Copper(I) Complexes with Thioether‐Functionalized Silylamido Ligands

Abstract The thioether‐functionalized aminosilanes Me 2 Si(NH‐C 6 H 4 ‐2‐SR) 2 (R=Ph, Me) were lithiated with n ‐BuLi and subsequently allowed to react with CuCl in the presence of PMe 3 . In the case of Me 2 Si(NH‐C 6 H 4 ‐2‐SPh) 2 , the dinuclear complex [Cu 2 {Me 2 Si(NC 6 H 4 ‐2‐SPh) 2 }(PMe 3 ) 2 ] was isolated. In [Cu 2 {Me 2 Si(NC 6 H 4 ‐2‐SPh) 2 }(PMe 3 ) 2 ] the copper atoms adopt a distorted trigonal‐planar coordination (Cu−N: 191.2(2) pm, Cu−P: 216.3(1) pm, Cu−S: 244.4(1) pm). The reaction of Li 2 Me 2 Si(N‐C 6 H 4 ‐2‐SMe) 2 with CuCl in the presence of PMe 3 led to rearrangement processes from which the ionic cluster compound [Cu(PMe 3 ) 4 ][Cu 5 {Me 2 Si(N‐C 6 H 4 ‐2‐S)(N‐C 6 H 4 ‐2‐S−Me)} 2 (PMe 3 ) 2 ] was isolated in low yield.imag

Noble Metal Complexes of a Bis-Caffeine Containing NHC Ligand

N -Heterocyclic carbenes (NHCs) have seen more and more use over the years. The go-to systems that are usually considered are derivatives of benzimidazole or imidazole. Caffeine possesses an imidazole unit and was already utilized as a carbene-type ligand; however, its use within a tridentate bis-NHC system has—to the best of our knowledge—not been reported so far. The synthesis of the ligand is straightforward and metal complexes are readily available via silver-salt metathesis. A platinum(II) and a palladium(II) complex were isolated and a crystal structure of the former was examined. For the Pt(II) complex, luminescence is observed in solid state as well as in solution

Alkaline‐earth metal dimesitylphosphinites and their ether adducts – A structural study in solution and in the crystalline state

Abstract Alkaline‐earth metalation of dimesitylphosphane oxide Mes 2 P(O)H ( 1 ) in ethereal solvents with dialkylmagnesium and alkylmagnesium bromide as well as the homoleptic bis(trimethylsilyl)amides of calcium, strontium, and barium yields [(L)MgR(μ‐OPMes 2 )] 2 (L/R=thf/Et ( 2‐Et ), Et 2 O/Br ( 2‐Br )), [(thf) 3 Ca(hmds)(OPMes 2 )] ( 3‐hmds ), [(thf) 3 Mg(OPMes 2 ) 2 ] ( 2‐thf ) and [(thf) 4 Ae(OPMes 2 ) 2 ] (Ae=Ca ( 3‐thf ), Sr ( 4‐thf ), and Ba ( 5‐thf )), depending on the applied stoichiometry. Exchange of thf ligands in 3‐thf by oligodentate ethers allows isolation of [(thf) 2 (dme)Ca(OPMes 2 ) 2 ] ( 3‐dme ), [(thf) 2 (diglyme)Ca(OPMes 2 ) 2 ] ( 3‐diglyme ) and [(thf)(triglyme)Ca(OPMes 2 ) 2 ] ( 3‐triglyme ). Contrary to this finding, oligodentate amines are unable to substitute ligated thf ligands in 3‐thf . In ethereal solutions, the heteroleptic complexes 2‐Et , 2‐Br and 3‐hmds show Schlenk‐type equilibria, interconverting these compounds into their homoleptic counterparts.imag

Organocatalyzed Ring‐Opening Polymerization of ( S )‐3‐Benzylmorpholine‐2,5‐Dione

Abstract A 3‐benzylmorpholine‐2,5‐dione monomer is synthesized from the natural amino acid l ‐phenylalanine and characterized by means of nuclear magnetic resonance and infrared spectroscopy, electrospray ionization mass spectrometry, and elemental analysis. Subsequent to preliminary polymerization studies, a well‐defined poly(ester amide) homopolymer is synthesized via ring‐opening polymerization using a binary catalyst system comprising 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) and a 1‐(3,5‐bis(trifluoromethyl)phenyl)‐3‐cyclohexylthiourea (TU) cocatalyst with a feed ratio of M/I/DBU/TU = 100/1/1/10. Kinetic studies reveal high controllability of the dispersities and molar masses up to conversions of almost 80%. Analysis by mass spectrometry hints toward excellent end‐group fidelity at these conditions. In consequence, utilization of hydroxyl‐functionalized poly(ethylene glycol) and poly(2‐ethyl‐2‐oxazoline) as macroinitiators results in amphiphilic block copolymers. Bulk miscibility of the building blocks is indicated by differential scanning calorimetry investigations. As more and more promising new drugs are based on hydrophobic molecules featuring aromatic moieties, the novel polyesteramides seem highly promising materials to be used as potential drug delivery vehicles

Alkali metal dithiocarbamato carboxylates (DTCCs) – synthesis, properties, and crystal structures

A series of alkali metal salts of dithiocarbamate‐substituted carboxylate (DTCC) anions were prepared by reaction of the parent amino acids with carbon disulfide and an alkali metal hydroxide. The target compounds, which were isolated in anhydrous form or as hydrates, were extensively characterized by elemental analyses, IR and NMR spectroscopy, thermal analyses, cyclic voltammetry, and single‐crystal X‐ray diffraction. The isolated compounds are more or less hygroscopic and display a varying dehydratization and decomposition behavior upon heating. The assumed degradation of the DTCC scaffold was found to depend on the substitution pattern as well as on the alkali metal counterion, and covers a range between 200 and 340 °C. In aqueous solution, the DTCC anions show irreversible electrochemical oxidations, where the corresponding redox potentials are governed by the substitution pattern of the nitrogen atom. Single‐crystal structural analyses of sodium and potassium derivatives revealed that these compounds exist as two‐ or three‐dimensional coordination polymers in the solid state, with the alkali‐metal ions adopting typical irregular coordination environments with coordination numbers of six or higher

In Situ Grignard Metalation Method for the Synthesis of Hauser Bases

The in situ Grignard Metalation Method ( i GMM) is a straightforward one‐pot procedure to quickly produce multigram amounts of Hauser bases R 2 N‐MgBr which are valuable and vastly used metalation reagents and novel electrolytes for magnesium batteries. During addition of bromoethane to a suspension of Mg metal and secondary amine at room temperature in an ethereal solvent, a smooth reaction yields R 2 N‐MgBr under evolution of ethane within a few hours. A Schlenk equilibrium is operative, interconverting the Hauser bases into their solvated homoleptic congeners Mg(NR 2 ) 2 and MgBr 2 depending on the solvent. Scope and preconditions are studied, and side reactions limiting the yield have been investigated. DOSY NMR experiments and X‐ray crystal structures of characteristic examples clarify aggregation in solution and the solid state

Forty Years after the Discovery of Its Nucleolytic Activity: [Cu(phen)(2)](2+) Shows Unattended DNA Cleavage Activity upon Fluorination

[Cu(phen)(2)](2+) (phen=1,10-phenanthroline) is the first and still one of the most efficient artificial nucleases. In general, when the phen ligand is modified, the nucleolytic activity of its Cu-II complex is significantly reduced. This is most likely due to higher steric bulk of such ligands and thus lower affinity to DNA. Cu-II complexes with phen ligands having fluorinated substituents (F, CF3, SF5, SCF3) surprisingly showed excellent DNA cleavage activity-in contrast to the unsubstituted [Cu(phen)(2)](2+)-in the absence of the otherwise required classical, bioabundant external reducing agents like thiols or ascorbate. This nucleolytic activity correlates well with the half-wave potentials E-1/2 of the complexes. Cancer cell studies show cytotoxic effects of all complexes with fluorinated ligands in the low mu m range, whereas they were less toxic towards healthy cells (fibroblasts)

A Planar Five‐Membered Aromatic Ring Stabilized by Only Two π‐Electrons

Many chemicals known today are partially or fully aromatic, since a ring framework experiences additional stabilization through the delocalization of π‐electrons. While aromatic rings with equal numbers of π‐electrons and ring atoms such as benzene are particularly stable, those with the minimally required two π‐electrons are very rare and yet remain limited to three‐ and four‐membered rings if not stabilized in the coordination sphere of heavy metals. Here we report the facile synthesis of a dipotassium cyclopentagallene, a unique example of a five‐membered aromatic ring stabilized by only two π‐electrons. Single‐crystal X‐ray diffraction revealed a planar Ga5 ring with almost equal gallium–gallium bond lengths, which together with computational and spectroscopic data confirm its aromatic character. Our results prove that aromatic stabilization goes far beyond what has previously been assumed as minimum π‐electron count in a five‐atom ring fragment.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Verband der Chemischen Industrie http://dx.doi.org/10.13039/100007215Peer Reviewe

Synthesis and Complexation Study of New Aminoalkynyl−amidinate Ligands

Abstract The current library of amidinate ligands has been extended by the synthesis of two novel dimethylamino‐substituted alkynylamidinate anions of the composition [Me 2 N−CH 2 −C≡C−C(NR) 2 ] − (R = i Pr, cyclohexyl (Cy)). The unsolvated lithium derivatives Li[Me 2 N−CH 2 −C≡C−C(NR) 2 ] ( 1 : R = i Pr, 2 : R = Cy) were obtained in good yields by treatment of in situ‐ prepared Me 2 N−CH 2 −C≡C−Li with the respective carbodiimides, R−N=C=N−R. Recrystallization of 1 and 2 from THF afforded the crystalline THF adducts Li[Me 2 N−CH 2 −C≡C−C(NR) 2 ] ⋅  n THF ( 1 a : R = i Pr, n =1; 2 a : R = Cy, n =1.5). Precursor 2 was subsequently used to study initial complexation reactions with selected di‐ and trivalent transition metals. The dark red homoleptic vanadium(III) tris(alkynylamidinate) complex V[Me 2 N−CH 2 −C≡C−C(NCy) 2 ] 3 ( 3 ) was prepared by reaction of VCl 3 (THF) 3 with 3 equiv. of 2 (75 % yield). A salt‐metathesis reaction of 2 with anhydrous FeCl 2 in a molar ratio of 2 : 1 afforded the dinuclear homoleptic iron(II) alkynylamidinate complex Fe 2 [Me 2 N−CH 2 −C≡C−C(NCy) 2 ] 4 ( 4 ) in 69 % isolated yield. Similarly, treatment of Mo 2 (OAc) 4 with 3 or 4 equiv. of 2 provided the dinuclear, heteroleptic molybdenum(II) amidinate complex Mo 2 (OAc)[Me 2 N−CH 2 −C≡C−C(NCy) 2 ] 3 ( 5 ; yellow crystals, 50 % isolated yield). The cyclohexyl‐substituted title compounds 2 a , 4 , and 5 were structurally characterized through single‐crystal X‐ray diffraction studies.imag

5-epi-Incensole: synthesis, X-ray crystal structure and absolute configuration by means of ECD and VCD studies in solution and solid state

Incensole 1 and its acetate 2, found in incense, demonstrate interesting biological activities. Incensole acetate 2 was prepared on a large scale by employing the Paul and Jauch protocol from the crude extracts of Boswellia papyrifera Hochst. 5-epi-Incensole 3, obtained as colorless crystals, was prepared from incensole acetate via three steps; deacetylation, oxidation and reduction. The structure of 5-epi-incensole 3 was elucidated by means of spectroscopic data analysis, and the absolute configuration was established by single crystal X-ray analysis in combination with electronic and vibrational circular dichroism. In particular, the applicability of the solid-state ECD/TDDFT protocol to a compound with only two non-conjugated alkene chromophores was verified