Dennis Rottschäfer

Silicon(IV) halides [{(Et ₃ B)anIPr}SiHCl ₂ ] ( 4 ) and [{(Et ₃ B)anIPr}SiBr ₃ ] ( 5 ) based on an anionic N ‐heterocyclic carbene (NHC) ligand (i.e., {(Et ₃ B)anIPr} = (Et ₃ B)C=C(H){N(Dipp)} ₂ C, Dip p = 2,6‐ i Pr ₂ C ₆ H ₃ ) are reported as crystalline solids. Compounds 4 and 5 featuring a four‐coordinated Si(IV) atom are prepared by reacting [Li{(Et ₃ B)anIPr}] ( 3 ) with HSiCl ₃ and SiBr ₄ , respectively. 4 and 5 are characterized by spectroscopic and X‐ray diffraction methods. Density functional theory (DFT) calculations have been performed to elucidate the electronic structures as well as the fluoride ion affinities (FIAs) of 4 and 5 . The calculated FIA, a measure of Lewis acidity, of 4 and 5 is about 46 or 55 kJ/mol larger than that of HSiCl ₃ and SiBr ₄ , respectively.

Diradicals based on a meta‐quinodimethane (m‐QDM) scaffold generally have a triplet ground state and are rather scarce. Herein, m‐QDM‐based non‐Kekulé diradicals [3,3′‐(NHC)₂BP] (3‐NHC) (NHC = SIPr = C{N(Dipp)CH₂}₂; IPr = C{N(Dipp)CH}₂, Me‐IPr = C{N(Dipp)CMe}₂; Dipp = 2,6‐iPr₂C₆H₃; BP = 1,1′‐C₆H₄C₆H₄) featuring N‐heterocyclic carbene (NHC) pendants are reported as crystalline solids. The EPR spectra of 3‐NHC show both allowed (Δm_s = 1) and forbidden (Δm_s = 2; ‘half‐field’) transitions characteristic for triplet diradicals. Variable temperature EPR studies however reveal a singlet ground state for 3‐SIPr. Consistent with the EPR spectra, calculations predict a remarkably small singlet‐triplet energy gap (ΔE_ST ≤ 0.26 kcal/mol) for the 3‐NHC compounds. The calculated singlet diradical character for the ground states of the 3‐NHC compounds amounts to ~99 %.

When bismuth atoms are incorporated into cyclic organic systems, this commonly goes along with strained or distorted molecular geometries, which can be exploited to modulate the physical and chemical properties of these compounds. In six‐membered heterocycles, bismuth atoms are often accompanied by oxygen, sulfur or nitrogen as a second hetero‐element. In this work, we present the first examples of six‐membered rings, in which two CH units are replaced by BiX moieties (X=Cl, Br, I), resulting in dihydro‐anthracene analogs. Their behavior in chemically reversible reduction reactions is explored, aiming at the generation of dibisma‐anthracene (bismanthrene). Heterometallic compounds (Bi/Fe, Bi/Mn) are introduced as potential bismanthrene surrogates, as supported by bismanthrene‐transfer to selenium. Analytical techniques used to investigate the reported compounds include NMR spectroscopy, high‐resolution mass spectrometry, single‐crystal X‐ray diffraction analyses, and DFT calculations.

Die erste 1,4‐Distabenzol‐1,4‐diid‐Verbindung [(ADC)Sb]₂ (5) auf der Basis eines anionischen Dicarbens (ADC) (ADC=PhC{N(Dipp)C}₂, Dipp=2,6‐iPr₂C₆H₃) wird als bordeauxroter Feststoff berichtet. Verbindung 5, die einen zentralen sechsgliedrigen C₄Sb₂‐Ring mit formalen Sb^I‐Atomen aufweist, kann als ein Basen‐stabilisiertes cyclisches Bis‐Stibiniden betrachtet werden, in dem jedes der Sb‐Atome zwei freie Elektronenpaare trägt. 5 geht eine 2e‐Oxidation mit Ph₃C[B(C₆F₅)₄] ein und bildet [(ADC)Sb]₂[B(C₆F₅)₄]₂ (6) als ziegelroten Feststoff. Jedes der Sb‐Atome von 6 hat ein ungepaartes Elektron und ein freies Elektronenpaar. Die offenschalige Singulett‐Diradikal‐Lösung (broken‐symmetry) für (6)²⁺ ist um 2.13 kcal mol⁻¹ stabiler als die geschlossenschalige Singulett‐Lösung. Der diradikalische Charakter von (6)²⁺ beträgt nach SS‐CASSCF (state‐specific complete active space self‐consistent field) und UHF (unrestricted Hartree‐Fock) 39 % bzw. 36 %. Die Behandlung von 6 mit (PhE)₂ ergibt [(ADC)Sb(EPh)]₂[B(C₆F₅)₄]₂ (7‐E) (E=S oder Se). Die Reaktion von 5 mit (cod)Mo(CO)₄ führt zu [(ADC)Sb]₂Mo(CO)₄ (8).

The first 1,4‐distibabenzene‐1,4‐diide compound [(ADC)Sb]₂ (5) based on an anionic dicarbene (ADC) (ADC=PhC{N(Dipp)C}₂, Dipp=2,6‐iPr₂C₆H₃) is reported as a bordeaux‐red solid. Compound 5, featuring a central six‐membered C₄Sb₂ ring with formally Sb^I atoms may be regarded as a base‐stabilized cyclic bis‐stibinidene in which each of the Sb atoms bears two lone‐pairs of electrons. 5 undergoes 2 e‐oxidation with Ph₃C[B(C₆F₅)₄] to afford [(ADC)Sb]₂[B(C₆F₅)₄]₂ (6) as a brick‐red solid. Each of the Sb atoms of 6 has an unpaired electron and a lone‐pair. The broken‐symmetry open‐shell singlet diradical solution for (6)²⁺ is calculated to be 2.13 kcal mol⁻¹ more stable than the closed‐shell singlet. The diradical character of (6)²⁺ according to SS‐CASSCF (state‐specific complete active space self‐consistent field) and UHF (unrestricted Hartree‐Fock) methods amounts to 36 % and 39 %, respectively. Treatments of 6 with (PhE)₂ yield [(ADC)Sb(EPh)]₂[B(C₆F₅)₄]₂ (7‐E) (E=S or Se). Reaction of 5 with (cod)Mo(CO)₄ affords [(ADC)Sb]₂Mo(CO)₄ (8).

Sulfinyl-substituted aminotroponiminate (ATI) complexes of the alkali metals Li–K and the heavy metal bismuth have been isolated and characterised. The sulfinyl group affects their coordination and redox properties in the solid state and in solution.

Aminotroponiminate (ATI) ligands are a versatile class of redox‐active and potentially cooperative ligands with a rich coordination chemistry that have consequently found a wide range of applications in synthesis and catalysis. While backbone substitution of these ligands has been investigated in some detail, the impact of electron‐withdrawing groups on the coordination chemistry and reactivity of ATIs has been little investigated. We report here Li, Na, and K salts of an ATI ligand with a nitro‐substituent in the backbone. It is demonstrated that the NO₂ group actively contributes to the coordination chemistry of these complexes, effectively competing with the N,N‐binding pocket as a coordination site. This results in an unprecedented E/Z isomerisation of an ATI imino group and culminates in the isolation of the first “naked” (i. e., without directional bonding to a metal atom) ATI anion. Reactions of sodium ATIs with silver(I) and tritylium salts gave the first N,N‐coordinated silver ATI complexes and unprecedented backbone substitution reactions. Analytical techniques applied in this work include multinuclear (VT‐)NMR spectroscopy, single‐crystal X‐ray diffraction analysis, and DFT calculations.

1,4‐Diarsinine‐1,4‐diide compound [(ADC^Ph)As]₂ (5) (ADC^Ph={C(DippN)}₂CPh, Dipp=2,6‐iPr₂C₆H₃) with a planar C₄As₂ ring fused between two 1,3‐imidazole scaffolds has been isolated as a red crystalline solid. Compound 5, formally comprising an 8π‐electron C₄As₂ ring, is antiaromatic and undergoes 2e‐oxidation with AgOTf to form the 6π‐electron aromatic system [(ADC^Ph)As]₂(OTf)₂ (6).

Das 1,4‐Diarsinin‐1,4‐diid [(ADC^Ph)As]₂ (5) (ADC^Ph={C(DippN)}₂CPh, Dipp=2,6‐iPr₂C₆H₃) mit einem planaren C₄As₂‐Ring, der an zwei 1,3‐Imidazol‐Ringen anelliert ist, wurde als roter, kristalliner Feststoff isoliert. Verbindung 5, die formal einen 8π‐Elektronen‐C₄As₂‐Ring enthält, ist antiaromatisch und geht eine 2e‐Oxidation mit AgOTf ein, die zum aromatischen 6π‐Elektronen‐System [(ADC^Ph)As]₂(OTf)₂ (6) führt.

Metalloradicals are key species in synthesis, catalysis, and bioinorganic chemistry. Herein, two iron radical cation complexes (3‐E)GaCl₄ [(3‐E)^.+ = [{(IPr)C(Ph)E}₂Fe(CO)₃]^.+, E = P or As; IPr = C{(NDipp)CH}₂, Dipp = 2,6‐iPr₂C₆H₃] are reported as crystalline solids. Treatment of the divinyldipnictenes {(IPr)C(Ph)E}₂ (1‐E) with Fe₂(CO)₉ affords [{(IPr)C(Ph)E}₂Fe(CO)₃] (2‐E), in which 1‐E binds to the Fe atom in an allylic (η³‐EEC_vinyl) fashion and functions as a 4e donor ligand. Complexes 2‐E undergo 1e oxidation with GaCl₃ to yield (3‐E)GaCl₄. Spin density analysis revealed that the unpaired electron in (3‐E)^.+ is mainly located on the Fe (52–64 %) and vinylic C (30–36 %) atoms. Further 1e oxidation of (3‐E)GaCl₄ leads to unprecedented η³‐EEC_vinyl to η³‐EC_vinylC_Ph coordination shuttling to form the dications (4‐E)(GaCl₄)₂.