Synthesis and Structures of Ruthenium and Iron Complexes Bearing an Unsymmetrical Pincer‐type Ligand with Protic Pyrazole and Tertiary Aminoalkyl Arms

Abstract

A protic pyrazole-armed NNN-type pincer ligand 2-(5-tertbutylpyrazol-3-yl)-6-(diethylaminomethyl)pyridine (LH) with a tertiary aminomethyl tether was synthesized as a new template for metalligand bifunctional catalysts furnished with proton-responsive pyrazole and hemilabile amine as the cooperating units. Treatment of LH with trans-[RuCl 2 (Me 2 SO) 4 ] and anhydrous FeCl 2 led to the formation of the pincer-type ruthenium complex [RuCl 2 (Me 2 SO-S)(LH)] (2) and ARTICLE Dedicated Cluster Scheme 1. Preparation of the unsymmetrical pincer-type ligand LH.

Protic Ruthenium Tris(pyrazol-3-ylmethyl)amine Complexes Featuring a Hydrogen-Bonding Network in the Second Coordination Sphere

“…However, their catalytic applications as well as complexation to heavier, π-electron-rich transition metals remain surprisingly rare. The versatility of the pyridine-armed tripodal tris­(pyridylmethyl)­amine (TPA) ligands in bioinorganic modeling and oxidation catalysis prompted us to scrutinize the coordination chemistry of a proton-responsive analogue of TPA, tris­(pyrazol-3-ylmethyl)­amine ligand LH 3 , in which the three β-protic pyrazoles − would serve as rigid proton-delivering groups to the coordination site with a larger space (Chart ). We describe here the synthesis and structures of LH 3 complexes of ruthenium and explore the catalytic role of the protic units in the second coordination sphere.…”

Hydrogenation and Cross-Coupling Reactions Catalyzed by Mn, Fe, and Co Aromatic Pincer Complexes

“…Such a mechanism comprises the transfer of a hydride from the ligand's benzylic carbon. Interestingly, another unsymmetrical Fe-pincer complex with a ligand containing pyrazole and tertiary aminoalkyl groups in the arms of the NNN-pincer ligand 23 was developed by Ikariya et al 59 Complex 23 was tested as a catalyst in the hydrogenation of ketones; however, it did not present any catalytic activity.…”

Recent Developments in Reactions and Catalysis of Protic Pyrazole Complexes

“…A tertiary amino group can also be incorporated into the protic pincer framework to afford unsymmetrical pincer-type complexes with a hemilabile arm. After our isolation of the ruthenium(II) and iron(II) complexes, such as 52 [65], Goldberg and co-workers reported the reactivities of the platinum(II) complexes bearing this unsymmetrical protic pincer ligand (Scheme 16) [47]. The methyl-pyrazolato complex 53, obtained from a dimethylplatinum(II) complex and the free ligand, undergoes protonation at the pyrazolato arm rather than the methyl ligand, as observed in the symmetrical bis(pyrazolato) com- A tertiary amino group can also be incorporated into the protic pincer framework to afford unsymmetrical pincer-type complexes with a hemilabile arm.…”

“…The methyl-pyrazolato complex 53, obtained from a dimethylplatinum(II) complex and the free ligand, undergoes protonation at the pyrazolato arm rather than the methyl ligand, as observed in the symmetrical bis(pyrazolato) com- A tertiary amino group can also be incorporated into the protic pincer framework to afford unsymmetrical pincer-type complexes with a hemilabile arm. After our isolation of the ruthenium(II) and iron(II) complexes, such as 52 [65], Goldberg and co-workers reported the reactivities of the platinum(II) complexes bearing this unsymmetrical protic pincer ligand (Scheme 16) [47]. The methyl-pyrazolato complex 53, obtained from a dimethylplatinum(II) complex and the free ligand, undergoes protonation at the pyrazolato arm rather than the methyl ligand, as observed in the symmetrical bis(pyrazolato) complex 16 (vide supra).…”