O2 activation at a trispyrazolylborato nickel(ii) malonato complex.

To support mechanistic inferences made for an iron-based dioxygenase model, a nickel analogue, i.e. a TpNi-malonate (1) was prepared. 1 proved to represent a rare case of a nickel complex reacting with O2 in a controlled manner - mechanistically different from the iron case - and leads to hydroxylation of the malonate.

A high-spin square planar iron(ii)-siloxide and its tetrahedral allogon - structural and spectroscopic models of Fe-zeolite sites.

The famous α-Fe active sites in Fe-zeolites have recently been revealed to correspond to mononuclear high-spin iron(ii) centres in square planar coordination environments. Here we report a first iron siloxide complex which represents a faithful structural and spectroscopic model of such sites. Notably, also an allogon with a distorted structure exists and could be crystallised.

A Hexanuclear Iron(II) Layer with Two Square-Planar FeO4 Units Spanned by Tetrasiloxide Ligands: Mimicking of Minerals and Catalysts.

A hexanuclear iron(II) siloxide complex has been prepared by reacting an incompletely condensed silsesquioxane first with NaOMe and then with Fe(OTf)2. In the process of product formation, the siloxane framework undergoes a transformation and it was shown that this happens already upon addition of base: Treatment of the ligand precursor with NaOMe leads to a completely condensed silsesquioxane cage with 12 Si atoms that is composed of 2 equiv of the tetrasiloxide ligands found in the product complex. Its iron centers form a two-dimensional array reminiscent of the situations found in minerals and two-dimensional oxide films caused by segregation of FeOx and silica. As the hexairon(II) assembly contains two high-spin square-planar FeO4 units-suggested to represent the active sites in Fe-zeolites, which react with N2O to generate strongly oxidizing sites-it was treated with Me3NO. This led to the oxidation of two of the iron centers to the oxidation state +III and elimination of one iron ion, so that a pentanuclear, mixed valent iron siloxide was formed. All complexes were fully characterized.

Reaction of a polydentate cysteine-based ligand and its nickel(ii) complex with electrophilic and nucleophilic methyl-transfer reagents - from S-methylation to acetyl coenzyme A synthase reactivity.

The L-cysteine derived N2S2 ligand precursor H2L and its nickel(ii) complex L2Ni2 were investigated with respect to their behaviour in contact with electrophilic and nucleophilic methylation reagents (H2L = (N,N'-dimethyl-(2R,5R)-bis-(sulfanylmethyl)-piperazine). Treatment of deprotonated L(2-) with MeI led to the selective methylation of the thiolate groups thus generating a novel potential ligand, Me2L, which is neutral and contains two thioether donors. The coordinating properties of Me2L were demonstrated by the synthesis of a first nickel(ii) complex: reaction with NiBr2 led to a mononuclear complex 2 where all donor atoms coordinate to the nickel ion, which completes its octahedral coordination sphere by the two bromide ligands. If, however, the complex [LNi]2 (1) is treated with MeI only one thiolate function per ligand moiety is methylated, while the other one remains a thiolate. This leads to [MeLNi](+) complex metal fragments, which trimerize including a µ3-bridging iodide ion to give the compound 3 that was tested with regards to ACS reactivity. While it behaved inert towards CO, attempts to replace the bridging iodide ligand by methyl units in reactions with nucleophilic methylation reagents led to a product, which could not be identified but reacted with CO. Work-up showed that this protocol had converted the thiolate function of MeL(-) into a thioester function, which corresponds to an ACS-like reactivity.

Dioxygenation of cysteamine to hypotaurine at a tris(pyrazolyl)borate iron(ii) unit - cysteamine dioxygenase mimicking?

A novel complex Tp(Me,Ph)Fe(SCH2CH2NH2) has been synthesized as a speculative model for ADO. Indeed its reaction with O2 led to the dioxygenation of the S atom and thus to hypotaurine. This finding may allow us to draw conclusions on the constitution of the ADO active site, whose structure is still unknown.

[An index for paresis and defective healing--an easily applied method for objectively determining therapeutic results in facial paresis (author's transl)]. / Parese- und Defektheilungs-Index. Ein leicht anwendbares Schema zur objektiven Bewertung von Therapieerfolgen bei Fazialisparesen.

Residuals of facial paralysis consist of a great variety of cosmetic and functional anomalies which differ in quality and/or quantity. An internationally standardized evaluation of such defects is mandatory for the assessment of the results of different therapeutic procedures. In the present study, a system has been developed to record the results of facial paralysis following therapy. Such a system does not require specialized training, instrumentation or require significant time for completion. A clearly-defined "Yes-No" evaluation criteria is established which creates a high interscorer reliability. The usefulness of this scoring system was tested by three examiners on 42 patients following facial nerve surgery, with an obtained interscorer reliability of 93%.