Crystal structure of potassium tri-ethyl-hydridoborate ('superhydride').

In the title compound, formally K+·C6H16B-, the contact sphere of potassium consists of eleven hydrogen atoms from three different anions, assuming an arbitrary cut-off of 3 Å. The shortest inter-action, 2.53 (2) Å, involves the hydridic hydrogen H01, which fulfils a bridging function in the formation of chains of KHBEt3 units parallel to the a axis [K1-H01i 2.71 (2) Å, K1-H01-K1ii 126.7 (9)°, operators x∓1/2, -y + , -z + 1].

Enantiomerically Pure Constrained Geometry Complexes of the Rare-Earth Metals Featuring a Dianionic N-Donor Functionalised Pentadienyl Ligand: Synthesis and Characterisation.

We report the preparation of enantiomerically pure constrained geometry complexes (cgc) of the rare-earth metals bearing a pentadienyl moiety (pdl) derived from the natural product (1R)-(-)-myrtenal. The potassium salt 1, [Kpdl*], was treated with ClSiMe2 NHtBu, and the resulting pentadiene 2 was deprotonated with the Schlosser-type base KOtPen/nBuLi (tPen=CMe2 (CH2 Me)) to yield the dipotassium salt [K2 (pdl*SiMe2 NtBu)] (3). However, 3 rearranges in THF solution to its isomer 3' by a 1,3-H shift, which elongates the bridge between the pdl and SiMe2 NtBu moieties by one CH2 unit. This is crucial for the successful formation of various monomeric C1 - or dimeric C2 -symmetric rare-earth cgc complexes with additional halide, tetraborohydride, amido and alkyl functionalities. All compounds have been extensively characterised by solid-state X-ray diffraction analysis, solution NMR spectroscopy and elemental analyses.

Synthesis and molecular structure of enantiomerically pure pentadienyl complexes of the rare-earth metals.

The enantiomerically pure pentadienyl (Pdl*) ligand derived from the natural product (1R)-(-)-myrtenal forms with MCl3 (M = La, Ce, Pr, and Nd) the corresponding homoleptic [(η5-U-Pdl*)3M compounds (1-M). These complexes were fully characterised by 1H NMR spectroscopy, elemental analyses and X-ray diffraction. They exhibit in solution and solid state idealized C3 symmetry, and their molecular structures also reveal that the Pdl* ligand adopts a U-conformation and coordinates exclusively with its less sterically encumbered face to the rare-earth metal atom. For the paramagnetic representatives an assignment of the 1H NMR resonances based on a simple dipolar model gave satisfactory results.

Preparation of enantiomerically pure open calcocene and strontocene complexes and their application in ring opening polymerizations of rac-lactide.

The synthesis of C2 symmetric enantiomerically pure open Ca and Sr metallocenes, [(η(5)-pdl*)2Ca(thf)] (1) and [(η(5)-pdl*)2Sr(thf)2] (2) (pdl* = dimethylnopadienyl) is described and these complexes were fully characterized. The solid state structures confirm that the pdl* ligands coordinate exclusively with the less sterically demanding site to the Ca and Sr atoms. These complexes are active catalysts for the controlled ring opening polymerization (ROP) of rac-lactide to give heterotactically enriched polylactides (PL) with narrow polydispersities (PDI = 1.29-1.31) and without adding further activators.

Pentadienyl chemistry of the heavy alkaline-earth metals revisited.

Open-metallocenes of the heavy alkaline-earth metals [(η(5)-Pdl')2M(thf)n] (M = Ca (1), Sr (2), n = 1; M = Ba (3), n = 2; Pdl' = 2,4-tBu2C5H5) are readily prepared by salt-metathesis between MI2 and KPdl' and characterized by NMR spectroscopy and X-ray diffraction studies.