Transition metals under focus are Ni, Pd, and Pt, which often are used in combination with main group metals compounds (Li, Mg, Al, Ge, Sn), and Co–Ir.
While plastic crystals (dynamically-orientationally disordered mesogens) are so far rare in organometallic chemistry, we discovered that formally five-coordinate ionic Ni(II) complexes [(π-allyl)NiL3]Y and neutral M(I) complexes (π-allyl)ML3 (M = Co, Rh, Ir) with L = PMe3, P(OMe)3, and other ligands undergo a phase transition from the ordered to a plastic phase. The plastic properties arise from mobility of the π-allyl group in the solid-state. For the ionic Ni compounds, besides motion of the anions Y, the cations appear to tumble on their site in the lattice, whereas the neutral M(I) complexes rotate about an axis. For recrystallization, some compounds require partial ordering in a glassy-crystalline state.
Among the most prominent anti-cancer drugs are cisplatin, carboplatin, and oxaliplatin. Therapy with these drugs is frequently associated with serious side-effects, and inherent or acquired platinum resistance is a major problem. Thus, there is an unabated need for remedy and probing new structures. We have studied parent bispidine (3,7-diazabicyclo[3.3.1]nonane, C7H14N2) and its derivatives, substituted at the remote 9-position, for usage as “carrier ligands” for Pt(II). The studies allow insight into parameters such as hydrogen-bonding, association, hydration, water solubility, and polarity of the complexes, relevant to cytostatic potency.
The cesium cation, Cs+, is the largest and least electrophilic singly charged metal ion. Isolation of Cs+ salts from aqueous solutions represents a problem in many areas, as there are (a) exploitation of cesium from minerals, (b) reprocessing of nuclear fuels and separation of the strong gamma emitter 137Cs, (c) decontamination of 137Cs containing waste solutions, and (d) preparation of 131/137Cs radioactive probes for a variety of applications. We have found that the fluorinated aryl boronate (FAB) anion [H2NB2(C6F5)6]– allows for 100% selective and quantitative separation of Cs+ from any aqueous solution, affording insoluble Cs[H2NB2(C6F5)6]. The high specificity for Cs+ arises from the specific conformation of the anion which is exclusively present in Cs[H2NB2(C6F5)6]. Thereby, Cs+ is bonded to five anions in a 3D lattice, and the unprecedented coordination number CN = 16 is reached, allowing for enhanced stability of the lattice.
Dr. Cui, Huiling
Forero Cortés, Paola Andrea
Prof. Dr. Pörschke, Klaus-Richard