Binuclear Nickel Complexes of a New Di(hydroxyphenyl)imidazolate

Here, we report a new di(hydroxyphenyl)imidazolate ligand with an N2O2 donor set synthesized by a modified Debus–Radziszewski procedure. Its binuclear nickel(II) complexes feature a weak antiferromagnetic interaction with J12 = −3.16 cm−1 between the two nickel(II) ions identified by magnetometry measurements. As follows from cyclic voltammetry experiments and DFT calculations, they undergo ligand-centered oxidation via the formation of cation radicals with short lifetimes that can be potentially stabilized by bulkier t-butyl groups in the ortho-positions of the ligand. The reported ligand widens the range of the building blocks available to molecular magnetism community and thus provides new ways to the design of magnetic materials with switchable properties

Binuclear Nickel Complexes of a New Di(hydroxyphenyl)imidazolate

Here, we report a new di(hydroxyphenyl)imidazolate ligand with an N2O2 donor set synthesized by a modified Debus–Radziszewski procedure. Its binuclear nickel(II) complexes feature a weak antiferromagnetic interaction with J12 = −3.16 cm−1 between the two nickel(II) ions identified by magnetometry measurements. As follows from cyclic voltammetry experiments and DFT calculations, they undergo ligand-centered oxidation via the formation of cation radicals with short lifetimes that can be potentially stabilized by bulkier t-butyl groups in the ortho-positions of the ligand. The reported ligand widens the range of the building blocks available to molecular magnetism community and thus provides new ways to the design of magnetic materials with switchable properties

The Dichotomy of Mn–H Bond Cleavage and Kinetic Hydricity of Tricarbonyl Manganese Hydride Complexes

Acid-base characteristics (acidity, pKa, and hydricity, ΔG°H− or kH−) of metal hydride complexes could be a helpful value for forecasting their activity in various catalytic reactions. Polarity of the M–H bond may change radically at the stage of formation of a non-covalent adduct with an acidic/basic partner. This stage is responsible for subsequent hydrogen ion (hydride or proton) transfer. Here, the reaction of tricarbonyl manganese hydrides mer,trans–[L2Mn(CO)3H] (1; L = P(OPh)3, 2; L = PPh3) and fac–[(L–L′)Mn(CO)3H] (3, L–L′ = Ph2PCH2PPh2 (dppm); 4, L–L′ = Ph2PCH2–NHC) with organic bases and Lewis acid (B(C6F5)3) was explored by spectroscopic (IR, NMR) methods to find the conditions for the Mn–H bond repolarization. Complex 1, bearing phosphite ligands, features acidic properties (pKa 21.3) but can serve also as a hydride donor (ΔG≠298K = 19.8 kcal/mol). Complex 3 with pronounced hydride character can be deprotonated with KHMDS at the CH2–bridge position in THF and at the Mn–H position in MeCN. The kinetic hydricity of manganese complexes 1–4 increases in the order mer,trans–[(P(OPh)3)2Mn(CO)3H] (1) mer,trans–[(PPh3)2Mn(CO)3H] (2) ≈ fac–[(dppm)Mn(CO)3H] (3) fac–[(Ph2PCH2NHC)Mn(CO)3H] (4), corresponding to the gain of the phosphorus ligand electron-donor properties