77462-41-0Relevant articles and documents
Synthesis and spectroscopy of binuclear phosphine bridged palladium hydrides: Pd2HX3[dppm]2 (X = Br, I; dppm = bis[diphenylphosphino]methane)
Kirss, Rein U.,Forsyth, David A.,Plante, Marc A.
, p. 206 - 215 (2007/10/03)
Reactions of orange-red dichloromethane solutions of Pd2 X2dppm2 (X=Br, I; dppm=bis{diphenylphosphino} methane) with aqueous, concentrated HBr or HI at ambient temperature yields dark green solids which analyze for Pd2HX3 dppm2 (1a X=Br and 1b X=I). No reaction is observed between Pd2X2dppm2 and aqueous, concentrated HCl. Line shape analysis of dynamic 31P-NMR spectra for 1a and 1b over a 100 °C range indicates that in each case a system involving two sets of chemically equivalent 31P nuclei, mutually coupled, is exchanging 31P environments via initial exchange with a less populated intermediate system in which all four 31P nuclei are equivalent. From lineshape analysis of the 31P spectra, activation parameters for the rates going to the symmetrical intermediates are as follows: 1a: Δ G ?(-78°)=7.8±0.2 kcal mol-1, Δ H ?=7.5 kcal mol-1, Δ S ?=-1.3 e.u. and for 1b: Δ G ? (-78°)=9.7±0.3 kcal mol-1, Δ H ?=8.9 kcal mol-1, Δ S ?=-3.9 e.u. Similar analysis of dynamic 1H spectra for 1b over a 80 °C range reveals two exchanging Pd-H sites with activation parameters for the exchange: Δ G ?(-78°)=9.5±0.3 kcal mol-1, Δ H ?=8.2 kcal mol-1, Δ S ?=-6.9 e.u. Compounds 1a and 1b decompose to a 1:2 mixture of Pd2X2dppm2 and PdX 2dppm in solution with the evolution of hydrogen. Compound 1b reacts with PPh3 yielding [HPPh3+] [I-] and Pd2I2dppm2 while reaction of 1b with KOH also yields Pd2I2dppm 2. Decomposition of 1b is unchanged in the presence of styrene with no evidence for the formation of iodoethylbenzene or ethylbenzene.
General route to halide-bridged organopalladium A-frame complexes and studies of reductive elimination from these bimetallic systems
Stockland Jr., Robert A.,Janka, Mesfin,Hoel, Gretchen R.,Rath, Nigam P.,Anderson, Gordon K.
, p. 5212 - 5219 (2008/10/08)
Reactions of [Pd2Cl2(μ-dppm)2] with RMgX (R = Me, Et, Bu, Ph, C6H4Me-4) at low temperature, followed by addition of CBr4 and excess NH4PF6 or 1 equiv of TIPF6, provided halide-bridged organopalladium A-frame complexes of the form [Pd2R2(μ-X)(μ-dppm)2]PF6. Mixed metal complexes were obtained similarly starting from [PdCtCl2(μ-dppm)2]. Unsymmetrical A-frames of the type [Pd2(C6H2Me3-2,4,6)R(μ-Cl)(μ-d ppm)2]+ were generated reaction of [Pd(C6H2Me3-2,4,6) (dppm)2]+ (obtained by treatment of [PdCl2 (cod)] w mesitylmagnesium bromide at low temperature, followed by 2 equiv of dppm) with [Pd2R2(μ-Cl)2 (AsPh3)2]. The organopalladium A-frames did not react readily with CO, but the corresponding acyl derivatives [Pd2(COR)2(μ-Cl)(μ-dppm)2]PF6 were produced by carbonylation of [Pd2R2(μ-Cl)2(AsPh3)2] followed by addition of dppm (R = Me, Et, Bn). Thermal decomposition of [Pd2(CH2Ph)2(μ-Cl)(μ-dppm)2]Cl was found to be first order in A-frame and resulted in quantitative formation of [Pd2Cl2(μ-dppm)2] and 1,2-diphenylethane. The methyl and aryl complexes underwent both reductive elimination and hydrogen abstraction reactions. [Pd2Et2(μ-Br)(μ-ddpm)2]PF6 decomposed by β-hydride elimination and subsequent reductive elimination to yield ethene and ethane, whereas the butyl derivative gave both 1- and 2-butene. Acetic acid was formed when [Pd2(COMe)2(μ-Cl)(μ-dppm)2]PF6 was heated in dmso-d6 solution, but decarbonylation was the predominant process in dioxane. The molecular structures of [Pd2(CH2Ph)2(μ-Br)(μ-dppm)2] PF6·H2O, 2C6H6 and [Pd2Cl2(μ-Cl)(μ-dppm)2]OH· 0.5(CH3)2CO are also described.
Kinetic and mechanistic aspects of sulfur recovery from Pd2I2(μ-S)(μ-dpm)2 using I2 and structures of Pd(II) complexes with the chelated monosulfide of dpm
Wong, Terrance Y.H.,Rettig, Steven J.,James, Brian R.
, p. 2143 - 2149 (2008/10/08)
The Pd2X2(μ-S)(dpm)2 complexes (2) (X = I, Br) react with halogens to yield PdX2(dpm) (3) and elemental sulfur. Kinetic and mechanistic studies on the X = I system in CHCl3 reveal that the reaction pr
Reactions of [PdX2(dppm)] complexes with grignard reagents
Stockland Jr., Robert A.,Anderson, Gordon K.,Rath, Nigam P.
, p. 5096 - 5101 (2008/10/08)
Reactions of [PdX2(dppm)] (X = Cl, Br) with a range of Grignard reagents have been investigated. Diorganopalladium complexes of the type [PdR2(dppm)] were obtained in good yield with the bulky mesityl or trimethylsilylmethyl groups,
Trimethylsilyl halide adducts of dinuclear phosphine-bridged palladium halide complexes: Synthesis, spectroscopy, and reactions of Pd2X2(dppm)2·Me3SiX′ (X, X′ = Cl, Br, I)
Kirss, Rein U.
, p. 3451 - 3458 (2008/10/08)
Reaction of Pd2X2(dppm)2 (1, X = Cl; 2, X = Br; 3, X = I) with Me3SiX′ (X′ = Cl, Br, I) in dichloromethane produced transient dark green solutions for all combinations of X and X′ with the exception of X = X′ = Cl. Net halide exchange was observed for reactions of 1 with Me3SiBr or Me3SiI and for 2 with Me3SiI, apparently without oxidative addition of the silicon-halide bond. Mono- and dinuclear palladium complexes Pd2(μ-CH2)Cl2(dppm)2 (4) and PdCl2(dppm) (5) also exchanged Pd-Cl bonds for Pd-Br bonds in reactions with Me3SiBr. Low-temperature 1H and 31P NMR spectroscopy provided evidence for formation of adducts of formulas Pd2Cl2(dppm)2·Me3-SiCl, Pd2Br2(dppm)2·Me3SiCl, Pd2Br2(dppm)2·Me3SiBr, Pd2I2(dppm)2·Me3SiBr, and Pd2I2(dppm)2·Me3SiI in the reactions of 1-3 with Me3SiX′. Dark green solids of formula Pd2X2(dppm)2·Me3SiX′ (6: (a) X = Cl, X′ = I; (b) X = Br, X′ = I; (c) X = Br, X′ = Br; (d) X = Cl, X′ = Br; (e) X = I, X′ = Br; (f) X = I, X′ = I) could be isolated from the reaction mixtures. The green color is proposed to result from a weakening of the metal-metal bond in 1-3 upon coordination of the trimethylsilyl halide. The presence of oxygen in reactions of 1-3 with Me3SiX′ (X = Cl, Br, I) did not interfere with the formation of the adduct but led to the formation of siloxanes and mononuclear palladium complexes PdXX′(dppm). There was no evidence for Si-Si bond formation in these systems. Halide exchange was also observed in reactions of 1, 2, and 5 with methyl iodide.
