Binuclear complexes of chromium,manganese and rhodium withN-hydroxyethyl-N,N′,N′-tribenzimidazolylmethylethylenediamine

Summary Three novel binuclear complexes, Cr₂Cl₆L·EtOH, Mn₂OAc₄L·EtOH, Rh₂Cl₆L.2H₂O, where L =N-hydroxyethyl-N,N,N-tribenzimidazolylmethylethylenediamine, have been prepared and characterized by elemental analyses, i.r., u.v.-vis. and e.s.r. spectra, and by magnetic susceptibility measurements. A weak antiferromagnetic spin exchange interaction exists between the metal ions in a binuclear unit for the dimanganese complex. Preliminary bioassays show that the manganese complex possesses antitumour activityin vitro.     

η3-Propargyl complexes of molybdenum, tungsten, and rhenium

The reactions of the Me _n C₆H_6−n M(CO)₃ (M=Cr, Mo, W;n=3, 5, 6) and C₅R₅M(CO)₃ (M=Mn, Re; R=H, Me) complexes with propargyl alcohol in acidic media under UV irradiation were studied. Novel Me _n C₆H_6−n M(CO)₂(η³-C₃H₃)BF₄ (M=Mo, W;n=3, 5, 6) and C₅R₅Re(CO)₂(η³-C₃H₃)CF₃SO₃ complexes with the 3ē-propargyl ligand were synthesized, and their properties compared with those of similar η³-allyl derivatives. The structure and dynamic propeties of the compounds obtained are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1796–1803, September, 1999.     

Kinetics of the reactions of methoxide ion with tricarbonyl-η-cycloheptatrienyl salts of chromium,molybdenum and tungsten

The kinetics of the reactions of methoxide ion, obtained using triethylamine/p-toluenesulphonic acid buffers in methanol, with tricarbonyl-η-cycloheptatrienylchromium, -molybdenum and -tungsten tetrafluoroborates have been investigated at 25°C using stopped-flow spectrophotometry. Two separate processes were identified. The first is a fast reversible formation of an initial product which probably arises either by direct attack at the metal or at a carbonyl ligand affording a carbomethoxy complex [(η⁷-C₇H₇M(CO)₂CO₂Me]. The second, slower, process involves addition of methoxide ion to the cycloheptatrienyl ring to give the observed product [(η⁶-MeOC₇H₇)M(CO)₃]. This latter reaction shows metal dependence; the second order rate constants are estimated to be in the proportions 50/10/1 (Cr/Mo/W).     

Diphenylbenchrotrenylphosphine - a new two-electron ligand in carbonyl-containing π-aromatic chromium and manganese complexes and in carbonyls of group vib metals

Photochemical substitution of CO ligands in C₆H₆Cr(CO)₃, C₅H₅Mn(CO)₃ and M(CO)₆ (M = Cr, Mo, W) for PPh₂C₆H₅Cr(CO)₃, ligands was used to synthesize novel complexes: C₆H₆Cr(CO)₂PPh₂C₆H₅Cr(CO)₃, C₅H₅Mn(CO)₂PPh₂C₆H₅Cr (CO)₃ and M(CO)₅PPh₂C₆H₅Cr(CO)₃.The complexes obtained have been characterized by elemental analysis, IR, ¹H, ¹³C, ³¹P NMR, and mass spectra.The protonation reaction and the hydrogen isotopic exchange of arenechromium carbonyl complexes in acid media have been studied.The ¹³C NMR spectra of M(CO)₅PPh₂C₆H₅Cr(CO)₃ show that the nature of the central metal atom influences the chemical shifts of the carbon nuclei of the carbonyl groups, shielding these atoms, increasing in the series W ⩽ Mo < Cr.     

Synthesis, characterization and magnetism of μ-chloranilato bi-nuclear chromium (III) complexes

Five new chloranilato-bridged binuclear chromium (III) complexes have been synthesized and identified as [Cr2(CA)L4]-(ClO4)4[L denotes 5-methyl-1,10-phenanthroline (Me-phen); 2,9-dimethyl-1, 10-phenanthroline ( Me2-phen); 5-chloro-1,10-phenanthroline(Cl-phen); diaminoethane (en) or 1,3-diaminopropane (pn)], where CA represents the dianion of chloranilic acid. Based on elemental analyses, molar conductivity and magnetic moment of room-temperature measurements, and IR and electronic spectral studies, it is proposed that these complexes have CA-bridged structures and consist of two chromium (III) ions, each in an octahedral environment. The complexes [Cr2(CA)(Me-phen)4](ClO4)4(1) and [Cr2(CA)(Me2-phen)4](ClO4)4(2) were further characterized by variable temperature (4.2-300 K) magnetic susceptibility measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, , giving the exchange parameter J = -7.8 cm-1 for (1) and J= -6.5 cm*1 for (2). This result     

Synthesis of benzocycloheptanones through coupling of δ,ε-unsaturated chromium carbene complexes and 2-alkynylbenzoyl derivatives

The coupling of pentenylcarbene complexes and 2-alkynylbenzoyl derivatives affords naphthocycloheptanones in a single step involving simultaneous construction of both the seven-membered ring and one of the aromatic rings. Aryl tethered systems undergo intramolecular cyclopropanation.     

The interconversion of η5 and η3 hapticities in cycloheptadienyl complexes of molybdenum and tungsten

[Mo(CO)₄(η⁵-C₇H₉)]⁺ (1) reacts with acetonitrile to give [Mo(CO)₂(NCMe)₃(η³-C₇H₉)]⁺ (3), which is precursor of a wide reange of η⁵-cycloheptadienyl complexes [Mo(CO)₂L₂(η⁵-C₇H₉)]⁺ [6, L = PPH₃; 7, L₂ = Ph₂PCH₂PPh₂; 8, L₂ = 1,3-cyclohexadiene; 9, L₂ = 2,2′-dipyridyl]; 9 reacts reversibly with NCMe to give [Mo(CO)₂(NCMe)(dipy)(η³-C₇H₉)]⁺ (10).     

Synthesis and selective silylation of ω-hydroxy functionalized (η-alkenyl)carbene complexes of chromium(0) and tungsten(0) Part 11. The chemistry of metallacyclic alkenylcarbene complexes

Tungsten(0) carbene complexes of the type (OC)₅WC(NMeCH₂CHCHCH₂OH)R 2 (R=Me: 2a; R=Ph: 2b) were generated by aminolysis of (OC)₅WC(OMe)R with cis-NHMeCH₂CHCHCH₂OH. Like their Cr-congeners 1, complexes 2 exist at room temperature as mixtures of Z- and E-isomers with regard to the C-N bond. The metallacyclic complexes (OC)₄WC(η²-NMeCH₂CHCHCH₂OH)R (4) were obtained in good yields upon photo-decarbonylation of 2. Deprotonation/silylation of the complexes (OC)₄MC(η²-NMeCH₂CHCHCH₂OH)Me (M=Cr: 3a; M=W: 4a) with one equivalent of ⁿBuLi/Me₃SiCl gave (OC)₄MC(η²-NMeCH₂CHCHCH₂OSiMe₃)CH₃ (M=Cr: 5; M=W: 6), whereas with two equivalents of ⁿBuLi/Me₃SiCl complexes (OC)₄MC(η²-NMeCH₂CHCHCH₂OSiMe₃)CH₂SiMe₃ (M=Cr: 7; M=W: 8) were formed. Hydrolysis of the latter yielded selectively (OC)₄MC(η²-NMeCH₂CHCHCH₂OH)CH₂SiMe₃ (M=Cr: 9; M=W: 10). The complexes 1-10 were analyzed in solution by one- and two-dimensional NMR spectroscopy (¹H, ¹³C, ²⁹Si, ¹H/¹H COSY, ¹H/¹H NOESY, ¹³C/¹H HETCOR).     

Synthesis and crystal structures of copper and manganese complexes withN,N′-dibenzyl-1,10-phenanthroline-2,9-dimethylamine

The new ligand, N,N-dibenzyl-1,10-phenanthroline-2,9-dimethylamine trihydrochloric acid monohydrate (L · 3HCl·H ₂ O), has been synthesized and characterized. Complexes of the ligand (L) with Cu^II and Mn^II were prepared and their crystal structures were determined. The copper ion is five-coordinated via three nitrogen atoms of the ligand and two chloride ions, while the manganese ion is six-coordinated by three nitrogens of the ligand, two chloride ions and one water molecule. In both complexes, the ligand behaves in a tri-dentate fashion and the uncoordinated nitrogen of the other arm is protonated.     

Ferrocene-containing ligands in the self-assembly of trinuclear μ3-oxocentered carboxylate complexes of chromium(III, III, III)carboxylate complexes of chromium(III, III, III)

New trinuclear μ₃-oxocentered chromium(III, III, III) complexes were obtained by the self-assembly of ferrocenecarboxylate ligands and the Cr₃O fragment. The complexes were investigated by fast-atom bombardment (FAB) mass spectrometry, cyclic voltammetry, and electronic and IR spectroscopy. V. I. Vernadskii Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine, 32/34 Prospekt Akademika Vernadskogo, Kiev 03142, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 4, pp. 233–237, July–August, 2000.     

Synthesis and properties of conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains

A versatile synthetic route to conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains was developed, and new ruthenium complexes with various ligands were synthesized and characterized. These bimetallic complexes showed a remarkable absorption in the visible region (λ_max: 452-483 nm), and undergo trans-to-cis isomerization under UV light irradiation for short time. Electrochemical study showed that the metal centers in bimetallic complexes containing the CHCHC₆H₄NNC₆H₄CHCH bridge interact with each other.     

Appended corrole manganese complexes:Catalysis and axial-ligand effect

A series of N-base appended corroles and their manganese complexes were synthesized and their binding constants with three different nitrogenous ligands, triethylamine, N-methylimidazole and pyridine, were evaluated by spectroscopy. Kinetic studies indicated that the presence of appended N- donor ligands may cause a significant enhancement of the rate of oxygen atom transfers （OAT） from （oxo）manganese（V） corrole to alkene, and the stronger axial ligand binding has impact on the rate of the oxidation reaction. Turnover frequency （TOF） for the catalytic oxidation of alkenes by appended manganese corroles varies with the following ligand order： acetamido 〈 pyridyl 〈 imidazolyl. The influence of the external axial ligands on the catalytic epoxidation was investigated by using appended acetamido manganese corrole as catalyst, with the results revealing that N-methylimidazole gave the best enhancement on the yields of total oxidation products among the investigated nitrogenous ligands.     

Synthesis, characterization and crystal structures of manganese (Ⅱ) complexes containing nitronyl nitroxide and its reduced derivative

Two novel adducts of formula Mn(hfac)2( NITPhCl )2 (1) and [Mn(hfac)2(IMHPhCl)]2(NIT-PhCl)·0.5H2O (2), where hfac = hexafluoroacetylacetonate, NITPhCl = 2-(3-chlorophenyl)-4,4,5,5-tetram-ethylimidazolyl-1-oxyl-3-oxide, IMHPhCl = 2-(3-chlorophenyl)-4, 4, 5, 5-tetramethylimidazolyl-3-oxide, have been prepared by the reaction of Mn(hfac)2·2H2O with NITPhCl. Compound 1 is triclinic, space group P-1with a = 1.3003(3) nm, 6 = 1.3138(3) nm,c = 1.4931 (3) nm, α = 83.74(3)°, β = 77.77(3)°, γ = 60.59(3)°, V=2.171(1)nm3, Z = 2. Compound 2 is triclinic, space group P-1 with a = 1.2994(3) nm, b = 1.4841(3) nm, c = 2.1031 (4) nm, a = 92.30(3)° ,p = 98.68(3)°, γ = 97.89(3)°, V= 3.964(2)nm3, Z = 2. Each manganese atom is hexacoordinated in both compounds and compound 2 is organized inchains by hydrogen bonds between neighboring pairs of NITPhCl and IMHPhCl.     

Determination of chromium,manganese and vanadium in sediments and soils by modifier—free slurry sampling electrothermal atomic absorption spectrometry

Slurried sediment and soil samples of the certified reference materials with a highly elevated level of the metals of interest (Mn, Cr and V) were analysed by electrothermal atomic absorption spectrometry (ETAAS) with Zeeman effect background correction. The method of slurry preparation and time-temperature programmes were optimized and, finally, the use of chemical modifiers was not necessary. The effect of alternate spectral lines and gas mini-flows on characteristic masses of analytes was studied. The homogeneity of samples and the influence of short sample grinding were also discussed. The simple, aqueous standard based calibration graphs (except Mn at the concentration > 1000 mg kg⁻¹) were applied for the quantification of results. The results of determinations obtained by slurry sampling agreed well with the cetified values, and the relative standard deviations (RSDs) for the over-all analytical procedure repeatability (at slurries concentration level about 2 mg/2 ml) were less than 9.5%, except manganese (10.4%).     

Hydrogen-bonded networks from η-semiquinone complexes of manganese tricarbonyl

The cationic manganese tricarbonyl complexes containing η⁶-2-methylhydroquinone (2a), η⁶-2,3-dimethylhydroquinone (3a), η⁶-2-t-butylhydroquinone (4a), η⁶-tetramethylhydroquinone (5a) and η⁶-4,4′-biphenol (6a) are readily deprotonated to the corresponding neutral (η⁵-semiquinone)Mn(CO)₃ (2b-6b) and anionic (η⁴-quinone)Mn(CO)₃⁻ (2c-5c) complexes. The X-ray structures of 2b-6b feature strong intermolecular hydrogen bonding interactions that result in the formation of supramolecular organometallic networks. Significantly, the substitution pattern at the semiquinone ring affects the stereochemistry of the hydrogen bonding interactions. NMR spectra of 2b, 3b and 5b reveal dynamic hydrogen bonding in solution.     

4,4′-Bipyridine complexes of molybdenum(II) and tungsten(II)

Treatment of [MI₂(CO)₃(NCMe)₂] with two equivalents of 4,4-bipyridine (4,4-bipy) in CH₂Cl₂ at room temperature gave the MeCN displaced products, [MI₂(CO)₃(4,4-bipy-N)₂] (1) and (2). Equimolar amounts of [MI₂(CO)₃(NCMe)₂] and L (L = PPh₃, AsPh₃ or SbPh₃) react to give [MI₂(CO)₃(NCMe)L], which when reacted in situ with 4,4-bipy yield the new complexes, [MI₂(CO)₃(4,4-bipy-N)L] (3)–(8). Reaction of equimolar quantities of [WI₂(CO)(NCMe)( ²-RC₂R)₂] (R = Me or Ph) and 4,4-bipy gave the new bis(alkyne) complexes, [WI₂(CO)(4,4-bipy-N)( ²-RC₂R)₂] (9) and (10). Treatment of [MI₂(CO)₃(NCMe)₂] with two equivalents of (9) or (10) in CH₂Cl₂ at room temperature affords the bimetallic complexes, [MI₂(CO)₃{WI₂(CO)(4,4-bipy-N,N)( ²-RC₂R)₂}₂] (11)–(14). Equimolar quantities of [MI₂(CO)₃(NCMe)(PPh₃)] (prepared in situ) and (9) or (10), react to give the 4,4-bipy-bridged complexes, [MI₂(CO)₃{WI₂(CO)(4,4-bipy-N,N)( ²-RC₂R)₂}(PPh₃)] (15)–(18). All the new complexes, (1)–(18) were characterised by elemental analysis (C, H and N), i.r. and ¹H-n.m.r. spectroscopy.