Synthesis and Characterization of Super Bulky β-Diketiminato Group 1 Metal Complexes

Sterically bulky β-diketiminate (or Nacnac) ligand systems have recently shown the ability to kinetically stabilize highly reactive low-oxidation state main group complexes. Metal halide precursors to such systems can be formed via salt metathesis reactions involving alkali metal complexes of these large ligand frameworks. Herein, we report the synthesis and characterization of lithium and potassium complexes of the super bulky anionic β-diketiminate ligands, known [TCHPNacnac]− and new [TCHP/DipNacnac]− (ArNacnac = [(ArNCMe)2CH]−) (Ar = 2,4,6-tricyclohexylphenyl (TCHP) or 2,6-diisopropylphenyl (Dip)). The reaction of the proteo-ligands, ArNacnacH, with nBuLi give the lithium etherate compounds, [(TCHPNacnac)Li(OEt2)] and [(TCHP/DipNacnac)Li(OEt2)], which were isolated and characterized by multinuclear NMR spectroscopy and X-ray crystallography. The unsolvated potassium salts, [{K(TCHPNacnac)}2] and [{K(TCHP/DipNacnac)}∞], were also synthesized and characterized in solution by NMR spectroscopy. In the solid state, these highly reactive potassium complexes exhibit differing alkali metal coordination modes, depending on the ligand involved. These group 1 complexes have potential as reagents for the transfer of the bulky ligand fragments to metal halides, and for the subsequent stabilization of low-oxidation state metal complexes.

An Active Catalyst System Based on Pd (0) and a Phosphine-Based Bulky Ligand for the Synthesis of Thiophene-Containing Conjugated Polymers

To address the limitations of conventional Pd catalysts in the polymerization of thiophene-containing conjugated polymers, an active catalyst system based on Pd (0) and a phosphine-based bulky ligand, L1, is explored systematically in Suzuki–Miyaura polymerizations using thiophene boronic acid pinacol ester as one of the monomers. This active catalyst is found very efficient in synthesizing a series of thiophene-containing linear and hyperbranched conjugated polymers. First, as a model example, coupling reactions between electron-rich/moderately hindered aryl or thienyl halides and thiophene boronic acid pinacol ester give excellent yields with lower catalyst loading and can be completed in a shorter reaction time relative to Pd(PPh3)4. Notably, high molecular weight thiophene-containing polymers are successfully synthesized by Suzuki–Miyaura polycondensation of 2,5-thiophene bis(boronic acid) derivatives with different dibromo- and triple bromo-substituted aromatics in 5–15 min.

Highly 2,3-selective polymerization of phenylallene and the derivatives by vanadium complexes

Vanadium complex containing bulky ligand were investigated for the allene polymerization. Such complexes exhibited distinguished 2,3-selectivity (>99 %) for phenylallene (PA) polymerization which were proved by the corresponding NMR spectra....

Crystal structure of bis(1-mesityl-1H-imidazole-κN 3)diphenylboron trifluoromethanesulfonate

The solid-state structure of bis(1-mesityl-1H-imidazole-κN 3)diphenylboron trifluoromethanesulfonate, C36H38BN4 +·CF3SO3 − or (Ph2B(MesIm)2OTf), is reported. Bis(1-mesityl-1H-imidazole-κN 3)diphenylboron (Ph2B(MesIm)2 + ) is a bulky ligand that crystallizes in the orthorhombic space group Pbcn. The asymmetric unit contains one Ph2B(MesIm)2 + cationic ligand and one trifluoromethanesulfonate anion that balances the positive charge of the ligand. The tetrahedral geometry around the boron center is distorted as a result of the steric bulk of the phenyl groups. Weak interactions, such as π–π stacking are present in the crystal structure.

Ligand-modulated ring-expansion

An unstrained metal-containing macrocycle was ring-expanded by a ring-opening metathesis strategy, leading to the formation of a bimetallic dimeric macrocycle. The reaction is driven by coordination of a bulky ligand, 2,6-lutidine, on the fourth coordination site of the palladium center. In the absence of metal, or with a less bulky ligand, the ring-expansion reaction does not proceed.

A DFT study on the mechanism and origins of the ligand-controlled regioselectivity of a palladium-catalyzed dearomatic reaction of 1-(chloromethyl)naphthalene with phenylacetonitrile

DFT calculations demonstrated that the bulky ligand tBuPPh2 generates para-substituted products, while the small ligand Me2PPh provides ortho-substituted products.