News...
Main Group Marriage ...
Schnöckel’s [(AlCp*)4] and Jutzi’s [SiCp*][B(C6F5)4] (Cp* = C5Me5) are landmarks in modern main-group chemistry with diverse applications in synthesis and catalysis. Despite the isoelectronic relationship between the AlCp* and the [SiCp*]+ fragments, their mutual reactivity is hitherto unknown. Here, we report on their reaction giving the complex salts [Cp*Si(AlCp*)3][WCA] ([WCA]− = [Al(ORF)4]− and [F{Al(ORF)3}2]−; RF = C(CF3)3). The tetrahedral [SiAl3]+ core not only represents a rare example of a low-valent silicon-doped aluminium-cluster, but also – due to its facile accessibility and high stability – provides a convenient preparative entry towards low-valent Si–Al clusters in general. For example, an elusive binuclear [Si2(AlCp*)5]2+ with extremely short Al–Si bonds and a high negative partial charge at the Si atoms was structurally characterised and its bonding situation analysed by DFT. Crystals of the isostructural [Ge2(AlCp*)5]2+ dication were also obtained and represent the first mixed Al–Ge cluster. Angewandte
Cationic Dialanes ...
Unique π-cyclopentadienyl-bridged dialanes are synthesized as complex salts with aluminate anions by comproportionation of aluminocenium cations [AlIII(Cp)(Cp*)]+ /[AlIIICp2]+ with [(AlICp*)4]. Very short Al–Al bond lengths occur in the positively charged Al24+ fragments. Intriguingly, the prepared asymmetric dialane shows a unique fluxional coordination of the cyclopentadienyl-ligands. Chem. Comm. tells you why…
Ni(I)-Benzene Cations ...
The metalloradical [Ni(C6H6)2]+, hitherto unknown in the condensed phase, was synthesized from [Ni(CO)4]+[WCA]– and benzene ([WCA]– = [F{Al(ORF)3}2]–; RF = C(CF3)3). The [Ni(C6H6)2]+ cation exhibits an asymmetric slipped η3-,η6-sandwich structure. Its magnetic properties were determined in solution and in the gas phase. Further deelectronation with the Ag+/0.5 l2 system led to the salt [Ni(C6H6)2]2+([WCA]–)2. Link.
Mixed low-valent group 13 cations...
Mixed low-valent group 13 cations have been prepared via addition of [(AlCp*)4] to the low-valent cation salts of Ga, In and Tl. Addition of an aza-crown ether Me3TACN resulted in isomerization to a novel Al4+ cluster. This Al4+ cluster could also be prepared in high yields via reaction of [Ga/Tl(Me3TACN)]+ complexes with [(AlCp*)4].
Too much Fluorine...?
Weakly coordinating anions improve electrolytes for magnesium ion batteries by inhibiting ion-pairing, increasing the electrochemical window and conductivity. A novel synthetic route towards clean and contaminant-free [Mg(L)x][Al(ORF)4]2 (L =MeCN, DME; x = 3;6; RF = C(CF3)3), containing [Al(ORF)4]− as one of the least coordinating anions, led to surprising electrochemical data, contradicting previously published results using this electrolyte salt in DME solution. See why: Link.
From [P5]+ to [P9]+...
New synthetic approaches to a series of [P9]X salts (X = [F{Al(ORF)3}2], [Al(ORF)4], (RF = C(CF3)3); Ga2Cl7) containing the homopolyatomic cation [P9]+ via a) oxidation of P4 with NO[F{Al(ORF)3}2] or b) the arene stabilized Co(I)-sandwich complex [Co(arene)2][Al(ORF)4] (arene = o-DFB, FB) or c) the reduction of [P5Cl2][Ga2Cl7] with Ga[Ga2Cl7] as Ga(I) source in the presence of P4 overcome the limitations of classical synthesis methods that proved unsuitable for phosphorus cations. Quantum chemical CCSD(T)-calculations suggest that [P9]+ formation from [Co(arene)2]+ occurs via the nido-type cluster [(o-DFB)CoP4]+, which resembles the isoelectronic, elusive [P5]+. Apparently the nido-cation [P5]+ forms intermediately in all reactions, particularly during the Ga(I) induced reduction of [P5Cl2]+ and the subsequent pick up of P4 to yield the final salt [P9][Ga2Cl7]. The solid state structure of [P9][Ga2Cl7] reveals the anticipated D2d-symmetric Zintl-type cage for the [P9]+ cation. Our approaches show great potential to bring other [Pn]+ cations from the gas to the condensed phase. Link.
Trimetallic Carbonyl Cluster Cation
10.08.2022 – The reactions of the trimetal dodecacarbonyls Ru3(CO)12 and Os3(CO)12 with typical inorganic oxidants lead to several unwanted side products. By contrast, the radical-cation of the commercially available 9,10-dichlorooctafluoroanthracene deelectronates the trimetal dodecacarbonyls under CO pressure to their respective trimetal tetradecacarbonyl dications, the first homotrimetallic transition metal carbonyl cations.
Subvalent Aluminum Cluster Cation
04.08.2022 - We report the gram-scale synthesis of a low-valent cationic aluminium complex salt by a metathesis reaction. The salt, [Al(AlCp*)3]+[Al(OC{CF3)3}4]–, is prepared from the Schnöckel complex, [(AlCp*)4] (Cp* = [C5Me5]–), in which aluminium is already in the +1 oxidation state. The [(AlCp*)4] reacts with Li[Al{OC(CF3)3}4] and the reaction mixture changes instantaneous from yellow to red. On crystallization of the reaction mixture, the [Al(AlCp*)3]+[Al(OC{CF3)3}4]– salt is obtained as dark purple crystals. Crystallographic data reveal the formation of a trigonal pyramidal geometry for the [Al(AlCp*)3]+ ion of the salt, which comprises a unique, central aluminium atom surrounded by three strongly-bound neutral AlCp* moieties. “This central Al+ atom acts as an acceptor of electrons from the attached AlICp* ligands,” explains Krossing. “As a result, the capacity of the AlICp* ligands to bond to each other is greatly reduced, or even absent, with (Cp*)Al---Al(Cp*) separations exceeding 300 pm.” In the solid state, the salt includes dimers, [Al8(Cp*)6]2+. These dications also exist at low temperatures and high concentrations in solution whereas at low concentrations, the salt exists in monomeric form and accordingly the colour changes from deep purple to red and then to yellow for the monomer. http://dx.doi.org/10.1038/s41557-022-01000-4
Iron Pentacarbonyl Cation Paper
25.05.2022 - With the precision of an eagle, the use of a strong and innocent deelectronator (i.e., a single-electron oxidant) generates the open-shell iron pentacarbonyl cation [Fe(CO)5]•+ for the first time in condensed phases. This radical cation was studied extensively in the gas phase and can now be isolated as a stable salt using the weakly coordinating aluminate anions [Al(ORF)4]− and [F-{Al(ORF)3}2]− (RF = C(CF3)3). Link
Sustainable Fuels. What are the Features of Good Combustion…?
18.06.2021 - The Freiburger Wissenschaftsmarkt 20/21 takes place from 07.06. - 26.06.2021. This year, it is an online event packed with interesting lectures from universities,
colleges and research facilities. As part of the Freiburger Materialforschungszentrum (FMF), the Krossing group (subgroup catalysis) participates with an educational contribution on combustion reactions and the research on new synthetis fuels.
Small Amount, Large Effect…
06.12.2020 - The mild oxidative surface fluorination of NCM811 cathode active material (CAM) leads to the reduction of the surface basic layer, reduces Co- and Mn-leaching as well as impedance built-up and thus leads to
optimized average charge and discharge voltages as well as improved cycle-life in LIB full cells. Apparently, the formed LiF layer protects the CAM and as fluxing agent also leads to increased press density of the during the process smoothened CAM surfaces.
Homoleptic Olefin Complex...
23.09.2020 - The earth-metal olefin complex [GaI(COD)2]+[Al(ORF)4]– (COD = 1,5-cyclooctadiene; RF= C(CF3)3) constitutes the first homoleptic olefin complex of any main-group metal accessible as a bulk compound.
Hexacarbonyls als Ligands...
15.09.2020 - The molecules M(CO)6 (M = Mo, W) act as ligands towards the silver ion giving the title compounds [Ag{M(CO)6}2]+[F‑{Al(ORF)3}2]– (RF = C(CF3)3). Their structures and bonding have been analyzed and compared to those of the very recently prepared isoelectronic complexes [Ag{M(CO)6}2]– (M = Nb, Ta).
Bis(arene) Niobium Cations…
01.09.2020 - The syntheses of the homoleptic bis(arene) niobium cations [Nb(arene)2]+ (arene = C9H12,
C7H8) with 16 valence electrons and heteroleptic arene-carbonyl cations [(CO)Nb(arene)2]+ (arene = C9H12,
C7H8) and [(arene)M(CO)4]+ (arene = C9H12, C6H6) obeying 18 valence electrons are described.
Stability of these complexes was achieved by using the weakly coordinating anions [Al(ORF)4]– or [F{Al(ORF)3}2]–
(RF = C(CF3)3). The limits of two synthesis routes starting from neutral Nb(arene)2 (arene = C9H12,
C7H8) or [NEt4][M(CO)6] (M = Nb, Ta) were investigated.
10.08.2020 - Soft shell, hard core: The synthesis of a highly Lewis acidic, dicationic strontium ansa‑arene complex as salt of weakly coordinating [Al(ORF)4]‑anion (ORF = C(CF3)3) is reported via a base-free strontium-perfluoroalkoxyaluminate Sr[Al(ORF)4]2 as source of a naked strontium dication. The strontium ansa-arene complex was successfully applied as catalyst in a CO2 reduction and a highly controlled isobutylene polymerization.
Boron Trifloride CAM-Coating...
07.08.2020 - Ni-rich cathode active material Li1+x[Ni0.85Co0.10Mn0.05]1−xO2 (NCM851005) was exposed to BF3 gas at room temperature with pressures between 25 and 2478 mbar. It mainly gave an LiBF4 coating by reaction with the basic surface lithium impurities. The electrochemical investigations up to full-cell level displayed a significantly improved long-term cycling behavior at 45°C for only 0.08 wt% BF3 coated NCM851005 material, compared to pristine NCM851005 material.
Stack by Stack and Brick by Brick
04.08.2020 - Starting from the mono-arene coordinated Group 13 complex cations of gallium and indium a series of heterobimetallic sandwich cations were generated. The obtained Group 13/14 metallocene cations contain apical free Group 13 elements in an unusual coordination environment. By tuning the reaction conditions, a heterobimetallic main-group sandwich coordination polymer containing indium and tin was accessed. The observed polymeric chain motif was further transferred to related complexes containing ferrocene as bridging ligand. Chem. Eur. J. 2020, online.
Silver Superatom Clusters...
02.07.2020 - The homoleptic group 5 carbonylates [M(CO)6]– (M = Nb, Ta) serve as ligands in carbonyl terminated heterobimetallic AgmMn-clusters containing 3 to 11 metal atoms. Based on our serendipitous [Ag6{Nb(CO)6}4]2+ (4a2+) precedent, we established access to such AgmMn-clusters of the composition [Agm{M(CO)6}n]x (M = Nb, Ta; m = 1, 2, 6; n = 2, 3, 4, 5; x = 1–, 1+, 2+). Salts of those molecular cluster ions were synthesized by the reaction of [NEt4][M(CO)6] and Ag[Al(ORF)4] (RF = C(CF3)3). Chem. Eur. J. 2020, online.
