Amido/Amine Triazacyclononane-Based Zirconium Complexes: Syntheses, Reactivity, and Structures

The reactions of [Zr(NMe2)4]2 with triamido−triazacyclonane ligand precursors, {NH(Ph)SiMe2}3tacn (H3N3[9]N3)
and {NH(C6H4F)SiMe2}3tacn (H3N3-F[9]N3), led to the formation of complexes [Zr(NMe2)2{N(Ph)SiMe2}2{NH(Ph)
SiMe2}tacn], 1, and [Zr(NMe2)2{N(o-C6H4F)SiMe2}2{NH(o-C6H4F)SiMe2} tacn], 2, where the zirconium is coordinated
to two remaining dimethylamido ligands and to a dianionic tacn-based ligand, [{N(Ph‘)SiMe2}2{NH(Ph‘)SiMe2}tacn]2-,
that formed from deprotonation of two amine pendent arms of the ligands' precursors. The third pendent arm of
H3N3[9]N3 and H3N3-F[9]N3 remains neutral and not bonded to the zirconium. Treatment of 1 with NaH led to the
synthesis of [Zr(NMe2){N(Ph)SiMe2}2tacn], 3, that results from the cleavage of the N−Si bond of the original neutral
pendent arm. Complexes [ZrCl{N(Ph‘)SiMe2}2tacn] (Ph‘ = C6H5, 4, and C6H4F, 5) have been obtained by reactions
of ZrCl4 with {MN(Ph‘)SiMe2}3tacn·2THF (M = Li, Na). Reactions of 4 and 5 with LiC⋮CPh led to the syntheses
of [Zr(CCPh){N(Ph‘)SiMe2}2tacn] (Ph‘ = C6H5, 6, and C6H4F, 7). The solid-state structure of 3 shows a chiral
metal center.