Metal‐to‐Ligand Alkyl Migration Inducing Carbon–Sulfur Bond Cleavage in Dialkyl Yttrium Complexes Supported by Thiazole‐Containing Amidopyridinate Ligands: Synthesis, Characterization, and Catalytic Activity in the Intramolecular Hydroamination Reaction

Abstract

Neutral Y(III) dialkyl complexes supported by tridentate N(-) ,N,N monoanionic methylthiazole- or benzothiazole-amidopyridinate ligands have been prepared and completely characterized. Studies on their stability in solution revealed progressive rearrangement of the coordination sphere in the benzothiazole-containing system through an unprecedented metal-to-ligand alkyl migration and subsequent thiazole ring opening. Attempts to synthesize hydrido species from the dialkyl precursor led to the generation of a dimeric yttrium species stabilized by a trianionic N(-) ,N,N(-) ,S(-) ligand as the result of metal-to-ligand hydride migration with chemoselective thiazole ring opening and subsequent dimerization through intermolecular addition of the residual YH group to the imino fragment of a second equivalent of the ring-opened intermediate. DFT calculations were used to elucidate the thermodynamics and kinetics of the process, in support of the experimental evidence. Finally, all isolated yttrium complexes, especially their cationic forms prepared by activation with the Lewis acid Ph3 C(+) [B(C6 F5 )4 ](-) , were found to be good candidate catalysts for intramolecular hydroamination/cyclization reactions. Their catalytic performance with a number of primary and secondary amino alkenes was assessed.

Benzoimidazole‐Pyridylamido Zirconium and Hafnium Alkyl Complexes as Homogeneous Catalysts for Tandem Carbon Dioxide Hydrosilylation to Methane

“…Pyridine dearomatization in the presence of Group IV transition metals is unprecedented, except for reactions that involve redox‐active ligands in the presence of selected metallocenes (Figure ; I ) . However, organolanthanide complexes are well known to undergo intramolecular metal‐to‐ligand alkyl migrations that cause pyridine dearomatization (Figure ; II ), which include deeper and unpredictable ligand rearrangements . Examples of pyridine dearomatization have also been described with a variety of late‐transition‐metal complexes (Figure ; III )…”

Metallacyclic yttrium alkyl and hydrido complexes: synthesis, structures and catalytic activity in intermolecular olefin hydrophosphination and hydroamination

“…Recently it was demonstrated that the activity of cationic alkyl rare-earth metal complexes in intramolecular hydroamination of aminoolefin is higher than that of neutral alkyl species. 25 The cationic alkyl species generated from 7 by the treatment with B(C 6 F 5 ) 3 , [HNMe 2 Ph][B(C 6 F 5 ) 4 ], [Ph 3 C][B(C 6 F 5 ) 4 ] (toluene, 20 °C) were tested as precatalysts for intermolecular hydroamination of styrene with pyrrolidine. Surprisingly in all cases no conversion was detected.…”

Selective Intermolecular C–H Bond Activation: A Straightforward Synthetic Approach to Heteroalkyl Yttrium Complexes Containing a Bis(pyrazolyl)methyl Ligand

“…Thus, the lengths of Y–C bonds between the yttrium center and terminal CH 2 SiMe 3 group in complexes 6 – 9 differ slightly (2.438(2) ( 6 ), 2.379(3) ( 7 ), 2.444(2) ( 8 ), and 2.462(2) ( 9 ) Å, respectively), and this deviation is in line with different coordination numbers of Y ions. However, all these values fall into the region characteristic for yttrium alkyl species supported by amidopyridinato, amidinato, and substituted cyclopentadienyl ligands. The bonds between yttrium ions and carbon atoms of bis­(pyrazolyl)­methyl ligands turned out to be substantially longer (2.553(2) Å, 6 ; 2.547(2) Å, 7 ; 2.564(2) Å, 8 ; 2.535(2) Å, 9 ) compared to YCH 2 SiMe 3 .…”