Expanding the Utility of β-Diketiminate Ligands in Heavy Group VI Chemistry of Molybdenum and Tungsten

We report the synthesis of 17 molybdenum and tungsten complexes supported by the ubiquitous BDI ligand framework (BDI = β-diketiminate). The focal entry point is the synthesis of four molybdenum and tungsten(V) BDI complexes of the general formula [MO(BDI^R)Cl₂] [M = Mo, R = Dipp (1); M = W, R = Dipp (2); M = Mo, R = Mes (3); M = W, R = Mes (4)] synthesized by the reaction between MoOCl₃(THF)₂ or WOCl₃(THF)₂ and LiBDI^R. Reactivity studies show that the BDI^Dipp complexes are excellent precursors toward adduct formation, reacting smoothly with dimethylaminopyridine (DMAP) and triethylphosphine oxide (OPEt₃). No reaction with small phosphines has been observed, strongly contrasting the chemistry of previously reported rhenium(V) complexes. Additionally, the complexes 1 and 2 are good precursors for salt metathesis reactions. While 1 can be chemically reduced to the first stable example of a Mo(IV) BDI complex 15, reduction of 2 resulted in degradation of the BDI ligand via a nitrene transfer reaction, leading to MAD (4-((2,6-diisopropylphenyl)imino)pent-2-enide) supported tungsten(V) and tungsten(VI) complexes 16 and 17. All reported complexes have been thoroughly studied by VT-NMR and (heteronuclear) NMR spectroscopy, as well as UV-vis and EPR spectroscopy, IR spectroscopy, and X-ray diffraction analysis.

A theoretical study of the valence tautomerism of 1H-pyrazolium-4-olates (X = O) and related compounds (X = S, Se, NH): relative stabilities, protonation effects, and tautomerization barriers

The valence isomerism of a series of heterocyclic mesomeric betaines (HMBs) belonging to class 5, called pseudo-semi-conjugated HMBs, has been studied theoretically both the neutral and the protonated species. These HMBs are 1H-pyrazol-2-ium-4-olates and related compounds where the oxygen atom has been replaced by S, Se atoms, and an NH group. The main conclusion of the present work is that the ring/open valence tautomerism is possible both for neutral and protonated although it has never been observed experimentally.

Structure and magnetism of a tetrahedral uranium(iii) β-diketiminate complex

We describe the functionalisation of the previously reported uranium(iii) β-diketiminate complex (BDI)UI₂(THF)₂ (1) with one and two equivalents of a sterically demanding 2,6-diisopropylphenolate ligand (ODipp) leading to the formation of two heteroleptic complexes: [(BDI)UI(ODipp)]₂ (2) and (BDI)U(ODipp)₂ (3). The latter is a rare example of a tetrahedral uranium(iii) complex, and it shows single-molecule magnet behaviour.

Crystal structure of 3-[(2-acetamido-phen-yl)imino]-butan-2-one

In the title compound, 3-[(2-acetamido-phen-yl)imino]-butan-2-one, C12H14N2O2, the imine C=N bond is essentially coplanar with the ketone C=O bond in an s-trans conformation. The benzene ring is twisted away from the plane of the C=N bond by 53.03 (14)°. The acetamido unit is essentially coplanar with the benzene ring. In the crystal, mol-ecules are connected into chains along the c axis through C-H⋯O hydrogen bonds, with two adjacent chains being hinged by C-H⋯O hydrogen bonds.

Metal free oxidation of vinamidine derivatives: a simple synthesis of α-keto-β-diimine ligands

Oxidation of vinamidinium salts with meta-chloroperbenzoic acid is the key synthetic step towards new persistent 1,3-di(amino)oxyallyl radical cations. When applied to parent vinamidines, this protocol allows for a simple straightforward synthesis of α-keto-β-diimine ligands, for which no convenient synthesis was previously available.

Oxidation of vinamidinium salts with meta-chloroperbenzoic acid not only provides access to new persistent 1,3-di(amino)oxyallyl radical cations, but also to α-keto-β-diimine ligands, for which no convenient synthesis was previously available.

Diverse modes of functionalisation of ruthenium coordinated β-ketoiminate analogues

Varying chelation assisted as well as solvent dependent reactivity profiles of isostructural β-ketoiminate analogues explicate their non-spectator behaviour and fractional redox non-innocence.

Rare earth metal bisamido complexes with an NNO tridentate ligand and catalytic activity for the selective polymerization of isoprene

A series of rare earth metal bisamido complexes was synthesized, which could effectively initiate the polymerization of isoprene to afford polyisoprene with high regio- and stereo-selectivity in the presence of cocatalysts.

A unique copper(ii)-assisted transformation of acetylacetone dioxime in acetone that leads to one-dimensional, quinoxaline-bridged coordination polymers

A novel Cu^II-assisted transformation of acetylacetone dioxime to coordinated quinoxaline has been discovered.

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.

Circular serendipity: in situ ligand transformation for the self-assembly of an hexadecametallic [CuII16] wheel

A [Cu₁₆^II] wheel has been isolated serendipitously from the reaction of acetylacetone dioxime with Cu^II and Ln^III ions. The ligand has been transformed in situ to three different forms, all found within the [Cu₁₆], with the original ligand absent.