Zirconium complexes having a chiral phosphanylamide in the co-ordination sphere

Abstract

The chiral phosphanylamido ligand, {N(CHMePh)(PPh₂)}⁻, has been introduced into co-ordination chemistry. As starting material the oily amines HN(R-*CHMePh)(PPh₂) (1a) and HN(S-*CHMePh)(PPh₂) (1b) were used. To reconfirm their absolute structure, 1b was oxidized with H₂O₂ in air to obtain HN(S-*CHMePh)(P(O)Ph₂) (2) as a solid compound. The solid-state structure of 2 was established by single-crystal X-ray diffraction. The lithium salts of both enantiomers Li{N(R-*CHMePh)(PPh₂)} (3a) and Li{N(S-*CHMePh)(PPh₂)} (3b) were prepared by deprotonation reaction of 1a,b. Compounds 3a,b were further reacted with zirconocen dichloride to give the chiral metallocenes [(η⁵-C₅H₅)₂Zr(Cl){η²-N(R-*CHMePh)(PPh₂)}] (4a) and [(η⁵-C₅H₅)₂Zr(Cl){η²-N(S-*CHMePh)(PPh₂)}] (4b). In an alternative approach to give chiral zirconium compounds, the neutral amine 1b was reacted with [(PhCH₂)₄Zr] to give the enantiomeric pure complex [(PhCH₂)₃Zr{η²-N(S-*CHMePh)(PPh₂)}] (5). The solid-state structures of all zirconium complexes were determined by single-crystal X-ray diffraction.