title: Reaction of Ta(NMe2)5 with O2: formation of aminoxy and unusual (aminomethyl)amide oxo complexes and theoretical studies of the mechanistic pathways.
abstract: Reaction of d0 Ta(NMe2)5 (1) with O2 yields two aminoxy complexes (Me2N)(n)Ta(eta2-ONMe2)(5-n) (n = 4, 2; 3, 3) as well as (Me2N)4Ta2[eta2-N(Me)CH2NMe2]2(mu-O)2 (4) and (Me2N)6Ta3[eta2-N(Me)CH2NMe2]2(eta2-ONMe2)(mu-O)3 (5) containing novel chelating (aminomethyl)amide-N(Me)CH2NMe2 ligands. The crystal structures of 2-5 have been determined by X-ray crystallography. (Me2N)4Ta(eta2-ONMe2) (2) converts to (Me2N)3Ta(eta2-ONMe2)2 (3) in its reaction with O2. In addition, the reaction of Ta(NMe2)5 with 3 gives 2 only at elevated temperatures. Density functional theory (DFT) calculations have been used to investigate the mechanistic pathways in the reactions of Ta(NMe2)5 (1) with triplet O2. Monomeric reaction pathways in the formation of 2-5 are proposed. A key step is the oxygen insertion into a Ta-N bond in 1 through an intersystem conversion from triplet to singlet energy surface to give an active peroxide complex (Me2N)4Ta(eta2-O-O-NMe2) (A4). The DFT studies indicate that the peroxide ligand plays an important role, including oxidizing an amide to an imine ligand through the abstraction of a hydride. Insertion of Me-N=CH2 into a Ta-amide bond yields the unusual -N(Me)CH2NMe2 ligands.
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: Shu-Jian
authors.initials: SJ
authors.lastname: Chen
authors.forename: Xin-Hao
authors.initials: XH
authors.lastname: Zhang
authors.forename: Xianghua
authors.initials: X
authors.lastname: Yu
authors.forename: He
authors.initials: H
authors.lastname: Qiu
authors.forename: Glenn P A
authors.initials: GP
authors.lastname: Yap
authors.forename: Ilia A
authors.initials: IA
authors.lastname: Guzei
authors.forename: Zhenyang
authors.initials: Z
authors.lastname: Lin
authors.forename: Yun-Dong
authors.initials: YD
authors.lastname: Wu
authors.forename: Zi-Ling
authors.initials: ZL
authors.lastname: Xue
mesh_terms: D000577:Amides / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry*; D008956:Models, Chemical; D008962:Models, Theoretical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D013635:Tantalum / Q000737:chemistry*
chemical_list: D000577:Amides; D000588:Amines; D002614:Chelating Agents; D009942:Organometallic Compounds; D013635:Tantalum; D010100:Oxygen