Ursula Bossek

Assembly and structural characterization of binuclear µ-oxo-di-µ-acetato bridged complexes of manganese(III). Analogues of the di-iron(III) centre in hemerythrin

The complexes [L2MnIII2(µ-O)(µ-MeCO2)2](ClO4)2, (1), and [L′2MnIII2(µ-O)(µ-MeCO2)2](ClO4)2·H2O, (2), where L and L′ represent the cyclic triamines 1,4,7-triazcyclononane and (N,N′,N″-trimethyl-1,4,7-triazacyclononane, have been synthesized from Mn(MeCO2)3·2H2O in water–ethanol mixtures; characterization by X-ray crystallography showed that both complexes contain a µ-oxo-di-µ-acetato-metal(III) core, as found in hemerythrin, and therefore these complexes may have bioinorganic significance.

Bioinorganic model complexes for the active site in manganese containing catalases. The crystal structures of [L2MnII2(μ-OH)(μ-O2CCH3)2] (PF6)·CH3OH and [L′2MnIII2(μ-O)(μ-O2CCH3)2] (I3)I·H2O

Abstract The crystal structures of [L2MnII(μ-OH)(μ- O2CCH3)2](PF6)·CH3OH (1) and [L′2MnIII2(μ-O)- (μ-O2CCH3)2](I3)I·H2O (2) have been determined by X-ray crystallography (L = N,N′,N″-trimethyl- 1,4,7-triazacyclononane, C9H21N3; L′ = 1,4,7-triazacyclononane, C6H15N3). 1 contains the μ-hydroxobis (μ-carboxylato)dimanganese(II) core whereas in 2 the μ-oxo-bis(μ-carboxylato)dimanganese(III) entity has been identified. 1 and 2 serve as model compounds for the active site of the manganese containing catalases isolated from Lactobacillus plantarum and Thermus thermophilus.

Pendent arm macrocyclic complexes: crystal structures of AI(TCTA) and In(TS-TACN)

Abstract Complexes of Al3+ and In3+ containing the pendent arm macrocycles 1,4,7-tris(acetato)-1,4,7-triazacyclononane (TCTA) and 1,4,7-tris(2-mercaptoethyl)-1,4,7-triazacyclononane (TS-TACN), respectively, have been synthesized and their crystal structures determined. Al(TCTA) contains an octahedral fac-N3O3 donor set, whereas In(TS-TACN) has an octahedral fac-N3S3 donor set. Average Al—O and In—S distances are 1.846 and 2.397 A, respectively.

A novel mixed-valent MnIII–MnIV-dimer, [L2Mn2(µ-O)2(µ-MeCO2)][BPh4]2·MeCN: crystal structure, magnetic properties, and e.s.r. spectrum (L = 1,4,7-triazacyclononane)

The green mixed-valence dimer [L2Mn2(µ-O)2(µ-MeCO2)][BPh4]2·MeCN (L = 1,4,7-triacacyclononane) is formed on hydrolysis of [L2Mn2(µ-O)(µ-MeCO2)2]2+ in water in the presence of air; characterization by X-ray crystallography showed the presence of the di-µ-acetato-dimanganese(III,IV) core, and temperature dependent magnetic susceptibility measurements indicate an S= 1/2 ground state and very strong intramolecular antiferromagnetic coupling (J–440 cm–1).

Asymmetric mixed valence manganese complexes containing the [MnIII(µ-O)2(µ-MeCo2)MnIV]2+ core and their catalase reactivity

Two asymmetrically ligated, dinuclear, mixed valence complexes [MnIVL (µ-O)2(µ-MeCO2)MnIII(MeCO2)2]1 and [MnIVL(µ-O)2(µ-MeCo2)MnIII(bpy)(MeOH)](ClO4)2·MeOH 2b have been synthesized (L = 1,4,7-trimethyl-1,4,7-triazacylononane, bpy = 2,2′-bipyridyl) and their structures have been determined by X-ray crystallography; 1 and 2b catalyse the disproportionation of aqueous H2O2.

Synthesis and structure of adduct stabilized Group III metal transition metal carbonyl complexes: new examples for FeGa, FeIn, WAl, CrAl and CrGa bonds

Abstract The carbonylmetallate dianions Fe(CO)42−, Cr(CO)52− and W(CO)52− react in THF with the Group III halogenides EX3 (E=Al, Ga, In; X=Cl, Br, I) and X2ER (E=Al, Ga; X=Cl R=Me, tBu). After the addition of chelating Lewis base [tmpda, pmdeta (tmpda=N,N,N′,N′-tetramethylpropylenediamine, pmdeta=N,N,N′,N′′,N′′-pentamethyldiethylenetriamine)] and solvent exchange with dichloromethane, the primary products undergo a second salt elimination reaction, yielding the following complexes: [(CO)4FeGa(X)(tmpda)] (X=I, Me) (1 and 2), [(CO)nMAl(X)(tmpda)] (M=Fe, W; n=4, 5; X=Cl, tBu) (3 and 4), [(CO)4FeIn(Br)(tmpda)] (5), [(CO)5CrE(Cl)(tmpda)] (E=Al, Ga) (6 and 7), [(CO)4FeIn(Br)(pmdeta)] (8) and cationic complex [(CO)4FeGa(pmdeta)]+I− (9). The new compounds were fully characterized by means of elemental analysis, IR and NMR spectroscopy. The structures of [(CO)4FeGa(Me)(tmpda)] (1), [(CO)4FeGa(I)(tmpda)] (2), [(CO)5WAl(tBu)(tmpda)] (4), [(CO)4FeIn(Br)(tmpda)] (5), [(CO)5CrAl(Cl)(tmpda)] (6), [(CO)4FeIn(Br)(pmdeta)] (8) and [(CO)4FeGa(pmdeta)]+I− (9) have been studied by single-crystal X-ray diffraction. Compound 1: orthorhombic space group Pnma, Z=4. a=13.240(16), b=11.623(14), c=10.316(13) A, α=90, β=90, γ=90°, V=1588(3) A3, and R=0.0364 (Rw=0.1037). Compound 2: triclinic space group P1, Z=2. a=8.2059(13), b=8.2783(13), c=14.348(2) A, α=75.155(3), β=83.953(3), γ=62.117(3)°, V=832.7(2) A3, and R=0.0346 (Rw=0.0828). Compound 4: monoclinic space group P21/n, Z=4. a=8.780(5), b=14.284(4), c=16.339(5) A, α=90, β=96.91(2), γ=90°, V=2034.2(14) A3, and R=0.0577 (Rw=0.1303). Compound 5: orthorhombic space group P212121, Z=4. a=7.534(3), b=14.978(9), c=15.192(9) A, α=90, β=90, γ=90°, V=1714.4(16) A3, and R=0.0409 (Rw=0.1363). Compound 6: monoclinic space group C2/c, Z=10. a=26.458(5), b=8.998(5), c=15.567(3) A, α=90, β=115.83(5), γ=90°, V=3336(2) A3, and R=0.0343 (Rw=0.0650). Compound 8: monoclinic space group C2/c, Z=16. a=30.717(7), b=8.746(2), c=28.677(6) A, α=90, β=94.99(5), γ=90°, V=7675(3) A3, and R=0.0526 (Rw=0.1591). Compound 9: monoclinic space group P21/c, Z=4. a=14.157(1), b=24.395(2), c=13.547(1) A, α=90, β=97.86(2), γ=90°, V=4633.9(8) A3, and R=0.0522 (Rw=0.1334).

Unusual solid-state reaction of [{CrL(acac)}2(µ-H3O2)][PF6]3. Isolation and crystal structures of [CrL(acac)F]PF6 and [CrL(acac)(O2PF2)]PF6(L = 1,4,7-trimethyl-1,4,7-triazacyclononane, acac = pentane-2,4-dionate)

From a concentrated aqueous solution of the mononuclear complexes [CrL(acac)(OH)]PF6·H2O and [CrL(acac)(OH2)][ClO4]2 at pH ≈ 6 the dinuclear H3O2–-bridged species [{CrL(acac)}2(µ-H3O2)][PF6]3 was isolated as a crystalline red solid (L = 1,4,7-trimethyl-1,4,7-triazacyclononane, acac = pentane-2,4-dionate). The dinuclear complex reacted at 145 °C in the solid state with evolution of 3 equivalents of HF, yielding quantitatively the mononuclear complexes [CrL(acac)F]PF6 and [CrL(acac)(O2PF2)]PF6 in equal amounts. Thus an unco-ordinated PF6– anion is thermally converted into a co-ordinated fluoride and a monodentate O2PF2– ligand. The crystal structures of [CrL(acac)(OH2)][ClO4]2, [CrL(acac)F]PF6 and [CrL(acac)(O2PF2)]PF6 have been determined by X-ray crystallography. The cobalt(III) complex [{CoL(acac)}2(µ-H3O2)][PF6]3 has also been prepared and structurally characterized. It is isostructural with the chromium analogue. Heating to its melting point at 190 °C did not induce solid-state transformation to mononuclear cobalt(III) species analogous to [CrL(acac)F]PF6 and [CrL(acac)(O2PF2)]PF6.

Syntheses and crystal structures of complexes [L′O(H2O)V(µ-O)WO2L]Cl(ClO4) and [L′(acac)MoIII(µ-O)MoVIO2L′][BPh4]2(L,L′= 1,4,7-triazacyclononane and its 1,4,7-trimethyl derivative; acac = pentane-2,4-dionate)

Reaction of an equimolar mixture of [VCl3L′] and [WO3L]·3H2O in MeOH–water (4 : 1) in the presence of air affords upon addition of NaClO4 blue [L′O(H2O)VIV(µ-O)WVIO2L]Cl(ClO4)1(L′= 1,4,7-trimethyl-1,4,7-triazacyclononane; L = 1,4,7-triazacyclononane). Crystals of 1 are monoclinic, space group P21/c, with a= 9.401(8), b= 20.61(1), c= 13.53(1)A, β= 102.47(7)°, and Z= 4. The complex is an asymmetric, heterodinuclear species consisting of vanadyl VOL′(OH2) and cis-LWVIO2 units which are asymmetrically bridged by an oxygen. A suspension of [MoIIIBr3L′] and excess of sodium penta-2,4-dionate(acac) in water reacts in the presence of air with formation of the asymmetric mixed-valence species [L′(acac)MoIII(µ-O)MoVIO2L′]2+. The bis(tetraphenylborate) salt 2 crystallizes in the monoclinic space group P21/a with a= 18.589(9), b= 18.30(1), c= 20.432(9)A, β= 104.73(4)° and Z= 4. The L′MoIII(acac) and cis-L′MoO2 units are linked by an asymmetric µ-oxo bridge with MoIII–Ooxo and MoVI–Ooxo distances of 2.034(4) and 1.808(4)A, respectively.

Synthesis, e.s.r. spectrum and magnetic properties of a heterobinuclear complex containing the {FeIII(µ-O)(µ-MeCO2)2MnIII}2+ core

The hydrolysis reaction of a 1:1 mixture of LFeCl3 and LMnCl3(L =N,N′N″-trimethyl-1,4,7-triazacyclononane) in aqueous sodium acetate solution yields green [LFeIII(µ-O)(µ-MeCO2)2MnIIIL]2+(90%) which displays strong intramolecular antiferromagnetic exchange coupling (J=–145 cm–1) yielding a doublet ground state; an e.s.r. spectrum showing hyperfine structure has been observed.

Synthesis of novel trimeric µ-oxo-bridged manganese(IV) complexes: [L3Mn3IV(µ2-O)3(µ3-XO4)]Br3(X = P, As, or VV; L = 1,4,7-triazacyclononane)

The reaction of (L2MnIII2(µ-O)(µ-MeCO2)2](CIO4)2 with Na2HPO4, (NH4)3VO4, or Na2HAsO4 in aqueous solution (pH ca. 9) in the presence of air yields, upon addition of NaBr, deep red crystals of [L3MnIV3(µ2-O)3(µ3-XO4)]Br3(X = P, As, or VV; L = 1,4,7-triazacyclononane); characterization of the µ-phosphato complex by X-ray crystallography showed the presence of discrete trimeric cations [L3MnIV3(µ-O)3(µ-PO4)]3+ where three MnIV centres are in a distorted octahedral fac-N3O3 donor set connected by three µ2-oxo bridges and a µ3-PO4 bridge.