Gabriele Haselhorst

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.

Synthesis, properties and crystal structures of [MoVL(O)l2]PF6′[MoIVL(O)l2], [MoVL(O)(OMe)2]PF6′[MoVILO2(OMe)]BPh4 and [Mo2L2O3(µ-O)l][BPh4]2(L = 1,4,7-trimethyl-1,4,7-triazacyclononane)

A series of mononuclear oxomolybdenum-(IV), -(V) and -(VI) complexes has been prepared from the precursor complex [MoVL(O)l2]PF62 where L = 1,4,7-triazacyclononane. Compound 2 is reduced by NEt3 in MeCN yielding [MoIVl(o)l2]3. The iodide ligands in 2 may be substituted by alkoxy ligands generating paramagnetic mononuclear complexes [MoVL(O)(OMe)l]PF64 and [MoVL(O)-(OMe)2]PF65. The latter is oxidized by H2O2to [MoVILO2(OMe)]BPh46. Complex 2 was found to form the dinuclear diamagnetic species [MoV2L2O2(µ-O)l2][PF6]27 which generates the asymmetric, diamagnetic mixed-valence complex [l(O)LMoIV(µ-O)MoVILO2]BPh48 in the presence of NaOH. Complex 8 undergoes a reversible one-electron-transfer oxidation and paramagnetic [l(O)LMoV(µ-O)MoVILO2]-[BPh4]29 has been isolated. The electrochemical, magnetic, and eletcronic structural as well as infrared and ESR spectral properties of new complexes have been investigated. The structures of 2, 3, 5, 6 and 9 have been determined by X-ray crystallography.

Synthesis and co-ordination chemistry of the macrocycle 1,4,7-triisopropyl-1,4,7-triazacyclononane

The bulky tridentate macrocycle 1,4,7-triisopropyl-1,4,7-triazacyclononane (L) has been prepared and its co-ordination chemistry investigated. Reaction of L with [M(CO)6] in refluxing mesitylene affords airstable [ML(CO)3](M = Cr 1, Mo 2 or W 3) in excellent yields. Oxidation of complexes 1 and 2 with SOCl2 in CCl4 yields [MLCl3](M = Cr 4 or Mo 5) whereas [MLBr3](M = Cr 6 or Mo 7) were obtained by using bromine as oxidant in CHCl3. Exhaustive oxidative decarbonylation of 2 in semi-concentrated nitric acid affords colourless [MoLO3]·3H2O 8 which reacts with phenyl isocyanate in dry toluene yielding [MoLO3]·(PhNH)2CO 9. In dry MeCN the ligand reacts with VCl3 to give [VLCl3]10 which undergoes ligand substitution in water in the presence of NaSCN to give [VL(NCS)3]11. When this reaction was carried out in the presence of oxygen [VOL(NCS)2]12 was obtained. The molecular structures of 2, 8 and 9 have been established by single-crystal X-ray analysis.