The first complexes containing imidazolium-2-amidinates as ligands (betaine-type adducts of imidazolium-based carbenes and carbodiimides, NHC-CDI) are reported. Interaction of the sterically hindered betaines ICyCDI(DiPP) and IMeCDI(DiPP) [both bearing 2,6-diisopropylphenyl (DiPP) substituents on the terminal N atoms] with Cu(I) acetate affords mononuclear, electroneutral complexes 1a and 1b, which contain NHC-CDI and acetate ligands terminally bound to linear Cu(I) centers. In contrast, the less encumbered ligand ICyCDI(p-Tol), with p-tolyl substituents on the nitrogen donor atoms, affords a dicationic trigonal paddlewheel complex, [Cu2(μ-ICyCDI(p-Tol))3](2+)[OAc(-)]2 (2-OAc). The nuclear magnetic resonance (NMR) resonances of this compound are broad and indicate that in solution the acetate anion and the betaine ligands compete for binding the Cu atom. Replacing the external acetate with the less coordinating tetraphenylborate anion provides the corresponding derivative 2-BPh4 that, in contrast with 2-OAc, gives rise to sharp and well-defined NMR spectra. The short Cu-Cu distance in the binuclear dication [Cu2(μ-ICyCDI(p-Tol))3](2+) observed in the X-ray structures of 2-BPh4 and 2-OAc, ca. 2.42 Å, points to a relatively strong "cuprophilic" interaction. Attempts to force the bridging coordination mode of IMeCDI(DiPP) displacing the acetate anion with BPh4(-) led to the isolation of the cationic mononuclear derivative [Cu(IMeCDI(DiPP))2](+)[BPh4](-) (3b) that contains two terminally bound betaine ligands. Compound 3b readily decomposes upon being heated, cleanly affording the bis-carbene complex [Cu(IMe)2](+)[BPh4(-)] (4) and releasing the corresponding carbodiimide (C(═N-DiPP)2).

Monomeric Ni and Pd hydroxides stabilized by the iPrPCP pincer ligand react with CO2 to give labile terminal bicarbonate complexes that readily lose CO2 and water to give binuclear carbonate complexes. Differential scanning calorimetry (DSC) has been used to monitor the decomposition of both bicarcabonates in the solid state. When the carbonate complexes are heated under reflux in thf in the presence of water, full decarboxylation takes place, restoring the starting hydroxides and demonstrating that CO2 insertion is a fully reversible process. The decarboxylation of the nickel carbonate complex is completed more readily, suggesting that the reaction of the Pd hydroxide with CO2 is more favourable than that of its nickel counterpart. This is supported by DFT calculations, which also shows that CO2 insertion takes place through a concerted Lipscomb‐type mechanism.

No abstract

Ligand exchange and oxidative addition reactions allow the synthesis of Ni(ii) and Pd(ii) complexes with deprotonable iminophosphine ligands. The acid–base behavior of iminophosphine ligands coordinated to organometallic Ni(ii) fragments is analyzed.

No abstract

No abstract

<p>A copper(I) complex [CuCl{<i>k</i>¹(P)-<b>1a</b>}{k²(P,N)-<b>1a</b>}] (<b>1a</b> = 2,5-bis(2-pyridyl)-1-phenylphosphole) with pseudo tetrahedral geometry was synthesized. In solution, <b>1a</b> displays a hemilabile behaviour leading to a dynamic equilibrium between four and three-coordinate specie. Its catalytic potential was tested in synthesis of propargylamines and 1,2,3-triazoles via three-component reactions. <a>Experimental results discussed on base to DFT calculations. </a></p>