The isolation and chemistry of tantalum dimethylamides containing resolved 3,3`-disubstituted-1,1`-bi-2,2`-naphthoxide ligands

Reaction of the tantalum dimethylamide substrates [Ta(NMe2)5] or mer,cis-[Ta(NMe2)2Cl3(HNMe2)] with one equivalent of the 3,3-disubstituted2,2-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.