Synthesis of Ln(III) chloride tetraphenylporphyrin complexes

The isolation and identification of the first examples of anhydrous lanthanide chloride tetraphenylporphyrin complexes have been described. The purple complexes were generated by the reaction of dilithiotetraphenylporphyrin bis(dimethoxyethane) with lanthanide trichloride tris(tetrahydrofuran) salts to yield the products in up to 85% yield. The crystal structures for the holmium and ytterbium complexes are also presented.

Three different bonding modes of cyano groups in the coordination polymer [Cu(en)2(H(2)O)][Cu(en)(2)Ni(2)Cu(2)(CN)(10)] x 2H(2)O (en is 1,2-diaminoethane)

Partial reduction of the Cu(II) ions in the aqueous system Cu(II)-en-[Ni(CN)(4)](2-) (1/1/1) (en is 1,2-diaminoethane) yields a novel heterobimetallic mixed-valence compound, poly[[aquabis(1,2-diaminoethane)copper(II)] [hexa-mu-cyano-tetracyanobis(1,2-diaminoethane)tricopper(I,II)dinickel(II)] dihydrate], [Cu(C(2)H(8)N(2))(2)(H(2)O)][Ni(2)Cu(3)(CN)(10)(C(2)H(8)N(2))(2)] x 2H(2)O or [Cu(en)(2)(H(2)O)][Cu(en)(2)Ni(2)Cu(2)(CN)(10)] x 2H(2)O. The structure is formed by a negatively charged two-dimensional array of the cyano complex [Cu(en)(2)Ni(2)Cu(2)(CN)(10)](n)(2n-), [Cu(en)(2)(H(2)O)](2+) complex cations and water molecules of crystallization. These last are involved in a complicated hydrogen-bonding system. The cyano groups act as terminal, mu(2)-bridging or mu(3)-bridging ligands.

The synthesis and reactivity of a molybdenum (IV) stretched-dihydrogen complex

Reaction of [Mo(NPh)(PMe3)3(o-(Me3SiN)2C6H4)] (1) with molecular hydrogen (ca. 1 atm) at -10 degrees C in toluene-d8 results in the formation of dihydrogen complex [Mo(NPh)(PMe3)2(H2)(o-(Me3SiN)2C6H4)] (2) by 1H and 31P NMR spectroscopy. In solution at -50 degrees C 1 and 2 are present in a 1:3 ratio, respectively. The nature of dihydrogen ligand bonding in 2 was probed by T1 analysis and analysis of the JH-D coupling constant in the deuterium hydride isotopomer of 2 giving H-H distances of 1.18 A and 1.17 A, respectively. When allowed to warm to 30 degrees C, 2 reacts affording [Mo(NPh)(PMe3)3(o-(Me3SiN)(NH)C6H4)] (3) over a 1 h period. The X-ray structures of 1 and 3 are reported.

Catalyzed Reformatsky reactions with ethyl bromofluoroacetate for the synthesis of alpha-fluoro-beta-hydroxy acids

The presence of catalytic amounts of CeCl(3) improves yields and simplifies procedure in the Reformatsky reactions of ethyl bromofluoroacetate with aldehydes and ketones to generate diastereomeric mixtures of alpha-fluoro-beta-hydroxy esters, some of which can be separated by crystallization or column flash chromatography. Diastereomerically pure alpha-fluoro-beta-hydroxy acids are obtained by mild alkaline hydrolysis of the resolved alpha-fluoro-beta-hydroxy esters. Detailed NMR data of new alpha-fluoro-beta-hydroxy esters and alpha-fluoro-beta-hydroxy acids are also presented.

A dimeric constrained-geometry titanium complex linked by double Ti-CH2-Al-CH2 heterocycles

In the structure of bis([N-[dimethyl(1eta5-2,3,4,6-tetramethylindenyl)silyl]cyclohexylamido-1kappaN](methyl-3kappaC)-di-mu3-methylene-1:2:3kappa3C;1:3:3'kappa3C-tris(pentafluorophenyl-2kappaC)titanium) benzene disolvate, [Me2Si(eta5-2,3,4,6-Me4C9H2)(C6H11N)]Ti[(mu3-CH2)Al(C6F5)3][AlMe(mu3-CH2)]2 or [Ti2(C21H7AlF15)2(C21H31NSi)2].2C6D6, the dimer is located on an inversion center, and the two Ti centers are linked by double Ti(mu3-CH2)Al(C6F5)3AlMe(mu3-CH2) heterocycles. The electron-deficient Ti centers are further stabilized by two alpha-agostic interactions between Ti and one H atom of each bridging methylene group.

[N-[dimethyl(eta5-2,3,4,6-tetramethylindenyl)silyl]cyclobutylamido-kappaN](eta4-1,4-diphenyl-1,3-buta-diene)titanium(II)

The titanium metal center in the title compound, [Ti(C19H27NSi)(C16H14)], is coordinated in a distorted tetrahedral geometry by a eta5-indenyl ligand, a dimethylsilyl-bridged N-cyclobutylamido ligand and an s-cis-eta4-1,4-diphenyl-1,3-butadiene ligand in a 'prone' pi-fashion, revealing a formal divalent Ti center.

Total synthesis of (+/-)-asteriscanolide

The total synthesis of asteriscanolide (1) has been achieved by taking advantage on an intermolecular Pauson-Khand cycloaddition and a ring-closing metathesis as key bond-forming transformations. The approach incorporates the cyclooctane stereogenic center prior to ring formation. Interestingly, the ring-closing metathesis generates a new eight-membered ring with an "in-out" intrabridgehead relationship.

The first synthesis and characterization of both diastereomers of a di[2.2]paracyclophane: 4,4'-bis(1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane)

The synthesis and characterization of both diastereomers of a system comprised of two [2.2]paracyclophane units linked through a single 4,4' bond are described. Both the meso and d,l diastereomers of 4,4'-bis(octafluoro[2.2]paracyclophane) have been prepared via a palladium-catalyzed reductive homocoupling reaction by copper, producing a 3:2 ratio of meso and d,l diastereomers. A similar reductive homocoupling of pseudo-o-iodotrifluoromethyloctafluoro[2.2]paracyclophane gave only the analogous meso diastereomer. Single-crystal X-ray structures were obtained for all of the diparacyclophane products.

Coordinatively unsaturated W(IV)-bis(pyridine) complexes, a reactive source of W(IV)

Addition of 2 equiv of a sigma-donor ligand (L = pyridine, 4-picoline, or quinoline) to complexes of the type [W(NPh)(eta(4)-arene)(o-(Me3SiN)2C6H4)] (arene = CH3CH2C6H5 (3), CH3CH2CH2C6H5 (4)) gave the W(IV)L2 compounds, [W(NPh)(o-(Me3SiN)2C6H4)(C5H5N)2] (5), [W(NPh)(o-(Me3SiN)2C6H4)(p-C6H7N)2] (6), and [W(NPh)(o-(Me3SiN)2C6H4)(C9H7N)2] (7). Synthesis of compounds 5 and 6 by Na degrees reduction of [W(NPh)(o-(Me3SiN)2C6H4)Cl2] in the presence of 3 equiv of L (L = 5, pyridine or 6, 4-picoline) is also presented. Compounds 5, 6, and 7 display hindered rotation of the donor ligands about the W-N bonds, resulting from a steric interaction with the Me3Si groups of the diamide ligand. The coordinative unsaturation of 5 and 6 has also been explored. Compounds 5 and 6 readily react with either CO and PMe3 to generated the six coordinate complexes [W(NPh)(o-(Me3SiN)2C6H4)(C5H5N)2(CO)] (8a), [W(NPh)(o-(Me3SiN)2C6H4)(C6H7N)2(CO)] (8b), [W(NPh)(o-(Me3SiN)2C6H4)(C5H5N)(PMe3)2] (10a), and [W(NPh)(o-(Me3SiN)2C6H4)(C6H7N)(PMe3)2] (10b), respectively.

Synthesis of L-4,4-difluoroglutamic acid via nucleophilic addition to a chiral aldehyde

Fluorine-containing derivatives of amino acids are assuming increasing importance as probes of biological function and enzyme mechanism. We now report a new, flexible route to enantiomerically pure L-4,4-difluoroglutamic acid that exploits the addition of difluorinated nucleophiles to configurationally stable alpha-aminoaldehydes. Conversion of the difluorinated adducts to L-4,4-difluoroglutamic acid can be accomplished in three steps by Barton-McCombie dehydroxylation and acid hydrolysis.