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Quantum chemical studies using density functional theory and ab initio methods have been carried out for the molecules L‐C3‐L with L=PPh3 (1), NHCMe (2, NHC=N‐heterocyclic carbene), and cAACMe (3, cAAC=cyclic (alkyl)(amino) carbene). The calculations predict that 1 and 2 have equilibrium geometries where the ligands are bonded with rather acute bonding angles at the linear C3 moiety. The phosphine adduct 1 has a synclinal (gauche) conformation whereas 2 exhibits a trans conformation of the ligands. In contrast, the compound 3 possesses a nearly linear arrangement of the carbene ligands at the C3 fragment. The bond dissociation energies of the ligands have the order 1, C3 stabilization: Quantum chemical studies using density functional theory and ab initio methods have been carried out for the molecules L‐C3‐L with L=PPh3 (1), NHCMe (2, NHC=N‐heterocyclic carbene), and cAACMe (3, cAAC= cyclic (alkyl)(amino) carbene). The calculations predict that 1 and 2 have equilibrium geometries where the ligands are bonded with rather acute bonding angles at the linear C3 moiety.

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+ (4 a 2+) 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) in the correct stoichiometry in 1,2,3,4‐tetrafluorobenzene at −35 °C. The solid‐state structures were determined by single‐crystal X‐ray diffraction methods and, owing to the thermal instability of the clusters, a limited scope of spectroscopic methods. In addition, DFT‐based AIM calculations were performed to provide an understanding of the bonding within these clusters. Apparently, the clusters 3 + (m=6, n=5) and 4 2+ (m=6, n=4) are superatom complexes with trigonal‐prismatic or octahedral Ag6 superatom cores. The [M(CO)6]− ions then bind through three CO units as tridentate chelate ligands to the superatom core, giving overall structures related to tetrahedral AX4 (4 2+) or trigonal bipyramidal AX5 molecules (3 +)., Anything is possible! [Agm{M(CO)6}n]x clusters (M=Nb, Ta; m=1, 2, 6; n=2, 3, 4, 5; x=1−, 1+, 2+) were synthesized by the reaction of [NEt4][M(CO)6] and Ag[Al(ORF)4] (RF=C(CF3)3) and the structure determined by single‐crystal X‐ray diffraction methods. The [M(CO)6] fragments serve as ligands in the obtained clusters. DFT‐based AIM calculations were performed to provide an understanding of the bonding situation and the cores of the cations were interpreted as superatoms.

The dissociation of hierarchically formed dimeric triple lithium bridged triscatecholate titanium(IV) helicates with hydrocarbyl esters as side groups is systematically investigated in DMSO. Primary alkyl, alkenyl, alkynyl as well as benzyl esters are studied in order to minimize steric effects close to the helicate core. The 1H NMR dimerization constants for the monomer–dimer equilibrium show some solvent dependent influence of the side chains on the dimer stability. In the dimer, the ability of the hydrocarbyl ester groups to aggregate minimizes their contacts with the solvent molecules. Due to this, most solvophobic alkyl groups show the highest dimerization tendency followed by alkenyls, alkynyls and finally benzyls. Furthermore, trends within the different groups of compounds can be observed. For example, the dimer is destabilized by internal double or triple bonds due to π–π repulsion. A strong indication for solvent supported London dispersion interaction between the ester side groups is found by observation of an even/odd alternation of dimerization constants within the series of n‐alkyls, n‐Ω‐alkenyls or n‐Ω‐alkynyls. This corresponds to the interaction of the parent hydrocarbons, as documented by an even/odd melting point alternation., A stabilizing effect: Clear trends can be found in the seemingly chaotic distribution of dimerization constants of hierarchically assembled helicates in DMSO, revealing the stabilizing effect of solvent‐supported London dispersion effects.

Fluoride abstraction from different types of transition metal fluoride complexes [LnMF] (M=Ti, Ni, Cu) by the Lewis acid tris(pentafluoroethyl)difluorophosphorane (C2F5)3PF2 to yield cationic transition metal complexes with the tris(pentafluoroethyl)trifluorophosphate counterion (FAP anion, [(C2F5)3PF3]−) is reported. (C2F5)3PF2 reacted with trans‐[Ni(iPr2Im)2(ArF)F] (iPr2Im=1,3‐diisopropylimidazolin‐2‐ylidene; ArF=C6F5, 1 a; 4‐CF3‐C6F4, 1 b; 4‐C6F5‐C6F4, 1 c) through fluoride transfer to form the complex salts trans‐[Ni(iPr2Im)2(solv)(ArF)]FAP (2 a‐c[solv]; solv=Et2O, CH2Cl2, THF) depending on the reaction medium. In the presence of stronger Lewis bases such as carbenes or PPh3, solvent coordination was suppressed and the complexes trans‐[Ni(iPr2Im)2(PPh3)(C6F5)]FAP (trans ‐2 a[PPh3]) and cis‐[Ni(iPr2Im)2(Dipp2Im)(C6F5)]FAP (cis ‐2 a[Dipp2Im]) (Dipp2Im=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) were isolated. Fluoride abstraction from [(Dipp2Im)CuF] (3) in CH2Cl2 or 1,2‐difluorobenzene led to the isolation of [{(Dipp2Im)Cu}2]2+2 FAP− (4). Subsequent reaction of 4 with PPh3 and different carbenes resulted in the complexes [(Dipp2Im)Cu(LB)]FAP (5 a–e, LB=Lewis base). In the presence of C6Me6, fluoride transfer afforded [(Dipp2Im)Cu(C6Me6)]FAP (5 f), which serves as a source of [(Dipp2Im)Cu)]+. Fluoride abstraction of [Cp2TiF2] (7) resulted in the formation of dinuclear [FCp2Ti(μ‐F)TiCp2F]FAP (8) (Cp=η5‐C5H5) with one terminal fluoride ligand at each titanium atom and an additional bridging fluoride ligand., A series of titanium, nickel, and copper complexes stabilized by the weakly coordinating anion (WCA) [(C2F5)3PF3]− (FAP anion) was obtained on reaction of the parent fluoride complexes with the strong Lewis acid (C2F5)3PF2. The reaction products depend on the solvent used or additional Lewis bases present during the fluoride transfer from the metal complexes to the phosphorane.

To develop new and flexible CuI containing luminescent substances, we extend our previous investigations on two metal‐centered species to four metal‐centered complexes. These complexes could be a basis for designing new organic light‐emitting diode (OLED) relevant species. Both the synthesis and in‐depth spectroscopic analysis, combined with high‐level theoretical calculations are presented on a series of tetranuclear CuI complexes with a halide containing Cu4X4 core (X=iodide, bromide or chloride) and two 2‐(diphenylphosphino)pyridine bridging ligands with a methyl group in para (4‐Me) or ortho (6‐Me) position of the pyridine ring. The structure of the electronic ground state is characterized by X‐ray diffraction, NMR, and IR spectroscopy with the support of theoretical calculations. In contrast to the para system, the complexes with ortho‐substituted bridging ligands show a remarkable and reversible temperature‐dependent dual phosphorescence. Here, we combine for the first time the luminescence thermochromism with time‐resolved FTIR spectroscopy. Thus, we receive experimental data on the structures of the two triplet states involved in the luminescence thermochromism. The transient IR spectra of the underlying triplet metal/halide‐to‐ligand charge transfer (3 m/XLCT) and cluster‐centered (3CC) states were obtained and interpreted by comparison with calculated vibrational spectra. The systematic and significant dependence of the bridging halides was analyzed., Highly luminescent! The synthesis and an in‐depth photophysical characterization of highly luminescent tetranuclear CuI complexes are presented. For these promising candidates for organic light‐emitting diodes, a pronounced luminescence thermochromism with clearly separated emission bands is observed. The corresponding excited state structures are determined by applying temperature‐dependent time‐resolved step‐scan FTIR spectroscopy in combination with DFT calculations.

A series of hafnium complexes with a reduced arene of the general formula [K(L)][Hf(Xy‐N3N)(arene)] (Xy‐N3N={(3,5‐Me2C6H3)NCH2CH2}3N3−, L=THF, 18‐crown‐6; arene=C10H8 2−, C14H10 2−) mimic the chemistry of hafnium in its formal oxidation state +II. All compounds were obtained upon reduction of the chlorido complex [HfCl(Xy‐N3N)(thf)] with two equivalents of potassium naphthalenide or anthracenide. The reducing nature and the basicity of the reduced anthracene ligand were explored in the reaction of benzonitrile and azobenzene, and by deprotonation of tert‐butylacetylene, respectively. The reduction of benzonitrile provides an initial double nitrile insertion product under kinetic control that rearranges after extrusion of one of the inserted nitriles to a hafnium imido complex as the thermodynamic product. The reduction of azobenzene resulted in a diphenylhydrazido(2−) complex. Treatment of terminal alkynes with the anthracene or diphenylhydrazido(2−) complex led to the selective protonation of the corresponding dianionic ligand., A reduced anthracene complex of hafnium(IV) reacts with two equivalents of benzonitrile to form the hafnium‐bis(iminyl) as the kinetic product that expulses one equivalent of benzonitrile to give an imido complex.

The first stable base‐free terminal uranium phosphinidene metallocene is presented; and its structure and reactivity have been studied in detail and compared to that of the corresponding thorium derivative. Salt metathesis reaction of the methyl iodide uranium metallocene Cp’’’2U(I)Me (2, Cp’’’=η 5‐1,2,4‐(Me3C)3C5H2) with Mes*PHK (Mes*=2,4,6‐(Me3C)3C6H2) in THF yields the base‐free terminal uranium phosphinidene metallocene, Cp’’’2U=PMes* (3). In addition, density functional theory (DFT) studies suggest substantial 5f orbital contributions to the bonding within the uranium phosphinidene [U]=PAr moiety, which results in a more covalent bonding between the [Cp’’’2U]2+ and [Mes*P]2− fragments than that for the related thorium derivative. This difference in bonding besides steric reasons causes different reactivity patterns for both molecules. Therefore, the uranium derivative 3 may act as a Cp’’’2U(II) synthon releasing the phosphinidene moiety (Mes*P:) when treated with alkynes or a variety of hetero‐unsaturated molecules such as imines, thiazoles, ketazines, bipy, organic azides, diazene derivatives, ketones, and carbodiimides., The first base‐free terminal uranium phosphinidene metallocene was prepared and it showed a distinctively different reactivity compared to the related thorium phosphinidenes.

Combined experimental and theoretical methods are used to gain fundamental understanding of the redox���properties of iron���vanadium oxo���alkoxide clusters as they related to modification of the heterometal number. The rational control of the electrochemical properties of polyoxovanadate���alkoxide clusters is dependent on understanding the influence of various synthetic modifications on the overall redox processes of these systems. In this work, the electronic consequences of ligand substitution at the heteroion in a heterometal���functionalized cluster was examined. The redox properties of [V5O6(OCH3)12FeCl] (1���[V5FeCl]) and [V5O6(OCH3)12Fe]X (2���[V5Fe]X; X=ClO4, OTf) were compared in order to assess the effects of changing the coordination environment around the iron center on the electrochemical properties of the cluster. Coordination of a chloride anion to iron leads to an anodic shift in redox events. Theoretical modelling of the electronic structure of these heterometal���functionalized clusters reveals that differences in the redox profiles of 1���[V5FeCl] and 2���[V5Fe]X arise from changes in the number of ligands surrounding the iron center (e.g., 6���coordinate vs. 5���coordinate). Specifically, binding of the chloride to the sixth coordination site appears to change the orbital interaction between the iron and the delocalized electronic structure of the mixed���valent polyoxovanadate core. Tuning the heterometal coordination environment can therefore be used to modulate the redox properties of the whole cluster., publishedVersion

2,4,6‐Tris(1‐diphenylphosphanyl‐1’‐ferrocenylene)‐1,3,5‐triazine (1) coordinates all three coinage metal(I) ions in a 1:1 tridentate coordination mode. The C3‐symmetric coordination in both solid state and solution is stabilised by an uncommon cation–π interaction between the triazine core and the metal cation. Intramolecular dynamic behaviour was observed by variable‐temperature NMR spectroscopy. The borane adduct of 1, 1BH3, displays four accessible oxidation states, suggesting complexes of 1 to be intriguing candidates for redox‐switchable catalysis. Complexes 1Cu, 1Ag, and 1Au display a more complicated electrochemical behaviour, and the electrochemical mechanism was studied by temperature‐resolved UV/Vis spectroelectrochemistry and chemical oxidation., One to hold them all: A redox‐active tris(ferrocenyl)triazine‐based tris‐phosphane was shown to bind all coinage metal(I) ions in the same trigonal‐planar mode, stabilised by rare triazine–metal interactions. The intriguing solution‐state chemistry of these complexes was investigated by using variable‐temperature NMR spectroscopy and spectroelectrochemistry.

The self‐assembly of platinum complexes is a well‐documented process that leads to interesting changes of the photophysical and electrochemical behavior as well as to a change in reactivity of the complexes. However, it is still not clear how many metal units must interact in order to achieve the desired properties of a large assembly. This work aimed to clarify the role of the number of interacting PtII units leading to an enhancement of the spectroscopic properties and how to address inter‐ versus intramolecular processes. Therefore, a series of neutral multinuclear PtII complexes were synthesized and characterized, and their photophysical properties at different concentration were studied. Going from the monomer to dimers, the growth of a new emission band and the enhancement of the emission properties were observed. Upon increasing the platinum units up to three, the monomeric blue emission could not be detected anymore and a concentration independent bright‐yellow/orange emission, due to the establishment of intramolecular metallophilic interactions, was observed., Three is better than two: Multinuclear PtII complexes provide valuable insight into the formation of closed shell Pt⋅⋅⋅Pt metallophilic interactions and into the corresponding MMLCT excited state. Persistent aggregation‐induced emission, which is independent from the media, is observed for the trinuclear species, demonstrating that three is better than two.

The complexes Ag(L)n[WCA] (L=P4S3, P4Se3, As4S3, and As4S4; [WCA]=[Al(ORF)4]− and [F{Al(ORF)3}2]−; RF=C(CF3)3; WCA=weakly coordinating anion) were tested for their performance as ligand‐transfer reagents to transfer the poorly soluble nortricyclane cages P4S3, P4Se3, and As4S3 as well as realgar As4S4 to different transition‐metal fragments. As4S4 and As4S3 with the poorest solubility did not yield complexes. However, the more soluble silver‐coordinated P4S3 and P4Se3 cages were transferred to the electron‐poor Fp + moiety ([CpFe(CO)2]+). Thus, reaction of the silver salt in the presence of the ligand with Fp−Br yielded [Fp−P4S3][Al(ORF)4] (1 a), [Fp−P4S3][F(Al(ORF)3)2] (1 b), and [Fp−P4Se3][Al(ORF)4] (2). Reactions with P4S3 also yielded [FpPPh3−P4S3][Al(ORF)4] (3), a complex with the more electron‐rich monophosphine‐substituted Fp + analogue [FpPPh3]+ ([CpFe(PPh3)(CO)]+). All complex salts were characterized by single‐crystal XRD, NMR, Raman, and IR spectroscopy. Interestingly, they show characteristic blueshifts of the vibrational modes of the cage, as well as structural contractions of the cages upon coordination to the Fp/FpPPh3 moieties, which oppose the typically observed cage expansions that lead to redshifts in the spectra. Structure, bonding, and thermodynamics were investigated by DFT calculations, which support the observed cage contractions. Its reason is assigned to σ and π donation from the slightly P−P and P−E antibonding P4E3‐cage HOMO (e symmetry) to the metal acceptor fragment.