10.1021/ja063282x.s003
Liam P. Spencer
Liam P.
Spencer
Chad Beddie
Chad
Beddie
Michael B. Hall
Michael B.
Hall
Michael D. Fryzuk
Michael D.
Fryzuk
Synthesis, Reactivity, and DFT Studies of Tantalum
Complexes Incorporating Diamido-<i>N</i>-heterocyclic Carbene
Ligands. Facile Endocyclic C−H Bond Activation
American Chemical Society
2006
tantalum alkylidene
ligand
metallaaziridine moiety
tantalum derivatives
DFT Studies
Metathesis reactions
alkane elimination reactions
Cl 2Ta
pendent amine donor
deuterium atoms
Attempts
trialkyl tantalum complexes
energy pathway
metallaaziridine ring forms
model complexes show
ArNHCH 2CH Ar
DFT calculations
2006-09-27 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Synthesis_Reactivity_and_DFT_Studies_of_Tantalum_Complexes_Incorporating_Diamido_i_N_i_heterocyclic_Carbene_Ligands_Facile_Endocyclic_C_H_Bond_Activation/3057370
The syntheses of tantalum derivatives with the potentially tridentate diamido-<i>N</i>-heterocyclic
carbene (NHC) ligand are described. Aminolysis and alkane elimination reactions with the diamine−NHC
ligands, <sup>Ar</sup>[NCN]H<sub>2</sub> (where <sup>Ar</sup>[NCN]H<sub>2</sub> = (ArNHCH<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>(C<sub>3</sub>N<sub>2</sub>); Ar = Mes, <i>p</i>-Tol), provided complexes with
a bidentate amide−amine donor configuration. Attempts to promote coordination of the remaining pendent
amine donor were unsuccessful. Metathesis reactions with the dilithiated diamido−NHC ligand (<sup>Ar</sup>[NCN]Li<sub>2</sub>) and various Cl<i><sub>x</sub></i>Ta(NR‘<sub>2</sub>)<sub>5-</sub><i><sub>x</sub></i> precursors were successful and generated the desired octahedral
<sup>Ar</sup>[NCN]TaCl<i><sub>x</sub></i>(NR‘<sub>2</sub>)<sub>3-</sub><i><sub>x</sub></i> complexes. Attempts to prepare trialkyl tantalum complexes by this methodology
resulted in the formation of an unusual metallaaziridine derivative. DFT calculations on model complexes
show that the strained metallaaziridine ring forms because it allows the remaining substituents to adopt
preferable bonding positions. The calculations predict that the lowest energy pathway involves a tantalum
alkylidene intermediate, which undergoes C−H bond activation α to the amido to form the metallaaziridine
moiety. This mechanism was confirmed by examining the distribution of deuterium atoms in an experiment
between <sup>Mes</sup>[NCN]Li<sub>2</sub> and Cl<sub>2</sub>Ta(CD<sub>2</sub>Ph)<sub>3</sub>. The single-crystal X-ray structures of <i><sup>p</sup></i><sup>-Tol</sup>[NCNH]Ta(NMe<sub>2</sub>)<sub>4</sub> (<b>3</b>),
<sup>Mes</sup>[NCNH]TaCHPh(CH<sub>2</sub>Ph)<sub>2</sub> (<b>4</b>), <i><sup>p</sup></i><sup>-Tol</sup>[NCN]Ta(NMe<sub>2</sub>)<sub>3</sub> (<b>7</b>), <sup>Mes</sup>[NCCN]Ta(CH<sub>2</sub><i><sup>t</sup></i><sup></sup>Bu)<sub>2</sub> (<b>11</b>), and <sup>Mes</sup>[NCCN]TaCl(CH<sub>2</sub><i><sup>t</sup></i><sup></sup>Bu) (<b>14</b>) are included.