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Research


Research

Our principal research interests are summarised here.

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Publications


Publications

A detailed listing of our publications can be found in this section.

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Team


Team

Current and former group members, also including some group pictures.

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Education


Education

Online documents and links to teaching materials.

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Facilities


Facilities

Our main research facilities are summarised in this subitem.

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Recent News

Homepage has moved: Our website has moved to a new location (link).

Chem. Sci. Inside Cover: Again, a great collaborative study with the Krossing group. The manuscript entitled “Completing the Triad: Synthesis and full Characterization of Homoleptic and Heteroleptic Carbonyl and Nitrosyl Complexes of the Group VI Metals” has just been published in Chem. Sci. (link).

Emmy Noether Fellowship for Dr. Alexander Hinz (link)! Congratulations for these great news!

Al/N-based FLPs? A series of alane-substituted imidazolyl compounds, featuring different architecture is presented. For dimeric species steric dependent formation of symmetric and an asymmetric species were observed. Reactivity studies with small molecules revealed no reactivity as hidden FLP. Nevertheless, ambiphilic behavior of the imidazolyl alanes has been observed in cases during this study, which has recently been accepted for publication (link).

Electronic Frustration: The sterically unencumbered α-borylated phosphorus ylide Me3PC(H)B(iBu)2 has been synthesized, characterized, and investigated with the aid of density functional theory calculations. The title compound has been demonstrated to react with various small molecules such as NH3, CO, CO2 and the heterocumulenes PhNCX. In part, different reaction products are found as compared to the previously reported derivative Ph3PC(Me)BEt2. For details, see the recent full-paper published in Chem. Eur. J. (link), which has been designated as “Hot Paper”.

Great canoeing tour in July 2019: not astonishingly, repeated capsizing was no problem on the hottest day ever measured in Germany…

Scorpionates meet Phosphines: In a recent Dalton Trans. we have described new phosphine-functionalised tris(pyrazolyl)methane ligands, their coordination flexibility and their ability to generate heterobimetallic complexes (link). The results have recently been highlighted in Chemistry Views (click here).

Cooperative effects in hydroamination catalysis (collaboration with Jan Paradies): Very high activities were observed in the redox-induced hydroamination of alkynes by employing a redox-active gold(I) complex featuring a phosphonite-based ligand. Very low catalyst loadings (down to 10 ppm) and very mild conditions (25°C) were used. The hydroamination proceeds roughly two-fold faster with the in-situ oxidized catalysts than with its reduced form. The results have now been published in Chem. Commun. (click here) as part of the ChemComm themed issue “Switchable Catalysis” (click here) and featured with an inside back cover.

Nature Communication published (collaboration with the Krossing group): Carbonyl Cations go Open Shell… Chromium hexacarbonyl was oxidized with the [NO]+ salt of a weakly coordinating anion. Depending on the conditions, the first 17 valence electron (VE) configurated, homoleptic carbonyl radical cation [Cr(CO)6]•+ (kinetic product), or the 18 VE species [Cr(CO)5(NO)]+, the first mixed chromium carbonyl/ nitrosyl cation, is formed (thermodynamic product). The results have now been published in Nature Communications (link). Congratulations to all co-authors!

♠ See also the press release of the University of Freiburg (link) and a “behind the paper” post by Jan Bohnenberger (link).
♠ Nature Communications Editors’ Highlights webpage on inorganic and physical chemistry (link)
♠ Selected further references: ChemistryViews (link); further links (Altmetric).

Electronic Frustration: The concept and the first example for electronic frustration within a C–B π-bond arising from the competition for a lone pair of electrons is reported. The α-borylated phosphorus ylide (α-BCP) Ph3PC(CH3)BEt2 has been synthesized, characterized, and investigated with the aid of density functional theory calculations. These show the presence of a highly polarized C–B π-bond, induced by the electron withdrawing Ph3P+ substituent. This competition for the C-based lone pair of electrons leads to an FLP-type reactivity (FLP = frustrated Lewis pair), which has been demonstrated by reacting the title compound with various small molecules such as CO, CO2, COS, CS2 or the heterocumulenes PhNCO and PhNCS. More information can be found in the recent Communication, which has been highlighted with a Frontispiece and selected as “Hot Paper” in Chem. Eur. J. (click here). The paper also belongs to the most accessed contributions to Chem. Eur. J. in 10/2018 (link).

Great group excursion to the Black Forest in August 2018: “Gertelbacher Wasserfälle”

The Cover Feature shows a strategy to modify the metal‐metal distance in dinuclear rhodium(I) complexes based on linker‐bridged bis(amidinate) ligands. As part of the collaborative research center SFB 3MET, our group aims at understanding the underlying principles governing cooperative effects in catalysis. To rationally synthesize polynuclear complexes with tuneable metal–metal distances, a series of chelating N‐donor ligands was developed, which would concomitantly have an influence on possible cooperative effects. More information can be found in the recent EurJIC Full-paper, which has been highlighted with a Cover Feature of issue 26 (click here). In addition, we have recently reported with Peter Roesky’s group on rhodium(I) and iridium(I) complexes of ferrocenyl-functionalized amidinates and bis(amidinates) (Organometallics 2019, in press).

 

Nice collaborative paper with the group of Ingo Krossing (Freiburg): A facile route to cationic NiI phosphine complexes starting from recently reported [Ni(cod)2][Al(ORF)4] (1, with RF = C(CF3)3) is described. [Ni(dppp)2][Al(ORF)4] (2), [Ni(dppe)2][Al(ORF)4] (3), three-coordinate [Ni(PPh3)3][Al(ORF)4] (4) and a remarkable two-coordinate NiI phosphine complex [Ni(PtBu3)2][Al(ORF)4] (5) were investigated. The results were recently published as “Hot Paper” in Chem. Eur. J. (click here).

Great group excursion in July 2017: biking, rafting, riding carousels, enjoying the time!

A dinuclear [FeRh] complex containing a redox-active [1]phosphaferrocenophane metalloligand was employed as redox-switchable rhodium catalyst in the hydrosilylation of terminal alkynes. As evidenced by activity and selectivity differences, distinct mechanisms are operating for the neutral and the cationic complex, namely the alternative Chalk–Harrod mechanism for [FeRh] and the classical variant for [FeRh]+. An “oxidatively induced reductive elimination” step was identified as the origin of the observed cooperative effect. The results were recently published as a Frontispiece-featured Communication in Chem. Eur. J. (click here).

Multidentate Silyl Ligands: A recent review summarises the use of multidentate Si-based ligand systems in transition metal coordination chemistry. These include tri- and tetradentate pincer and scorpionate-type ligands, which have been developed in recent years in order to tailor both steric and electronic properties for achieving a defined control over the reactivity of a transition metal complex. A discussion of synthetic and structural aspects of several subgroups of ligand architectures is presented (click here).

Redox-switchable catalysis: Palladium(II) complexes of two differently substituted [1]phosphaferrocenophanes FcPR (R = Mes, biaryl) and of diphenylferrocenyl phosphine Ph2PFc were applied in redox-switchable Buchwald-Hartwig cross-coupling reactions. The results were recently published as part of the themed collection „Switchable Catalysis and Related Reactions“ in Inorg. Chem. Front. (click here).

The redox-switchable germylene [Fc(NMes)2Ge] based on a [3]ferrocenophane ligand arrangement, alongside some transition metal complexes, are reported. The change in the ligating properties upon oxidation were elucidated by DFT calculations on neutral and cationic bimetallic model complexes. The results were recently published in Chem. Eur. J. (click here).

Congratulations to Michael and Wolfram for their Procter & Gamble awards for the best MA-theses in 2015/2016! The picture taken at the ceremony on November 10 shows the recipients alongside the P&G representative and the MA-theses supervisors.

Great group excursion to the Black Forest in July 2016: “Flussbettwanderung im Murgtal”… somewhat slippery when wet 😉

Our collaborative study with the group of Rodrigue Lescouëzec (see below) was recently featured on the front-cover of issue 8 (see also here).

Collaborative study within a Co-tutelle framework between the KIT and Sorbonne Universités, UPMC (Prof. Lescouëzec): A straightforward access to a new cyanide-bridged {Fe4Co4} “molecular box” containing a potassium ion, namely  K@{[FeII(Tp)(CN)3]4[CoIII(pzTp)]3[CoII(pzTp)]} (1) (with Tp and pzTp = tris- and tetrakis(pyrazolyl)borate, respectively), is provided alongside its full characterisation. A detailed analysis of the molecular structure (X-ray diffraction, mass spectrometry, NMR spectroscopy) and electronic properties (EPR spectroscopy, SQUID magnetometry, UV/Vis spectroscopy, cyclic voltammetry) reveals that 1 shows slow magnetic relaxation and a remarkable photomagnetic effect at low temperature, which is reminiscent to some FeCo Prussian Blue Analogues (PBAs) and ascribed to a photo-induced electron transfer. However, in contrast with these inorganic polymers, the overall neutral compound 1 is soluble and remarkably stable in organic solvents such as CH2Cl2. Moreover, 1 shows an interesting redox versatility, electrochemical experiments revealing the possible access to six stable redox states. The results were recently published in Chem. Sci. (click here).