The titanium tris-anilide cation [Ti(N[^tBu]Ar)₃]⁺stabilized as its perfluoro-tetra-phenylborate salt: structural characterization and synthesis in connection with redox activity of 4,4′-bipyridine dititanium complexes

Abstract

This work explores the reduction of 4,4'-bipyridine using two equivalents of the titanium(iii) complex Ti(N[(t)Bu]Ar)3 resulting in formation of a black, crystalline complex, (4,4'-bipy){Ti(N[(t)Bu]Ar)3}2, for which an X-ray structure determination is reported. The neutral, black, 4,4'-bipyridine-bridged bimetallic was found to be redox active, with mono- and di-anions being accessible electrochemically, and with the mono- and di-cations also being accessible chemically, and isolable, at least when using the weakly coordinating anion [B(C6F5)4](-) as the counter-ion. It proved possible to crystallize the salt [(4,4'-bipy){Ti(N[(t)Bu]Ar)3}2][B(C6F5)4]2 for a single-crystal X-ray structure investigation; in this instance it was revealed that the aromaticity of the 4,4'-bipyridine ligand, that had been disrupted upon reduction, had been regained. A rare cationic d(0) metal tris-amide complex, shown by X-ray crystallography to contain an intriguing pyramidal TiN3 core geometry, namely {Ti(N[(t)Bu]Ar)3}(+), could also be isolated when using [B(C6F5)4] as the essentially non-interacting counter-ion. This highly reactive cation should be considered as a potential intermediate in the plethora of reactions wherein Ti(N[(t)Bu]Ar)3 has been shown to effect the reduction of substrates including halogenated organic molecules, carbonyl compounds, organic nitriles, and metal complexes.

Ein Dimetalloxycarben‐Bindungsmodus und der reduktive Kupplungsmechanismus zur Bildung von Oxalat ausgehend von CO2

“…[5] Der Versuch, ein durch Koordination am Titanzentrum stabilisiertes CO 2 -Anion durch Deprotonierung des Formiatliganden mit einer starken Brønsted-Base zu erhalten, scheiterte an der Abspaltung von Kohlenmonoxid und der Bildung eines anionischen terminalen Oxokomplexes, [5] der mit CO 2 einen Carbonatkomplex bildet. [15] [16] ,r ealisiert, wodurch formal der symmetrische, kationische,v erbrückende Formiatkomplex mit einem schwach koordinierenden Gegenanion [( 4 ], entstand (Schema 1). [17] Das 1 H-NMR-Spektrum von 4[B(C 6 F 5 ) 4 ]w eist eine deutliche Verschiebung des Signals des Formiatprotons von d = 8.00 ppm für 2 nach d = 6.25 ppm [18] 4 ], die geeignet für rçntgendiffraktometrischeS tudien waren, wurden aus konzentrierter Lçsung in Diethylether bei À35 8 8Ce rhalten (Abbildung 1).…”

“…Zwei Diethylethermoleküle im Gitter sowie alle Wasserstoffatome mit Ausnahme von H1 wurden weggelassen. Ausgewählte Atomabstände[] und Winkel [8 8]: C1-O1 1.257(3), C1-O2 1.239(3), Ti1-O1 1.9592(16), Ti2-O2 2.0750(15);Ti1-O1-C1 167.47(16),T i2-O2-C1 137.11(15), O1-C1-O2 124.6(2).…”

Countercation Effect on CO2 Binding to Oxo Titanate with Bulky Anilide Ligands

“…The comparably weak Ti−O interaction [1.8079(18) Å; single bond: 1.99 Å] increases the electron demand of titanium. The nitrogen lone‐pair of an anilide satisfies this demand through donation of electron density to the metal center . This leads to a tilt of its aryl moiety towards the oxo ligand, but no palpable aluminum cation–aryl interaction occurs that would be expected for this common structural motif…”

“…The nitrogen lonepair of an anilide satisfies this demand through donation of electron density to the metal center. [30] This leads to at ilt of its aryl moiety towards the oxo ligand, but no palpable aluminum cation-aryl interaction occurs that would be expected for this commons tructural motif. [18] CO 2 binding studies with the Mg and Al oxo species Species[ (thf) 2 MgMe][1]r eacts with CO 2 to yield the acetate moiety through addition of MgÀMe to one of the carbonoxygen double bonds, which is aw ell-known reaction for Grignardr eagents.…”

H2 Binding, Splitting, and Net Hydrogen Atom Transfer at a Paramagnetic Iron Complex

“…Reactivity of these diamagnetic dihydrogen complexes is easily probed by NMR spectroscopy. 3 Reactions of paramagnetic metal complexes with H 2 have important implications for biological processes involving hydrogenase 4 and nitrogenase 5 enzymes, yet detailed reports of H 2 binding/splitting with paramagnetic complexes are rare. 1a,6 H 2 binding to paramagnetic metal complexes has been postulated only in a few instances, 7 and three paramagnetic H 2 complexes have been isolated and thoroughly characterized ( Figure 1A-B).…”