Mono- and bimetallic amidinate samarium complexes – synthesis, structure, and hydroamination catalysis

Abstract

Two similar amidinate samarium catalysts were synthesized in order to investigate the difference between a monometallic and a bimetallic system in the catalytic hydroamination cyclization reaction.

Investigating a Redox Active Samarium Complex in Catalytic Reactions

“…Within each amidinate ligand‐samarium interaction there is a longer (Sm−N2 2.459(7) Å and Sm−N3 2.459(6) Å) and a shorter bond (Sm−N1 2.446(6) Å and Sm−N4 2.428(6) Å). This bond interactions are in the range of literature known examples (2.28 – 2.52 Å) [23–24] . The samarium nitrogen bond to the N(SiMe 3 ) 2 − ligand (Sm−N5 2.249(5) Å) is also in the range of literature known bonds [23–24,31−33] .…”

“…Recently, we reported on samarium amidinate complexes as catalysts for the hydroamination reaction. While the monoamidinate [Sm( Dipp L Ph ){N(SiMe 3 ) 2 } 2 ] ( D ) was obtained by using the bulky N,N’ ‐bis(2,6‐diisopropylphenyl)benzamidinate ligand ( Dipp L Ph ) (Scheme 3), the bisamidinate samarium compound [Sm{ iPr L Phen }{N(SiMe 3 ) 2 }(THF)] ( E ) (Scheme 3) was formed by employing the rigid ligand system 4,5‐bis(diisopropylamidinate)phenanthrene ( i Pr L Phen ) [23–24] . Both complexes are functionalized by N(SiMe 3 ) − groups, which act as leaving groups of the precatalyst in the hydroamination reaction.…”

“… The mono and bisamidinate samarium amido complexes [Sm( Dipp L Ph ){N(SiMe 3 ) 2 } 2 ] ( D ) and [Sm{ iPr L Phen }{N(SiMe 3 ) 2 }(thf)] ( E ) [23–24] …”

“…Herein, we showcase the coordination of the new ferrocenyl ethynyl functionalized amidinate ligand to samarium. The resulting complex was subsequently used as a catalyst in intramolecular hydroamination and dehydrocoupling reactions [21–27] . Furthermore, the redox activity of the ferrocene backbone of the complex was investigated by cyclovoltammetry (CV) as well as in aforementioned catalytic reactions.…”

N,N′-Bis[2,6-bis(1-methylethyl)phenyl]pyridine-4-carboximidamide toluene hemisolvate

“…Amidine compounds are well developed in organic chemistry (Patai & Rappoport, 1991). Their derivatives are also good chelators for transition metals and their complexes have found widespread use in catalysis, polymerization reactions, as functional materials, and in supramolecular chemisty (Bambirra et al, 2004;Kazeminejad et al, 2019;Qian et al, 2010;Loh et al, 2014;Boeré et al, 1998;Chartrand & Hanan, 2008).…”