The isolation and chemistry of tantalum dimethylamides containing resolved 3,3′-disubstituted-1,1′-bi-2,2′-naphthoxide ligandsElectronic supplementary information (ESI) available: ORTEP views of (R)-7, (R,S)-8, (S)-9 and (S)-12. See http://www.rsc.org/suppdata/dt/b2/b212910h/

Abstract

Reaction of the tantalum dimethylamide substrates [Ta(NMe2)5] or mer,cis-[Ta(NMe2)2Cl3(HNMe2)] with one equivalent of the 3,3′-disubstituted-2,2′-dihydroxy-1,1′-binaphthyl [H2O2C20H10(R)2-3,3′] (R = SiMe3, 1; SiMe2Ph, 2; SiMePh2, 3; SiPh3, 4) leads to the series of amine adducts [Ta(O2C20H10R2-3,3′)(NHMe2)(NMe2)3] (R = SiMe3, 5; SiMe2Ph, 6; SiMePh2, 7; SiPh3, 8) and [Ta(O2C20H10R2-3,3′)(NHMe2)(NMe2)Cl2] (R = SiMe3, 9; SiMe2Ph, 10; SiMePh2, 11; SiPh3, 12). Structural analyses by X-ray diffraction of (S)-5, (R)-7 and (R,S)-8 show a pseudo-octahedral geometry about tantalum with the coordinated dimethylamine ligand located cis to the two naphthoxide oxygen atoms. In the case of (S)-9, (R)-10 and (S)-12, the solid-state structure consists of both chloride ligands being located trans to the two naphthoxide oxygen atoms. Solution NMR spectroscopic properties of 5–12 are consistent with an identical structure being adopted in solution with the amine ligands being strongly bound in all cases. When (S)-5 is heated under vacuum the dimethylamine ligand is lost leading to [Ta(O2C20H10{SiMe3}2-3,3′)(NMe2)3] (S)-13. Reaction of (S)-5 with SiCl4 leads to a mixture of [Ta(O2C20H10{SiMe3}2-3,3′)(NHMe2)Cl3] (S)-14 and [Ta(O2C20H10-{SiMe3}2-3,3′)Cl4][Me2NH2] (S)-15. The solid-state structure of (S)-15 was determined. The amine/amide ligands in (S)-12 undergo insertion of CS2 leading to the dimethyldithiocarbamate, (S)-[Ta(O2C20H10-3,3′-{SiPh3}2)(CS2NMe2)2Cl] (S)-16. The solid state structure of (S)-16 consists of a pentagonal bipyramidal geometry about Ta with an axial oxygen and chloride ligand.