Advances in lanthanide cyclononatetraenyl chemistry.

Cyclononatetraenyl (Cnt) is a nine-membered monoanionic aromatic ligand. Despite its early discovery in 1963, it has been rarely utilised in coordination chemistry, which is mainly due to its large diameter and easy skeletal rearrangement. Only in 2017, the first lanthanide Cnt complex was synthesised, marking the beginning of a new era in organolanthanide chemistry.

Tin-Chelated Trisphosphineoxide Scorpionate Rare-Earth Porphyrinate Complexes: Synthesis and Photophysical Properties.

A series of seven-coordinated monoporphyrinate rare-earth(III) complexes featuring a novel tripodal tin-chelated trisphosphineoxide scorpionate ligand with the general formula [(TPP)Ln(PPhO)Sn] (Ln = Y, La, Dy, Er, Ho, Yb; TPP = 5,10,15,20-tetraphenylporphyrinate) were synthesized by reactions of the potassium tripodal scorpionate ligand [Sn(PPhO)K] with porphyrinate rare-earth metal chlorides [(TPP)LnCl(dme)] (Ln = Y, Dy, Er, Ho, Yb) or porphyrinate lanthanum borohydride [(TPP)LaBH(thf)]. The complexes were characterized by single-crystal X-ray diffraction, NMR spectroscopy, and ion mobility mass spectrometry. All complexes emit weak red TPP-based fluorescence, accompanied by near-infrared emission of Er, Ho (rather weak), and Yb (relatively intense with a quantum yield of 1% in dichloromethane solution) of the corresponding complexes.

Unconventional Insertions of Internal Alkynes into a Mixed-Valent Silaiminyl-Silylene.

The reactivity of a mixed-valent silaiminyl-silylene [LSi-Si(NDipp)L] (L = PhC(NBu), Dipp = 2,6-Pr-CH) toward various substituted internal alkynes was investigated. In contrast to previous reports that primarily yield [Si(μ-C)Si]-modified rings via 1,2-addition of two silylenes in the center of the molecule, our study reveals a novel reaction pathway. The introduction of [R-C≡C-R] (R = Ph or SiMe, R = Ph or C≡CSiMe) gave unconventional insertion into one of the amidinate ligands, followed by migration of the {NBu} group to bridge two Si atoms.

Visible light photoflow synthesis of a Cu(ii) single-chain polymer nanoparticle catalyst.

We herein pioneer the visible light ( = 410 nm) mediated flow synthesis of catalytically active single-chain nanoparticles (SCNPs). Our design approach is based on a copolymer of poly(ethylene glycol) methyl ether methacrylate and a photocleavable 2-((((2-nitrobenzyl)oxy)carbonyl)amino)ethyl methacrylate monomer which can liberate amine groups upon visible light irradiation, allowing for single-chain collapse the complexation of Cu(ii) ions. We initially demonstrate the successful applicability of our design approach for the batch photochemical synthesis of Cu(ii) SCNPs and transfer the concept to photoflow conditions, enabling, for the first time, the continuous production of functional SCNPs.

Dye Induced Luminescence Properties of Gold(I) Complexes with near Unity Quantum Efficiency.

To study the effect of a dye on the photoluminescence (PL) properties of metal complexes, a series of gold(I) complexes were synthesized, containing a 7-amino-4-methylcoumarin luminophore. The complexes are comprised of a coumarin moiety featuring different ancillary ligands, specifically N-heterocyclic carbenes, triphenylphosphine, and diphenyl-2-pyridylphosphine. The synthesized gold(I) complexes are luminescent both in solution and the solid state at room temperature and 77 K.

6-(6-Methyl-1,2,4,5-Tetrazine-3-yl)-2,2'-Bipyridine: A N-Donor Ligand for the Separation of Lanthanides(III) and Actinides(III).

Here, we report the synthesis of the 6-(6-methyl-1,2,4,5-tetrazine-3-yl)-2,2'-bipyridine (MTB) ligand that has been developed for lanthanide/actinide separation. A multimethod study of the complexation of MTB with trivalent actinide and lanthanide ions is presented. Single-crystal X-ray diffraction measurements reveal the formation of [Ce(MTB)(NO)], [Pr(MTB)(NO)HO], and [Ln(MTB)(NO)MeCN] (Ln = Nd, Sm, Eu, Gd).

De- and Rearomatisation of Pyridine in Silylene Chemistry.

Traditional methods relying on metal-ligand cooperation for activating pyridine bonds in de- and rearomatisation are being challenged by the abundant metal-free element species as alternatives. Here, we investigated the de/re-aromatisation of pyridine facilitated by pyridylamino-functionalised silylene reactions with ketones and ketene. The reactivity outcome is highly dependent on the substituents on the ketones.

Phospholyl and Arsolyl Triple-Decker Sandwich Complexes of Europium(II) and Strontium(II).

To study the influence of heteroatoms on the photophysical properties of divalent Eu and Sr complexes, the synthesis of the phospholyl and arsolyl compounds [{(Dtp)(thf)M}{μ-η:η-CH}] (M = Eu and Sr; Dtp = 3,4-dimethyl-2,5-bis(-butyl)phospholyl) and [{(Dtas)(thf)M}{μ-η:η-CH}] (M = Eu and Sr; Dtas = 3,4-dimethyl-2,5-bis(-butyl)arsolyl) is reported. Organometallic compounds of divalent europium with P and As heterocyclic ligands have not been described previously. They were prepared by salt elimination reactions from potassium phospholyl or arsolyl, KCH, and EuI(thf) or SrI.

Reactivities of phosphaalkynes towards diverse bis-silylenes.

Bis-silylenes do not only act as strong chelating σ-donor ligands, but also exhibit cooperative behaviour in the activation of small molecules. Three different P-Si containing molecules were prepared from the reaction between BuCP and different bis-silylenes, which are bridged by ferrocenediyl, diaminobenzene, or -carborane.

Luminescent Tetranuclear Copper(I) and Gold(I) Heterobimetallic Complexes: A Phosphine Acetylide Amidinate Orthogonal Ligand Framework for Selective Complexation.

The synthesis of phosphine acetylide amidinate stabilized copper(I) and gold(I) heterobimetallic complexes was achieved by reacting ligand [{PhPC≡CC(NDipp)}Li(thf)] (Dipp=2,6-N,N'-diisopropylphenyl) with CuCl and Au(tht))Cl, yielding the eight membered ring [{PhPC≡CC(NDipp)}Cu] and the twelve membered ring [{PhPC≡CC(NDipp)}Au]. {PhPC≡CC(NDipp)}Cu] features a Cu unit, which is bridged by two amidinate ligands, served as a metalloligand to synthesize the heterobimetallic Cu/Au complexes [{(AuX)PhPC≡CC(NDipp)}Cu] (X=Cl, CF). In these reactions, the central ring structure is retained.

Cycloheptatrienyl-Bridged Triple-Decker Complexes.

The first structurally characterized organometallic multidecker sandwich complexes featuring a cycloheptatrienyl ring (Cht, CH) in the coordination sphere are presented. The synthesis of inverse sandwich complexes of the rare earth elements Y and Er with a bridging cycloheptatrienyl ligand of the type [(thf)(BH)Ln(μ-η:η-Cht)Ln(BH)(thf)] is described first. The subsequent introduction of the Cot ligand (Cot = 1,4-(PrSi)CH) into the coordination sphere of the rare earth cations resulted in the isolation of unprecedented triple-decker compounds with the formula [(thf)K{(η-Cot)Ln}(μ-η:η-Cht)], bearing a seven-membered aromatic carbon ring as a middle deck.

Förster resonance energy transfer within single chain nanoparticles.

Single chain nanoparticles (SCNPs) are a highly versatile polymer architecture consisting of single polymer chains that are intramolecularly crosslinked. Currently, SCNPs are discussed as powerful macromolecular architectures for catalysis, delivery and sensors. Herein, we introduce a methodology based on Förster Resonance Energy Transfer (FRET) to evidence the folding of single polymer chains into SCNPs fluorescence readout.

[GeRu(CO)HI]: A Germanium-Centered Ruthenium Carbonyl Cluster with Aromatic Ring Current.

The carbonyl cluster compound [GeRu(CO)HI] is unique in regard to its structure and bonding with a GeRu cluster core, a planar GeRuHI unit, extensive multi-center bonding, and an aromatic ring current similar to benzene (9-10 nA T). The open-shell cluster core is a Ge-centered five-membered Ru(Ru) ring with CO ligands and an additional H and I atom, each bridging two Ru atoms on opposite sides of the cluster core. The compound is prepared at 130 °C in a weakly-coordinating ionic liquid.

Unique Double and Triple Decker Arrangements of Rare-Earth 9,10-Diborataanthracene Complexes Featuring Single-Molecule Magnet Characteristics.

Herein, we present the first report on the synthesis of rare-earth complexes featuring a 9,10-diborataanthracene ligand. This 14-π-electron ligand is highly reductive and was previously used in small-molecule activation. Salt elimination reactions between dipotassium 9,10-diethyl-9,10-diborataanthracene [K(DEDBA)] and [Ln(η-Cot)(BH)(thf)] (Cot=1,4-(PrSi)CH) in a 1 : 1 ratio yielded heteroleptic sandwich complexes [K(η-Cot)Ln(η-DEDBA)] (Ln=Y, Dy, Er).

It's not just the size that matters: crystal engineering of lanthanide-based coordination polymers.

Synthesis and characterization of Lewis base free coordination polymers of selected lanthanides are presented. For this purpose, the substituted Cot ligand (Cot = 1,4-bis-triisopropylsilyl-cyclo-octatetraendiide) was used to synthesize homoleptic, anionic multidecker compounds of the type [K{Ln(ɳ-Cot)}]. Depending on the solvent used for crystallization and the ionic radii of the lanthanide cations, three different categories of one-dimensional heterobimetallic coordination polymers were obtained in the solid state.

Synthesis, Structural Characterization, and Magnetic Properties of Lanthanide Arsolyl Sandwich Complexes.

A series of trivalent lanthanide sandwich complexes [(η-CRAs)Ln(η-CH)] using three different arsolyl ligands are reported. The complexes were obtained via salt elimination reactions between potassium arsolyl salts and lanthanide precursors [LnI(COT)(THF)] (Ln = Sm, Dy, Er; COT = η-CH). The resulting compounds exhibit classical sandwich complex structures with one notable exception.

Bi- and tridentate coordination behaviour of a novel bis(phosphinimino)methanide ligand.

Herein, we report the synthesis of a novel ferrocenyl-functionalized bis(phosphinimino)methane ligand (CH (PPh NFc) ). Deprotonation of CH (PPh NFc) with KN(SiMe ) gave the dimeric species [K{CH(PPh NFc) }] , which was further reacted with ECl (E=Ge, Sn) to yield the tetrylene compounds [{CH(PPh NFc) }ECl]. The ligand and the resulting tetrylenes were examined for their electrochemical properties with the aid of cyclic voltammetry.

Role of Bis(phosphinimino)methanides as Universal Ligands in the Coordination Sphere of Metals across the Periodic Table.

The coordination chemistry of bis(phosphinimino)methanide ligands is widespread and accompanies a large number of metal ions in the periodic table ranging from lithium to neptunium. This unique class of ligand systems show copious coordination chemistry with the main-group, transition, rare-earth, and actinide metals and are considered to be among the most attractive ligand systems to researchers. The bis(phosphinimino)methanide metal complexes offer an extensive range of applications in various fields and have been demonstrated as one of the universal ligand systems to stabilize the metal ions in not only their usual but also their unusual oxidation states.

Reactivity of [Cp*Fe(η -As )] towards Carbenes, Silylenes and Germylenes.

The reaction behavior of [Cp*Fe(η -As )] (I) (Cp*=C Me ) towards carbenes and their heavier analogs was investigated. The reaction of I with NHCs (NHCs=N-heterocyclic carbenes) results in the first substitution products of polyarsenic ligand complexes by NHCs [Cp*Fe(η -As NHC)] (1 a: NHC=IMe=1,3,4,5-tetramethylimidazolin-2-ylidene, 1 b: NHC=IMes=1,3-bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene). In contrast, the reaction of I with CAAC ( CAAC=2,6-diisopropylphenyl)-4,4-diethyl-2,2-dimethyl-pyrrolidin-5-ylidene) leads to a fragmentation and the formation of an unprecedented As -sawhorse-type compound [As (As CAAC) ] (2).

Single Chain Nanoparticles in Catalysis.

Over the last six decades folded polymer chains-so-called Single Chain Nanoparticles (SCNPs)-have evolved from the mere concept of intramolecularly crosslinked polymer chains to tailored nanoreactors, underpinned by a plethora of techniques and chemistries to tailor and analyze their morphology and function. These monomolecular polymer entities hold critical promise in a wide range of applications. Herein, we highlight the exciting progress that has been made in the field of catalytically active SCNPs in recent years.

Heteroleptic copper(I) complexes with coumarin-substituted aminodiphosphine and diimine ligands: synthesis and photophysical studies.

The synthesis of heteroleptic Cu(I) complexes with coumarin-functionalized aminodiphosphine and diimine ligands is described. The complexes show yellow to deep-red phosphorescence in the solid state at ambient temperature with quantum yields up to 21%. The emission color of the complexes can be tuned by systematic modifications in the ligand system.

Synthesis and properties of cyclic sandwich compounds.

Cyclic nanometre-scale sandwich complexes assembled from individual building blocks were synthesized. Sandwich complexes, in which a metal ion is π-coordinated by two planar aromatic organic rings belong to the foundations of organometallic chemistry. They have been successfully used in a wide variety of applications ranging from catalysis, synthesis and electrochemistry to nanotechnology, materials science and medicine.

Diverse Reactions of Formazanate/Formazan with Tetrylenes: Reduction, C-H Bond Activation, Substitution and Addition.

The reactivity of the formazanate potassium salt [L K(thf)] (L PhNNC(4- BuPh)NNPh) with the group 14 chlorotetrylenes [{PhC( BuN) }ECl] (E=Si, Ge, Sn) was investigated. Three corresponding compounds with unique configurations were formed, demonstrating the diverse reactivity of the system. In addition to the anticipated salt metathesis reactions of the potassium salt with the chlorine function of tetrylenes, unexpected reduction/insertion steps into the N=N bond of the formazanate (Si, Ge) and subsequent C-H activation (Ge) were also observed.

Visible-Light-Induced Control over Reversible Single-Chain Nanoparticle Folding.

We introduce a class of single-chain nanoparticles (SCNPs) that respond to visible light (λ =415 nm) with complete unfolding from their compact structure into linear chain analogues. The initial folding is achieved by a simple esterification reaction of the polymer backbone constituted of acrylic acid and polyethylene glycol carrying monomer units, introducing bimane moieties, which allow for the photochemical unfolding, reversing the ester-bond formation. The compaction and the light driven unfolding proceed cleanly and are readily followed by size exclusion chromatography (SEC) and diffusion ordered NMR spectroscopy (DOSY), monitoring the change in the hydrodynamic radius (R ).

Mono-cyclononatetraenyl lanthanide complexes.

The synthesis of the first half-sandwich complexes based on the cyclononatetraenyl (Cnt = CH) ligand ([Ln(-Cnt)(-BH)(thf)] (Ln = La, Ce)) is reported. The title compounds were obtained from the reaction of [Ln(BH)(thf)] and [K(Cnt)]. Further solvation of [Ln(-Cnt)(-BH)(thf)] with tetrahydrofuran (THF) resulted in a reversible decoordination of the Cnt ring and the formation of the ionic species [Ln(-BH)(thf)][Cnt].