C-3-symmetric Ti(IV) triphenolate amino complexes as sulfoxidation catalysts with aqueous hydrogen peroxide

The Ti(IV) complex 2c bearing a C-3-symmetric triphenolate amine ligand is an air and moisture tolerant complex that efficiently catalyzes sulfoxidation reactions at room temperature without previous activation (catalyst loading down to 0.01%, TONs up to 8000, TOFs up to 1700 h(-1), quantitative yields). Reactions were performed with aqueous hydrogen peroxide as oxidant, which adds value to the methodology from the environmental viewpoint

Effective synthesis of ortho-substituted triphenol amines via reductive amination

An efficient synthesis of ortho-substituted triphenolamines via reductive amination is reported. This approach allows access to this increasingly important class of ligands in a structurally systematic way using either commercially or easily synthesizable building block

Discrimination of Octahedral versus Trigonal Bipyramidal Coordination Geometries of Homogeneous TiIV , VV , and MoVI Amino Triphenolate Complexes through Nitroxyl Radical Units

A new stable radical-containing ligand and the corresponding VV, TiIV, and MoVI complexes have been synthesized and studied by electron paramagnetic resonance (EPR) spectroscopy. To achieve this goal, a novel strategy for the post-derivatization of a triphenolamine (TPA) ligand has been developed. This has allowed the effective embedding of three TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) radicals in the corresponding metal complexes. In these systems, dipolar interactions among the organic radicals are strongly dependent on the geometry assumed in solution: a |Δms| = 2 transition is observed when the geometry of the complexes is octahedral, whereas no signal is detected with trigonal bipyramidal geometries.This research was supported by the Università di Padova, Italy(grant numbers PRAT-CPDA123307 and CPDA153122, Attrezza-ture Scientifiche Finalizzate Alla Ricerca 2014) and the ItalianMinistero dell'Università e della Ricerca (MIUR) (PRIN-2010-112010CX2TLM_002, E. B. fellowship). This work was carried outwithib the framework of the COST Action CM1205, CatalyticRoutines for Small Molecules Activation (CARISMA). The SpanishDirección General de Investigación (BeWell Grant numberCTQ2013-40480-R) and L'Agència de G estió d'Ajuts Universitarisi de Recerca (AGAUR) (grant number 2014-SGR-17) are also ac-knowledged. CIBER-BBN is an initiative funded by the VI Na-tional R&D&i Plan 2008–2011, Iniciativa Ingenio 2010, Consol-ider Program, CIBER Actions and financed by the Instituto deSalud Carlos III with assistance from the European Regional De-velopment Fund.Peer reviewe

Discrimination of Octahedral versus Trigonal Bipyramidal Coordination Geometries of Homogeneous Ti-IV, V-V, and Mo-VI Amino Triphenolate Complexes through Nitroxyl Radical Units

A new stable radical-containing ligand and the corresponding V-V, Ti-IV, and Mo-VI complexes have been synthesized and studied by electron paramagnetic resonance (EPR) spectroscopy. To achieve this goal, a novel strategy for the post-derivatization of a triphenolamine (TPA) ligand has been developed. This has allowed the effective embedding of three TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) radicals in the corresponding metal complexes. In these systems, dipolar interactions among the organic radicals are strongly dependent on the geometry assumed in solution: a vertical bar Delta m(s)vertical bar = 2 transition is observed when the geometry of the complexes is octahedral, whereas no signal is detected with trigonal bipyramidal geometries

Discrimination of Octahedral versus Trigonal Bipyramidal Coordination Geometries of Homogeneous Ti-IV, V-V, and Mo-VI Amino Triphenolate Complexes through Nitroxyl Radical Units

A new stable radical-containing ligand and the corresponding V-V, Ti-IV, and Mo-VI complexes have been synthesized and studied by electron paramagnetic resonance (EPR) spectroscopy. To achieve this goal, a novel strategy for the post-derivatization of a triphenolamine (TPA) ligand has been developed. This has allowed the effective embedding of three TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) radicals in the corresponding metal complexes. In these systems, dipolar interactions among the organic radicals are strongly dependent on the geometry assumed in solution: a vertical bar Delta m(s)vertical bar = 2 transition is observed when the geometry of the complexes is octahedral, whereas no signal is detected with trigonal bipyramidal geometries

Ti(IV)-amino triphenolate complexes as effective catalysts for sulfoxidation

C 3 -symmetric Ti (IV) amino triphenolate complexes efficiently catalyze, without previous activation and in excellent yields, the oxidation of sulfides at room temperature, using both CHP and the more environment friendly aqueous hydrogen peroxide as terminal oxidants, with catalyst loadings down to 0.01%. The Ti(IV) catalysts and the intermediate Ti(IV)-peroxo complexes have been characterized in solution by 1H NMR and ESI-MS techniques and via density functional studies

Effective synthesis of ortho-substituted trithiophenol amines by Miyazaki-Newman-Kwart rearrangement

An efficient synthesis of ortho-substituted trithiophenol amines from commercially available salicaldehydes by Miyazaki-Newman-Kwart rearrangement/threefold reductive amination is reported. The rearrangement has been carried out on salicaldehyde-O-thiocarbamates using microwave induced heating, which furnishes a series of thiosalicaldehyde-S-carbamates in high yield. The thiocarbamate has three roles: it enables effective S-O rearrangement, acts as a protecting group during the threefold reductive amination and can be easily removed under reductive conditions. The three-step synthesis has an overall yield ranging from 30-35%, and it enables access to a series of increasingly important C(3v) symmetric ligands in a structurally systematic wa

Stereoselective dimerization of racemic C3-symmetric Ti(IV) amine triphenolate complexes

A novel, mononuclear Ti(IV) amine triphenolate complex obtained by reaction of Ti(OiPr)(4) with tris(2-hydroxy-3-phenylbenzyl)amine bearing phenyl ortho-substituents affords quantitatively and spontaneously the corresponding heterochiral micro-oxo dinuclear compound whereas an analogous chiral, enantiopure complex maintains its mononuclear structure even in the presence of an excess of water