No abstract

Single-wall carbon nanotubes (SWCNTs) and well-aligned thin multiwall carbon nanotubes (MWCNTs) were successfully synthesized via pyrolysis of a powder mixture of ferrocene and anthracene or 9,10-dibromoanthracene. It is shown that the size of the MWCNTs can be tuned just by changing the ratio of ferrocene/anthracene in the mixture. A lower ratio resulted in low-diameter MWCNTs containing up to five graphene layers only; a high ratio has led to thick MWCNTs with more than 25 layers. Furthermore, there are two extreme cases, the pyrolysis of powders at a low ratio of 1:7 that gives rise to carbon nanospheres and the pyrolysis of pure ferrocene in a H2 flow that mainly gives rise to metal nanoparticles. When powder mixtures of ferrocene and 9,10-dibromoanthracene are pyrolyzed, both SWCNTs and spherical carbon-coated iron nanoparticles are obtained.

The carbodiphosphorane Ph3PCPPh3 (1) readily reacts with Ni(CO)4 in toluene to give the substitution product (CO)3NiC(PPh3)2 (2). If the reaction is carried out in THF solution, additionally red crystals of the dicarbonyl complex (CO)2NiC(PPh3)2 (3) are formed. 2 smoothly converts into 3 when dissolved in THF. The compounds have been characterized by single-crystal X-ray diffraction. Quantum chemical calculations at the DFT level of theory (B3LYP) are given for the geometries of model compounds 1a−3a with PH3 ligands instead of PPh3, which are in good agreement with the experimental results for 1−3. The metal−ligand bond energies are also predicted at B3LYP. The calculated Ni−C(PH3)2 bond energy of 3a (D 0 = 33.7 kcal/mol) is nearly the sum of the Ni−C(PH3)2 (D 0 = 20.9 kcal/mol) and first Ni−CO bond energy of 2a (D 0 = 16.3 kcal/mol). The analysis of the metal−ligand bonding using the CDA method shows that there is mainly ligand → metal donation and much less metal → ligand back-donation between Ni and C(PH3)2 in 2a. Donation and back-donation become stronger and back-donation becomes more important in 3a than in 2a.

Treatment of the alkynes R′CtCH (R′ ) Me, n-Pr) with dialkylgallium hydrides, R 2 GaH (R ) Me, Et), yielded symmetrical carbon-gallium cage compounds with release of dihydrogen and subsequent addition of Ga-H to the CtC triple bonds. Heteroadamantanetype compounds (GaR) 6 (CR′) 4 were formed in which the positions of the methylene bridges of the carbon skeleton in adamantane were occupied by coordinatively unsaturated, tricoordinate gallium atoms.

Die Umsetzung des Carbodiphosphorans Ph3P=C=PPh3 (1) mit InMe3 in THF und von AlBr3 in Toluol liefert die Addukte [Me3In{C(PPh3)2}] (2) und [Br3Al{C(PPh3)2}] (3) mit sehr guten Ausbeuten. 1 reagiert nicht mit SnCl2 und Me3SnCl; als Nebenprodukt konnten jedoch geringe Mengen des Hydrolyseprodukts [HC(PPh3)2][Me3SnCl2] (6) als Einkristalle erhalten werden. 2 löst sich in HCCl3 unter Bildung der Salze [HC(PPh3)2][MeInCl3] (5a) und [HC(PPh3)2][Me2InCl2] (5b). Wenige Kristalle von [HC(PPh3)2][Me2In(OSiMe2OSiMe2O)] (4) wurden als Reaktionsprodukt von 2 mit dem Silikon‐Schliffett bei Kristallisationsversuchen von 2 erhalten. Beim Versuch, 2 mit CS2 in THF umzusetzen wurde das THF‐Spaltungsprodukt [HC(PPh3)2][CH3CH2CH2OCS2] (7) in 60 %iger Ausbeute erhalten. Sämtliche Verbindungen wurden durch Einkristallstrukturanalysen charakterisiert, inklusive das bei der Darstellung von 3 angefallene Nebenprodukt [Br3Al{OP(C6H5)2CH2P(C6H5)3}][AlBr4] (8) sowie die zur Synthese von 1 verwendete salzartige Verbindung [ClC(PPh3)2]Cl (9).