The syntheses of complexes MH2L4 and their protonated analogues [MH3L4]+ (M = Fe (1), Ru (2), Os (3); R = Me (a), Et (b)) are described. The structures of 1a, 1b, and 3a were determined in X-ray diffraction studies. The solution structures of complexes 1−3 were established by detailed NMR investigations. 1a, 2b, and 3a form equilibrium mixtures of two isomers in solution. The iron (1a) and ruthenium (2b) complexes isomerize between six-coordinate M(II) dihydrogen cis-[MH(H2)L4]+ and seven-coordinate M(IV) trihydride [M(H)3L4]+ molecular geometries:  the first is a distorted octahedron and the second can be viewed as a hydride-capped M(PR3)4 tetrahedron. Complex 3a is a pentagonal bipyramidal trihydride cis-[Os(H)3(PMe3)4]+ in equilibrium with the hydride-capped tetrahedral structural form. Trihydrides 1b and 3b are exclusively represented by the latter structural type. The cationic molecule 2a corresponds to a dihydrogen complex cis-[RuH(H2)(PMe3)4]+. The metal fragment [MH(PR3)4]+ is thus most reactive toward oxidative addition of H2 for osmium and iron, with a notably lower ability to reduce H2 for ruthenium. This trend and related properties are due to electronic rather than steric factors. All [MH3(PR3)4]+ species (1−3) are fluxional in solution. The intramolecular hydride exchanges and isomerizations were studied between 20 and −140 °C and quantitatively described in terms of their activation parameters. On the basis of these, mechanistic interpretations are provided. Finally the acid/base properties of the [MH3(PR3)4]+/M(H)2(PR3)4 systems were established in a series of NMR experiments in THF-d 8. The pK a values range from 10.3 to 12.9 units and increase in the following order:  1a (10.3) < 2b (10.7) < 2a (10.9) < 3a (11.2) < 3b (12.9). This series demonstrates a higher acidity than that of the related [MH(H2)(PP)2]+ molecules with bidentate ligands. The complexes with monodentate phosphine ligands [MH3(PR3)4]+ (1−3) represent a new and distinguished family with structural, dynamic, and acid/base properties remarkably different from most of the other known [MH3L4]+ representatives.

Reduction of no-carrier added [188Re04]-(ng range) in thf-[NBu4]C1 with BH3.thf under an atmosphere of CO yields [ 188ReC13(CO)3]2-and [ 188Re3(p-H)3(CO)12]; under similar conditions as with [188Re04]-, the first p-hydrido-bridged 99Tc hydrido carbonyl complex is prepared and structurally characterised.We have recently reported a simple one-pot synthesis of the useful MI precursor complexes [NEt4]2[MC13(C0)3] (M = Tc la, Re lb) starting directly from [NBu4][MO4] under ambient conditions. 1 Dissolution of 1 in water yields the corresponding air-stable 'aqua ion' [M(OH2)3(CO)3]+ (M = 99Tc 2a, Re 2b, 188Re 2c).2 Technetium-99m carbonyl complexes of appropriately derivatized ligands may find applications in nuclear medicine, as recently demonstrated by the imaging of brain receptors using a technetium(v) complex.3 2c can be used as a direct radiolabelling agent for proteins and applied in radioimmunotherapy.4 The synthetic conditions for the preparation of l a or lb, as depicted in Scheme 1, are almost identical. We found that the main product is [M2(p-C1)3(CO)& which can, by addition of [NEt4]C1, be quantitatively converted into l a and lb. However, adaptation of the synthetic conditions to trace amounts of [188Re04]-(37 MBq = 1 ng) revealed at least two products, as evidenced by TLC [Rf = 0.39 corresponds to 2a with one unknown species at R f = 0.69). The amount of the unknown species increased with the amount of BH3.thf. Consequently, the reduction of [Tc04]-was performed exclusively in the presence of BH3.thf, 1 atm of CO in thf and at room temperature. TLC experiments confirmed the compound

The effect of streptothricin F on macromolecular syntheses in intact cells and cell-free protein synthesis of E. coli was studied. The results indicate that protein synthesis is the primary site of inhibition by streptothricin F in growing E. coli cells. Cell-free polypeptide synthesis from E. coli directed by poly (U) was inhibited, while poly (A) and poly (C) directed polypeptide syntheses were both stimulated by the drug. Furthermore, streptothricin F caused misreading of translation of poly (U), poly (A) and poly (C) directed protein syntheses in E. coli systems. The extent of misreading by streptothricin F increases with increasing drug concentrations.The results are compared with those of other miscoding antibiotics. In rat liver extracts protein synthesis directed by poly (U) or endogenous mRNA was not inhibited.

In the spinel system Li,-,Ti204 the Li content was reduced by oxidative extraction by means of a solution of I, as well as Br, in CH3CN or by oxygen. The extraction is associated with a transition of Ti3+ to Ti4+: the system is L i , -Y T i~! Y T i~~Y 0 4 . Consequently, with increasing y the charge carrier concentration decreases from the starting value of 0.5 electrons/Ti ion for LiTi204. The extraction proceeds in two steps. At the beginning, the Ti20, framework remains intact and the transition to superconductivity increases with decreasing charge carrier concentration to a maximal value of 13.2K. Separated by a two-phase region for medium extraction levels for higher y values, a Li depleted material of approximate composition Lio,,Ti,04 is obtained. The crystal structure of Lio.3Ti,0, can be deduced from the original spinel lattice by a partial Ti migration from 16d to 16c and 8a sites (space group Fd3m). Consequently, the Ti,04 framework of Lio,3Ti,0, is disconnected and the material is no longer superconducting.

Ausgehend von (Et4N)2[Re(CO)3Br3] lassen sich durch einfache Ligandenaustauschreaktionen weitere Rhenium(I)‐ und Rhenium(III)‐Carbonylkomplexe herstellen. In Abwesenheit starker Oxidationsmittel bleibt die faciale Re1(CO)3‐Einheit bei gleichzeitigem Austausch der Bromoliganden erhalten. Mit Trimethylsilylisothiocyanat kann so (Et4N)2[Re(CO)3(NCS)3] in guten Ausbeuten und hoher Reinheit hergestellt werden. Die Verbindung kristallisiert monoklin in der Raumgruppe P21/n, a = 18,442(5), b = 17,724(3), c = 18,668(5) Å, β = 92,54(1)°, Z = 8. Die NCS−‐Liganden sind jeweils über ihr Stickstoffatom an das Metall gebunden. Die Umsetzung von [Re(CO)3Br3]2− mit Br2 führt zum Rhenium(III)‐Anion [Re(CO)2Br4]−. Das Tetraethylammoniumsalz dieses Komplexes kristallisiert orthorhombisch in der nichtzentrosymmetrischen Raumgruppe Cmc21, a = 8,311(1), b = 25,480(6), c = 8,624(1) Å, Z = 4. Die Carbonylliganden befinden sich in cis‐Stellung zueinander. Ihr starker trans‐Einfluß bewirkt eine Aufweitung der ReBr‐Bindungslänge um mindestens 0,05 Å.