The stability constants of lanthanide complexes with the potentially octadentate ligand CHX OCTAPA 4– , which contains a rigid 1,2-diaminocyclohexane scaffold functionalized with two acetate and two picolinate pendant arms, reveal the formation of stable complexes [log K LaL = 17.82(1) and log K YbL = 19.65(1)]. Luminescence studies on the Eu 3+ and Tb 3+ analogues evidenced rather high emission quantum yields of 3.4 and 11%, respectively. The emission lifetimes recorded in H 2 O and D 2 O solutions indicate the presence of a water molecule coordinated to the metal ion. 1 H nuclear magnetic relaxation dispersion profiles and 17 O NMR chemical shift and relaxation measurements point to a rather low water exchange rate of the coordinated water molecule ( k ex 298 = 1.58 × 10 6 s –1 ) and relatively high relaxivities of 5.6 and 4.5 mM –1 s –1 at 20 MHz and 25 and 37 °C, respectively. Density functional theory calculations and analysis of the paramagnetic shifts induced by Yb 3+ indicate that the complexes adopt an unprecedented cis geometry with the two picolinate groups situated on the same side of the coordination sphere. Dissociation kinetics experiments were conducted by investigating the exchange reactions of LuL occurring with Cu 2+ . The results confirmed the beneficial effect of the rigid cyclohexyl group on the inertness of the Lu 3+ complex. Complex dissociation occurs following proton- and metal-assisted pathways. The latter is relatively efficient at neutral pH, thanks to the formation of a heterodinuclear hydroxo complex.

Herein we report a Suzuki-Miyaura type cross-coupling between an aryl halide and a functionalized boronic acid palladacycle in the absence of an external catalyst. This reaction is an unprecedented case of catalysis in palladium metallacycle chemistry.

The potential of 15-crown-5 ethers to link large cations, such as potassium, is limited by the quasi-parallel arrangement of two oxygen donor moieties upon appropriate orientation of the corresponding ether-ring-containing molecules. Substrates bearing the two crown ethers that are capable of achieving such coordination are hitherto unknown. The synthesis and isolation of a tailor-made dinuclear palladacycle bearing 15-crown-5 ether rings on the metallated phenyls offers such a possibility, providing the adequate environment for the formation of the sandwiched [K(metallacycle-15-crown-5) ] moiety. This synthetic strategy also culminates in the isolation of the first palladacycle able to entrap a potassium cation through bonding to two 15-crown-5 ether rings in a single molecule.

Palladacycles of the type [Pd(PhPCHPPh-P,P)(C,N:C,N)] (C,N:C,N = bis(N-2,3,4-trimethoxybenzylidene)-4,4'-sulfonyldianiline or -4,4'-oxydianiline) can undergo a spontaneous slow chelate-to-bridging diphosphane coordination shift in solution. Following this strategy a tailor-made synthetic procedure was devised that culminates in isolation of double A-frame tetranuclear palladium complexes.

A dinuclear iminophosphorane palladacycle produces the missing link in the triphenylphosphane chalcogenide series of metallacycles.