COMPLEXES - UNIQUE BUILDING-BLOCKS FOR SUPRAMOLECULAR MACROCYCLES - C-13 NMR ANALYSIS OF THE NATURE OF THE PALLADIUM-CARBON BOND, Organometallics, 16(9), 1997, pp. 1897-1905
The high-yield preparation, by double oxidative addition, of nine nove
l platinum and palladium bis(trans-M(PR3)(2)X)aryl (M = Pt or Pd; R =
PPh3 or PEt3; X = Br or I; aryl = 1,4-benzene, 4,4'-biphenyl, 4,4''-te
r-p-phenyl, 4,4'-tolane, or 4,4'-benzophenone) complexes from the reac
tion of Pt(PPh3)4, Pt(PEt3)(4), or Pd(PPh3)(4) with the respective dih
alo aromatic in toluene is described. These complexes were fully chara
cterized by elemental analysis, mass spectrometry, and NMR (H-1, C-13{
H-1} and P-31{H-1}) and vibrational (IR or Raman) spectroscopies. The
single-crystal molecular structure of 4,4'-bis(trans -Pt(PEt3)(2)I)bip
henyl (2a) was determined by X-ray crystallography. The key structural
feature of this complex is the dihedral angle of 18.9 degrees between
the two planes defined by the phenyl groups of the biphenyl linkage.
The nature of the palladium-carbon bond is investigated by C-13{H-1) N
MR spectroscopy; Taft's sigma(R) parameter is found to correlate in a
linear fashion with [delta(C-ipso) - delta(C-0)] for these palladium c
omplexes. These data indicate the C-13 chemical shift of C-ipso is lin
early related to the amount of pi-electron density of the carbon bound
to the palladium center. The potential utility of these bimetallic pl
atinum and palladium complexes as subunits in the generation of organo
metallic macrocycles is described.