The Reaction of Cs2[Tc(NO)F5] with BF3 in Acetonitrile: Formation and Structure of [{Tc(NO)(CH3CN)4}2(μ‐F)](BF4)3

The deep blue, paramagnetic Cs₂[Tc^II(NO)F₅] is formed during reactions of pertechnetate, acetohydroxamic acid, and CsF in aqueous HF. A reaction of Cs₂[Tc(NO)F₅] with BF₃ · MeOH in acetonitrile gives yellow blocks of the fluorido‐bridged dimer [{Tc^I(NO)(CH₃CN)₄}₂F](BF₄)₃. The compound is stable as solid and in acetonitrile solutions. The complex cation contains a bent μ‐F^– ligand and two linear nitrosyl groups.     

Solid state molecular structures of transition metal hexafluorides

Single-crystal structure determinations of all nine transition metal hexafluorides (Mo, Tc, Ru, Rh, W, Re, Os, Ir, and Pt) at -140 degrees C are presented. All compounds crystallize alike and have the same molecular structure. The bond length sequence r(w-F) congruent with r(Re-F) congruent with r(Os-F) < r(Ir-F) < r(Pt-F) is confirmed and paralleled by the sequence r(Mo-F) congruent with r(Tc-F) congruent with r(Ru-F) < r(Rh-F). Within the limits of precision, no systematic deviation from octahedral symmetry can be established. DFT and ab initio calculations predict octahedral structures for MoF6 and RhF6 and tetragonally distorted structures for ReF6 and RuF6. The energy barrier toward octahedral structures is only 2.5 kJ mol(-1) in the two latter cases. Calculated electron affinities are in the sequence MoF6 < TcF6 < RhF6 < RuF6 with a value of 6.98 eV for the latter. O2+RhF6- crystallized in an undisordered manner in P, isostructural to the low-temperature form of O2+AuF6-. RhF6- has a D4h compressed octahedral structure, while AuF6- is essentially octahedral. The absorption spectrum of TcF6 and the 19F and 195NMR spectra of PtF6 are presented.     

Post-synthetic modification of Zr-metal-organic frameworks through cycloaddition reactions

Cycloaddition reactions are highly attractive for post-synthetic modification of metal-organic frameworks (MOFs). We report herein on cycloaddition reactions with PIZOF(R(1),R(2))s, which are porous interpenetrated Zr-based MOFs with Zr(6)O(4)(OH)(4)(CO(2))(12) as the nodes and the dicarboxylates (-)O(2)C[PE-P(R(1),R(2))-EP]CO(2)(-) (P: phenylene, E: ethynylene; R(1), R(2): side chains at the central phenylene unit) as the linkers. 1,3-Dipolar cycloaddition between the pendant ethyne moieties of PIZOF(OMe,OCH(2)C≡CH) and 4-methylbenzyl azide resulted in 98% conversion of the ethyne groups. Reactions of PIZOF(OMe,O(CH(2))(3)furan) with maleimide, N-methylmaleimide, and N-phenylmaleimide converted 98, 99, and 89% of the furan moieties into the Diels-Alder adducts. However, no reaction occurred with maleic anhydride. High-resolution (1)H NMR spectra were crucial in determining the conversion and identifying the reaction products. Of all the reagents (NaOD/D(2)O, D(2)SO(4), Bu(4)NF, CsF, CsF/DCl, and KHF(2)) tested for the disassembly of the PIZOFs in [D(6)]DMSO, the combination of CsF and DCl was found to be the best. The disassembly at room temperature was fast (5-15 min), and after the addition of K(2)CO(3) the (1)H NMR data were identical to those of the diacids (=protonated linkers) dissolved in pure DMSO. This allowed for simple structure elucidation through data comparison. CsF/DCl dissolves not only PIZOFs but also the hydrolytically very stable UiO-66.     

Zur Kenntnis der Schmelzdiagramme gesättigter Fettsäuren

Zusammenfassung Im Schmelzdiagramm von Palmitinsäure: Stearinsäure wurde auf mikroskopischem Wege das Auftreten dreier Mischkristallphasen festgestellt, wovon die Mischphase des mittleren Konzentrationsbereiches nicht wie bisher in der Regel üblich als Verbindung, sondern als stabilisierte Zwischenphase betrachtet wird. Der für das genannte System gefundene Aufbau des Diagramms gilt im allgemeinen für alle Systeme geradzahliger gesättigter Fettsäuren, die sich in ihrer Kettenlänge um 2 bis 4 C-Atome unterscheiden.

---

Summary By microscopic procedure the fusion diagram of palmitic acid: stearic acid was shown to contain three mixed crystal phases. The mixed crystal phase of the middle concentration ranges is to be considered not a compound, as was the former belief, but rather as a stabilized intermediate phase. The structure of the diagram found for this particular system holds in general for all systems of even-numbered saturated fatty acids, which differ by 2 to 4 carbon atoms in their chain lengths.

---

Résumé On montre microscopiquement, dans le diagramme de fusion acide stéarique-acide palmitique, l'existence de trois sortes de cristaux mixtes dont la phase mixte du domaine de concentration intermédiaire est considérée comme une phase stable intermédiaire, mais pas comme un composé, étant jusqu'ici considérée en règle générale. La structure trouvée pour le diagramme ci-dessus s'accorde, en général, avec tous les systèmes d'acides gras saturés à nombre pair qui diffèrent par deux à quatre atomes de carbone.

---

---

Herrn Universitätsprofessor Dr.L. Ebert zum 60. Geburtstag gewidmet.