title: Dehydrogenation of secondary amines: synthesis, and characterization of rare-earth metal complexes incorporating imino- or amido-functionalized pyrrolyl ligands.
abstract: The dehydrogenation of pyrrolyl-functionalized secondary amines initiated by rare-earth metal amides was systematically studied. Reactions of the rare-earth metal amides [(Me(3)Si)(2)N](3)RE(μ-Cl)Li(THF)(3) with pyrrolyl-functionalized secondary amines 2-(t)BuNHCH(2)-5-R-C(4)H(2)NH (R = H (1), R = (t)Bu (2)) led to dehydrogenation of the secondary amines with isolation of imino-functionalized pyrrolyl rare-earth metal complexes [2-(t)BuN=CH-5-R-C(4)H(2)N](2)REN(SiMe(3))(2) (R = H, RE = Y (3a), Dy (3b), Yb (3c), Eu (3d); R = (t)Bu, RE = Y (4a), Dy (4b), Er (4c)). The mixed ligands erbium complex [2-(t)BuNCH(2)-5-(t)Bu-C(4)H(2)N]Er[2-(t)BuN=CH-5-(t)BuC(4)H(2)N](2)ClLi(2)(THF) (4c') was isolated in a short reaction time for the synthesis of complex 4c. Reaction of the deuterated pyrrolyl-functionalized secondary amine 2-((t)BuNHCHD)C(4)H(3)NH with yttrium amide [(Me(3)Si)(2)N](3)Y(μ-Cl)Li(THF)(3) further proved that pyrrolyl-amino ligands were transferred to pyrrolyl-imino ligands. Treatment of 2-((t)BuNHCH(2))C(4)H(3)NH (1) with excess (Me(3)Si)(2)NLi gave the only pyrrole deprotonated product {[η(5):η(2):η(1)-2-((t)BuNHCH(2))C(4)H(3)N]Li(2)N(SiMe(3))(2)}(2) (5), indicating that LiN(SiMe(3))(2) could not dehydrogenate the secondary amines to imines and rare-earth metal ions had a decisive effect on the dehydrogenation. The reaction of the rare-earth metal amides [(Me(3)Si)(2)N](3)RE(μ-Cl)Li(THF)(3) with 1 equiv. of more bulky pyrrolyl-functionalized secondary amine 2-[(2,6-(i)Pr(2)C(6)H(3))NHCH(2)](C(4)H(3)NH) (6) in toluene afforded the only amine and pyrrole deprotonated dinuclear rare-earth metal amido complexes {(μ-η(5):η(1)):η(1)-2-[(2,6-(i)Pr(2)C(6)H(3))NCH(2)]C(4)H(3)N]LnN(SiMe(3))(2)}(2) (RE = Nd (7a), Sm (7b), Er (7c)), no dehydrogenation of secondary amine to imine products were observed. On the basis of experimental results, a plausible mechanism for the dehydrogenation of secondary amines to imines was proposed.
authors.affiliation: Laboratory of Functionalized Molecular Solids, Ministry of Education, School of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui 241000, PR China.
authors.forename: Qinghai
authors.initials: Q
authors.lastname: Li
authors.forename: Shuangliu
authors.initials: S
authors.lastname: Zhou
authors.forename: Shaowu
authors.initials: S
authors.lastname: Wang
authors.forename: Xiancui
authors.initials: X
authors.lastname: Zhu
authors.forename: Lijun
authors.initials: L
authors.lastname: Zhang
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Feng
authors.forename: Liping
authors.initials: L
authors.lastname: Guo
authors.forename: Fenhua
authors.initials: F
authors.lastname: Wang
authors.forename: Yun
authors.initials: Y
authors.lastname: Wei
mesh_terms: D000577:Amides / Q000737:chemistry; D000588:Amines / Q000737:chemistry*; D006865:Hydrogenation; D007097:Imines / Q000737:chemistry; D008674:Metals, Rare Earth / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*
chemical_list: D000577:Amides; D000588:Amines; D007097:Imines; D008674:Metals, Rare Earth; D009942:Organometallic Compounds; D011758:Pyrroles