Markus Teichert

Crown Ethers, Double‐Decker, and Sandwich Complexes: Cation‐Mediated Formation of Metallatopomer Coronates

Metallacoronates or metallacrown ether sandwich complexes? As with organocrown ethers, the size of the encapsulated cation (Na+, Ca2+, or K+) determines which product is formed—a crown ether, a dimeric crown ether, or a sandwich complex (see below). H2L = ketipinate.

Enantiomerisation of tetrahedral homochiral [M4L6] clusters: Synchronised four Bailar twists and six atropenantiomerisation processes monitored by temperature-dependent dynamic 1H NMR spectroscopy

Temperature-dependent 1H NMR studies prove homochiral, racemic [([symbol: see text])/([symbol: see text])]-((NH4)4[symbol: see text] [Mg4(L1)6]) (1) to be kinetically stable on the NMR timescale. Due to steric reasons, rotation around the central C-C single bond in (L1)2- is blocked, which prevents 1 from enantiomerisation. Most interestingly, however, the 1H NMR spectrum of racemic 2a reveals dynamic temperature dependence. This phenomenon can be explained by simultaneous Bailar twists at the four octahedrally coordinated magnesium centres, synchronised with the sterically unhindered atropenantiomerisation processes around the C-C single bonds of the six ligands (L2)2-, leading to the unprecedented enantiomerisation ([symbol: see text])-2a [symbol: see text] ([symbol: see text])-2a. The profound nondissociative rearrangement occurs without the formation of diastereoisomers. Supplementary support for the interpretation of the temperature-dependent dynamic 1H NMR spectra of 2a is presented by additional studies of [([symbol: see text])/([symbol: see text])]-((EtNH3)4 [symbol: see text] [Mg4(L2)6]) (2b). In 2a and 2b, the ether methylene protons exhibit identical temperature dependence. However, with addition, the methylene protons of the ethyl ammonium groups of 2b display similar temperature dependence as the ligand ether methylene protons.

Self‐Assembly of {2}‐Metallacryptands and {2}‐Metallacryptates

Reaction of H2L (1) with potassium or strontium hydride, or lanthanum(III) chloride, followed by iron(III) chloride, yielded the {2}-ironcryptates 2a–c. The mono-, di-, and trivalent guest cations are endohedrally encapsulated. In contrast, the dinuclear trispyridinium ironcryptand 2d was generated from the reaction of H2L (1) with only iron(III) chloride. The potassium metallacryptate 2a′ was formed from the triple-helicate 2d by addition of potassium carbonate. The new compounds 2b, 2c, and 2d were unequivocally characterised by X-ray diffraction analyses.

Metal-Directed Formation of Tetra-, Hexa-, Octa-, and Nonanuclear Complexes of Magnesium, Calcium, Manganese, Copper, and Cadmium

Efficacious metal control of self-assembly of dialkylketipinate dianions leads to completely different supramolecular assemblies. The structures of grid 1, double-decker 2, triple-decker 3, and metalla-spherand 4 were characterized by X-ray crystallographic analyses or by NMR spectroscopy.

Octanuclear Bis(triple‐helical) Metal(II) Complexes

The reaction of H2L1 and H2L2 with divalent metal ions leads to octanuclear bis(triple-helical) metal(II) complexes of the general composition [Zn8O2L26] (3) and [M8O2L16] (4: M = Cd2+; 5: M = Mn2+). NMR studies of the diamagnetic cadmium complex 4c show six equivalent ligands. Unambiguous characterisation of 5b was achieved by X-ray crystallographic analysis.

Kronenether, Doppeldecker- und Sandwichkomplexe: kationengesteuerter Aufbau von metallatopomeren Coronaten

Metallacoronat oder Metallakronenether-Sandwichkomplex? Wie bei den Kronenethern bestimmt auch beim Metallakronenethersystem [Cu3L3] die Grose des eingeschlossenen Kations (Na+, Ca2+ oder K+), welches Produkt entsteht – ein Kronenether, ein dimerer Kronenether oder ein Sandwichkomplex (siehe unten). H2L = Ketipinsaureester.

Two dinuclear rhodium complexes with a non-A-frame and a distorted A-frame skeleton and two iPr2PCH2PiPr2 molecules as bridging ligands

Abstract The π -allyl(carbonyl)rhodium(I) complex [Rh( η 3 -C 3 H 5 )(CO)( κ 2 - i Pr 2 PCH 2 P i Pr 2 )] ( 2 ), which was obtained from [Rh( η 3 -C 3 H 5 )( κ 2 - i Pr 2 PCH 2 P i Pr 2 )] ( 1 ) and CO, reacted with H 2 at room temperature to give the dinuclear hydrido compound [{Rh(CO)( μ -H)( μ - i Pr 2 PCH 2 P i Pr 2 )} 2 ] ( 3 ) in nearly quantitative yield. The X-ray crystal structure analysis of 3 confirmed a distorted square-planar coordination sphere around both metal centers with one hydride and the CO group as well as the two phosphorus atoms of the bis(phosphino)methane ligands in trans disposition. The reaction of 1 with excess methylformiate led to the formation of the μ -carbonato complex [{Rh(CO)( μ - i Pr 2 PCH 2 PPr 2 )} 2 ( μ -O 2 CO)] ( 4 ) with an A-frame type skeleton. The carbonate ligand is possibly formed from HCO 2 Me by initial C–H cleavage and subsequent hydrolysis of the resulting CO 2 Me unit.