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Allyl Complexes (allyl + complex)
Selected AbstractsChemInform Abstract: Synthesis, Structure and Catalytic Activity of a Bimacrocyclic NHC Palladium Allyl Complex.CHEMINFORM, Issue 52 2008Ole Winkelmann Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Interactions of Cationic Palladium(II)- and Platinum(II)-,3 -Allyl Complexes with Fluoride: Is Asymmetric Allylic Fluorination a Viable Reaction?EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2006Lukas Hintermann Abstract The complex cations [M(,3 -R2All)(PPFPz{3- tBu})]+ (M = PdII, R2All = 1,3-diphenylallyl, 1,3-dicyclohexylallyl, indenyl; M = PtII, R2All = 1,3-diphenylallyl; PPFPz-{3- tBu} = 3- tert -butyl-1-{1-[2-diphenylphosphanyl-ferrocenyl]ethyl}-1H -pyrazole)have been prepared as salts with PF6, or SbF6,. They have been characterized by NMR spectroscopy in solution and by X-ray crystallography in the solid state. Their reactions with sources of nucleophilic and "naked" fluoride have been investigated by multinuclear NMR spectroscopy. The PdII complexes did not undergo any nucleophilic substitution with concomitant release of allyl fluorides. The dicyclohexylallyl fragment was released as a 1,3-diene by elimination, but with other allyl complexes nonspecific decomposition reactions predominated. The complex [Pt(,3 -1,3-Ph2C3H3)(PPFPz{3- tBu})]PF6 underwent an anion exchange with Me4NF to give [Pt(1,3-Ph2C3H3)(PPFPz{3- tBu})]F which existed as a mixture of interconverting allyl isomers in solution at ambient temperature. For the bromide salt, [Pt(,3 -1,3-Ph2C3H3)(PPFPz{3- tBu})]Br, allyl isomerization was slow at ambient temperature. Precursors of Pt0 reacted with bromo-1,3-diphenylprop-2-ene to give [Pt2(,-Br)2(,3 -1,3-Ph2All)2] and precursors of Pd0 underwent oxidative additions with bromo- and fluoro-1,3-diphenyl-2-propene to give 1,3-diphenylallyl complexes of PdII. Therefore, the nucleophilic attack of fluoride on the allyl fragment of PdII complexes is endergonic, and the high energy barrier of this step is difficult to overcome in a catalytic allylic fluorination reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis of Diastereomerically Enriched Cyclic Homoallylic Alcohols Using Molybdenum ,-Allyl Complexes.CHEMINFORM, Issue 51 2002Marie E. Krafft Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis, Characterization, and Reactivity of Lanthanide Complexes with Bulky Silylallyl LigandsISRAEL JOURNAL OF CHEMISTRY, Issue 4 2002Timothy J. Woodman The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH2CHCHSiMe3) (1) reacts with YCl3 in tetrahydrofuran to give the tris -allyl complex Y(CH2CHCHSiMe3)3 (2), while K(CH2CHCHSiMe2tBu) (3) affords Y(CH2CHCHSiMe2tBu)3(THF)1.5 (4). Slow re-crystallization of 4 from light petroleum in the presence of tert -butylcyanide led to multiple insertion to give the sec -amido complex Y{NHC(tBu)(CH)3SiMe2tBu}2{,2 -NHC(tBu)CH=CHCH2SiMe2tBu)CH(CHCHSiMe2tBu)CtBuNH}(THF)·(CH3CH(Me)(CH2)2CH3) (5), which was crystallographically characterized. The reaction of ScCl3(THF)3 with two equivalents of Li{1,3-C3H3(SiMe3)2} in tetrahydrofuran gives the bis -allyl complex {1,3-C3H3(SiMe3)2}2Sc(,-Cl)2Li(THF)2 (6), while the analogous reaction of K{1,3-C3H3(SiMe3)2} (7) with either LaCl3 or YCl3 in tetrahydrofuran affords the bis -allyl complexes MCl{1,3-C3H3(SiMe3)2}2(THF)x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono -allyl complex NdI2{1,3-C3H3(SiMe3)2}(THF)1.25 (10). The reactions of 8 and 9 with triisobutyl aluminum in benzene- d6 show allyl exchange between lanthanide and aluminum. Complexes 8, 9, and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene. [source] Cationic Scandium Allyl Complexes Bearing Mono(cyclopentadienyl) Ligands: Synthesis, Novel Structural Variety, and Olefin-Polymerization CatalysisCHEMISTRY - AN ASIAN JOURNAL, Issue 8-9 2008Nan Yu Abstract The one-pot salt-metathesis reaction of ScCl3, cyclopentadienyl lithium salts, and allylmagnesium chlorides afforded with ease the corresponding base-free half-sandwich scandium di(,3 -allyl) complexes [(C5Me4SiMe3)Sc(C3H5)2] (1,a), [(C5Me5)Sc(C3H5)2] (1,b), and [(C5Me5)Sc(2-MeC3H4)2] (1,c) in high yields. Reaction of 1,a with 1,equivalent of [PhNMe2H][B(C6F5)4] in toluene gave rapidly the N,N -dimethylaniline-coordinated cationic mono(,3 -allyl) complex [(C5Me4SiMe3)Sc(,3 -C3H5)(,6 -PhNMe2)][B(C6F5)4] (2). The similar reaction of 1,a with [Ph3C][B(C6F5)4] yielded the analogous toluene-separated ion pair [(C5Me4SiMe3)Sc(,3 -C3H5)(,6 -PhMe)][B(C6F5)4] (3). When [PhNMe2H][BPh4] was treated with 1,a, the contact ion pair [(C5Me4SiMe3)Sc(,3 -C3H5)( ,,,6 -Ph)BPh3] (4) was obtained. Recrystallization of 2, 3, and 4 in THF yielded the corresponding thf-separated ion pair complexes [(C5Me4SiMe3)Sc(,3 -C3H5)(thf)2][B(C6F5)4] (5) and [(C5Me4SiMe3)Sc(,3 -C3H5)(thf)2][BPh4] (6). The N,N -dimethylaniline-coordinated cationic scandium allyl complex 2 and the toluene-coordinated analogue 3 showed high activity (activity: 3>2) toward the polymerization and copolymerization of isoprene and norbornene to afford random copolymers with a broad range of isoprene content (33,86,mol,%). The tight ion pair 4 and the thf-coordinated complexes 5 and 6 showed no activity under the same conditions. These results offer unprecedented insight into the structure,activity relationship of a cationic metal polymerization-catalyst system. [source] Better Performance of Monodentate P -Stereogenic Phosphanes Compared to Bidentate Analogues in Pd-Catalyzed Asymmetric Allylic AlkylationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2010Arnald Grabulosa Abstract The cationic allylpalladium complexes 3a,3f, 4a, 4e, 5e of type [Pd(,3 -2-Me-C3H4)P2]PF6 were synthesized using a group of monodentate P -stereogenic phosphanes, P=PPhRR, (a,f) and diphosphanes (PhRPCH2)2 (1a, 1e) or PhRPCH2Si(Me)2CH2PPhR (2e). The analogous cationic complexes with the disubstituted allyl group (,3 -1,3-Ph2 -C3H3) and monodentate phosphanes were not isolated as stable solids; only [PdCl(,3 -1,3-Ph2 -C3H3)P] (6a, 6d) were obtained. Palladium allyl complexes were screened as precatalysts in the allylic substitution of rac -3-acetoxy-1,3-diphenyl-1-propene (I) and (E)-3-acetoxy-1-phenyl-1-propene (III) with dimethyl malonate as the nucleophile. The various catalytic precursors showed a wide range of activity and selectivity. The bismonodentate phosphane complexes 3 are more active than the bidentate analogues. With regard to the regioselectivity, precursors containing monodentate phosphanes favour the formation of the linear product in the allylic substitution of cinnamyl acetate (III) compared with those containing bidentate phosphanes. With substrate I, compounds with the diphosphanes 1a and 1e, containing a five-membered chelate ring, gave low enantioselectivities (less than 10,% ee), but those with the diphosphane 2e, forming a six-membered chelate ring or with two monodentate phosphanes, afforded products with moderate enantioselectivity under standard conditions (ee up to 74,%). The results show that the performance of precursors containing monodentate phosphanes was superior to those containing bidentate ligands in both activity and selectivity. [source] Synthesis, Characterization, and Reactivity of Lanthanide Complexes with Bulky Silylallyl LigandsISRAEL JOURNAL OF CHEMISTRY, Issue 4 2002Timothy J. Woodman The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH2CHCHSiMe3) (1) reacts with YCl3 in tetrahydrofuran to give the tris -allyl complex Y(CH2CHCHSiMe3)3 (2), while K(CH2CHCHSiMe2tBu) (3) affords Y(CH2CHCHSiMe2tBu)3(THF)1.5 (4). Slow re-crystallization of 4 from light petroleum in the presence of tert -butylcyanide led to multiple insertion to give the sec -amido complex Y{NHC(tBu)(CH)3SiMe2tBu}2{,2 -NHC(tBu)CH=CHCH2SiMe2tBu)CH(CHCHSiMe2tBu)CtBuNH}(THF)·(CH3CH(Me)(CH2)2CH3) (5), which was crystallographically characterized. The reaction of ScCl3(THF)3 with two equivalents of Li{1,3-C3H3(SiMe3)2} in tetrahydrofuran gives the bis -allyl complex {1,3-C3H3(SiMe3)2}2Sc(,-Cl)2Li(THF)2 (6), while the analogous reaction of K{1,3-C3H3(SiMe3)2} (7) with either LaCl3 or YCl3 in tetrahydrofuran affords the bis -allyl complexes MCl{1,3-C3H3(SiMe3)2}2(THF)x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono -allyl complex NdI2{1,3-C3H3(SiMe3)2}(THF)1.25 (10). The reactions of 8 and 9 with triisobutyl aluminum in benzene- d6 show allyl exchange between lanthanide and aluminum. Complexes 8, 9, and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene. [source] Synthesis and reactivity of allyl nickel(II) N -heterocyclic carbene enolate complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007Stefan Benson Abstract Two new N -heterocyclic carbene enolate nickel(II) allyl complexes have been prepared and their activity towards ethylene polymerization was investigated. It was found that in the presence of diethyl zinc, the carbene enolate complex bearing a nitro substituent produces highly linear polyethylene of modest molecular weight and high polydispersity. The influence of the reaction parameters on catalytic activity and the characteristics of the resulting polymer were investigated through systematic variation of the time, temperature, and diethyl zinc concentration. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45:3637,3647, 2007 [source] | ||||||||||