Synthesis, Characterization, and Reactivity of a Versatile Dinuclear Palladium β-Diiminate Complex

Palladium alkyl complexes with a formazanate ligand: synthesis, structure and reactivity

The synthesis of formazanate palladium complexes is reported. Ligand-based redox-reactions and insertions of unsaturated substrates into the Pd–CH₃ bond are studied.

On the non-innocence of “Nacnacs”: ligand-based reactivity in β-diketiminate supported coordination compounds

While β-diketiminate (BDI or ‘nacnac’) ligands have been widely adopted to stabilize a wide range of metal ions in multiple oxidation states and coordination numbers, in several occurrences these ligands do not behave as spectators and participate in reactivity.

Tuning steric and electronic effects in transition-metal β-diketiminate complexes

β-Diketiminates are widely used supporting ligands for building a range of metal complexes with different oxidation states, structures, and reactivities. This Perspective summarizes the steric and electronic influences of ligand substituents on these complexes, with an eye toward informing the design of new complexes with optimized properties. The backbone and N-aryl substituents can give significant steric effects on structure, reactivity and selectivity of reactions. The electron density on the metal can be tuned by installation of electron withdrawing or donating groups on the β-diketiminate ligand as well. Examples are shown from throughout the transition metal series to demonstrate different types of effects attributable to systematic variation of β-diketiminate ligands.

Coordination of β-Ketoimine-Derived Ligands at Main Group and Transition Metals

The β-ketoimine HC[MeC(O)][MeC(NHt-Bu)] (1H) (Me = methyl) was used as a ligand in the synthesis of organo-aluminium and gallium compounds. With Al, the NH functionality was deprotonated to form the N,O-chelating β-ketoiminate ligand in Al{HC[MeC(O)][MeC(Nt-Bu)]}Me2 (3) (t-Bu = tertiary butyl), whereas the neutral form coordinated to trimethylgallium via the oxygen atom to form the adduct GaMe3·{HC[MeC(O)][MeC(NHt-Bu)]} (4). Reaction of 1H with Ar†NH2 (Ar† = 2-t-BuC6H4) afforded the new N-aryl β-ketoimine HC[MeC(O)][MeC(NHAr†)] (2H), which reacted with Pd(OAc)2 (OAc = acetate = CH3CO2–) to afford the heteroleptic dimer {Pd[HC(MeC(O))(MeC(NAr†))](μ-OAc)}2 ([5]2). The homoleptic bis(β-ketoiminate) Pd{HC[MeC(O)][MeC(NAr†)]}2 (6) was isolated as a minor product of this reaction. The crystal structures of compounds 3, 4, [5]2, and 6 are reported.

Supramolecular features in the engineering of 3d metal complexes with phenyl-substituted imidazoles as ligands: the case of copper(ii)

Interesting packing features are present in eleven Cu(ii) complexes with phenyl-substituted imidazoles.

Classical and non-classical redox reactions of Pd(II) complexes containing redox-active ligands

Reactivity studies of a Pd(II)-verdazyl complex reveal novel ligand-centred reduction processes which trigger pseudo-reductive elimination at Pd. Reaction of the complex with water induces a ligand-centred redox disproportionation. The reduced verdazyl ligands can also be reversibly protonated.

Zinc(II) and Nickel(II) Benzoate Complexes from the Use of 1-methyl-4,5-diphenylimidazole

Two new complexes, [Zn(O(2)CPh)(2)(L)(2)].2MeOH (1.2MeOH) and [Ni(2)(O(2)CPh))(4)(L)(2)].2MeCN (2.2MeCN), have been synthesized and characterized by X-ray analysis in the course of an ongoing investigation of the M(II)/X(-)/L [M(II) = Co, Ni, Cu, Zn; X(-) = Cl(-), Br(-), I(-), NCS(-), NO(3) (-), N(3) (-), PhCO(2) (-); L = 1-methyl-4,5-diphenylimidazole] reaction system, aiming at understanding and assessing the relative strength and the way in which the intermolecular interactions control the supramolecular organization of these compounds. In the mononuclear complex 1.2MeOH, the benzoate ion acts as a monodentate ligand resulting in a distorted tetrahedral N(2)O(2) coordination environment. Complex 2.2MeCN exhibits a dinuclear paddle-wheel structure; each Ni(II) has a square pyramidal NiNO(4) chromophore with four benzoate oxygens in the basal plane and the pyridine-type nitrogen atom of one ligand L at the apex. The structure of 1.2MeOH is stabilized by intramolecular pi-pi interactions between aromatic rings of adjacent 4,5-diphenylimidazole moieties; it is a feature also evidenced in similar compounds of the type [MX(2)L(2)].