O,N,N-Pincer ligand effects on oxidatively induced carbon–chlorine coupling reactions at palladium

The syntheses of two families of sterically tuneable O,N,N pro-ligands are reported, namely the 2-(phenyl-2′-ol)-6-imine-pyridines, 2-(C6H4-2′-OH),6-(CMe[double bond, length as m-dash]NAr)C5H3N [Ar = 4-i-PrC6H4 (HL1a), 2,6-i-Pr2C6H3 (HL1b)] and the 2-(phenyl-2′-ol)-6-(amino-prop-2-yl)pyridines, 2-(C6H4-2′-OH),6-(CMe2NHAr)C5H3N [Ar = 4-i-PrC6H4 (HL2a), 2,6-i-Pr2C6H3 (HL2b)], using straightforward synthetic approaches and in reasonable overall yields. Interaction of HL1a/c and HL2a/b with palladium(II) acetate affords the O,N,N-pincer complexes, [{2-(C6H4-2′-O)-6-(CMe[double bond, length as m-dash]NAr)C5H3N}Pd(OAc)] (Ar = 4-i-PrC6H4 (1a), 2,6-i-Pr2C6H3 (1b)) and [{2-(C6H4-2′-O)-6-(CMe2NHAr)C5H3N}Pd(OAc)] (Ar = 4-i-PrC6H4 (2a), 2,6-i-Pr2C6H3 (2b)), which can be readily converted to their chloride derivatives, [{2-(C6H4-2′-O)-6-(CMe[double bond, length as m-dash]NAr)C5H3N}PdCl] (Ar = 4-i-PrC6H4 (3a), 2,6-i-Pr2C6H3 (3b)) and [{2-(C6H4-2′-O)-6-(CMe2NHAr)C5H3N}PdCl] (Ar = 4-i-PrC6H4 (4a), 2,6-i-Pr2C6H3 (4b)), respectively, on reaction with an aqueous sodium chloride solution. Treating each of 3a, 3b, 4a and 4b with two equivalents of di-p-tolyliodonium triflate at 100 °C in a toluene/acetonitrile mixture affords varying amounts of 4-chlorotoluene along with the 4-iodotoluene by-product with the conversions highly dependent on the steric and backbone properties of the pincer complex employed (viz.4a > 3a > 4b > 3b); notably, the least sterically bulky and most flexible amine-containing 4a reaches 90% conversion to 4-chlorotoluene in 15 h as opposed to 17% for imine-containing 3b. In the case of 3a, the inorganic palladium species recovered from the reaction has been identified as the Pd(II) salt [{2-(C6H4-2′-O)-6-(CMe[double bond, length as m-dash]N(4-i-PrC6H4)C5H3N}Pd(NCMe)][O3SCF3] (5a), which was independently prepared by the reaction of 3a with silver triflate in acetonitrile. Single crystal X-ray structures are reported for HL1a, HL2a, 1a, 1b, 2a, 2b, 3a and 5a

Organo-palladium(II) complexes bearing unsymmetrical N,N,N-pincer ligands: synthesis, structures and oxidatively induced coupling reactions

The 2-(2'-aniline)-6-imine-pyridines, 2-(C6H4--2'-NH2)-6-(CMe=NAr)C5H3 N (Ar = 4-i-PrC6H4 (HL1a), 2,6-i-Pr2C6H3 (HL1b)), have been synthesised via sequential Stille cross-coupling, deprotection and condensation steps from 6-tributylstannyl-2-(2-methyl-1,3-dioxolan-2-yl)pyridine and 2-bromonitrobenzene. The palladium(II) acetate N,N,N-pincer complexes, [{2-(C6H4-2'-NH)-6-(CMe=NAr)C5H3N}Pd(OAc)] (Ar = 4-i-PrC6H4 (1a), 2,6-i-Pr2C6H3 (1b)), can be prepared by reacting HL1 with Pd(OAc) 2 or, in the case of 1a , more conveniently by the template reaction of ketone 2-(C6H4-2'-NH2)-6-(CMe=O)C5H3N, Pd(OAc)2 and 4-isopropylaniline; ready conversion of 1 to their chloride analogues, [{2-(C6H4-2'-NH)-6-(CMe=NAr)C5H3N}PdCl] (Ar = 4-i-PrC6H4 (2a), 2,6-i-Pr2C6H3 (2b)), has been demonstrated. The phenyl-containing complexes, [{2-(C6H4-2'-NH)-6-(CMe=NAr)C5H3N}PdPh] (Ar = 4-i-PrC6H4 (3a), 2,6-i-Pr2C6H3 (3b)), can be obtained by treating HL1 with (PPh3)2 PdPh(Br) in the presence of NaH or with regard to 3a, by the salt elimination reaction of 2a with phenyllithium

Molybdenum Disubstituted Alkylidene Complexes

Through relatively straightforward techniques that begin with Mo(NAr)(CH-t-Bu)[OCMe(CF3)2]2 (Ar = 2,6-i-Pr2C6H3), we have prepared Mo(NAr)(CMePh)(OMesityl)2, [Mo(NAr)(CMePh)(OC6F5)2]2, Mo(NAr)(CMePh)(OC6F5)2(MeCN), Mo(NAr)(CMePh)(OC6F5)2(bipyridyl), Mo(NAr)(CMePh)(Cl)2(bipyridyl), Mo(NAr)(CMePh)(Cl)(OHMT)(MeCN) (OHMT = O-2,6-(2,4,6-Me3C6H2)2C6H3), and Mo(NAr)(CMePh)(Pyrrolide)(OHMT). X-ray studies reveal that in five compounds the alkylidene isomer (A) is that in which the phenyl group in the alkylidene points toward the imido nitrogen. In Mo(NAr)(CMePh)(OC6F5)2(MeCN) the isomer in which the methyl group points toward the imido nitrogen (isomer B) has cocrystallized with isomer A (12%). In two 14e compounds that contain isomer A, the Mo═C-C angles differ by 30-36°, consistent with a Mo...C-Hβ agostic interaction. Several of the complexes reported here react readily with ethylene, 1-decene, or cyclooctene to give the expected products, thus confirming their viability as initiators or intermediates in metathesis reactions

I. Magnesium Promoted Coupling of Carbodiimides and Terminal Acetylenes, II. Bismuth Compounds Supported by Di(amido) Chelating Ligands

The work presented in this thesis is divided into two parts, both of which investigate the chemistry of main group elements supported by N,N'-donor ligands. Part 1 investigates the use of Mg(mesC{NCy}₂)(N{SiMe₃}₂)(THF) (mes = 2,4,6- Me₃C₆H₃, Cy = C₆H₁₁) as a pre-catalyst for the coupling of terminal acetylenes to carbodiimides. A catalytic cycle for the reaction is proposed, based on a series of stoichiometric reactions. Ligand redistribution via Schlenk equilibria is a prominent feature of the proposed catalytic cycle. The scope of catalysis was also investigated, indicating a strong dependence on the sterics and electronics of both the carbodiimide and the terminal acetylene. Investigation of other magnesium species identified other pathways into the catalytic cycle. Part 2 explores the derivitisation of Bi(Me₂Si{NAr})Cl (Ar = 2,6-i-Pr₂C₆H₃) to form a number of novel bismuth(III) species of the general formula Bi(Me₂Si{NAr})X (X = alkyl, aryl, amide, aryloxide, phosphide). In addition, a number of cationic bismuth species have been isolated from the reaction of Bi(Me₂Si{NAr})Cl with ECl₃ (E = Al, Ga). Preliminary investigations reveal that the amide and aryloxide derivatives are active as initiators for the ring-opening polymerisation of lactide and ε-caprolactone. A number of bismuth(III) compounds bearing the related di(amido)ether ligands [O(Me₂Si{NAr})₂]²⁻ have also been synthesised

Magnesium-catalysed hydroboration of isonitriles

A β-diketiminato magnesium alkyl complex is shown to be an effective pre-catalyst for the first reported catalytic hydroboration of organic isonitriles, RNC, with HBpin.</p

Theoretical Study on Bonding and Catalytic Properties of N-heterocyclic Carbenes and Aluminum Carbenoids

氮杂环卡宾(N-heterocycliccarbene，NHC)中sp2杂化的卡宾碳具有独特的σ2π0电子结构，表现出较强的σ给电子能力和一定的π电子接受能力。作为σ型的配体，NHC可以与过渡金属(Transitionmetal，TM)原子相互作用形成σ-型配合物，并导致过渡金属中心呈现出富电子特征，使其在催化反应中具有较高的反应活性。强亲核性的NHC进攻醛，可以使其由亲电试剂反转为亲核试剂，所产生的Breslow中间体具有较高的反应活性，能与多种亲电试剂发生丰富的化学反应。当醛上具有不饱和共轭链时，反应的活性位点可以传递到远端δ位的碳原子上，并发生和1，6&#8722;Michael加成反应...In the N-heterocyclic carbene (NHC), the carbene carbon adopts the sp2 hybridization with a special σ2π0 electronic structure, and shows the ability of stronger σ-electron donor and weak π-electron acceptor. The σ dative bond between NHC and the transition metal (TM) results in a rich electron TM center with high catalytic reactivity. As a nucleophilic catalyst, NHC combines with an electrophilic ...学位：理学博士院系专业：化学化工学院_物理化学学号：2052013015388

Synthesis of Molybdenum and Tungsten Alkylidene Complexes That Contain Sterically Demanding Arenethiolate Ligands

Imido alkylidene complexes of Mo and W and oxo alkylidene complexes of W that contain thiophenoxide ligands of the type S-2,3,5,6-Ph[subscript 4]C[subscript 6]H (STPP) and S-2,6-(mesityl)[subscript 2]C[subscript 6]H[subscript 3] (SHMT = S-hexamethylterphenyl) have been prepared in order to compare their metathesis activity with that of the analogous phenoxide complexes. All thiolate complexes were significantly slower (up to ∼10× slower) for the metathesis homocoupling of 1-octene or polymerization of 2,3-dicarbomethoxynorbornene, and none of them was Z-selective. The slower rates could be attributed to the greater σ-donating ability of a thiophenoxide versus the analogous phenoxide and consequently a higher electron density at the metal in the thiophenoxide complexes.National Institutes of Health (U.S.) (Grant GM-59426