STUDIES ON THE PROPERTIES OF SCHIFF BASE TYPE ARYLMERCURY COMPOUNDS Ⅲ TRANSMETALLATION REACTION OF SCHIFF BASE TYPE ARYLMERCURY COMPOUNDS WITH METALLIC TIN

The transmetallation reaction of 4 Schiff base type arylmercury compounds with metallic tin has been carried out in refluxing xylene.It was found that the reaction proceeds in the same manner as that of chloro[2-(phenylazo)phenyl]mercury(Ⅱ) to give dichlorobisaryltin(Ⅳ).The ~1H NMR spectra of the products provide evidence for the presence of N→Sn intramolecular coordination.The formation of dichlorobisaryltin(Ⅳ)as a unique product probably arises from the N→Sn intramolecular coordination which results in the increasing of the stability of the molecule.

In Situ Monitoring of Transmetallation in Electric Potential-Promoted Oxidative Coupling in a Single-Molecule Junction

To monitor and investigate chemical reactions in real time and in situ is a long-standing,challenging goal in chemistry.Herein,an electric potential-promoted oxidative coupling reaction of organoboron compounds without the addition of base is reported,and the transmetallation process involved is monitored in real time and in situ with the scanning tunneling microscopy break single-molecule junctions(STMBJ)technique.We found that the electric potential applied determined the transmetallation.At low-bias voltage,the first-step transmetallation process occurred and afforded Au─C-bonded aryl gold intermediates.The electronic properties of organoboron compounds have a strong influence on the transmetallation process,and electron-rich compounds facilitate this transformation.At high-bias voltage,the second-step transmetallation process took place,and the corresponding intermediate(highly reactive diaryl metal complex)was detected with the assistance of Pd(OAc)_(2).Our work demonstrates the applications of STMBJ on in situ monitoring and catalyzing of chemical reactions and provides a new methodology to fabricate singlemolecule devices.

Synthesis of Lanthanide Cryptates by Transmetalation Reaction

New lanthanide cryptates [LnL](ClO_4)_3 (Ln=Eu 3+, Ce 3+, Pr 3+, Sm 3+, Gd 3+, Tb 3+; L=1, 4, 12, 15, 18, 26, 31, 39, 42, 43, 44-undecaazapentacyclo-[13.13.13.1 6, 10.1 20, 24.1 33, 37]-tetratetraconta-4, 6, 8, 10(44), 11, 18, 20, 22, 24(43), 25, 31, 33, 35, 37(42), 38-penta decaene) were synthesized by transmetalation reaction of lanthanide perchlorates with its barium cryptate which was obtained by [2+3] template condensation of tren with 2,6-diformylpyridine in the presence of barium perchlorate, and characterized by elemental analysis, IR and electrospray mass spectrum.

Products and Kinetics of the Reaction of Monomeric Target Bis-(Acetylacetonato) Copper(II) with Transmetalator Bis-(Diethoxydithiophosphato) Zinc(II) in Methylene Chloride

Reaction of bis-(acetylacetonato) copper(ΙΙ) (A) with transmetalator Zn((EtO)2PS2)2 (B2;Et = ethyl) in methylene chloride is a simple irreversible second-order process over a wide temperature range which is the first example of a second-order reaction of mononuclear target A with a transmetalator. The plots of kobsd vs [A] are linear, meaning that there is one A and one B2 in the activated complex of the slowest reaction step. The slowest step is precursor formation on the basis that B2 is an exceptionally weak complex. The product of the A/B2 reaction is the strong successor complex Zn(acac)2•Cu(ps)2. The data are compared with those for reactions of the same target (A) with S-methyle isopropylidenehydrazinecarbodithioate-carbodithioato-metal(II) complexes M(SN)2 (M=Ni (C1) and Zn (C2)). The reaction is not like that of A with Ni ((MeO)2PS2)2 (B1;Me=methyl), because it is irreversible and also consistent with the measured lower relative thermodynamic stability of B2 compared to B1.

Vanadium(V) Complexes Containing Unsymmetrical N-Heterocyclic Carbene Ligands: Highly Efficient Synthesis and Catalytic Behavior towards Ethylene/Propylene Copolymerization

The highly efficient method has been developed for the synthesis of NHC·VOCl_(3) containing symmetrical or unsymmetrical Nheterocyclic carbene(NHC) ligands by the transmetallation reaction of NHC·AgCl with VOCl_(3).The total isolated yield of VOCl_(3)[1,3-(2,4,6-Me_(3)C_(6)H_(2))_(2)(NCH=)_(2)C:](V4') reached 86% by transmetallation reaction,which is much higher than that(48%) by direct coordination method.This methodology has also been used to synthesize the novel vanadium complexes containing unsymmetrical NHC ligands of VOCl_(3)[PhCH_(2)NCH=CHNR)C:](V5',R=2,4,6-Me_(3)C_(6)H_(2);V6',R=2,4-Me_(2)-6-Ph-C_(6)H_(2);V7',R=2,6-^(i)Pr_(2)-C_(6)H_(3)) with high yield,which could not be obtained by direct coordination method.The catalytic activity and copolymerization ability would be improved by introducing unsymmetrical NHC ligands due to their less steric bulky effect.The vanadium complex V5' containing unsymmetrical NHC ligand exhibits higher catalytic activity(3.7×10^(5)g_(copolymer)·mol^(-1) of V·h^(-1)) than that of V4' containing symmetrical NHC ligand.Moreover,the higher propylene incorporation ratio(45.6 mol%) in the copolymers of ethylene with propylene could be obtained by using V5' than that(39.9%) by using V4'.The results would provide a highly efficient strategy for the synthesis of early transition metal complexes containing versitile NHC ligands,affording the catalyst with both high catalytic activity and copolymerization ability for the synthesis of high performance polyolefin elastomers.

Synthesis of 9,10-Phenanthrenes via Rh(III)-Catalyzed[4+2]Annulation of 2-Biphenylboronic Acids with Diazo Compounds

A Rh(III)-catalyzed,transmetalation triggered C—H activation/annulation of 2-biphenylboronic acids with diazo compounds fromβ-keto esters or 1,3-dicarboxylates has been developed,leading to the synthesis of two kinds of 9,10-phenanthrenes.Notably,a rhodacyle was synthesized by treating the rhodium catalyst with stoichiometric amounts of 2-biphenylboronic acids and pyridine,which was further verified to be active for the catalytic system.The reactions proceeded under redox-neutral and air-tolerant conditions to produce a series of all-carbon six-membered rings with high efficiency.

Rhodium-catalyzed enantio-and diastereoselective carboamidation of bicyclic olefins toward construction of remote chiral centers and axis

The precise control of multiple chiral elements through a single step catalytic process remains a significant challenge in asymmetric catalysis.Reported herein is rhodium-catalyzed three-component asymmetric carboamidation between aryl boronic acid,achiral strain-activated symmetric bicyclic olefins bearing a prochiral C-N or N-N axis,and dioxazolones.The reaction proceeded effectively in excellent enantio-and diastereoselectivity under mild conditions to produce the bicyclic framework with six contiguous chiral centers as well as a N-N or C-N chiral axis.The reaction featured excellent functional group tolerance,chemoselectivity,and stereoselectivity.Mechanistic studies indicated that the coupling system proceeded via initial transmetalation,followed by stereo-determining migratory insertion into the olefin and electrophilic amidation.

Theoretical Investigation of the Mechanism of Rh(III)-catalyzed Annulation of 2-Biphenylboronic Acid with Activated Alkene

The mechanism is investigated for Cp^(tBu)Rh(OH)_(2)-catalyzed annulation of 2-biphenylboronic acid with three activated alkenes using M06-2X functional.The reaction comprises transmetalation via two steps and following C-H activation producing reactive Rh-biphenyl complex with two Rh—Cσbonds.After the coordination/insertion of alkenes,respective fused or bridged cyclic products are yielded depending on different alkenes accompanied by the release of CptBuRh.The promotion of Cp^(tBu)Rh(OH)_(2) lies in the barrier decrease of transmetalation and C-H activation ready for coordination/insertion ensuring the smooth progress of common rate-limiting reductive elimination.The stereoselective transfer and ring rotation are specific for benzoquinone and cyclopropenone.The role of Rh(III)catalyst and release of Rh(I)is supported by Multiwfn analysis on frontier molecular orbital(FMO)of specific transiton states(TSs)and Mayer bond order(MBO)value of vital bonding,breaking.

The role of Cul in the siloxane-mediated Pd-catalyzed cross-coupling reactions of aryl iodides with aryl lithium reagents

Experiments indicate that a catalytic amount of Cul plays an important role in the siloxane-mediated Pd-catalyzed cross-coupling reactions with the direct use of organolithium reagents.Addition of organolithium to the siloxane transfer agent generates an organosilicon intermediate.DFT calculations indicate that Cul initially accelerates the Si-Pd(Ⅱ) transmetalation of the organosilicon intermediate by the formation of CuI_(2)^(-).Subsequently,CuI_(2)^(-)works as a shuttle between the Si-Cu(Ⅰ) and Cu(Ⅰ)-Pd(Ⅱ)transmetalation processes.