Carbon-bridged Bis Research Articles

Rare Carbon-Bridged Bimetallic Lanthanide (Nd or Sm) and Tl(I) Geminal Carbon Derivatives of a Bis(iminophosphorano)methanediide

The bimetallic carbon-bridged bis(iminophosphorano)methanediide complexes [CpNd(Tl){C(Ph2P═NSiMe3)2}Cl2Li(THF)2]·Et2O (2) and [SmCl3Tl{C(Ph2P═NSiMe3)2}Li(THF)2]2 (3) were prepared from reactions of...

Two Rare-Earth Complexes (Sm, La) Based on a Carbon-Bridged Bis(phenolate): Synthesis and Crystal Structures

Two rare earth metal complexes based on the carbon-bridged bis(phenolate) ligand, 2,2'-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (LH2), have been synthesized. Reaction of LH2 with (C5H5)3Sm(THF) in a 1.5 : 1 molar ratio in THF at 50°C produced rare earth metal bis(phenolate) complex (C5H5)Sm(L)(THF)2 (I) in almost quantitative yields. Complex I reacted with 0.5 molar ratio of LH2 in toluene at 80°C afforded (L)Sm(LH)(THF)2 (II) as the final product in good yield. Reaction of LNa2 with LaCl3 in a 2 : 1 molar ratio in THF at room temperature produced hetero-nuclear rare earth metal bis(phenolate) complex (L)La(LH)(THF)2Na(THF)2 (III). In addition, II and III were characterized by X-ray single-crystal diffraction analysis (CIF file CCDC nos. 1500917 (II) and 1826699 (III)) as well as characterizations including elemental analyses and IR spectra of both complexes. Furthermore, detail reasons of the difference of structures are presented. The ionic radii of the rare earth metal plays a significant role in the structure difference of two complexes.

Synthesis and Structure of a Bis(indolyl)-Coordinated Titanium Diamido Complex, and Its Catalytic Applications in the Intermolecular Hydroamination of Alkynes

Abstract Titanium bis(diethylamido) complex 1, which contains a carbon-bridged bis(indolyl) ligand, was obtained in 69% yield from the reaction of Ti(NEt2)4 with the corresponding bis(indole) ligand. Its molecular structure in the crystal was unequivocally determined by a single-crystal X-ray diffraction analysis. Furthermore, we examined applications of 1 as a catalyst for the intermolecular hydroamination of alkynes. When using phenylacetylene or 1-hexyne as alkynes, the Markovnikov products were obtained selectively, while the reaction with 1-phenyl-1-propyne afforded an imine of phenylacetone.

Bis(aminoaryl) Carbon-Bridged Oligo(phenylenevinylene)s Expand the Limits of Electronic Couplings.

Carbon-bridged bis(aminoaryl) oligo(para-phenylenevinylene)s have been prepared and their optical, electrochemical, and structural properties analyzed. Their radical cations are class III and class II mixed-valence systems, depending on the molecular size, and they show electronic couplings which are among the largest for the self-exchange reaction of purely organic molecules. In their dication states, the antiferromagnetic coupling is progressively tuned with size from quinoidal closed-shell to open-shell biradicals. The data prove that the electronic coupling in the radical cations and the singlet-triplet gap in the dications show similar small attenuation factors, thus allowing charge/spin transfer over rather large distances.

Polymerization of conjugated dienes with a homogeneous Ziegler–Natta catalytic system based on a carbon-bridged bis(phenolate) yttrium alkyl complex

1,3-Diene polymerization with some controllable characteristics was carried out and catalyzed by a triisobutylaluminum modified MAO activated complex [(EDBP)Y(CH2SiMe3)(THF)3].

Heteroleptic lanthanide amide complexes bearing carbon-bridged bis(phenolate) ligands: synthesis, structure and their application in the polymerization of ε-caprolactone

A convenient method for the synthesis of anionic lanthanide amide complexes bearing carbon-bridged bis(phenolate) ligands is described and the catalytic activity of the complexes in the ring-opening polymerization of ε-caprolactone was studied.

Synthesis and characterization of samarium bis(phenolate) complexes and their catalytic activity for the polymerization of l-lactide

The synthesis, structure and catalytic activity for the polymerization of l-lactide of samarium complexes supported by the carbon-bridged bis(phenolate) ligand 2,2′-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP2−) are described. The reaction of (C5H5)3Sm(THF) with MBMPH2 in a 1:1M ratio in THF at 50°C produced the bis(phenolato) samarium complex (C5H5)Sm(MBMP)(THF)2 (1) in a nearly quantitative yield. Complex 1 is a useful precursor for synthesizing bis(phenolato) samarium aryloxides. Complex 1 reacted with MBMPH2 in toluene at 80°C to give the complex (MBMP)Sm(MBMPH)(THF)2 (2). The reactions of complex 1 with some mono-phenols, including 2,6-di-tert-butyl-4-methylphenol, 2,6-diisopropylphenol, 2,6-dimethylphenol and 4-methoxyphenol, in toluene produce the complexes (MBMP)Sm(OC6H2-But2-2,6-Me-4)(THF)2 (3), (MBMP)Sm(OC6H3-Pri2-2,6)(THF)3 (4), (MBMP)Sm(OC6H3-Me2-2,6)(DME)2 (5) and [(MBMP)Sm(OC6H4-OMe-4)(THF)2]2 (6). All of these complexes were well characterized by elemental analyses, IR spectra and single-crystal X-ray structure determination, except for complex 2. It was found that complexes 3–6 are efficient initiators for l-lactide polymerization.

Synthesis and characterization of carbon-bridged bis(phenolate) lanthanum alkoxides and their catalytic behavior for the polymerization of L-lactide

Four lanthanum alkoxides stabilized by a carbon-bridged bis(phenolate) ligand were synthesized and their catalytic behavior for the ring-opening polymerization of L-lactide was explored. Reactions of [(MBMP)LaCp(THF)2] (MBMP2− = 2,2′-methylene-bis(6-tert-butyl-4-methyl phenoxo)) with HOCH2Ph, HOCH2CF3, HOCH(CH3)2, and HOCH2CH2N(CH3)2, respectively, in a 1:1 molar ratio in THF gave the dimeric lanthanum alkoxo complexes [(MBMP)Ln(Sm-OR)(THF)2]2 (OR = OCH2Ph (1), OCH2CF3 (2), OCH(CH3)2 (3), OCH2CH2N(CH3)2 (4)]. These complexes were well characterized, and the definitive molecular structure of complex 1 was determined. It was found that complexes 1 to 4 are efficient initiators for the ring-opening polymerization of L-lactide. The structure of the alkoxo groups has a significant effect on the catalytic behavior, and complex 2 can initiate L-lactide polymerization in a controlled manner.

Synthesis, characterization of carbon-bridged Bis(phenolate) neodymium complexes and their catalytic activity for ring-opening polymerization of cyclic esters

Three carbon-bridged bis(phenolate) neodymium complexes, [(MBMP)2Nd(μ3–Cl)Li(THF)2Li(THF)] (1), [(MBBP)2Nd(μ3-Cl)Li(THF)2Li(THF)] (2) and [(THF)2Nd(EDBP)2Li(THF)] (3) have been synthesized by one-pot reaction of NdCl3 and LiCH2SiMe3 with 6,6′-methylenebis(2-tert-butyl-4-methylphenol) (MBMP-H2), 6,6′-methylenebis(2,4-di-tert-butylphenol) (MBBP-H2) or 6,6′-(ethane- 1,1-diyl)bis(2,4-di-tert-butylphenol) (EDBP-H2), respectively, in a molar ratio of 1:4:2. The definitive structures of complexes 2 and 3 were determined by X-ray diffraction studies. Experimental results show that 1–3 efficiently initiate the ring-opening polymerization (ROP) of ε-caprolactone and ROP of L-lactide.

Unexpected Formation of Ga4C2H4 Heteroadamantane Cages by the Reaction of Carbon-Bridged Bis(dichlorogallium) Compounds with tert-Butyllithium

Reactions of the carbon-bridged bis(dichlorogallium) compounds (Cl2Ga)2C(SiR2R′)-CH2-Ph (1a, R = R′ = Me; 1b, R = Ph, R′ = Me; 1c, R = Me, R′ = CMe3) with four equivalents of tert-butyllithium yielded bis[tert-butyl(hydrido)digallium] compounds {[(Me3C)(H)Ga]2C(SiR2R′)-CH2-Ph}2 (3a to 3c), via β-elimination and release of isobutene. 3a to 3c are dimeric in solution and the solid state and contain unprecedented Ga4C2H4 heteroadamantane structures in which four metal atoms are bridged by four hydrogen and two carbon atoms. In contrast, n-propyllithium gave the monomeric tetra(n-propyl)digallium compound (nPr2Ga)2C(SiMe3)-CH2-Ph (2) under similar conditions, which has two coordinatively unsaturated gallium atoms and may be applicable as a chelating Lewis acid.

Synthesis and Structural Diversity of Heterobimetallic Lanthanide–Potassium Complexes and Catalytic Activity for Amidation of Aldehydes with Amines

Four heterobimetallic lanthanide–potassium complexes stabilized by the carbon-bridged bis(phenolate) ligand MBMP2– (MBMP = 2,2′-methylene bis(6-tert-butyl-4-methylphenolate)), [{(MBMP)2La(THF)2}2K][K(THF)6] (1), [(MBMP)Nd(μ-MBMP)K(THF)]2 (2), [(THF)2Sm(MBMP)2K(THF)2] (3), and [(THF)2Yb(MBMP)2K(THF)3] (4), were synthesized, and their structural features were provided. It was found that the ionic radii of lanthanide metals have a profound effect on the structures of the heterobimetallic complexes. Complexes 1 to 4 are efficient catalysts for amidation reactions of aldehydes with amines to produce amides in good to excellent yields under mild conditions.

Synthesis and characterization of alkali-metal aryloxo compounds and their catalytic activity for l-lactide polymerization

Three new alkali-metal compounds stabilized by aryloxo groups were synthesized and fully characterized. The reactions of carbon-bridged bis(phenol)s MBMPH 2 (MBMPH 2 = 2,2′-methylene-bis(6- tert-butyl-4-methylphenol)) with sodium and potassium metals in tetrahydrofuran (THF) gave the desired alkali-metal complexes [MBMPNa 2(THF) 3] 2 ( 1) and [(MBMPK 2) 2(THF) 5] 2 ( 2), respectively, in high isolated yields. A similar reaction of aminophenol [HNOH] ([HNOH] = N- p-methyl-phenyl(2-hydroxy-3,5-di- tert-butyl)benzylamine) with sodium gave the monosodium salt [HNONa(THF)] 2 ( 3). Compounds 1– 3 were well characterized, including X-ray structure determination. Compound 1 has a dimeric structure, and each sodium atom is four-coordinated with four oxygen atoms to form a distorted tetrahedron. Compound 2 has a centrosymmetric tetrameric structure. The coordination environments around the four potassium atoms are different. K1 is four-coordinated, K2 is three-coordinated, K3 is five-coordinated, whereas the coordination sphere of K4 is completed by one aryloxo oxygen atom and two oxygen atoms from two THF molecules and six carbon atoms from one arene ring of the bis(phenolate) ligand. Compound 3 has a dimeric structure, and each of the sodium atoms is four-coordinated to form a distorted tetrahedron. It was found that compounds 1– 3 can efficiently initiate the ring opening polymerization of l-lactide in the absence of alcohol, yielding polymers with high molecular weights for a wide range of monomer-to-initiator ratios.

Synthesis, reactivity and structural characterization of lanthanide hydroxides stabilized by a carbon-bridged bis(phenolate) ligand

Controlled hydrolysis of the carbon-bridged bis(phenolate) lanthanide cyclopentadienyl complexes (MBMP)Ln(C 5 H 5 )(THF) 2 in THF at −78 °C afforded the corresponding lanthanide hydroxides as dimers [{(MBMP)Ln(μ-OH)(THF) 2 } 2 ] (Ln = Nd ( 1 ), Yb ( 2 )), which reacted with phenyl isocynate in THF to give the desired O–H addition products, [(MBMP)Ln(μ-η 1 :η 2 -O 2 CNHPh)(THF) 2 ] 2 (Ln = Nd ( 3 ), Yb ( 4 )) in excellent isolated yields. The synthesis of lanthanide hydroxo complexes stabilized by a carbon-bridged bis(phenolate) ligand 2,2’-methylene-bis(6- tert -butyl-4-methylphenoxo) (MBMP 2− ) was described, and their reactivity toward phenyl isocyanate was explored. Reactions of (MBMP)Ln(C 5 H 5 )(THF) 2 with a molar equiv. of water in THF at −78 °C afforded the bis(phenolate) lanthanide hydroxides as dimers [{(MBMP)Ln(μ-OH)(THF) 2 } 2 ] [Ln = Nd ( 1 ), Yb ( 2 )] in high yields. Complexes 1 and 2 reacted with phenyl isocyanate in THF, after workup, to give the desired O−H addition products, [(MBMP)Ln(μ-η 1 :η 2 -O 2 CNHPh)(THF) 2 ] 2 [Ln = Nd ( 3 ), Yb ( 4 )] in excellent isolated yields. These complexes were well characterized, and the molecular structures of complexes 2 to 4 were determined by X-ray crystallography. The ytterbium atom in complex 2 is coordinated to six oxygen atoms to form a distorted octahedral geometry, whereas each metal center in complexes 3 and 4 is seven-coordinated, and the coordination geometry can be best described as a distorted pentagonal bipyramid.

Synthesis, characterization and reactivity of heteroleptic rare earth metal bis(phenolate) complexes

The synthesis, characterization and reactivity of heteroleptic rare earth metal complexes supported by the carbon-bridged bis(phenolate) ligand 2,2'-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP2-) are described. Reaction of (C5H5)3Ln(THF) with MBMPH2 in a 1:1.5 molar ratio in THF at 50 degrees C produced the heteroleptic rare earth metal bis(phenolate) complexes (C5H5)Ln(MBMP)(THF)n (Ln=La, n=3 (); Ln=Yb (), Y (), n=2) in nearly quantitative yields. The residual C5H5- groups in complexes to can be substituted by the bridged bis(phenolate) ligands at elevated temperature to give the neutral rare earth metal bis(phenolate) complexes, and the ionic radii have a profound effect on the structures of the final products. Complex reacted with MBMPH2 in a 1:0.5 molar ratio in toluene at 80 degrees C to produce a dinuclear complex (MBMP)La(THF)(micro-MBMP)2La(THF)2 () in good isolated yield; whereas complexes and reacted with MBMPH2 under the same conditions to give (MBMP)Ln(MBMPH)(THF)2 (Ln=Yb (), Y ()) as the final products, in which one hydroxyl group of the phenol is coordinated to the rare earth metal in a neutral fashion. The reactivity of complexes and with some metal alkyls was explored. Reaction of complex with 1 equiv. of AlEt3 in toluene at room temperature afforded unexpected ligand redistributed products, and a discrete ion pair ytterbium complex [(MBMP)Yb(THF)2(DME)][(MBMP)2Yb(THF)2] () was isolated in moderate yield. Furthermore, reaction of complex with 1 equiv. of ZnEt2 in toluene gave a ligand redistributed complex [(micro-MBMP)Zn(THF)]2 () in reasonable isolated yield. Similar reaction of complex with ZnEt2 also afforded complex ; whereas the reaction of complex with 1 equiv. of n-BuLi in THF afforded the heterodimetallic complex [(THF)Yb(MBMP)2Li(THF)2] (). All of these complexes were well characterized by elemental analyses, IR spectra, and single-crystal structure determination, in the cases of complexes , and -.

Well-defined bis(phenolate) lanthanide methoxides as efficient initiators for the polymerization of cyclic carbonate and lactide

Lanthanide methoxides supported by carbon-bridged bis(phenolate) ligands 2,2′-methylene-bis(6-tert-butyl-4-methylphenoxo) (MBMP2−) [(MBMP)Ln(µ-OMe)(THF)2]2 (Ln = Nd (1), Yb (2)) were synthesized in high yields by the protolysis reaction using (C5H5)3Ln(THF) as starting materials, and complex 1 was structurally characterized. The coordination geometry around the center metal can be best described as a distorted octahedron. Complexes 1 and 2 were shown to be efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) and L-lactide. The mechanism of DTC polymerization was explored by the end group analysis of the oligomer.

Facile synthesis and characterization of neutral carbon-bridged bis(phenolate) lanthanide derivatives

The reactions of (C 5H 5) 3Ln(THF) with 2,2′-ethylene-bis(4,6-di- tert-butylphenol) (EDBPH 2) in a 1:1 molar ratio in THF gave the cyclopentadienyl bis(phenolate) lanthanide complexes (C 5H 5)Ln(EDBP)(THF) 2 (Ln = Yb ( 1), Sm ( 2), Nd ( 3)) in nearly quantitative yields. The coordinated THF can be readily replaced by DME to give (C 5H 5)Ln(EDBP)(DME) (Ln = Yb ( 1a), Sm ( 2a)). Complexes 1 to 3 further reacted with 1 equivalent of isopropanol in THF to yield the neutral bis(phenolate) lanthanide isopropoxide [(EDBP) 2Ln( μ-OPr i)(THF) 2] 2 (Ln = Yb ( 4), Sm ( 5), Nd ( 6)) in high yields. The definitive molecular structures of complexes 1a, 5 and 6 were determined by X-ray diffraction analysis.

Carbon-Bridged Bis(phenolato)lanthanide Alkoxides: Syntheses, Structures, and Their Application in the Controlled Polymerization of ε-Caprolactone

A convenient method for the synthesis of lanthanide alkoxo complexes supported by a carbon-bridged bis(phenolate) ligand 2,2'-methylenebis(6-tert-butyl-4-methylphenoxo) (MBMP2-) is described. The reaction of (C5H5)3Nd with MBMPH2 in a 1:1 molar ratio in THF gave the bis(phenolato)lanthanide complex (C5H5)Nd(MBMP)(THF)2 (1) in a nearly quantitative yield. Complex 1 further reacted with 1 equiv of 2-propanol in THF to yield the bis(phenolato)lanthanide isopropoxide [(MBMP)2Nd(mu-OPr(i))(THF)2]2 (2) in high yield. Complex 2 can also be synthesized by the direct reaction of (C5H5)3Nd with MBMPH2 in a 1:1 molar ratio and then with 1 equiv of 2-propanol in situ in THF. Thus, the analogue bis(phenolato)lanthanide alkoxides [(MBMP)2Ln(mu-OR)(THF)2]2 [R = Pr(i), Ln = Yb (3); R = Me, Ln = Nd (4), Yb (5); R = CH2Ph, Ln = Nd (6), Yb (7)] were obtained by the reactions of (C5H5)3Ln (Ln = Nd, Yb) with MBMPH2 and then with 2-propanol, methanol, or benzyl alcohol, respectively. The ytterbium complex {[(MBMP)2Yb(THF)2]2(mu-OCH2Ph)(mu-OH)} (8) was also isolated as a byproduct. The single-crystal structural analyses of complexes 1-3 and 8 revealed that the coordination geometry around lanthanide metal can be best described as a distorted tetrahedron in complex 1 and as a distorted octahedron in complexes 2, 3, and 8. A O-H...Yb agostic interaction was observed in complex 8. Complexes 2-7 were shown to be efficient catalysts for the controlled polymerization of epsilon-caprolactone.