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We report a systematic study of the stoichiometric reactions of isolated arylpalladium hydroxo and halide complexes with arylboronic acids and aryltrihydroxyborates to evaluate the relative rates of the two reaction pathways commonly proposed to account for transmetalation in the Suzuki-Miyaura reaction. On the basis of the relative populations of the palladium and organoboron species generated under conditions common for the catalytic process and the observed rate constants for the stoichiometric reactions between the two classes of reaction components, we conclude that the reaction of a palladium hydroxo complex with boronic acid, not the reaction of a palladium halide complex with trihydroxyborate, accounts for transmetalation in catalytic Suzuki-Miyaura reactions conducted with weak base and aqueous solvent mixtures. 相似文献
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Barrios-Landeros F Carrow BP Hartwig JF 《Journal of the American Chemical Society》2008,130(18):5842-5843
We report that oxidative addition of bromobenzene to Pd(PtBu3)2 occurs by an unusual autocatalytic mechanism. Studies on the effect of various additives showed that the degree of rate acceleration followed the trend: (PtBu3)Pd(Ph)(Br) approximately (HPtBu3)Br < [(PtBu3)Pd(mu-Br)]2 < (PtBu3)2Pd(H)(Br). Studies on the reactions of Pd(PtBu3)2 in the presence of (PtBu3)2Pd(H)(Br) showed that the concentration of (PtBu3)2Pd(H)(Br) decreased only after the Pd(0) complex had been consumed. These data indicated that the catalyst in this process is (PtBu3)2Pd(H)(Br). Thermal decomposition of the three-coordinate oxidative addition product (PtBu3)Pd(Ar)(Br) during the reaction of Pd(PtBu3)2 and bromoarenes ultimately leads to formation of (PtBu3)2Pd(H)(Br). Parallel reactions of bromobenzene with (PtBu3)2Pd(H)(Br) and Pd(PtBu3)2 showed that the bromoarenes reacted considerably faster with the Pd(II) species than with the Pd(0) species. We therefore propose a catalytic cycle for oxidative addition in which PBut3.HBr reacts with the Pd(0) species to form (PtBu3)2Pd(H)(Br), and (PtBu3)2Pd(H)(Br) reacts with the bromoarene, possibly though the anionic species [HPtBu3+][(PtBu3)Pd(Br)-], to form [Pd(PtBu3)(Ar)(Br)]. 相似文献
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The technique of ferromagnetic resonance at 23 GHz has been used to determine the first three anisotropy constants of pure Ni down to 4.2K. A temperature and orientation dependent linewidth has also been observed. 相似文献
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Lief GR Carrow CJ Stahl L Staples RJ 《Chemical communications (Cambridge, England)》2001,(17):1562-1563
The syntheses and solid-state structures of the first three-membered nickel-phosphorus-nitrogen ring compounds, having anionic four-electron P=N moieties are reported. 相似文献
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Ingo Schranz Christopher J. Carrow Richard J. Staples 《Journal of organometallic chemistry》2008,693(6):1081-1095
The polycyclic Group 14 amides [P(μ-NtBu)2P(tBuN)2]M, M = Ge (4), Sn (5) were synthesized from cis-[P(μ-NtBu)2P(tBuNLi · THF)2] and GeCl2 · dioxane or SnCl2, respectively. Oxidation of these heterocarbenoids or of the analogous diazastannylene [MeSi(μ-tBuN)2SiMe(tBuN)2]Sn with O2, S8 and Sen furnished the chalcogenides {[P(μ-NtBu)2P(tBuN)2]GeO}2 (6), {[P(μ-NtBu)2P(tBuN)2]SnE}2, E = O (7), S (8), Se (9), {[SP(μ-NtBu)2P(tBuN)2]SnS}2 (10), and {[MeSi(μ-tBuN)2SiMe(tBuN)2]SnE}2, E = S (11), Se (12), respectively. All products (6-12) were shown by single-crystal X-ray methods to consist of dimeric molecules with central (M-E)2 rings, M = Group 14 element, E = chalcogen. The exclusive formation of dimeric compounds with bridging M-E-M bonds, vs. alternative monomeric structures with terminal ME bonds, is rationalized in terms of the thermodynamic favorability of the dimers. The case is made that most, if not all, currently known Group 14 chalcogenides, even those labeled “kinetically stabilized”, are really thermodynamic products. 相似文献
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Schranz I Lief GR Carrow CJ Haagenson DC Grocholl L Stahl L Staples RJ Boomishankar R Steiner A 《Dalton transactions (Cambridge, England : 2003)》2005,(20):3307-3318
Nickel(ii) chloride reacts with the bis(tert-butylamino)diazadiphosphetidine {Bu(t)(H)NP(micro-NBu(t))(2)PN(H)Bu(t)} to form trans-[{Bu(t)(H)NP(micro-NBu(t))(2)PN(H)Bu(t)}(2)NiCl(2)]. In solution and the solid-state each heterocyclic ligand coordinates nickel through one phosphorus atom only. For comparison the solid-state structure of the known trans-[NiCl(2)(PEt(3))(2)] was also determined and it was found that the two complexes have almost identical bond parameters about nickel. The nickel-amidophosphine complexes [{Bu(t)OP(micro-NBu(t))(2)PNBu(t)}NiCl(PBu(n)(3))], [(PBu(n)(3))ClNi{Bu(t)NP(micro-NBu(t))(2)PNBu(t)}NiCl(PBu(n)(3))], and [{Me(2)Si(micro-NBu(t))(2)PNBu(t)}NiCl(PBu(n)(3))] were synthesized and X-ray structurally characterized. In these mono- and di-nuclear nickel complexes the nickel ions are coordinated in pseudo square-planar fashions, by one trialkylphosphine ligand, one chloride ligand and one kappaP,N-coordinated amidophosphine moiety from tert-butylamido-substituted heterocycles. Attempts to create nickel complexes chelated in a kappa(2)P fashion by the o-phenylenediamine-tethered mono- and di-anionic 1-{Me(2)Si(micro-NBu(t))(2)PN} 2-{Me(2)Si(micro-NBu(t))(2)PNH}C(6)H(4) and 1,2-{Me(2)Si(micro-NBu(t))(2)PN}C(6)H(4), respectively, afforded instead [1,2-{Me(2)Si(micro-NBu(t))(2)PN}{Me(2)Si(micro-NBu(t))(2)PN}C(6)H(4)NiCl] and [1,2-{Me(2)Si(micro-NBu(t))(2)PN}{Me(2)Si(micro-NBu(t))(2)PN}C(6)H(4)Ni{PEt(3)}], each complex having kappaP,N and kappaP coordinated amidophosphine ligands. 相似文献