Heterobimetallic complexes of lanthanide and lithium metals with dianionic guanidinate ligands: Syntheses, structures and catalytic activity for amidation of aldehydes with amines

Rare‐Earth Amido and Borohydrido Complexes Supported by Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in Polymerization of Cyclic Esters

“…The lengths of the covalent Ln(1)–N(5) bond ( 3 : 2.295(3) Å; 4 : 2.389(3)–2.408(4) Å) are comparable with those in the formerly described amido yttrium [{Me 3 SiNC(Ph)N} 2 (CH 2 ) 3 ]Y(2,6‐Pr i 2 C 6 H 3 NH)DME (2.237(4) Å), {(3,5‐Me 2 C 3 HN 2 ) 3 B}Y[κ 3 ‐(4‐NH=(C 8 N 2 H 4 )(2‐NHC 6 H 4 ))]{(Me 2 N) 3 P=O} (2.309(5) Å) and neodymium complexes [3,5‐Bu t 2 ‐2‐O‐C 6 H 2 CH=N‐C 5 H 4 N] 2 NdN(SiMe 3 ) 2 (2.385(3) Å), [{Me 3 SiNC(Ph)N} 2 (CH 2 ) 3 ]Nd(2,6‐Pr i 2 C 6 H 3 NH)DME (2.342(7) Å), [{(NC 5 H 4 )NHCH 2 (3,5‐Bu t 2 ‐C 6 H 2 ‐2‐OH)}NdN(SiMe 3 ) 2 (THF)] 2 (2.372(3) Å) . The Ln–N amidinate distances in 3 and 4 are somewhat different (κ 4 ‐NNOO‐ligand 2.378(3)–2.379(3) Å ( 3 ), 2.473(2)–2.483(2) Å ( 4 ); κ 2 ‐NN‐ligand 2.21(2)–2.45(2) Å, average 2.34(6) Å ( 3 ), 2.415(5)–2.487(4) Å, average 2.46(2) Å ( 4 )), but are comparable with the corresponding values measured in the related seven‐coordinate yttrium amidinate complexes [{1,3‐C 6 H 4 (NC(Ph)NSiMe 3 ) 2 } 3 Y(THF)Y(µ‐Cl)Li(THF) 3 ] (2.341(6), 2.455(6) Å), [Y{ o ‐CH 3 O‐C 6 H 4 NC(Ph)N(SiMe 3 )}Cl 2 (THF) 2 ] 2 (2.384(2), 2.375(2) Å), [(2,6‐Et 2 C 6 H 3 N) 2 C(4‐Me‐C 6 H 4 )] 2 Y(THF)(Cl)(µ‐Cl)Li(THF) 3 (2.402(6)–2.464(5) Å), [1,8‐C 10 H 6 {NC(Bu t )N‐2,6‐Me 2 ‐C 6 H 3 } 2 ]YCl(DME) (2.331(1)–2.369(1) Å) [{Me 3 SiNC(Ph)N} 2 (CH 2 ) 3 ]YCl(DME) (2.360(3)–2.379(3) Å) and seven‐coordinate neodymium complexes (2.385(2)–2.604(7) Å) , . The C–N bond lengths within the amidinate fragments in 3 and 4 fall into a narrow interval ( 3 : 1.321(8)–1.333(9) Å, 4 : 1.313(4)–1.333(9) Å) thus being indicative of delocalization of the negative charge over the NCN fragments.…”

“…The C–N bond lengths within the amidinate fragments in 3 and 4 fall into a narrow interval ( 3 : 1.321(8)–1.333(9) Å, 4 : 1.313(4)–1.333(9) Å) thus being indicative of delocalization of the negative charge over the NCN fragments. The Ln–O bond lengths in [Bu t C(NC 6 H 4 ‐2‐OMe) 2 ] 2 LnN(SiMe 3 ) 2 ( 3 : 2.594(2), 2.628(2) Å, 4 : 2.656(2), 2.668(2) Å) are slightly longer than the lengths of coordination bonds Ln(III)‐O (DME or THF) reported for the related yttrium [{Me 3 SiNC(Ph)N} 2 (CH 2 ) 3 ]Y(2,6‐Pr i 2 C 6 H 3 NH)(DME) (2.237(4) Å), [1,2‐C 6 H 4 {NC(Ph)NSiMe 3 } 2 ]YCl(THF) 2 (2.321(2) Å) and neodymium complexes [{Me 3 SiNC(Ph)N} 2 (CH 2 ) 3 ]Nd(2,6‐Pr i 2 C 6 H 3 NH)DME (2.585(2), 2.553(2) Å), Nd[(Pr i N)(NC 6 H 4 ‐p‐Cl)C(NHPr i )] 3 THF (2.551(5) Å) . The 1 H NMR (400 MHz, C 7 D 8 , 25 °C) spectrum of diamagnetic complex 3 displays a single set of signals due to the amidinate ligand [(2‐OMe‐C 6 H 4 N) 2 C(Bu t )] – and the N(SiMe 3 ) 2 group.…”

Tandem Photoredox Catalysis: Enabling Carbonylative Amidation of Aryl and Alkylhalides

“…The method afforded the corresponding aryl amide products in good to excellent yield (55 -79%) with a strong preference for secondary aliphatic cyclic amines (11b, 24-25) and secondary acyclic amines (26). Primary aliphatic amines were tolerated (27)(28)(29)(30) although an increase of equivalents of n-hexyl amine and tert-butyl amine (27,29) was necessary to achieve full conversion. Allyl amine, containing a terminal alkene that is susceptible to radical addition by aryl 22 and alkyl 23 acyl radicals, gave 31 without unwanted substitution or polymerization by-products.…”

“…A third mechanism, Path C proceeds via nucleophilic addition of the amine to the acyl radical giving the ahydroxy radical 83 via amine-assisted intermolecular proton transfer. 29 Formation of the amide proceeds via oxidation of a-hydroxy radical (83) by the Ir2 + catalyst or by radical chain propagation. The oxidation potential of a series of hydroxybenzyl and hydroxyalkyl radical species (83) was estimated by DFT calculations ( Supplementary Table S1) and the oxidation of these intermediates by Ir2 + catalyst is thermodynamically feasible.…”

Metal-catalysed approaches to amide bond formation

“…Shen and co-workers have reported several bimetallic lanthanide complexes used to catalyse this reaction. Their 2010 paper 15 details the first structurally characterised complex of lanthanide and lithium metals with dianionic guanidinate ligands, with the Nd demonstrating its effectiveness for amidation of aldehydes with amines at just 1 mol% catalyst loading at room temperature.…”