Synthesis and reactions of dinuclear palladium complexes containing methyls and hydride on adjacent palladium centers: Reductive elimination and carbonylation reactions

Abstract

was monitored by an in-stream thermocouple which had been previously calibrated against a second thermocouple in the sample position. Automatic peak search and indexing procedures yielded the monoclinic reduced primitive cell The final cell parameters and specific collection parameters are given in Table 7 .The 4143 raw intensity data were converted to structure factor amplitudes and their esd's by correction for scan speed, background, and Lorentz and polarization effects. No correction for crystal decomposition was necessary. Inspection of the azimuthal scan data showed a variation Imln/Imar = 0.75 for the average curve. An empirical correction for absorption, based on the azimuthal scan data, was applied to the intensities since it was not possible to accurately measure the sample crystal. Removal of systematically absent and redundant data left 3775 unique data.The structure was solved by Patterson methods and refined via standard least-squares and Fourier techniques. In a difference Fourier map calculated following refinement of all non-hydrogen atoms with anisotropic thermal parameters, peaks corresponding to the expected positions of most of the hydrogen atoms were found. A difference Fourier map calculated after inclusion of all other hydrogen atoms clearly showed the position of the hydride ligand attached to the metal. All hydrogen atoms were then allowed to refine with isotropic thermal parameters. A secondary extinction parameter was refined in the final cycles of leastsquares. The final residuals for 267 variables refined against the 3100 data for which F2 > 3 1 P 1 were R = 2.04%, wR = 2.53%, and GOF = 1.356. The R value for all 3775 data was 3.49%.The quantity minimized by the least-squares program was w(lFollFC1)* where w is the weight of a given observation. The p factor, used to reduce the weight of intense reflections, was set to 0.025 in the last cycles of the refinement. The analytical forms of the scattering factor tables of the neutral atoms were used, and all non-hydrogen scattering factors were corrected for both the real and imaginary components of anomalous dispersion. Inspection of the residuals ordered in ranges of sin ( B ) / X , IFo[, and parity and value of the individual indices showed no unusual features or trends. The largest peak in the final difference Fourier map had an electron density of 2.14 e-/A3 and was located only 0.74 A from the iridium atom. All other peaks in the final difference Fourier map had densities of less than 1 e-/A3. The positional parameters of the atoms and the estimated standard deviations are given in Table 8. Structure factor amplitudes were provided as supplementary material in the preliminary comm~nication.~ Acknowledgment.Abstract: The transmetalation reaction of trimethylaluminum with the palladium chloride dimer Pd2C1,(p-dppm), (1) (dppm = bis(dipheny1phosphino)methane) at -78 O C gave an intermediate, Pd2C1Me(p-dppm), ( 2 ) , which disproportionated at -10 OC to yield the trans-face-to-face palladium dimer Pd2C12Me2(p-dppm), (3) and a palladium ...

Synthesis and spectroscopy of binuclear phosphine bridged palladium hydrides: Pd2HX3[dppm]2 (X=Br, I; dppm=bis[diphenylphosphino]methane)

“…Substitution of DBr for HBr in equation 1 yields a dark green product spectroscopically identical to 1a with the exception of the missing Pd Á/H resonance at (/8.46 ppm. The chemical shifts for the Pd Á/H resonances are well within the range reported for palladium hydride complexes [6] [10] [11].…”

“…Palladium hydride resonances in di-and polynuclear palladium phosphine hydride complexes have been observed over a wide range of chemical shift values ranging from 5.01 ppm (septuplet) for the bridging hydride in [Pd 4 dppm 4 H 2 ]Cl 2 [10] to (/12.42 ppm (triplet) for the terminal palladium hydride [Pd 2 (mCl)H(CH 3 )dppm 2 ][BPh 4 ] [11]. The bridging hydride ligands in cationic [Pd 2 R 2 (m-H)dppm 2 ) ' ][PF 6 ( ] [6], are distinguished by quintets for the Pd Á/H resonances between (/7.8 to (/9 ppm.…”

New Diphosphane Ligands Based on Bisphenol A Backbones − Synthesis and Coordination Chemistry

“…[17] The P 1 ϪP 2a distance was found to be 7.4470(13) Å . Other binuclear palladium complexes with a face-to-face structure that have been described in literature most often have two chlorine ligands coordinated to the metal center instead of one (4) chlorine and one methyl ligand.…”

Synthesis, X-ray crystal structure, and reactivity of Pd2(μ-dotpm)2 (dotpm=bis(di-ortho-tolylphosphino)methane)

“…Binuclear complexes Pd 2 (l-P-P) 2 are of interest because they contain two coordinatively unsaturated palladium(0) centers that are potential catalysts for the activation of organic halides [1][2][3] and hydrosilanes [1,2,4]. Another attractive feature of Pd 2 (l-P-P) 2 complexes is that there is a weak ''closed-shell" bonding interaction between the d 10 -d 10 metal centers [5][6][7][8][9][10][11] that can potentially promote a cooperative catalytic system in which the substrate is bonded to and activated by both metal centers [5].…”