Behavior of a Dynamic Covalent Library Driven by Combined Pd(II) and Biphasic Effectors for Metal Transport between Phases.

This work reports the effect of Pd(II) as chemical effector on an acylhydrazone-based dynamic covalent library (DCL) in biphasic systems (water/chloroform). The constituents of the DCL are self-built and distributed in the two phases, two of them are lipophilic enough to play the role of a carrier agent that may transfer Pd(II) from the aqueous phase to the organic phase. Upon addition of Pd(II), the DCL of components exhibits a strong amplification of the constituent that is the most adapted to stabilize Pd(II) in chloroform as well as its agonist in water. This evolution is driven by the combination of the interaction of the DCL with Pd(II) and the presence of the two phases. This study paves the way to a novel approach for liquid/liquid extraction and metal recovery by means of adaptive extractant species generated in situ by a DCL.

Early/Late Heterobimetallic Tantalum/Rhodium Species Assembled Through a Novel Bifunctional NHC-OH Ligand.

The straightforward synthesis of a new unsymmetrical hydroxy-tethered N-heterocyclic carbene (NHC) ligand, HL, is presented. The free ligand exhibits an unusual OH-carbene hydrogen-bonding interaction. This OH-carbene motif was used to yield 1) the first tantalum complex displaying both a Fischer- and Schrock-type carbene ligand and 2) a unique NHC-based early/late heterobimetallic complex. More specifically, the protonolysis chemistry between the ligand's hydroxy group and imido-alkyl or alkylidene-alkyl tantalum precursor complexes yielded the rare monometallic tantalum-NHC complexes [Ta(XtBu)(L)(CH2 tBu)2 ] (X=N, CH), in which the alkoxy-carbene ligand acts as a chelate. In contrast, HL only binds to rhodium through the NHC unit in [Rh(HL)(cod)Cl] (cod=cycloocta-1,5-diene), the hydroxy pendant arm remaining unbound. This bifunctional ligand scaffold successfully promoted the assembly of rhodium/tantalum heterobimetallic complexes upon either 1) the insertion of [Rh(cod)Cl]2 into the Ta-NHC bond in [Ta(NtBu)(L)(CH2 tBu)2 ] or 2) protonolysis between the free hydroxy group in [Rh(HL)(cod)Cl] and one alkyl group in [Ta(NtBu)(CH2 tBu)3 ].