Controlling Coordination Geometries: Ru-Carbene Complexes with Tetra-NHC Ligands.

The synthesis of the first ruthenium(II) complexes bearing open-chain tetra-N-heterocyclic carbene (tetra-NHC) ligands via in situ transmetalation is described. The ruthenium complexes show differing coordination geometries depending on the length of the alkyl linker. Replacement of the two cis acetonitrile ligands in the methylene bridged ruthenium complex by nucleophiles also influences the coordination geometry. Both structural motifs were evaluated in transfer hydrogenation (TH) of acetophenone, and in particular the sawhorse-type coordinated system exhibits remarkable activity with turnover frequencies of more than 100 000 h(-1).

Application of open chain tetraimidazolium salts as precursors for the synthesis of silver tetra(NHC) complexes.

The synthesis of 3-((1H-imidazol-1-yl)methyl)-1-methyl-1H-imidazol-3-ium iodide 1 for the synthesis of multidentate tetra-N-heterocyclic carbene (NHC) structures is described. Two acyclic open chain tetra(NHC) precursors are synthesized together with their corresponding silver complexes. On the basis of nuclear magnetic resonance (NMR) spectroscopy and single crystal X-ray diffraction (XRD) data, the coordination geometry of the silver complexes is discussed. Dependent on the length of the alkyl bridge of the tetradentate ligand either a double helix structure with four linear-coordinated silver cations or a twisted geometry with two linear-coordinated silver cations is obtained.

Development of evidence-based quality indicators for deep brain stimulation in patients with Parkinson's disease and first year experience of implementation of a nation-wide registry.

INTRODUCTION: Deep Brain Stimulation (DBS) is a complex, invasive and cost-intensive therapy that requires a high level of expertise. To date, data on quality of DBS in clinical routine in the German health care system are lacking. METHODS: The development of evidence-based QIs for DBS in PD patients was performed following a standardized process by a multidisciplinary board between 2014 and 2016. The process was initiated by the German Parkinson Society and followed international recommendations for developing QIs including: a systematic literature search; an appraisal of the published evidence; a consensus-based selection of the QI set; and a pilot study to assess the feasibility in implementing the QIs in clinical routine. RESULTS: A set of 28 QIs for determining the quality of DBS in PD was established by the board covering different dimensions of health care quality (structure, process, and outcome) in different treatment phases of DBS care (pre-operative, peri-operative, and post-operative). Implementation in clinical practice was tested in a pilot study comprising three hospitals delivering DBS care. The feasibility of the QI set was evaluated positively by the participating physicians and hospitals. Mean time to document one patient was 25 min. The German-wide implementation of the defined indicator set within a dedicated quality registry (QualiPa) started in June 2016. CONCLUSION: QIs are a necessary requirement to monitor hospital performance in DBS care. The evidence-based approach to develop the proposed indicator set is expected to assure transparency, acceptance and long-term applicability of the QI set in Germany.

Exploring Coordination Modes: Late Transition Metal Complexes with a Methylene-bridged Macrocyclic Tetra-NHC Ligand.

A tetranuclear silver(I) N-heterocyclic carbene (NHC) complex bearing a macrocyclic, exclusively methylene-bridged, tetracarbene ligand was synthesized and employed as transmetalation agent for the synthesis of nickel(II), palladium(II), platinum(II), and gold(I) derivatives. The transition metal complexes exhibit different coordination geometries, the coinage metals being bound in a linear fashion forming molecular box-type complexes, whereas the group 10 metals adapt an almost ideal square planar coordination geometry within the ligand's cavity, resulting in saddle-shaped complexes. Both the Ag(I) and the Au(I) complexes show ligand-induced metal-metal contacts, causing photoluminescence in the blue region for the gold complex. Distinct metal-dependent differences of the coordination behavior between the group 10 transition metals were elucidated by low-temperature NMR spectroscopy and DFT calculations.

Structural diversity of late transition metal complexes with flexible tetra-NHC ligands.

The synthesis of copper, gold, nickel, palladium, platinum, and iron complexes with open chain tetra-N-heterocyclic carbene (NHC) ligands via transmetalation using silver NHC complexes is presented. The obtained complexes show differing coordination geometries depending on both ligand structure and metal. While the complexes of the coinage metals form di- or tetranuclear structures, the group 10 metal complexes exhibit a distorted square planar coordination geometry at the metal centers. In the case of iron an enhanced flexibility of the ligand - caused by a longer alkyl bridge - leads to octahedral complexes with a sawhorse-type coordination by the tetracarbene ligand and two cis acetonitrile ligands. To the best of our knowledge, this is the first known example of a tetracarbene ligand in sawhorse-type coordination within an octahedral coordination sphere. The remaining cis-labile sites are prone to exchange reactions as shown by addition of trimethylphosphine.