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C1-symmetric vanadyl Schiff-base complexes were synthesized by reacting vanadium(IV) acetylacetonate with (S)-3-[(1-(2-hydroxynaphthalen-1-yl)naphthalen-2-ylimino]methyl]-phenanthrene-4-ol and (S)-2-{[1-(2-hydroxynaphthalen-1-yl)naphthalen-2-ylimino]methyl}tetraphene-1-ol. The complexes were characterized by MALDI-TOF-MS, UV–vis, and circular dichroism (CD) spectroscopy. The catalysts showed moderate activity for the oxidation of thioanisole to methyphenylsulfoxide with hydrogen peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide as the oxidants.

A novel porphyrin, whose [Formula: see text]-system has been extended via the presence of two additional carbon–carbon triple bonds on opposite meso-positions and by fusion of a single naphthalene unit simultaneously bridging the third meso-position and the [Formula: see text]-carbon of one of the pyrroles, has been synthesized in good yield. Absorption, magnetic circular dichroism, emission, and theoretical spectra are reported for the fused and unfused trans-naphthalene free base and zinc porphyrins. The fusing of one of the naphthalene moieties results in significant changes to the absorption spectrum and, very unusually, the bridged meso-[Formula: see text]-pyrrole fusion results in quenching of the MCD Faraday pseudo-A term in the porphyrin’s B band (S2). This unique effect was interpreted as resulting from the origin of the electronic structure of the second excited state (the B state). The [Formula: see text] and [Formula: see text] polarizations are completely mixed by the electronic effects of the non-symmetric extended conjugation of the [Formula: see text] ring. Analysis of the origin of the MCD signal indicates that the presence of this novel mixed polarization leads to negligible angular momentum in the important B state. To our knowledge, this is the first report in which the magnetic moment in a porphyrin’s intensely absorbing B band has been quenched while the angular momentum in the Q band, the first excited state, remains as normal. This implies that the photophysical properties of the B state are likely very different than those of the Q state, which has novel and significant implications for applications, especially in non-linear spectroscopy.

The purpose of this study is to determine if arthrodesis, compared with open reduction and internal fixation (ORIF), produces favorable American Orthopaedic Foot and Ankle Society (AOFAS) and visual analogue scale (VAS) scores, and to determine if differences in complication, revision surgery, and secondary arthrodesis rates exist for patients with Lisfranc fracture/dislocation injuries. Searches were performed in PubMed using the keywords “Lisfranc fracture,” “metatarsal fracture,” “ORIF,” “open reduction internal fixation,” “arthrodesis,” and “fusion.” These criteria left 183 articles for review. Exclusions left 21 articles and 2 translations of Chinese abstracts. Data analysis was performed using Student’s 2-sample t test for samples of equal variance, and chi-square test for goodness of fit. The t test revealed a significant difference ( P = .03) between the average AOFAS score for patients who underwent primary arthrodesis (84.7 ± 6.14) compared with those who were treated with ORIF (78.9 ± 5.09). There was no significant difference for the average VAS scores ( P = .33) of the arthrodesis and ORIF groups. The complication rate of arthrodesis patients was significantly lower than ORIF patients ( P = .04), and the rates of revision surgery ( P = .22) and secondary arthrodesis ( P = .53) were not significant between the groups. The results of this study indicate that arthrodesis may be a better surgical option than ORIF, due to the higher functional scores and the lower complication rate. Levels of Evidence: Level III: A meta-analysis

The bimetallic title compound contains an FeIII center coordinated by one chloride ligand, four N atoms and a bridging oxo ligand in a distorted octa­hedral geometry. The bridging oxo ligand is connected to a second FeIII atom with three coordinating chloride ligands., The first FeIII atom in the solvated title compound, [Fe2Cl4O(C26H28N4)]·CHCl3, adopts a distorted six-coordinate octa­hedral geometry. It is coordinated by one chloride ligand, four N atoms from the (1R,2R)-N,N′-bis­[(quinolin-2-yl)methyl]cyclo­hexane-1,2-di­amine ligand, and a bridging oxido ligand attached to the second FeIII atom, which is also bonded to three chloride ions. A very weak intra­molecular N—H⋯Cl hydrogen bond occurs. In the crystal, the coordination complexes stack in columns, and a grouping of six such columns create channels, which are populated by disordered chloro­form solvent mol­ecules. Although the Fe—Cl bond lengths for the two metal atoms are comparable to the mean Fe—Cl bond lengths as derived from the Cambridge Structural Database, the Fe—O bond lengths are notably shorter. The solvent chloro­form mol­ecule exhibits ‘flip’ disorder of the C—H moiety in a 0.544 (3):0.456 (3) ratio. The only directional inter­action noted is a weak C—H⋯Cl hydrogen bond.

The zinc(II) atom in the title compound, [Zn(C48H31N4)(CF3SO3)](CF3SO3)·1.5CH2Cl2, adopts a distorted five-coordinate square-pyramidal geometry. It is coordinated by one trifluoromethanesulfonate ligand and four N atoms of theN2-[(benzo[h]quinolin-2-yl)methyl]-N2′-[(benzo[h]quinolin-2-yl)methylidene]-1,1′-binaphthyl-2,2′-diamine ligand. The complex is present as a single-strandedP-helimer monohelical structure incorporating π–π and/or σ–π interactions. One of the imine bonds present in the original ligand framework is reduced, leading to variations in bond lengths and torsion angles for each side of the ligand motif. The imine-bond reduction also affects the bond lengths involving the metal atom with the N-donor atoms located on the imine bond. There are two molecules of the complex in the asymmetric unit. One of the molecules exhibits positional disorder within the coordinating trifluoromethanesulfonate ion making the molecules symmetrically non-equivalent.

Tridentate (ONO) C1-symmetric Schiff base ligands were synthesized by the condensation of (S)-2-amino-2′-hydroxy-1,1′-binaphthyalene with 4-hydroxy-3-phenanthrenecarboxaldehyde or 1-hydroxybenz[a]anthracene-2-carboxaldehyde. C2-symmetric titanium(IV) Schiff base complexes, TiL2, were synthesized and characterized with these ligands. The complex with the benz[a]anthryl unit crystallizes in a facial coordination mode, OC-6-1′3′-C, whereas complex with phenanthryl unit crystallizes in a meridional mode, OC-6-22′-A. A comparison between the complexes and the ligands were done in solution using circular dichroism spectroscopy. Preliminary catalytic studies showed that these complexes can catalyze asymmetric carbonyl-ene addition reactions of 2-methoxypropene with aromatic aldehydes with moderate selectivity. The ligands and complexes were characterized by NMR, HRMS, single crystal X-ray diffraction and CD spectroscopy.

In the title compound, the zinc(II) atom exhibits a a distorted five-coordinate square-pyramidal geometry and is coordinated by one tri­fluoro­methane­sulfonate ligand and four N-donor atoms. The resulting complex shows a single-stranded P-helimer structure incorporating π–π and/or σ–π inter­actions., The zinc(II) atom in the title compound, [Zn(C48H31N4)(CF3SO3)](CF3SO3)·1.5CH2Cl2, adopts a distorted five-coordinate square-pyramidal geometry. It is coordinated by one tri­fluoro­methane­sulfonate ligand and four N atoms of the N 2-[(benzo[h]quinolin-2-yl)meth­yl]-N 2′-[(benzo[h]quinolin-2-yl)methyl­idene]-1,1′-binaphthyl-2,2′-di­amine ligand. The complex is present as a single-stranded P-helimer monohelical structure incorporating π–π and/or σ–π inter­actions. One of the imine bonds present in the original ligand framework is reduced, leading to variations in bond lengths and torsion angles for each side of the ligand motif. The imine-bond reduction also affects the bond lengths involving the metal atom with the N-donor atoms located on the imine bond. There are two mol­ecules of the complex in the asymmetric unit. One of the mol­ecules exhibits positional disorder within the coordinating tri­fluoro­methane­sulfonate ion making the mol­ecules symmetric­ally non-equivalent.

Chiral [VO(salen)] complexes (R,R)-7 and (R,R)-8 were synthesised by ligand replacement from [VO(acac)2] with the resolved (1R,2R)-cyclohexyl ligands 3,3′-[(1R,2R)-1,2-cyclohexane-diylbis(nitrilomethylidyne)]bis-4-phenanthrenol [(R,R)-3] and 3,3′-[(1R,2R)-1,2-cyclohexanediylbis(nitrilomethylidyne)]bisbenz[a]anthracen-1-ol [(R,R)-4], respectively. Similarly, complexes (R)-9 and (R)-10 were synthesised using the (R)-binaphthyl ligands 3,3′-[(1R)-(1,1′-binaphthalene)-2,2′-diylbis(nitrilomethylidyne)]bis-4-phenanthrenol [(R)-5] and 3,3′-[(1R)-(1,1′-binaphthalene)-2,2′-diylbis(nitrilomethylidyne)]bis-benz[a]anthracen-1-ol [(R)-6], respectively. These complexes were characterised by IR spectroscopy, ESI-TOF-MS, electronic absorption spectroscopy and circular dichroism (CD). Single crystal X-ray analysis of (R,R)-7 and (R,R)-8 revealed distorted square pyramidal geometries and a 1:1 ratio of diastereomeric M and P helical conformers. Solution CD studies in THF combined with DFT calculations indicate that the M conformer dominates in solution for (R,R)-7. Preliminary catalytic oxidation of thioanisole with H2O2 and 1 % [VO(salen)] showed good selectivity for sulfoxides over sulfones but low enantioselectivities (8 to 33 %) which are solvent dependent but insensitive to the catalyst used.

A symmetrical salen ligand is formed by the condensation of (1R,2R)-diaminocyclohexane with 4-hydroxy-3-phenanthrenecarboxaldehyde. Crystallographic characterization of the metal complexes (ZnII, FeII, and FeIII) show 1:1 mixtures of diastereomeric M and P helical molecules. ECD spectra of the ZnII complex combined with DFT simulations strongly suggest that the M conformation is dominant in solution. This is supported by 1H and 13C NMR data, which are consistent with a single species in solution.Key words: zinc, iron, ECD, DFT, salen complexes.

A new Schiff-base ligand is prepared by a two-step reaction of 3-formylsalicylic acid and (1R, 2R)-diaminocyclohexane in alcoholic solvents. The 1:1 condensation product exists as a zwitterion in the solid state and forms pleated hydrogen-bonded sheets. Metalation of the ligand with divalent iron, nickel, cobalt, and zinc resulted in the formation of double-stranded monohelices with exclusively M-helicity. Each complex has two tridentate ligands, with the carboxylic acid groups remaining uncoordinated. In the crystal lattice, these complexes form extended M-helical strands through intermolecular hydrogen bonding interactions. Metalation of the ligand with copper salts resulted in a distinctly different type of complex, in which the ligand has transformed into a symmetric tetradentate salen ligand with uncoordinated carboxylic acid groups.

A series of enantiopure C_1-symmetric metallocenes, {(SiMe_2)_2[η^5-C_5H(CHMe_2)_2][η^5-C_5H_2((S)-CHMeCMe_3)]}ZrCl_2, (S)-2, {(SiMe_2)_2[η^5-C_5H(CHEt_2)_2][η^5-C_5H_2((S)-CHMeCMe_3)]}ZrCl_2, (S)-6, and {(SiMe_2)_2[η^5-C_5HCy_2][η^5-C_5H_2((S)-CHMeCMe_3)]}ZrCl_2, (S)-7 (Cy = cyclohexyl), zirconocene dichlorides that have an enantiopure methylneopentyl substituent on the “upper” cyclopentadienyl ligand, and diastereomerically pure precatalysts, {(SiMe_2)_2[η^5-C_5H((S)-CHMeCy)(CHMe_2)][η^5-C_5H_3]}ZrCl_2, (S)-8a and (S)-8b, which have an enantiopure, 1-cyclohexylethyl substituent on the “lower” cyclopentadienyl ligand, has been synthesized for use in the polymerization of chiral α-olefins. When activated with methylaluminoxane, these metallocenes show unprecedented activity for the polymerization of bulky racemic monomers bearing substitution at the 3- and/or 4-positions. Due to the optically pure nature of these single site catalysts, they effect kinetic resolution of racemic monomers: the polymeric product is enriched with the faster reacting enantiomer, while recovered monomer is enriched with the slower reacting enantiomer. The two components are easily separated. For most olefins surveyed, a partial kinetic resolution was achieved (s = k_(faster)/k_(slower) ≈ 2), but, in one case, the polymerization of 3,4-dimethyl-1-pentene, high levels of separation were obtained (s > 15). ^(13)C NMR spectroscopy of poly(3-methyl-1-pentene) produced with (S)-2 indicates that the polymers are highly isotactic materials. X-ray crystal structure determinations for (S)-2, {(SiMe_2)_2[η^5-C_5H(CHMe_2)_2][η^5-C_5H_2((S)-CHMeCMe_3)]}Zr(SC_6H_5)_2, (S)-6, and (S)-7 have been used in combination with molecular mechanics calculations to examine the prevailing steric interactions expected in the diastereomeric transition states for propagation during polymerization. Precatalysts (S)-8a and (S)-8b are less selective polymerization catalysts for the kinetic resolution of 3-methyl-1-pentene than are (S)-2, (S)-6, and (S)-7.

The Diels−Alder cycloaddition reaction between enoyl−oxazolidinones 3 and dienes is efficiently catalyzed by zirconocene bis(triflate) catalysts (4 and 8) in CH2Cl2 or nitroalkane solvents. The use...

The reversible oxidative addition reactions of methyl(halogeno)tin and methyl(halogeno)germanium compounds to electron-rich platinum(II) complexes of the type [PtMe2(diimine)] have been studied. Complete kinetic and thermodynamic parameters have been obtained by VT 1H NMR for the reversible oxidative addition of Me3EX (E = Sn, X = Cl, Br, I) to [PtMe2(bpy-tbu2)] (bpy-tbu2 = 4,4‘-di-tert-butyl-2,2‘-bipyridyl) and related compounds, while partial data have been obtained for the reductive elimination of Me2SnCl2 from [PtClMe2(Me2SnCl)(bpy-tbu2)] and for the oxidative addition of Me3GeCl to [PtMe2(bpy-tbu2)]. UV−visible spectroscopic studies have also yielded equilibrium constants and ΔG° for the reversible oxidative addition reactions of Me3SnX (X = Cl, Br, I) to [PtMe2(diimine)]. Thermodynamic studies quantitatively establish the halogen effect on the oxidative addition reactions studied according to the favorability series I > Br > Cl. Kinetic studies clearly point to an SN2 mechanism for the reactions stu...

The thermal decomposition of a number of complexes of the type [PtMe2(Me3E)X(diimine)] (E = Si, Ge, Sn; X = Cl, Br, I) has been studied. The thermal stability of complexes, as determined by thermogravimetric analysis (TGA), varies depending on the diimine ligand in the order 2,2‘-bipyridyl (bpy) > 4,4‘-di-tert-butyl-2,2‘-bipyridyl (bpy-tbu2) > N-(2-(dimethylamino)ethyl)pyridine-2-aldimine (paen-me2) > (2-imino-n-propyl)pyridine (py-n-pr). Stability also varies according to the trends E = Sn ≈ Ge > Si and X = I > Br > Cl. The products of thermal decomposition have also been determined by 1H NMR and three distinct modes of decomposition are evident: reductive elimination of Me3EX, reductive elimination of Me4E, and α-elimination of Me2E. The competition between reductive elimination of Me3EX and Me4E depends primarily on the halide, X, with the ratio Me3EX:Me4E highest for X = Cl and lowest for X = I. The competition between reductive elimination and α-elimination depends primarily on E, with the tendency ...

The reactions of group 14 compounds MenEX4-n (E = Si, Ge, Sn; X = Cl, Br, I) with electron-rich [PtMe2(diimine)] complexes give facile trans oxidative addition of the E−X bond (E = Si, X = Br, I; E...

The aldol condensations of α- and β-(benzyloxy) aldehydes with enol silanes, catalyzed by Cp2Zr(OTf)2·THF or Cp2Zr(OTf)2, in a variety of solvents were studied. The simple diastereoselectivity of these reactions is modest and comparable to that observed using simple aldehydes of similar steric requirements. Studies have revealed that TMSOTf is directly produced on reaction with the zirconocene catalyst with the enol silane in nitroalkane solvent or is formed during catalysis in dichloromethane solution. Although TMSOTf is known to catalyze cross-aldol reactions under these conditions, the rate of this process is not always competitive with that observed using the zirconocene catalysts. In particular, sterically unhindered or aromatic aldehydes react via a mechanism that appears to be mainly Zr-catalyzed, based on both the difference in rate between Zr- and Si-mediated reactions as well as differences in enol silane/silyl triflate reactivity in crossover-type experiments. With sterically hindered aldehydes...

Enantio- and diastereoselective Diels−Alder reactions between dienophiles 1 and cyclopentadiene are catalyzed by a chiral, dicationic complex formed on reaction of the chiral ansa-zirconocene 2 (X ...

An enantiomerically pure C2-symmetric salen ligand with benz[a]anthracene siderams produces M helical complexes (FeII and ZnII) in solution. Interconversion to produce a 1:1 mixture of helical conformers in the solid state is possible, despite overlapped sidearms.

The coordination chemistry of four enantiopure tetradentate bis(iminoquinoline) ligands with nickel(II) salts is reported. The previously reported ligands CBQ, CPQ, BBQ, and BPQ result from the condensation of (1R,2R)-cyclohexyldiamine or (R)-BINAM with two equivalents of 2-formylbenzo[h]quinoline or 8-isopropyl-2-quinolinecarboxaldehyde {CBQ = (1R,2R)-cyclohexanediamine-N,N'-bis(benzo[h]quinoline-2-ylmethylene), CPQ = (1R,2R)-cyclohexanediamine-N,N'-bis[[(8-isopropyl)-2-quinolinyl]methylene], BBQ = [(R)-1,1'-binaphthalene]-2,2'-diamine-N,N'-bis(benzo[h]quinoline-2-ylmethylene), BPQ = [(R)-1,1'-binaphthalene]-2,2'-diamine-N,N'-bis[[(8-isopropyl)-2-quinolinyl]methylene]}. Reaction of NiI(2) with the (1R,2R)-cyclohexyl ligands gives the mononuclear distorted trigonal-bipyramidal (TBP) complexes [Ni(N(3)-CBQ)I(2)] and [Ni(N(3)-CPQ)I(2)]. Incomplete iodide abstraction from [Ni(N(3)-CPQ)I(2)] with AgOTf leads to partial replacement of the iodide with hydroxide from adventitious water to give [Ni(N(3)-CPQ)I(1.6)(OH)(0.4)] (distorted TBP). The corresponding reaction with [Ni(N(3)-CBQ)I(2)] again fails to remove all of the iodide, resulting instead in conversion to the syn dinuclear [Ni(2)(CBQ)(μ-X)(2)I(2)] (X = Cl(0.925)I(0.075)) complex, where chloride abstraction from the solvent (CH(2)Cl(2)) has resulted in a mixed halide system and the metal centers are square-pyramidal. Reaction of Ni(OTf)(2) with CBQ leads to the isolation of the octahedral cation [Ni(CMBQ)(2)](2+), with CMBQ [(1R,2R)-cyclohexanediamine-mono-N-(benzo[h]quinoline-2-ylmethylene)] being the partial hydrolysis product of CBQ. [Ni(CMBQ)(2)][OTf](2) crystallizes as a 1:1 mixture of P and M helical diastereomers. The coordination of NiI(2) with the (R)-BINAM derived ligands yields the anti dinuclear P-helical complexes [Ni(2)(BBQ)(μ-I)(2)I(2)] and [Ni(2)(BPQ)(μ-I)(2)I(2)]: one nickel ion is coordinated in each bidentate iminoquinoline pocket and the geometry at the metal centers is distorted square-pyramidal. Characterisation by (1)H NMR, UV-Vis, electronic circular dichroism (ECD) spectroscopy, combustion analysis, and HRMS is reported in addition to structural and halide abstraction studies.

The synthesis of two 2-formylquinolines is reported via the Skraup method followed by SeO(2) oxidation. Each aldehyde is condensed with (1R,2R)-diaminocyclohexane and (R)-BINAM, yielding four enantiomerically-pure bis(imine-quinoline) ligands. The neutral ligands are reacted with ZnCl(2) to give complexes with bis(bidentate) coordination of ZnCl(2) units. X-Ray structural characterization of three complexes shows them to have a single-stranded helical motif, with M helicity, except in one case where a 1:1 mixture of M and P helices is seen. The ligands and complexes are further characterized spectroscopically by solution (1)H and (13)C NMR, UV-vis and ECD.

A new chiral binaphthyl salen ligand with rigid polyaromatic sidearms gives monohelical complexes (Fe(II) and Zn(II)) of predetermined handedness.

The trimethyltin undergo a very fast, reversible oxidative addition reaction with [PtMe2(Bu2bipy)], Bu2bipy = 4,4′-di-tert-butyl-2,2′-bipyridine, to give [PtXMe2(SnMe3)(Bu2bipy)] for which a complete energy profile can be obtained by using variable-temperature NMR methods; the reaction with X = I is the fastest known oxidative addition and activation energies when X = Cl suggest detailed structure for the transition state.