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Pd(0)-catalyzed intramolecular C-H alkenylation was achieved with excellent yields and enantioselectivity for the construction of planar chiral ferrocenes. It is compatible with a broad range of substrates and various functional groups. Notably, the enantioselective and diastereoselective synthesis of planar chiral ferrocenes was realized by cascade C-H arylation and alkenylation reaction for the first time. Additionally, the product was easily converted into a N,O-bidentate ligand, showing promising chiral induction in asymmetric alkynylation of 1-naphthaldehyde. [ABSTRACT FROM AUTHOR]

A highlyefficient synthesis of planar chiral ferrocenylpyridinederivatives via Pd-catalyzed intramolecular C–H arylation wasdeveloped, and quantitative yields and excellent enantioselectivitywere obtained for a wide range of substrates. Notably, the catalystloading could be lowered to 0.2 mol %, which represents the highestcatalytic efficiency found for asymmetric C–H bond activation(TON up to 495). These compounds could be easily transformed to pyridine N-oxides, displaying promising catalytic reactivity in the asymmetric opening of meso-epoxide. Moreover, computational investigations wereconducted to clarify the origin of the excellent enantioselectivity.The compatibility of large-scale synthesis and low catalyst loadingshould enhance the practicality of the synthetic application of thecurrent method. [ABSTRACT FROM AUTHOR]

As the active site mimics of [FeFe]-hydrogenases, 14 new butterfly [2Fe2E] (E = Se, S) cluster complexes have been prepared by various synthetic routes. The N-substituted single-butterfly [2Fe2Se] complexes [(μ-SeCH2)2NC(O)R]Fe2(CO)6(1, R = Me; 2, R = Ph; 3, R = PhCH2O) were prepared by reactions of the in situ formed (μ-LiSe)2Fe2(CO)6with RC(O)N(CH2Cl)2, whereas the corresponding [2Fe2S] complexes [(μ-SCH2)2NC6H4R-p]Fe2(CO)6(4, R = CO2Et; 5, R = CH2OH) were produced by reaction of the in situ generated (μ-HS)2Fe2(CO)6with aqueous CH2O followed by treatment with p-RC6H4NH2. The parent single-butterfly [2Fe2Se] complex [(μ-SeCH2)2NH]Fe2(CO)6(6) could be prepared by reaction of the N-substituted complex 3with deprotecting reagent BBr3, BF3·OEt2/EtSH, or BF3·OEt2/Me2S, whereas the N-substituted single-butterfly [2Fe2Se] complexes [(μ-SeCH2)2NC(O)R]Fe2(CO)6(7, R = Et; 8, R = PhCH2) were produced by reactions of 6with acylating agents RC(O)Cl in the presence of Et3N. While the known parent single-butterfly [2Fe2S] complex [(μ-SCH2)2NH]Fe2(CO)6reacted with 2,6-[ClC(O)]2C5H3N to afford double-butterfly [2Fe2S] complex [Fe2(CO)6(μ-SCH2)2NC(O)]2(2,6-C5H3N) (9), the new N-hydroxyethyl-substituted single-butterfly [2Fe2Se] complex [(μ-SeCH2)2N(CH2)2OH]Fe2(CO)6(10) could be obtained by the in situ reaction of (μ-HSe)2Fe2(CO)6with (HOCH2)2N(CH2)2OH. Interestingly, complex 10could react with [ClC(O)]2CH2or 1,3,5-[ClC(O)]3C6H3in the presence of Et3N to give the corresponding double-butterfly [2Fe2Se] complex [Fe2(CO)6(μ-SeCH2)2N(CH2)2O2C]2CH2(11) and triple-butterfly complex [Fe2(CO)6(μ-SeCH2)2N(CH2)2O2C]3(1,3,5-C6H3) (12), whereas the known single-butterfly [2Fe2S] complex [(μ-SCH2)2N(CH2)2OH]Fe2(CO)6could react with 2,6-[ClC(O)]2C5H3N and 1,3,5-[ClC(O)]3C6H3in the presence of Et3N to afford the corresponding double-butterfly [2Fe2S] complex [Fe2(CO)6(μ-SCH2)2N(CH2)2O2C]2(2,6-C5H3N) (13) and triple-butterfly complex [Fe2(CO)6(μ-SCH2)2N(CH2)2O2C]3(1,3,5-C6H3) (14), respectively. All the new complexes 1–14have been characterized by elemental analysis and spectroscopy, as well as by X-ray crystallography for 1–4, 7–9, and 14. In addition, the electrochemical study indicated that complexes 1and 2can catalyze the proton reduction of HOAc to give hydrogen. [ABSTRACT FROM AUTHOR]

Reactions of 2,6-(ArNCH)2C6H3Li with CrCl2(THF)2afford two trinuclear bis(imino)aryl NCN pincer Cr(II) complexes {[2,6-(ArNCH)2C6H3]Cr(μ-Cl)2}2Cr [Ar = 2,6-Me2C6H3(1a), 2,6-Et2C6H3(1b)], and a mononuclear bis(imino)aryl NCN pincer Cr(II) complex [2,6-(ArNCH)2C6H3]Cr(μ-Cl)2Li(THF)2[Ar = 2,6-iPr2C6H3(1c)], respectively. Similar reactions of 2,6-(ArNCH)2C6H3Li with CrCl3(THF)3produce only mononuclear bis(imino)aryl NCN pincer Cr(III) complexes [2,6-(ArNCH)2C6H3]CrCl2(THF) [Ar = 2,6-Me2C6H3(2a), 2,6-Et2C6H3(2b), 2,6-iPr2C6H3(2c)]. X-ray crystallographic analysis reveals that the terminal Cr(II) atoms in 1aand 1band the Cr(II) atom in 1cpossess a distorted trigonal bipyramidal coordination environment with the Cipsoatom of the pincer ligand and two chloride atoms in the equator and the two imine nitrogen atoms in the apical positions, while the Cr(III) complexes 2a, 2b, and 2call adopt a distorted octahedral geometry around the chromium metal. Upon activation with trialkylaluminum and [Ph3C][B(C6F5)4]−, the Cr(III) complexes show high catalytic activity for isoprene polymerization and afford polyisoprene with predominately trans-1,4 units, whereas the Cr(II) complexes are inert under the same conditions. [ABSTRACT FROM AUTHOR]

A series of new half-sandwich chromium(III) complexes chelated with (2-((arylimino)methyl)phenyl)tetramethylcyclopentadienyl ligands, 2-(ArNCH)C6H4Me4CpCrCl2(Ar = 2,6-Me2C6H3(1), 2,6-Et2C6H3(2), 2,6-iPr2C6H3(3), 4-MeC6H4(4)), have been synthesized from the reaction of CrCl3with the lithium salt of the corresponding ligand 2-(ArNCH)C6H4Me4CpLi (Ar = 2,6-Me2C6H3(LiL1), 2,6-Et2C6H3(LiL2), 2,6-iPr2C6H3(LiL3), 4-MeC6H4(LiL4)). Free ligands HL1−HL4were prepared by the condensation reaction of 2-(tetramethylcyclopentadienyl)benzaldehyde with 2,6-dialkylaniline. The free ligands were characterized by 1H NMR spectroscopy, while the chromium(III) complexes were characterized by elemental analyses and single-crystal X-ray crystallography. The X-ray crystallographic analysis indicates that the imine N atom in these complexes coordinates to the central chromium atom. Upon activation with AlR3and Ph3CB(C6F5)4, these complexes exhibit high catalytic activity for ethylene polymerization and produce polyethylene with moderate to high molecular weights. These chromium(III) complexes can also be activated with AlR3alone. In the latter case, they show slightly lower catalytic activity for ethylene polymerization in comparison to the AlR3/Ph3CB(C6F5)4activated catalyst systems. The effects of ligand structure, polymerization temperature, AlR3, and Al/Cr molar ratio on the catalytic behavior of these complexes were examined. [ABSTRACT FROM AUTHOR]

Reactions of 2,6-(ArNCH)2C6H3Li with AlEt2Cl afford a number of NCN pincer aluminum complexes (2,6-(ArNCH)2C6H3)AlEt2(Ar = Ph (1), 2,6-Me2C6H3(2), 2,6-Et2C6H3(3), 2,6-iPr2C6H3(4)). Similar reactions of 2,6-(ArNCH)2C6H3Li with ZnEtCl produce bisligated zinc complexes (2,6-(ArNCH)2C6H3)2Zn (Ar = Ph (5), 2,6-Me2C6H3(6), 2,6-Et2C6H3(7)) and monoligated NCN pincer zinc complex (2,6-(ArNCH)2C6H3)ZnEt (Ar = 2,6-iPr2C6H3(8)). All complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes 3, 4, 6, 7, and 8were determined by X-ray crystallography. The X-ray diffraction analysis reveals that both complexes 3and 4adopt a distorted trigonal-bipyramidal geometry around the aluminum central metal with three carbon atoms in the equator and the two imine nitrogen atoms in the apical positions. Complexes 6and 7adopt a distorted tetrahedral geometry around their zinc metal centers, while complex 8adopts a square-planar geometry around its metal center. All these Al and Zn complexes are efficient initiators for l-lactide ring-opening polymerization in the presence of benzyl alcohol, and the polymerization reaction takes place in an immortal manner. The productivity of the Zn complexes is generally higher than that of the Al complexes under similar conditions. [ABSTRACT FROM AUTHOR]

As a continuation of our studies on biomimetic chemistry and butterfly cluster chemistry, two series of “closed” and “open” butterfly [2Fe2Se] cluster complexes have been prepared in satisfactory yields. Thus, treatment of Fe3(CO)12with (HSeCH2)2CHOH in toluene at reflux gave the expected “closed” butterfly [2Fe2Se] cluster complex [(μ-SeCH2)2CH(OH)]Fe2(CO)6(A), whereas the “open” butterfly cluster complex (μ-EtSe)[(μ-SeCH2CH(OH)(CH2Br)]Fe2(CO)6(B) was unexpectedly produced along with complex Avia a sequential reaction of (μ-Se2)Fe2(CO)6with Et3BHLi, followed by treatment with (BrCH2)2CHOH. The other “closed” and “open” cluster complexes 1−6could be further prepared by the hydroxy transformation and CO substitution reactions of complexes Aand B. For example, (i) reaction of Awith PPh3and decarbonylating agent Me3NO afforded PPh3-monosubstituted complex [(μ-SeCH2)2CH(OH)]Fe2(CO)5(PPh3) (1), (ii) further reaction of 1with the acylating agent PhC(O)Cl in the presence of Et3N produced the benzoate-functionalized complex [(μ-SeCH2)2CH(O2CPh)]Fe2(CO)5(PPh3) (2), (iii) treatment of Awith the phosphatizing agent Ph2PCl in the presence of Et3N or simply with PhPCl2yielded the phosphite-functionalized complexes [(μ-SeCH2)2CH(OPPh2-η1)]Fe2(CO)5(3) and [(μ-SeCH2)2CH(OPPhCl-η1)]Fe2(CO)5(4), and (iv) treatment of Bwith 4-pyridinecarboxylic chloride or Ph2PCl in the presence of Et3N resulted in formation of the “open” butterfly cluster complexes (μ-EtSe)[μ-SeCH2CH(CH2Br)(O2CC5H4N-4)]Fe2(CO)6(5) and (μ-EtSe)[μ-SeCH2CH(CH2Br)(OPPh2-η1)]Fe2(CO)5(6). All the new complexes have been characterized by elemental analysis and spectroscopy, as well as for A, 1−4, and 6by X-ray crystallography. Both 1H and 77Se NMR spectral studies demonstrated that complexes Band 5consist of three isomers of e-Et/a-R, e-Et/e-R, and a-Et/e-R, whereas complex 6exists only as one isomer of e-Et/a-R. On the basis of an electrochemical study, it was found that the “closed” and “open” complexes Aand Bcan catalyze the proton reduction of TsOH and HOAc to give hydrogen, respectively. [ABSTRACT FROM AUTHOR]

The tridentate ligand N-(2-((2,6-diisopropylphenylimino)methyl)phenyl)quinolin-8-amine ( HL) was prepared. Treatment of HLwith 1 equiv of Ln(CH 2SiMe 3) 3(THF) 2afforded the corresponding rare-earth metal bis(alkyl) complexes LLn(CH 2SiMe 3) 2(THF) n(Ln = Sc, n= 0 ( 1); Y, n= 1 ( 2); Lu, n= 0 ( 3)) in high yields. Variable-temperature 1H NMR spectral analysis showed that these complexes were fluxional at room temperature. Complexes 1and 3were THF-free, where the metal center adopted a square-pyramidal geometry, while in 2the metal center generated a distorted octahedral geometry owing to the coordination of a THF molecule. All these complexes catalyzed the ring-opening polymerization of ε-caprolactone with high activities in living fashion, among which the Lu complex was proved to be more active than its Sc and Y analogues. [ABSTRACT FROM AUTHOR]

A series of new rare-earth metal bis(alkyl) complexes [L1−3Ln(CH2SiMe3)2(THF)n] (L1= MeC4H2SCH2NC6H4(Ph)2PNC6H2Me3-2,4,6: Ln = Sc, n= 1 (1a); Ln = Lu, n= 1 (1b); L2= MeC4H2SCH2NC6H4(Ph)2PNC6H3Et2-2,6: Ln = Sc, n= 1 (2a); Ln = Lu, n= 1 (2b); Ln = Y, n= 1 (2c); L3= MeC4H2SCH2NC6H4(Ph)2PNC6H3iPr2-2,6: Ln = Sc, n= 0 (3a)) and L4Sc(CH2SiMe3)2(THF) (4a) (L4= C6H5CH2NC6H4(Ph)2PNC6H3Et2-2,6) have been prepared by reaction of rare-earth metal tris(alkyl)s with the corresponding HL1−4ligands via alkane elimination. Complexes 1a, 1b, 2a−2c, and 4aare monomeric with a coordinating THF molecule. Each metal ion is coordinated by a NPN ligand, two trans-located alkyl groups, and a THF molecule, forming a distorted trigonal-bipyramidal geometry. Complex 3ais THF-free, adopting a distorted tetrahedron geometry. In combination with AlR3and borate, these complexes have shown medium activity and good trans-1,4 selectivity for the polymerization of butadiene. The resultant polymer has moderate molecular weight (Mn= 10 000−18 000) with narrow molecular weight distribution (Mw/Mn< 1.6) and trans-1,4 regularity varying from 49.2% up to 91.3%. The catalyst performances are strongly dependent on the orthosubstituent of the N-aryl ring and the presence of the thiophene moiety of the ligands and the type of aluminum alkyls and the lanthanide metal used. The scandium complex 2adisplays the highest trans-1,4 selectivity. [ABSTRACT FROM AUTHOR]

The N,N-bidentate ligands 2-(N-2,6-R)iminomethyl)pyrrole (HL1, R dimethylphenyl; HL2, R diisopropylphenyl) have been prepared. HL1reacted readily with 1 equiv of lanthanide tris(alkyl)s, Ln(CH2SiMe3)3(THF)2, affording lanthanide bis(alkyl) complexes L1Ln(CH2SiMe3)2(THF)n(1a, Ln Lu, n2; 1b, Ln Sc, n1) via alkane elimination. Reaction of the bulky ligand HL2with 1 equiv of Ln(CH2SiMe3)3(THF)2gave the bis(pyrrolylaldiminato) lanthanide mono(alkyl) complexes L22Ln(CH2SiMe3)(THF) (2a, Ln Lu; 2b, Ln Sc), selectively. The N,N-bidentate ligand HL3, 2-dimethylaminomethylpyrrole, reacted with Ln(CH2SiMe3)3(THF)2, generating bimetallic bis(alkyl) complexes of central symmetry (3a, Ln Y; 3b, Ln Lu; 3c, Ln Sc). Treatment of the N,N,N,N-tetradentate ligand H2L4, 2,2‘-bis(2,2-dimethylpropyldiimino)methylpyrrole, with equimolar Lu(CH2SiMe3)3(THF)2afforded a C2-symmetric binuclear complex (4). Complexes 3a, 3b, 3c, and 4represent rare examples of THF-free binuclear lanthanide bis(alkyl) complexes supported by non-cyclopentadienyl ligands. All complexes have been tested as initiators for the polymerization of isoprene in the presence of AlEt3and Ph3CB(C6F5)4. Complexes 1a, 1b, and 3ashow activity, and 1bis the most active initiator, whereas 2a, 2b, 3b, 3c, and 4are inert. The microstructure of the resultant polyisoprene has a cis-1,4 or trans-1,4 configuration depending on the initiator applied. [ABSTRACT FROM AUTHOR]

Treatment of indenyl-modified imidazolium bromide C9H7CH2CH2(NCHCHN(C6H2Me3-2,4,6)CH)Br ((IndH-NHC-H)Br) with rare earth metal tetra(alkyl) lithium (Ln(CH2SiMe3)4Li(THF)4) or with (trimethylsilylmethyl)lithium (LiCH2SiMe3) and rare earth metal tris(alkyl)s (Ln(CH2SiMe3)3(THF)2) sequentially afforded the first NHC-stabilized monomeric rare earth metal bis(alkyl) complexes (Ind-NHC)Ln(CH2SiMe3)2(1, Ln Y; 2, Ln Lu; 3, Ln Sc) via double-deprotonation reactions. Complexes 1−3are THF-free isostructural monomers. The monoanionic Ind-NHC species bond to the central metal ion in a 5:1constrained geometry configuration (CGC) mode, which combine with the two cis-located alkyl moieties to form a tetrahedron ligand core, leading to the chirality of the complexes. Under the presence of activators AlEt3and Ph3CB(C6F5)4, complex 2showed catalytic activity toward the polymerization of isoprene to afford 3,4-regulated polyisoprene (91%). [ABSTRACT FROM AUTHOR]