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 (H3N39]N3) and {NH(C6H4F)SiMe2}3tacn (H3N3-F9]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 H3N39]N3 and H3N3-F9]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 triple bond 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.