Oxorhenium(V)‐ and Tricarbonylrhenium(I) Complexes with Substituted Pyrazoles as Products of the Degradation of Hydrotrispyrazolylborates

Hydrotris(3, 5‐dimethylpyrazol‐1‐yl)borate and hydrotris(3‐phenylpyrazol‐1‐yl)borate decompose during reactions with [ReOCl₃(PPh₃)₂] and [NEt₄]₂[Re(CO)₃Br₃], respectively. The generated pyrazole ligands form complexes with the rhenium(V) oxo and the rhenium(I ) tricarbonyl cores. X‐ray crystal structures of the oxo‐bridged dimer [Cl(PPh₃)(O)Re(μ‐O)(μ‐Me₂pz)₂Re(O)(HMe₂pz)Cl] ( 1 ) and [Re(CO)₃(HPhpz)₂(Phpz)] ( 2 ) (HMe₂pz = 3, 5‐dimethylpyrazole, HPhpz = 3‐phenylpyrazole) show that the substituted pyrazoles can readily deprotonate and act as monodentate or bridging anionic ligands. Re‐N bond lengths between 2.09 and 2.14Å have been observed for the bridging and between 2.12 and 2.23Å for the terminal pyrazole ligands.     

Trends in electrochemical biosensors

The development of electrochemically based biosensors is discussed in the context of what has been learned from the successful development of glucose biosensors. Some future trends are discussed.     

Zu Struktur,Bindung und Ligandenaustauschverhalten von Nitrosyltechnetium(II)-Verbindungen Eine. EPR-Untersuchung

Structure, Bonding, and Ligand Exchange Behaviour of Nitrosyl-Technetium (II) Compounds. An EPR Study EPR investigations on the nitrosyltechnetium(II) compounds (Bu₄N)₂[Tc(NO)Cl₅], (Bu₄N)[Tc(NO)Br₄], (Bu₄N)[Tc(NO)I₄], and (Ph₄As)₂[Tc(NO)(NCS)₅] having a 4 t low-spin configuration are reported. The EPR parameters g?, Ã^Tc as well as ligand hyperfine data are used to analyze the bonding properties. The isotropic parameters g₀ and a are found to be clearly correlated to the composition of the coordination sphere. Therefore, they can be used to characterize mixed-ligand complexes unambiguously. The formation of mixed-ligand complexes was investigated for ligand-exchange reactions on [Tc(NO)Cl₅]^2? and [Tc(NO)Br₄]^?. In these investigations unsaturated dichalcogeno ligands are included.     

SOCl2 and POCl3 as reducing agents for TcO 4 − formation and EPR detection of Tc(VI)-compounds

Pertechnetate, TcO ₄ ^– , is reduced by thionyl chloride and phosphoryl chloride, respectively, to yield semistable Tc(VI) intermediates which can easily be detected by EPR spectroscopy. Spectra are recorded in liquid and frozen solutions. EPR data as well as chemical behaviour suggest the compounds obtained to be oxochloro complexes of technetium(VI).     

A 13C endor study on Copper(II)/Zinc(II) bis-(diethyl-dithiocarbamate) Cu/Zn(et2dtc)2

¹³C ENDOR spectra of Cu(et₂dtc)₂ substituted into a single crystals of Zn(et₂dtc)₂ are reported. The symmetry of the incorporated guest molecule appears to be considerably influenced by the Zn(et₂dtc)₂ host lattice. The unexpectedly large isotropic ¹³C hfs coupling can be understood assuming a “transannular overlap” mechanism.     

Phosphaniminato-Komplexe von Cobalt und Zink mit Heterocubanstruktur. Die Kristallstrukturen von [CoI(NPMe3)]4 und [ZnI(NPMe3)]4

Phosphoraneiminato Complexes of Cobalt and Zinc with Heterocubane Structure. Crystal Structures of [CoI(NPMe₃)]₄ and [ZnI(NPMe₃)]₄ The title compounds have been prepared from CoI₂ and ZnI₂, respectively, and Me₃SiNPMe₃ by fusion reactions at 180°C in the presence of sodium fluoride. They crystallize from dichloromethane as dark green (Co) or colourless (Zn) single crystals including three molecules CH₂Cl₂ per formula unit, which were characterized by crystal structure determinations. [CoI(NPMe₃)]₄ · 3 CH₂Cl₂: Space group P3m1, Z = 2, structure solution with 2376 independent reflections, R = 0.033. Lattice dimensions at ?50°C: a = b = 1455.8, c = 1270.5 pm. [ZnI(NPMe₃)]₄ · 3 CH₂Cl₂: Space group P3m1, Z = 2, structure solution with 2197 independent reflections, R = 0.043. Lattice dimensions at ?60°C: a = b = 1454.9, c = 1270.5 pm. Both complexes are isostructural with one another. They form heterocubane structures in which the metal atoms are linked via μ₃-N-bridges of the phosphoraneiminato groups with M₄N₄ bridge-type bond angles close to 90°.     

Synthese,EPR und Röntgenkristallstrukturanalyse von mer-Trichloro(2,2′-bipyridin)nitridotechnetium(VI), einem neuen Nitridokomplex des Technetium(VI)

Synthesis, EPR and X-Ray Structure of mer-Trichloro(2,2′-bipyridine)nitridotechnetium(VI) — a new Technetium(VI) Nitrido Complex mer-Trichloro(2,2′-bipyridine)nitridotechnetium(VI) has been prepared by the reaction of (NBu₄)[TcNCl₄] with 2,2′-bipyridine in acetonitrile, whereas the same procedure gives in methanol the technetium(V) cation [TcNCl(bipy)₂]⁺. The EPR spectrum of [TcNCl₃(bipy)] suggests a meridional coordination of the three chloro ligands. [TcNCl₃(bipy)] crystallizes monoclinic in the space group P2₁/n; a = 8.572(1), b = 15.462(1), c = 10.110(1) Å, β = 104.21(1)°, Z = 4. The R value converged at 0.034 on the basis of 3 040 reflections. The technetium atom is distorted octahedrally coordinated with the chloro ligands meridionally cis with respect to the nitrido nitrogen. The Tc? N(1) bond length is 1.669(4) Å, and the Tc? N(3) bond (2.371(4) Å) is significantly lengthened due to the structural trans labilizing influence of the “N^3?” ligand.     

Gold complexes with potentially tri- and tetradentate phosphinothiolate ligands

Reactions of [Au(PPh3)Cl], (Bu4N)[AuCl4] and the organometallic gold complex [Au(damp-C1,N)Cl2] (damp- = 2-(N,N-dimethylaminomethyl)phenyl) with the potentially tri- and tetradentate proligands PhP(C6H3-SH-2-R-3)2 (H2L1a, R = SiMe3; H2L1b, R = H) and P(C6H4-SH-2)3 (H3L2) result in the formation of mono- or dinuclear gold complexes depending on the precursor used. Monomeric complexes of the type [AuL1Cl] are formed upon the reaction with [Au(damp-C1,N)Cl2], but small amounts of dinuclear [AuL1]2 complexes with gold in two different oxidation states, +1 and +3, have been isolated as side-products. The dinuclear compounds are obtained in better yields from [AuCl4]-. A dinuclear complex having two Au(III) centers can be isolated from the reaction of [Au(PPh3)Cl] with H3L2, whereas from the reaction with H2L1b the mononuclear [Au(Ph3P)HL1b] is obtained, which contains a three-coordinate gold atom. Comparatively short gold-gold distances have been found in the dinuclear complexes (2.978(2) and 3.434(1) A). They are indicative of weak gold-gold interactions, which is unusual for gold(III).     

Tricarbonyl Complexes of Rhenium(I) with Acetylpyridine Benzoylhydrazone and Related Ligands

Novel rhenium(I) tricarbonyl complexes have been prepared by reactions of (Et₄N)₂[Re(CO)₃Br₃] with acetylpyridine benzoylhydrazone, Hapbhyd, di(2‐pyridyl)ketone benzoylhydrazone, Hpy₂bhyd, bis(2‐pyridine)ketone, py₂CO, and pyridinealdehyde terephtalaldehydebishydrazone, pytehyd. The ligands remain protonated when no supporting base is added and the following complexes have been isolated: [Re(CO)₃Br(Hapbhyd)], [Re(CO)₃Br(Hpy₂bhyd‐py, hyd)], [Re(CO)₃Br(Hpy₂bhyd‐py¹, py²)], [Re(CO)₃Br(py₂CO‐N, N)] and [Re(CO)₃Br(pytehyd)]. Addition of triethyl amine results in deprotonation of Hapbhyd and the formation of [Re(CO)₃(OH₂)(apbhyd)], whereas Hpy₂bhyd is hydrolysed and a rhenium complex with the monoanionic bis(2‐pyridyl)hydroxymethanolato ligand, {py₂C(OH)O}^‐, is formed. The same compound, [Re(CO)₃{py₂C(OH)O}], is obtained when triethyl amine and water are added to a mixture of (Et₄N)₂[Re(CO)₃Br₃] and py₂CO. The air‐stable products have been studied by spectroscopic methods and X‐ray crystallography.     

Oxorhenium(V) Complexes with Thiosemicarbazones

Neutral oxorhenium(V) complexes with thiosemicarbazones derived from 2‐pyridine formamide, HL¹, are formed when [ReOCl₃(PPh₃)₂] reacts with equimolar amounts of the ligands. Reduction of the metal and the formation of rhenium(III) complexes of the composition [Re(L¹)₂]⁺ occurs when an excess of thiosemicarbazones is used and the reaction is performed in boiling toluene for a prolonged period of time. The thiosemicarbazones deprotonate and act as tridentate ligands as has been confirmed by an X‐ray structure of [ReOCl₂(L^1b)], where HL^1b is 2‐pyridineformamide‐N(4)‐ethylthiosemicarbazone and the ligand occupies the equatorial coordination sphere of the complex together with one of the chloro ligands.