Preparation and Characterization of Dinuclear Chromium(III) Complexes of a Hexadentate Tetraaza‐Dithiophenolate Ligand

The ability of the tetraaza‐dithiophenolate ligand H₂L² (H₂L² = N,N′‐Bis‐[2‐thio‐3‐aminomethyl‐5‐tert‐butyl‐benzyl]propane‐1,3‐diamine) to form dinuclear chromium(III) complexes has been examined. Reaction of Cr^IICl₂ with H₂L² in methanol in the presence of base followed by air‐oxidation afforded cis,cis‐[(L²)Cr^III₂(μ‐OH)(Cl)₂]⁺ ( 1a ) and trans,trans‐[(L²)Cr^III₂(μ‐OH)(Cl)₂]⁺ ( 1b ). Both compounds contain a confacial bioctahedral N₂ClCr^III(μ‐SR)₂(μ‐OH)Cr^IIIClN₂ core. The isomers differ in the mutual orientation of the coligands and the conformation of the supporting ligand. In 1a both Cl^? ligands are cis to the bridging OH function. In 1b they are in trans‐positions. Reaction of the hydroxo‐bridged complexes with HCl yielded the chloro‐bridged cations cis,cis‐[(L²)Cr^III₂(μ‐Cl)(Cl)₂]⁺ ( 2a ) and trans,trans‐[(L²)Cr^III₂(μ‐Cl)(Cl)₂]Cl ( 2b ), respectively. These bridge substitutions proceed with retention of the structures of the parent complexes 1a and 1b .     

Tailored synthesis,spectroscopic, catalytic,and antibacterial studies of dinuclear ruthenium (II/III) chloro sulfoxide complexes with 5-nitro-o-phenanthroline as a spacer

A dinucleating spacer incorporating o-phenanthroline has been synthesized and characterized. The reaction of this spacer with ruthenium precursors resulted in formation of dinuclear complexes, [cis,fac-RuCl₂(SO)₃ (μ-nphen)cis,cis-RuCl₂(SO)₂], [trans,mer-RuCl₂(SO)₃ (μ-nphen)trans, cis-RuCl₂(SO)₂], and [X]⁺[trans-RuCl₄(SO)(μ-nphen)mer-RuCl₃(SO)]^?, where SO = dimethylsulfoxide/tetramethylenesulfoxide, nphen = 5-nitro-o-phenanthroline, and X⁺ = [(dmso)₂H]⁺, Na⁺, and [(tmso)H]⁺. These complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibility, FT-IR, FAB-Mass, ¹H-NMR, ¹³C{¹H}-NMR, and electronic spectroscopy. [trans,mer-RuCl₂(dmso)3(μ-nphen)trans,cis-RuCl₂(dmso)₂] was also characterized on the basis of ¹H–¹H COSY NMR. The coordination of one ruthenium is through heterocyclic nitrogen of the o-phenanthroline and the second is through the oxygen of the nitrito group. Catalytic activity of these complexes has been investigated in hydrolysis of benzonitrile. All the complexes possess antibacterial activity against Escherichia coli and are compared to Chloramphenicol.     

Oxomolybdenum(VI) complexes with glycine bisphenol [O,N,O,O′] ligand: synthesis and catalytic studies

The oxomolybdenum(VI) complex [MoOCl(L)] with a tetradentate glycine bisphenol ligand (H₃L) was prepared by reaction of [MoO₂Cl₂(DMSO)₂] with a ligand precursor in hot toluene. The product was isolated in moderate yield as separable cis and trans isomers along with the third minor component, [MoO₂(HL)]. The solid-state structure of trans-[MoOCl(L)] was determined by X-ray diffraction. The ligand has tetradentate coordination through three oxygens and one nitrogen, which is located trans to the terminal oxo whereas the sixth coordination site is occupied by a chloride. Both cis and trans isomers of [MoOCl(L)] are active catalysts for epoxidation of cis-cyclooctene and sulfoxidation of tolyl methyl sulfide. The cis isomer gave higher activity in epoxidation and sulfoxidation reactions at room temperature than the trans isomer but they performed identically at 50?°C.     

Reactions of platinum complexes with 4,7-phenanthroline: crystal structures of mono- and binuclear platinum(II) complexes containing 4,7-phenanthroline

The reaction of a mixture of cis and trans-[PtCl₂(SMe₂)₂] with 4,7-phen (4,7-phen = 4,7-phenanthroline) in a molar ratio of 1 : 1 or 2 : 1 resulted in the formation of mono and binuclear complexes trans-[PtCl₂(SMe₂)(4,7-phen)] (1) and trans-[Pt₂Cl₄(SMe₂)₂(μ-4,7-phen)] (2), respectively. The products have been fully characterized by elemental analysis, ¹H, ¹³C{¹H}, HHCOSY, HSQC, HMBC, and DEPT-135 NMR spectroscopy. The crystal structure of 1 reveals that platinum has a slightly distorted square planar geometry. Both chlorides are trans with a deviation from linearity 177.66(3)°, while the N–Pt–S angle is 175.53(6)°. Similarly, the reaction of a mixture of cis and trans-[PtBr₂(SMe₂)₂] with 4,7-phen in a 1 : 1 or 2 : 1 mole ratio afforded the mono or binuclear complexes trans-[PtBr₂(SMe₂)(4,7-phen)] (3) and trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)] (4), respectively. The crystal structure of trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)].C₆H₆ reveals that 4,7-phen bridges between two platinum centers in a slightly distorted square planar arrangement of the platinum. In this structure, both bromides are trans, while the PtBr₂(SMe₂) moieties are syn to each other. NMR data of mono and binuclear complexes of platinum 1–4 show that the binuclear complexes exist in solution as a minor product, while the mononuclear complexes are major products.     

Synthesis and Structural Characterization of Dinuclear Oxorhenium(V) Complexes with Bidentate Imidazole Derivatives

The oxo-bridged dinuclear complexes [(μ-O){ReOCl₂(L)}₂] [L = 2-(1-ethylaminomethyl)-1-methylimidazole (eami); 2-(1-methylaminomethyl)-1-methylimidazole (mami); 2-(1-ethylthiomethyl)-1-methylimidazole (etmi)] were prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with L in acetone. X-ray crystallographic studies of the eami and etmi complexes show that these ligands coordinate in a bidentate manner, and that the cis, cis-N₂Cl₂ and cis, cis-NSCl₂ equatorial planes are nearly orthogonal to the O=Re-O-Re=O backbone.     

Schiff Base Complexes of Rhodium(I) with Tridentate N-Methyl-S-methyldithiocarbazate Ligands

Schiff bases derived from the condensation of β-diketones with N-methyl-S-methyldithiocarbazates yield cis dicarbonyl complexes Rh(CO)₂ (Schiff) on reaction with [Rh(μ-Cl)(CO)₂]₂. Those derived from aromatic aldehydes form trans dicarbonyl complexes. These complexes with excess of triphenylphosphine give only Rh(CO)(PPh₃)(Schiff). cis-1,5-cyclooctadiene (COD) reacts with cis dicarbonyl complexes to yield the carbonyl-free product Rh(COD)(Schiff); similar reactions have not been observed in the case of trans-dicarbonyl complexes. Oxidative addition of bromine to these complexes yields dibromo derivative in which the Schiff base acts as bidentate chelate. Rh(PPh₃)₂(Schiff) complexes have been obtained from the reaction of above Schiff bases with Rh(PPh₃)₃Cl. The structures of these new complexes have been determined based on IR and ¹H NMR spectra.     

Synthesis and characterization of diiron(I) 1,2-dimethylethanedithiolate complexes with bridging or chelating 1,2-bis(diphenylphosphino)ethylene

The reaction of complex [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₆ (1) with trans-1,2-bis(diphenylphosphino)ethylene (trans-dppv) in the presence of Me₃NO?2H₂O in CH₂Cl₂/CH₃CN afforded complex {[μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₅}₂(trans-dppv) (2) with a bridging dppv. Complex [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₄(cis-dppv) (3) was prepared by the reaction of 1 with cis-dppv and Me₃NO?2H₂O. The new complexes 2 and 3 were characterized by elemental analysis, spectroscopy, and X-ray diffraction analysis.     

Chiral Ruthenium-Oxo Complexes for Enantioselective Epoxidation of trans-Stilbene

Two oxoruthenium(IV) complexes containing C₂ symmetric 1,1′-biisoquinoline (biqn) and (R,R)-3,3′-(1,2-dimethylethylenedioxy)-2,2′-bipyridine (diopy*) were prepared, and both are active oxidants for alkene epoxidations. The oxidation of styrene and cis- and trans-β-methylstyrenes by [(Cn)(diopy*)-Ru^IV(O)](ClO₄)₂ did not proceed enantioselectively, but the same oxidant can attain a moderate enantioselectivity of 33%ee for the trans-stilbene oxidation to trans-stilbene oxide. A head-on approach model, where the C=C is directed from the top to the O=Ru moiety, is proposed to account for the facial differentiation of the trans-stilbene oxidation.     

Synthesis and properties of bis(dialkylphosphino)ethane iron dihydrides

Syntheses and properties of the iron bisphosphinoethane complexes FeH₂(PP)₂ and FeHCl(PP)₂[PP?R₂PCH₂CH₂CH₂PR₂, where R?Me (PP?DMPE), Et(PP?DEPE), and n-Pr (PP?DprPE)] are reported. The complexes can be formed by reduction of the corresponding dichlorides FeCl₂(PP)₂ with lithium aluminium hydride in THF solution provided that ethanol or more acidic reagents are not employed during the reaction work-up. The dihydrides are notably basic compounds and can be protonated reversibly by alcohols. The dihydrides exist as equilibrating mixtures of cis and trans isomers in solution. The cis isomers of each of the dihydrides are fluxional on the NMR timescale and NMR studies indicate that the interconversion of cis isomers does not necessarily proceed via the trans isomer.     

Synthesis, characterization, and C-H activation reactions of novel organometallic O-donor ligated Rh(III) complexes

The synthesis and characterization of the O-donor ligated, air and water stable organometallic complexes trans- (2), and cis-(hfac-O,O)₂Rh(CH₃)(py) (3), trans-(hfac-O,O)₂Rh(C₆H₅)(py) (4), cis-(hfac-O,O)₂Rh(C₆H₅)(py) (5), and cis-(hfac-O,O)₂Rh(Mes)(py) (6) (where hfac-O,O = κ²-O,O-1,1,1,5,5,5-hexafluoroacetylacetonato) are reported. These compounds are analogues to the O-donor iridium complexes that are active catalysts for the hydroarylation and C-H activation reactions as well as the bis-acetylacetonato rhodium complexes, which we recently reported. The trans-complex 2 undergoes a quantitative trans to cis isomerization in cyclohexane to form 3, which activates C-H bonds in both benzene and mesitylene to form compounds 5 and 6, respectively. All of these compounds are air and water stable and do not lead to decomposition products. Complex 5 promotes hydroarylation of styrene by benzene to generate dihydrostilbene.     

Synthesis,spectroscopic characterization and antibacterial sensitivity of some chloro dimethylsulfoxide/tetramethylenesulfoxide ruthenium(II) and ruthenium(III) complexes with 2-aminobenzothiazole

Synthesis and characterization of seven ruthenium(II) and ruthenium(III) complexes of sulfoxide with 2-aminobenzothiazole are reported. Three different formulations exist: [cis,cis,cis-RuCl₂(SO)₂(2-abtz)₂] and [trans,trans,trans-RuCl₂(SO)₂(2-abtz)₂] and [trans-RuCl₄(SO)(2-abtz)] ^? [X]⁺ (where SO?=?dimethyl sulfoxide (dmso) or tetramethylenesulfoxide (tmso); 2-abtz?=?2-aminobenzothiazole and [X]⁺?=?[H(abtz)]⁺, [Na⁺]. These complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibility, FTIR, ¹H NMR, ¹³C{¹H} NMR and electronic spectroscopy. Some of the complexes were screened for their antibacterial activity and are found to be potent against the gram negative bacteria Escherichia coli.     

Influence of Central Metalloligand Geometry on Electronic Communication between Metals: Syntheses,Crystal Structures,MMCT Properties of Isomeric Cyanido‐Bridged Fe2Ru Complexes,and TDDFT Calculations

To investigate how the central metalloligand geometry influences distant or vicinal metal‐to‐metal charge‐transfer (MMCT) properties of polynuclear complexes, cis‐ and trans‐isomeric heterotrimetallic complexes, and their one‐ and two‐electron oxidation products, cis/trans‐ [Cp(dppe)Fe^IINCRu^II(phen)₂CN‐Fe^II(dppe)Cp][PF₆]₂ (cis/trans‐ 1 [PF₆]₂), cis/trans‐[Cp(dppe)Fe^IINCRu^II(phen)₂CNFe^III‐(dppe)Cp][PF₆]₃ (cis/trans‐ 1 [PF₆]₃) and cis/trans‐[Cp(dppe)Fe^IIINCRu^II(phen)₂CN‐Fe^III(dppe)Cp][PF₆]₄ (cis/trans‐ 1 [PF₆]₄) have been synthesized and characterized. Electrochemical measurements show the presence of electronic interactions between the two external Fe^II atoms of the cis‐ and trans‐isomeric complexes cis/trans‐ 1 [PF₆]₂. The electronic properties of all these complexes were studied and compared by spectroscopic techniques and TDDFT//DFT calculations. As expected, both mixed valence complexes cis/trans‐ 1 [PF₆]₃ exhibited different strong absorption signals in the NIR region, which should mainly be attributed to a transition from an MO that is delocalized over the Ru^II‐CN‐Fe^II subunit to a Fe^III d orbital with some contributions from the co‐ligands. Moreover, the NIR transition energy in trans‐ 1 [PF₆]₃ is lower than that in cis‐ 1 [PF₆]₃, which is related to the symmetry of their molecular orbitals on the basis of the molecular orbital analysis. Also, the electronic spectra of the two‐electron oxidized complexes show that trans‐ 1 [PF₆]₄ possesses lower vicinal Ru^II→Fe^III MMCT transition energy than cis‐ 1 [PF₆]₄. Moreover, the assignment of MMCT transition of the oxidized products and the differences of the electronic properties between the cis and trans complexes can be well rationalized using TDDFT//DFT calculations.     

Synthesis and anticancer activity of chalcogenide derivatives and platinum(II) and palladium(II) complexes derived from a polar ferrocene phosphanyl–carboxamide

The polar phosphanyl‐carboxamide, 1′‐(diphenylphosphanyl)‐1‐[N‐(2‐hydroxyethyl)carbamoyl]ferrocene ( 1 ), reacts readily with hydrogen peroxide and elemental sulfur to give the corresponding phosphane‐oxide and phosphane‐sulfide, respectively, and with platinum(II) and palladium(II) precursors to afford various bis(phosphane) complexes [MCl₂( 1 ‐κP)₂] (M = trans‐Pd, trans‐Pt and cis‐Pt). The anticancer activity of the compounds was evaluated in vitro with the complexes showing moderate cytotoxicities towards human ovarian cancer cells. Moreover, the biological activity was found to be strongly influenced by the stereochemistry, with trans‐[PtCl₂( 1 ‐κP)₂] being an order of magnitude more active than the corresponding cis isomer. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and catalytic properties in olefin epoxidation of dioxomolybdenum(vi) complexes bearing a bidentate or tetradentate salen-type ligand

The monomeric cis-dioxomolybdenum(VI) complexes [MoO₂(oep-saldpen)] and [MoO₂Cl₂(oep-H₂saldpen)], with a tetradentate [N₂(imine)O₂] and bidentate [N₂(imine)] salen-type ligand functionalised with two pyrrole derivative pendant arms [oep-H₂saldpen = 1,2-diphenylethylenebis(3-oxyethylpyrrole)salicylideneimine], were synthesised and characterised by ¹H NMR, IR and Raman spectroscopy. The solid-state structure of the free ligand oep-H₂saldpen was determined by single crystal X-ray diffraction. Assignment of the vibrational spectra of the molybdenum complexes was supported by carrying out ab initio calculations for the possible isomers using [MoO₂(salen)] and [MoO₂Cl₂(H₂salen)] as model compounds [H₂salen = N,N′-ethylenebis(salicylideneimine)]. The oep-saldpen complexes were examined as catalysts for the epoxidation of cyclooctene, (R)-(+)-limonene, styrene, α-pinene, and cis and trans-β-methylstyrene, with tert-butyl hydroperoxide as the oxidant. Both complexes exhibited high selectivity for the epoxidation reaction, with the bis(chloro) complex being always the more active of the two.     

基于偶氮联吡啶配体的银和钴配位聚合物的构筑与性质

通过将2个4,4’-联吡啶基团用偶氮基团连接,我们合成了新的配体顺式-和反式-1,2-二（（4,4’-联吡啶）-3-氮烯）（cis-L和trans-L）,并利用trans-L与银离子和钴离子构筑了配位聚合物{[Ag₂（trans-L）（ClO₄）₂]·4CH₃CN}_n（1）和{[Co（trans-L）₂（H₂O）₂]（ClO₄）₂}_n（2）。其中1为一维梯形链,链与链之间通过π-π以及Ag…Ag相互作用堆积;2为三维无限dendrimer结构,其Co中心具有合适的氧化还原电位,在以荧光素为光敏剂的条件下,可作为光催化剂实现光解水放氢。     

Synthesis and spectral properties of mixed-ligand platinum(II) complexes with (-)-<Emphasis Type="Italic">S</Emphasis>-NOBIN and sulfoxides

Synthesis was carried out of the new mixed-ligand square-planar platinum(II)complexes {Pt(R2SO)[(-)-S-NOBIN]Cl₂}, where (-)-S-NOBIN was S-2-amino-2′-hydroxy-1,1′-binaphthyl (R = Me, Et). The complexes are of interest as catalysts for asymmetrical synthesis. The detailed analysis of NMR, UV, and CD spectra of these compounds was performed. These complexes were established to be a mixture of the corresponding cis- and trans-isomers.     

Unknown cis-[(DMSO)2ClCuII(μ-Cl)2CuIICl(DMSO)2] isomer obtained via new [Cu4Cl8(DMSO)8(hmta)] template complex

A missed cis isomeric form of a well-known trans-[CuCl₂(DMSO)₂]_n complex has been prepared via the tetranuclear [Cu₄Cl₈(DMSO)₈(hmta)] complex. Structurally, both complexes were found to be molecular i.e. [Cu₄Cl₈(DMSO)₈(hmta)] consists of isolated tetracoordinated hexamethylenetetramine molecules, whereas the cis-complex consists of isolated [(DMSO)₂ClCu^II(μ-Cl)₂Cu^IICl(DMSO)₂] clusters. It should also be noted that the cis-configuration of DMSO molecules in [(DMSO)₂ClCu^II(μ-Cl)₂Cu^IICl(DMSO)₂] was directly transferred from that of [Cu₄Cl₈(DMSO)₈(hmta)], while the trans-[CuCl₂(DMSO)₂]_n isomer was always formed as a final stable product.     

Selective formation of thecis isomer of the nitridotechnetium(V) complex with 2,2′:6′,2″-terpyridine

The reaction of [TcNCl₂(PPh₃)₂] with 2,2′:6′,2″-terpyridine producedcis-[TcNCl₂(terpy)] selectively. The resulting complexes were characterized by¹H NMR and IR spectroscopy. The geometries of thecis andtrans isomers were estimated by theoretical calculations following a density functional method. Thecis isomer is likely more stable than thetrans one with respect to thetrans influence of the nitrido ligand. Furthermore, the behavior of nitridotechnetium complexes in polar solvents was compared to Os-analogues.     

基于偶氮联吡啶配体的银和钴配位聚合物的构筑与性质

通过将2个4,4''-联吡啶基团用偶氮基团连接,我们合成了新的配体顺式-和反式-1,2-二（（4,4''-联吡啶）-3-氮烯）（cis-L和trans-L）,并利用trans-L与银离子和钴离子构筑了配位聚合物{[Ag₂（trans-L）（ClO₄）₂]·4CH₃CN}_n（1）和{[Co（trans-L）₂（H₂O）₂]（ClO₄）₂}_n（2）。其中1为一维梯形链,链与链之间通过π-π以及Ag…Ag相互作用堆积;2为三维无限dendrimer结构,其Co中心具有合适的氧化还原电位,在以荧光素为光敏剂的条件下,可作为光催化剂实现光解水放氢。     

Electron impact mass spectra of some nickel(II) and palladium(II) complexes of diphenylphosphinoacetone and 3-diphenylphosphinobutan-2-one

The electron impact mass spectral fragmentation of five newly synthesized Ni(II) and Pd(II) complexes of diphenylphosphinoacetone (HL), i.e. trans-[ NiCl₂(HL)₂] and trans-[PdCl₂(HL)₂] and their enolates cis-[NiL₂] and cis-[PdL₂] and the bis-enolate of 3-diphenylphosphinobutan-2-one (HLMe), trans-[Ni(LMe)₂], is discussed. The proposed fragmentation mechanisms and the ion structures were confirmed by high-resolution data for three of the compounds and by Ni and Pd isotope abundances. The results obtained reveal that a mass spectral differentiation is useful in the identification of these types of complexes. Especially with phosphinoenolate bis-chelates molecular ion peaks are observed.