“…In this context, the achievements in development of novel and efficient synthetic methodologies for these types of reactions have been acknowledged with the 2010 Nobel Prize in Chemistry. Much attention has been paid to the design and development of powerful Pd-catalysts/precursors [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,37,38,39,40,41,42,43] that contain bulky and electron-rich ligands (such as phosphines and N -heterocyclic carbenes, NHCs) and to their potential synthetic applications [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36] in the Pd-catalyzed cross-couplings of various substrates (such as allyl, aryl, and vinyl halides and olefins). Catalytic activity enhancement of Pd (0) ( L ) n -precursors is greatly influenced by the electronic and steric properties of electron-rich and bulky L- ligands [1,2,3,4,5,6,7,8,18,19,20,21,22,23,24…”
Section: Introductionmentioning
confidence: 99%
“…In previous studies using hemilabile multidentate ligands [37,38,39,40,41,42,43,44,45,46,47], exceptional oxidation state and specific coordination selectivity have been observed for the Pd([9]ane B 2 A ) L 2 complexes with mixed soft A and hard B tridentates. The uncommon geometric structures of Pd([9]ane B 2 A ) L 2 complexes with an axial ( A …Pd) interaction were mainly formed under the following restrictive conditions: (1) coordination bonds of P - and N -functionalized derivatives are present [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39] and (2) polymeric side chain interactions exist [40,41,42].…”
Section: Introductionmentioning
confidence: 99%
“…In the Pd complex with an apical (hard N …Pd) interaction [42], the apical interaction was explained by an antibonding interaction between the lone pair of the apical N site and the d z2 -orbital of the Pd II species. In the ligand exchange reaction of square-planar Pd complexes, a vertical L …Pd interaction also has been optimized [43,44,45,46,47]. The mechanism of hydration exchange processes in the five-coordinate Pd II intermediates suggested two models for the axial interaction: σ-donor…d z 2 -orbital and HOH…d z 2 -orbital.…”
Abstract:The geometric structures of Pd-complexes {Pd ([9]aneB 2 A)L 2 and Pd ([9]aneBAB)L 2 where A = P, S; B = N; L = PH 3 , P(CH 3 ) 3 , Cl − }, their selective orbital interaction towards equatorial or axial (soft A…Pd) coordination of macrocyclic [9]aneB 2 A tridentate to PdL 2 , and electron density transfer from the electron-rich trans L-ligand to the low-lying unfilled a 1g (5s)-orbital of PdL 2 were investigated using B3P86/lanl2DZ for Pd and 6-311+G** for other atoms. The pentacoordinate endo- [Pd([9]complex with an axial (soft A--Pd) quasi-bond was optimized for stability. The fifth (soft A--Pd) quasi-bond between the σ-donor of soft A and the partially unfilled a 1g (5s)-orbital of PdL 2 was formed. The pentacoordinate endo-Pd ([9]aneB 2 A)(L-donor) 2 ] 2+ complex has been found to be more stable than the corresponding tetracoordinate endo-Pd complexes. Except for the endo-Pd pentacoordinates, the tetracoordinate Pd([9]aneBAB)L 2 complex with one equatorial (soft A-Pd) bond is found to be more stable than the Pd([9]aneB 2 A)L 2 isomer without the equatorial (A-Pd) bond. In particular, the geometric configuration of endo- [Pd([9]anePNP)(L-donor) 2 ] 2+ could not be optimized.
“…In this context, the achievements in development of novel and efficient synthetic methodologies for these types of reactions have been acknowledged with the 2010 Nobel Prize in Chemistry. Much attention has been paid to the design and development of powerful Pd-catalysts/precursors [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,37,38,39,40,41,42,43] that contain bulky and electron-rich ligands (such as phosphines and N -heterocyclic carbenes, NHCs) and to their potential synthetic applications [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36] in the Pd-catalyzed cross-couplings of various substrates (such as allyl, aryl, and vinyl halides and olefins). Catalytic activity enhancement of Pd (0) ( L ) n -precursors is greatly influenced by the electronic and steric properties of electron-rich and bulky L- ligands [1,2,3,4,5,6,7,8,18,19,20,21,22,23,24…”
Section: Introductionmentioning
confidence: 99%
“…In previous studies using hemilabile multidentate ligands [37,38,39,40,41,42,43,44,45,46,47], exceptional oxidation state and specific coordination selectivity have been observed for the Pd([9]ane B 2 A ) L 2 complexes with mixed soft A and hard B tridentates. The uncommon geometric structures of Pd([9]ane B 2 A ) L 2 complexes with an axial ( A …Pd) interaction were mainly formed under the following restrictive conditions: (1) coordination bonds of P - and N -functionalized derivatives are present [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39] and (2) polymeric side chain interactions exist [40,41,42].…”
Section: Introductionmentioning
confidence: 99%
“…In the Pd complex with an apical (hard N …Pd) interaction [42], the apical interaction was explained by an antibonding interaction between the lone pair of the apical N site and the d z2 -orbital of the Pd II species. In the ligand exchange reaction of square-planar Pd complexes, a vertical L …Pd interaction also has been optimized [43,44,45,46,47]. The mechanism of hydration exchange processes in the five-coordinate Pd II intermediates suggested two models for the axial interaction: σ-donor…d z 2 -orbital and HOH…d z 2 -orbital.…”
Abstract:The geometric structures of Pd-complexes {Pd ([9]aneB 2 A)L 2 and Pd ([9]aneBAB)L 2 where A = P, S; B = N; L = PH 3 , P(CH 3 ) 3 , Cl − }, their selective orbital interaction towards equatorial or axial (soft A…Pd) coordination of macrocyclic [9]aneB 2 A tridentate to PdL 2 , and electron density transfer from the electron-rich trans L-ligand to the low-lying unfilled a 1g (5s)-orbital of PdL 2 were investigated using B3P86/lanl2DZ for Pd and 6-311+G** for other atoms. The pentacoordinate endo- [Pd([9]complex with an axial (soft A--Pd) quasi-bond was optimized for stability. The fifth (soft A--Pd) quasi-bond between the σ-donor of soft A and the partially unfilled a 1g (5s)-orbital of PdL 2 was formed. The pentacoordinate endo-Pd ([9]aneB 2 A)(L-donor) 2 ] 2+ complex has been found to be more stable than the corresponding tetracoordinate endo-Pd complexes. Except for the endo-Pd pentacoordinates, the tetracoordinate Pd([9]aneBAB)L 2 complex with one equatorial (soft A-Pd) bond is found to be more stable than the Pd([9]aneB 2 A)L 2 isomer without the equatorial (A-Pd) bond. In particular, the geometric configuration of endo- [Pd([9]anePNP)(L-donor) 2 ] 2+ could not be optimized.
“…Although this distance is too long for a bonding interaction (Pd−O bonds are on the order of 2.1−2.2 Å), it is within the sum of the van der Waals radii (3.10 Å) of the atoms concerned . Square planar complexes of Pd(II) commonly form weak axial bonding interactions with hydrogen, nitrogen, and sulfur atoms; a few examples of axial Pd−O interactions have also been reported, with Pd−O distances of 2.653−3.084 Å. , Despite this weak bonding interaction with O4, the ligand arrangement about the metal center of 10 β remains nearly square planar; the Pd atom lies 0.032 Å below the least-squares plane containing P1, P2, C19, and N1. 1 Solid-state structure of palladacycle 10 β .…”
Five enantiopure palladacycles containing palladium bonded to a stereogenic carbon and an N-coordinated oxindole were synthesized by the reaction of alkenyl aryl triflates 2 and 9 with Pd(0) bisphosphine complexes. Two palladacyclic complexes, 3beta and 10alpha, were characterized by single-crystal X-ray crystallography. The reactivity of neutral palladacycles 3beta and 10beta was studied in detail. These unusual palladium alkyls, which have three accessible beta-hydrogens, are thermally stable at temperatures as high as 120 degrees C. At higher temperature, or at room temperature in the presence of weak acids, these complexes epimerize at the stereogenic carbon bonded to palladium. The mechanism of the acid-promoted epimerization was studied in detail. During this epimerization, cationic palladium alkyls 13/14 and 33 and cationic palladium hydride alkene complexes 31 and 32 are in rapid equilibrium.
The Pd (II) complexes trans-[PdCl 2 (μ-L)] 2 and [Pd(acac)(L)][BF 4 ] (L = RS (CH 2 ) 2 O(CH 2 ) 2 SR, R = Me, Et, n Pr, i Pr, n Bu, i Bu, n-hexyl, benzyl) were obtained through the reaction of Pd(cod)Cl 2 or [Pd(acac)(MeCN) 2 ][BF 4 ] with one equivalent of oxadithioether (L). The structural features of these complexes were analyzed by nuclear magnetic resonance (NMR) and Fouriertransform infrared spectroscopy (FTIR), as well as electrospray ionisation mass spectrometry and density functional theory calculations. The complexes diμ-(2,10-dimethyl-6-oxa-3,9-dithiaundecane-κ 2 S,S 0 )-bis[trans-dichloropalladium (II)] and (acetylacetonate-κ 2 O,O 0 )(2,10-dimethyl-6-oxa-3,9-dithiaundecane-κ 2 S, S 0 )palladium (II) tetrafluoroborate were characterized by X-ray diffractometry. The X-ray structures of each complex indicate an axial M-O interaction formed by the endodentate conformation of the oxadithioether ligand. Palladium (II) dichloride complexes with oxadithioethers were demonstrated to have a 16-membered dinuclear structure with a trans-configured S 2 PdCl 2 fragment. In the case of cationic palladium acetylacetonate complexes, only mononuclear complexes with a cis configuration of the oxadithioether fragment were observed. Variable temperature 1 H and 13 C NMR studies of the complexes demonstrate dynamic bonding of the oxadithioether ligands consistent with the presence of diastereoisomers that differ in the orientation of the S-R groups along with both endodentate and exodentate bonding modes in solution. FTIR studies of the complexes indicate the presence of isomers in the solid state. The palladium catalyst precursors trans-[PdCl 2 (μ-L)] 2 and [Pd (acac)(L)][BF 4 ] were found to be active in the addition polymerization of norbornene. In the presence of cocatalysts, such as diisobutylaluminum chloride and boron trifluoride etherate, Pd (II) complexes exhibited activities in the range of 10 5 to 10 7 g of polymer (mol of Pd) À1 h À1 . The catalyst systems
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