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The new ligand, 1,1-bis((N-p-tolylimino)diphenylphosphoranyl)ethane (1,1-BIPE), 1, has been synthesized by means of a Staudinger reaction of 1,1-bis(diphenylphosphino)ethane (1,1-dppe) with 2 equiv of p-tolylazide. Bridge-splitting reactions of Pt(2)Cl(4)(PR(3))(2) with 1 readily afforded sigma-N monodentate complexes, [PtCl(2)(PR(3)){1,1-BIPE-sigmaN}] (2a, PR(3) = PEt(3); 2b, PR(3) = PMe(2)Ph). Conversion of 2 into the six-membered platinacycle [PtCl(PR(3)){1,1-BIPE-sigmaN,sigmaN'}](+)[X](-) (3) (X = Cl, PtCl(3)(PR(3)), BF(4)) took place after prolonged stirring, its reaction rate being strongly dependent on the type of phosphine (>5 days for 2ain the presence of NaBF(4), 1 h for 2b) and the metal-to-ligand ratio. The compounds 1, 2, and 3 have been fully characterized by (1)H, (31)P{(1)H}, and (13)C{(1)H} NMR and IR spectroscopy, elemental analysis, or FAB mass spectroscopy. The molecular structures of CHCH(3)(PPh(2)=NC(6)H(4)-4-CH(3))(2) (1) and [PtCl(PMe(2)Ph){(N(pTol)=PPh(2))(2)CHCH(3)}](+)[Cl](-) (3b) have been determined by X-ray crystallography. Crystal data for 1: space group P2(1)/c with a = 8.9591(5) ?, b = 19.1961(12) ?, c = 21.9740(9) ?, beta = 105.069(4) degrees, V = 3649.1(3) ?(3), and Z = 4. The structure refinement converged to R = 0.080 and R(w) = 0.109. Crystal data for 3b: monoclinic, space group P2(1)/c with a = 12.4021(7) ?, b = 16.9705(11) ?, c = 23.760(2) ?, beta = 109.544(5) degrees, V = 4712.7(5) ?(3), and Z = 4. The structure refinement converged to R1 = 0.057, wR2 = 0.122. Variable temperature NMR spectroscopy has revealed that complexes 3 exclusively adopt a twisted boat conformation with the methyl group in equatorial position at low temperature, in agreement with the solid state structure of 3b as determined by X-ray crystallography. Boat-to-boat inversion is assumed to take place at temperatures above 293 K. Furthermore, for 3, hindered rotation of one of the p-tolyl substituents on nitrogen has been established at low temperatures. 相似文献
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Jeroen W. Sprengers Marcel A. Duin Cornelis J. Elsevier 《Journal of organometallic chemistry》2003,679(2):149-152
A highly active and selective in situ formed platinum(N-heterocyclic carbene) catalyst for the hydrosilylation of styrene with triethylsilane is described, which unlike all other known hydrosilylation catalysts, selectively yields hydrosilylation products, but (almost) no dehydrogenative silylation products. 相似文献
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The synthesis of an air‐stable series of Pd0 complexes with unsymmetric bidentate N‐pyridine N‐heterocyclic carbene ligands has been described. The carbenes were generated by synthesis of the silver(I) complexes from the imidazolium salts, followed by transmetallation of the C‐N ligands to obtain the target electron‐rich zerovalent palladium compounds. The bidentate coordination behaviour of the ligands was confirmed by 1H, 13C NMR and X‐ray spectroscopy. The complexes are active precatalysts for the selective transfer semihydrogenation of alkynes to Z‐alkenes, with selectivities up to 99%. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Stefan Warsink Peter Hauwert Maxime A. Siegler Anthony L. Spek Cornelis J. Elsevier 《应用有机金属化学》2009,23(6):225-228
The synthesis of an air‐stable series of Pd0 complexes with dissymmetric bidentate N‐heterocyclic carbene–amine ligands has been performed. The key step is an unprecedented carbene transfer from AgI to obtain electron‐rich zero‐valent palladium precatalysts. The coordination behavior of the ligands was determined with X‐ray crystallography. Surprising results were obtained in the catalysis of transfer semi‐hydrogenation, where the addition of base appeared not to be necessary to obtain the desired product stereoselectively. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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New N‐Alkyl‐substituted imidazolium salts as well as a series of their corresponding [Pd(NHC)(MA)2] complexes have been obtained by three routes in good yield. The previously reported synthesis for the analogous N‐aryl substituted [Pd(NHC)(MA)2] complexes has been improved. The N‐alkyl‐substituted [Pd(NHC)(MA)2] complexes are thermally more labile than their N‐aryl counterparts. Catalytic transfer semi‐hydrogenation of phenylpropyne resulted in good to excellent chemo‐ and stereo‐ selectivity conversion into (Z)‐phenylpropene. The size of the alkyl substituents correlates with the rate of hydrogenation in the sense that more bulky substituents give rise to faster transfer hydrogenation rates. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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