%0 Generic
%A Spencer, Liam P.
%A Beddie, Chad
%A Hall, Michael B.
%A Fryzuk, Michael D.
%D 2006
%T Synthesis, Reactivity, and DFT Studies of Tantalum
Complexes Incorporating Diamido-N-heterocyclic Carbene
Ligands. Facile Endocyclic C−H Bond Activation
%U 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
%R 10.1021/ja063282x.s003
%2 https://ndownloader.figshare.com/files/4763119
%K tantalum alkylidene
%K ligand
%K metallaaziridine moiety
%K tantalum derivatives
%K DFT Studies
%K Metathesis reactions
%K alkane elimination reactions
%K Cl 2Ta
%K pendent amine donor
%K deuterium atoms
%K Attempts
%K trialkyl tantalum complexes
%K energy pathway
%K metallaaziridine ring forms
%K model complexes show
%K ArNHCH 2CH Ar
%K DFT calculations
%X The syntheses of tantalum derivatives with the potentially tridentate diamido-N-heterocyclic
carbene (NHC) ligand are described. Aminolysis and alkane elimination reactions with the diamine−NHC
ligands, Ar[NCN]H2 (where Ar[NCN]H2 = (ArNHCH2CH2)2(C3N2); Ar = Mes, p-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 (Ar[NCN]Li2) and various ClxTa(NR‘2)5-x precursors were successful and generated the desired octahedral
Ar[NCN]TaClx(NR‘2)3-x 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 Mes[NCN]Li2 and Cl2Ta(CD2Ph)3. The single-crystal X-ray structures of p-Tol[NCNH]Ta(NMe2)4 (3),
Mes[NCNH]TaCHPh(CH2Ph)2 (4), p-Tol[NCN]Ta(NMe2)3 (7), Mes[NCCN]Ta(CH2tBu)2 (11), and Mes[NCCN]TaCl(CH2tBu) (14) are included.
%I ACS Publications