14917-14-7Relevant academic research and scientific papers
Metallocomplexes, exhibiting catecholate binding mode for o-quinone, annulated with dithiete cycle
Cherkasov, V. K.,Kuropatov, V. A.,Martyanov, K. A.,Rumyantcev, R. V.
, (2021/09/20)
Novel catecholate complexes (ditCat)SbPh3 (1), (ditCat)Ni(2,2′-bpy) (2) and (3,6-tBu-ditCat)VCp2 (3), containing annulated dithiete cycle, were synthesized by reactions of bifunctional o-quinone, annulated with dithiete ring (ditQ) w
Reductive elimination of aryl carboxylates from acyl(aryloxy)nickel(II) and -palladium(II) complexes
Komiya, Sanshiro,Akai, Yasushi,Tanaka, Kohkichi,Yamamoto, Takakazu,Yamamoto, Akio
, p. 1130 - 1136 (2008/10/08)
Acyl(p-cyanophenoxy)nickel(II) and -palladium(II) complexes, M(COR)(OC6H4-p-CN)L2 (M = Ni, Pd; L2 = bpy, (PEt3)2), have been prepared by insertion reactions of CO into the metal-carbon bonds of the corresponding methylnickel(II) and -palladium(II) complexes. Addition of π-acids such as CO, maleic anhydride, and acrylonitrile selectively induces reductive elimination of p-cyanophenyl acetate from acylnickel(II) complexes, whereas thermolysis of the complexes mainly results in decarbonylation. In contrast, reductive elimination from the palladium analogue proceeds smoothly on thermolysis, and no apparent accelerating effect of added π-acids is observed. Kinetic studies of both reductive eliminations reveal that the former proceeds via an associative mechanism involving a five-coordinate intermediate, whereas the latter proceeds via two mechanisms, one being a dissociative pathway involving a three-coordinate species and the other being a direct reductive elimination from a four-coordinate species.
Preparation of Ni- or Pt-Containing Cyclic Esters by Oxidative Addition of Cyclic Carboxylic Anhydrides and Their Properties
Sano, Kenji,Yamamoto, Takakazu,Yamamoto, Akio
, p. 2741 - 2747 (2007/10/02)
Metal containing cyclic ester complexes, L (L=1,2-bis(diphenylphosphino)ethane (dpe) or 2,2'-bipyridine (bpy); R1, R2=H or CH3) and Ln )L=tricyclohexylphosphine (PCy3) or dpe; n=1 or 2), have been prepared by oxidative addition of cyclic carboxylic anhydrides to zero-valent metal complexes.These complexes have been characterized by elemental analysis and spectroscopies (IR as well as 1H-, 13C1H>-, and 31P1H>-NMR) and chemical rectivities.Rate of the oxidative addition of succinic anhydride to Ni(bpy)(cod) (cod=1,5-cyclooctadiene) is expressed by a second order rate equation, R=k, and temperature dependence of k gives the activation energy of 68 kJ mol-1.The reaction of methylsuccinic anhydride with Ni(cod)2 in the presence of tertiary phosphine or bpy affords two isomers, Ln and Ln, corresponding to two modes of C-O bond cleavage in methylsuccininc anhydride promoted by Ni; dependence of the ratio between the two isomers on the kind of ligand added and reaction conditions has been examined.
Insertion of Carbon Monoxide into Nickel-Alkyl Bonds of Monoalkyl- and Dialkylnickel(II) Complexes, NiR(Y)L2 and NiR2L2. Preparation of Ni(COR)(Y)L2 from NiR(Y)L2 and Selective Formation of Ketone, Diketone, and Aldehyde from NiR2L2
Yamamoto, Takakazu,Kohara, Teiji,Yamamoto, Akio
, p. 2161 - 2168 (2007/10/02)
Reactions of monoalkylnickel(II) complexes, NiR(Y)L2 (R=CH3, C2H5; Y=Cl, suc(succinimido), pht(phthalimido), OC6H4-p-CN; L=1/2 bpy (2,2'-bipyridine), PEt3 (triethylphosphine)), with CO afford monoacylnickel(II) complexes, Ni(COR)(Y)L2, which are characterized by elemental analysis and spectroscopies (IR and NMR).Reactions of the acylnickel(II) complexes with alcohols and aniline give the corresponding esters and amides, respectively.Exposure of Ni(COR)(Y)L2 to dry air leads to oxidation of RCO to a RCOO ligand giving a complex formulated as NI(OCOR)(Y)L2.Reactions of dimethylnickel(II) complexes, Ni(CH3)2L2 (L=1/2 bpy, PEt3, 1/2dpe (1,2-bis(diphenylphosphino)ethane, 1/2 dpp (1,3-bis(diphenylphosphino)propane), with carbon monoxide afford acetone and/or 2,3-butanedione in medium to high yields, the acetone/2,3-butanedione ratio varying with the ligand L, reaction temperature, and additives such as maleic anhydride and triphenylphosphine.Generally the acetone/2,3-butanedione ratio decreases with increase in thermal stabilities of Ni(CH3)2L2.Ni(C2H5)2(bpy) and Ni(n-C3H7)2(bpy) give 3-pentanone and 4-heptanone, respectively, on treating them with CO, whereas Ni(C2H5)2(dpe) produces C2H5CHO and C2H4.
Oxidative Addition of Aryl Carboxylates to Ni(0) Complexes Involving Cleavage of the Acyl-O Bond
Yamamoto, Takakazu,Ishizu, Junichi,Kohara, Teiji,Komiya, Sanshiro,Yamamoto, Akio
, p. 3758 - 3764 (2007/10/02)
Reactions of aryl carboxylates RCOO-p-C6H4X (R=CH3, C2H5, n-C3H7; X=H, CH3, OCH3, CN) with bis(1,5-cyclooctadiene)nickel, Ni(cod)2, in the presence of phosphine ligands yield olefin (R(-H)), p-XC6H4OH, and nickel carbonyl complex(es) when the R group has a β hydrogen, whereas CH4, C2H6, nichel carbonyl complex(es), and nickel phenoxide are formed when the R group is CH3.The formation of the products is accounted for by assuming oxidative addition of the ester to nickel involving the cleavage of the acyl-O bond of RCOO-p-C6H4X followed by decarbonylation of the acylnickel complex and decomposition of the alkylnickel complex: RCOO-p-C6H4X + NiLn -> RCONiLnOC6H4X -> RNiLnOC6H4X + CO.The intermediate alkyl(phenoxo)nickel-type complex NiCH3(OC6H5) was in fact isolated in the reaction of phenyl acetate with Ni(cod)2 in the presence of 2,2'-bipyridine.The rate of the reaction is first order with respect to the concentration of the zerovalent nickel complex and the pseudo-first-order rate constant increases with with the increase in the basicity of the phosphine ligand added and with the increase of the electron-withdrawing ability of X.On the basis of these results a mechanism involving a nucleophilic attack at the carbonyl carbon by nickel is proposed.The activation parameters for the reaction of C2H5COOC6H5 with the mixture of Ni(cod)2 and PPh3 are ΔH=21+/-2 kcal/mol, ΔS=-8.8+/-2.9 eu.
