Cationic methylpalladium complexes with hemilabile bidentate ligands of alpha-amino-pyridines, in the form of [R(1)HNCR(2)H(o-C(6)H(5)N)]Pd(Me)(NCMe)}(BF(4)) (R(1) = (i)Pr, (t)Bu, Ar R(2) = H, Me) have been found to be effective precursors for catalytic copolymerization of ethylene and norbornene under mild conditions. The copolymer products exhibit predominant alternating microstructures which are
作者:Frank W. Vergeer、Martin Lutz、Anthony L. Spek、Maria J. Calhorda、Derk J. Stufkens、František Hartl
DOI:10.1002/ejic.200401040
日期:2005.6
unsaturated +Ru(CO)2(iPr-AcPy·–/0) moiety to bind a Lewis base, the heteronuclear biradical and zwitterionic photoproducts live significantly shorter than their triosmium counterparts. The influence of the weaker Os2–Ru(iPr-AcPy) bond on the redox reactivity is clearly reflected in very reactive radical anions formed upon electrochemical reduction of [Os2Ru(CO)10(iPr-AcPy)]. The dimer [–Os(CO)4-Os(CO)4-Ru(CO)2(iPr-AcPy)]22–
Three different palladium(II) complexesPd(NN′)Cl2 and two different palladium(0) complexesPd(NN′)(dmfu) (dmfu = dimethylfumarate) containing NN′ pyridyl-imine ligands, have been prepared and used as pre-catalysts for the coupling between iodobenzene and methyl acrylate (Meac) (Heck reaction). All the reactions have been conducted in DMF at 80 °C, using Et3N as base and a Pd:PhI:Meac:Et3N = 1:1000:1100:1000
制备了三种含有NN'吡啶亚胺配体的钯(II)配合物Pd(NN')Cl 2和两种钯(0)配合物Pd(NN')(dmfu)(dmfu =富马酸二甲酯) -用于碘代苯和丙烯酸甲酯(Meac)之间偶联的催化剂(Heck反应)。所有反应均在80°C的DMF中进行,使用Et 3 N作为碱,Pd:PhI:Meac:Et 3 N = 1:1000:1100:1000摩尔比。在所有情况下,均已观察到反应2.5小时内碘代苯完全转化为反式-肉桂酸甲酯,钯(II)配合物获得的TOF值最高(1253)。在催化反应结束时,二聚体[Pd 2 I 6 ] [Et3 NH] 2已被回收,指出了起始复合物物种中钯的部分损失。Hg(0)中毒测试显示了催化反应的非均质性质,这表明Pd(NN')络合物可作为金属钯的储库。一旦底物被完全消耗,二聚体[Pd 2 I 6 ] [Et 3 NH] 2可能由可溶性钯(0)颗粒形成,该颗粒由复
Palladium(0) Complexes with Unsymmetric Bidentate Nitrogen Ligands for the Stereoselective Hydrogenation of 1-Phenyl-1-propyne to (<i>Z</i>)-1-Phenyl-1-propene
作者:Martijn W. van Laren、Marcel A. Duin、Chantal Klerk、Michele Naglia、Dominga Rogolino、Paolo Pelagatti、Alessia Bacchi、Corrado Pelizzi、Cornelis J. Elsevier
DOI:10.1021/om0108346
日期:2002.4.1
small changes in substituents apply, the various complexes show very different stabilities under hydrogenation conditions. The complex Pd(C5H4N-(C(H)N(CH2)2OH)-2)(dmfu) exhibits a good selectivity for the (Z)-alkene but decomposes just before full conversion of the alkyne, whereas the complex Pd(C5H4N-(C(H)Ni-Pr)-2)(dmfu) exhibits a good selectivity and stability under hydrogenation conditions and
通式为6-R''-C 5 H 3 N-(C(R')NR)-2(R''的双齿或三齿氮配体的一系列零价钯配合物Pd(NN)(烯烃)= H,Me,CH NR′; R′= H,Me; R =烷基,芳基或氨基)和富马酸二甲酯(dmfu)已被制备,随后被用作1-苯基-的均相立体选择性半氢化中的预催化剂。 1-丙炔。获得了Pd(C 5 H 4 N-(C(Me)N i -Pr)-2)(dmfu)的X射线结构。尽管仅应用相对较小的取代基变化,但是各种配合物在氢化条件下显示出非常不同的稳定性。复数Pd(C 5 H 4 N-(C(H)N(CH 2)2 OH)-2)(dmfu)对(Z)烯烃具有良好的选择性,但在炔烃完全转化之前会分解,而络合物Pd(C 5 H 4 N-(C(H )N i -Pr)-2)(dmfu)在加氢条件下表现出良好的选择性和稳定性,是将1-苯基-1-丙炔立体选择性加氢为(Z)-1-苯基-1-丙烯的合适催化剂。
Photochemistry of the Triangular Clusters Os<sub>3</sub>(CO)<sub>10</sub>(α-diimine): Homolysis of an Os−Os Bond and Solvent-Dependent Formation of Biradicals and Zwitterions
作者:Jos Nijhoff、Maarten J. Bakker、František Hartl、Derk J. Stufkens、Fu、Rudi van Eldik
DOI:10.1021/ic9707319
日期:1998.2.23
Several clusters Os-3(CO)(10)(alpha-diimine) (alpha-diimine = pyridine-2-carbaldehyde N-R-imine or 1,4-di-R-1,4-diazabutadiene) were synthesized and studied with respect to their spectroscopic and photochemical properties. According to the resonance Raman spectra the visible absorption band of these clusters belongs to electronic transitions having Os-to-a-diimine charge transfer (MLCT) character with a variable degree of pi-delocalization within the Os(alpha-diimine) moiety. Upon irradiation into these transitions zwitterions Os-(CO)(4)-Os(CO)(4)-Os+-(S)(CO)(2)(alpha-diimine) are formed in coordinating solvents (S) and biradicals *Os(CO)(4)-Os(CO)(4)-Os+(CO)(2)(alpha-diamine(.-)) in noncoordinating solvents and in THF at ambient temperature. The zwitterions live seconds in nitrile solvents and minutes in pyridine, and they largely regenerate the parent clusters. Quantum yields of zwitterion formation are wavelength independent and range from 10(-2) to 3 x 10(-2) with an activation energy varying from 440 to 720 cm(-1). For one of the clusters the quantum yield of zwitterion formation in pyridine was studied in dependence of applied pressure. The activation volume Delta V-double dagger = +7.0 +/- 0.5 cm(3) mol(-1) derived from these measurements indicates that the effect of bond cleavage is partially offset by coordination of the solvent. In apolar solvents biradicals are formed instead of zwitterions, which could be detected with nanosecond time-resolved absorption spectroscopy, while their adducts with nitrosodurene were observed with EPR spectroscopy. Their lifetimes vary from 5 ns to 1 mu s depending on the solvent and the alpha-diimine. The biradicals transform into zwitterions in the presence of a Lewis base. in addition, they produce with low efficiency an isomeric product in which the cr-diimine bridges between two Os atoms. The formation of very similar photoproducts (biradicals, cr-diimine-bridged isomeric products, charge-separated species) as in the case of binuclear metal-metal-bonded complexes such as (CO)(5)MnMn(CO)(3)(alpha-diimine) points to the occurrence of a primary photoprocess in which an Os-Os bond is broken homolytically. This reaction most likely occurs from a reactive (3) sigma pi* state after surface crossing from the unreactive but optically accessible MLCT states.