Organometallic chemistry of chiral diphosphazane ligands: Synthesis and structural characterisation

Abstract

The diphosphazane ligands of the type, (C₂₀H₁₂O₂)PN(R)P(E)Y₂ (R = CHMe₂ or (S)-*CHMePh; E = lone pair or S; Y₂ = O₂C₂₀H₁₂ or Y = OC₆H₅ or OC₆H₄Me-4 or OC₆H₄OMe-4 or OC₆H₄Bu^t-4 or C₆H₅) bearing axially chiral 1,1'-binaphthyl-2,2′-dioxy moiety have been synthesised. The structure and absolute configuration of a diastereomeric palladium complex, [PdCl₂{ηsu2}-((O₂C₂₀H₁₂)PN((S)-*CHMePh)PPh₂] has been determined by X-ray crystallography. The reactions of [CpRu(PPh₃)₂Cl] with various symmetrical and unsymmetrical diphosphazanes of the type, X₂PN(R)PYY′ (R = CHMe₂ or (S)-*CHMePh; X = C₆H₅ or X₂ = O₂C₂₀H₁₂; Y=Y′= C₆H₅ or Y = C₆H₅, Y′ = OC₆H₄Me-4 or OC₆H₃Me₂-3,5 or N₂C₃HMe₂-3,5) yield several diastereomeric neutral or cationic half-sandwich ruthenium complexes which contain a stereogenic metal center. In one case, the absolute configuration of a trichiral ruthenium complex, viz. [Cp*Ruη₂-Ph₂PN((S)-*CHMePh)*PPh (N₂C₃HMe₂-3,5)Cl] is established by X-ray diffraction. The reactions of Ru₃(CO)₁₂ with the diphosphazanes (C₂₀H₁₂O₂)PN(R)PY₂ (R = CHMe₂orMe; Y₂=O₂C₂₀H₁₂or Y= OC₆H₅ or OC₆H₄Me-4 or OC₆H₄OMe-4 or OC₆H₄Bu^t-4 or C₆H₅) yield the triruthenium clusters [Ru₃(CO)₁₀{η-(O₂C₂₀H₁₂)PN(R)PY₂}], in which the diphosphazane ligand bridges two metal centres. Palladium allyl chemistry of some of these chiral ligands has been investigated. The structures of isomeric η³-allyl palladium complexes, [Pd(η³-l,3-R′₂-C₃H₃){η²-(rac)-(0₂C₂₀H₁₂)PN(CHMe₂)PY₂}](PF₆) (R′ = Me or Ph; Y = C₆H₅ or OC₆H₅) have been elucidated by high field two-dimensional NMR spectroscopic and X-ray crystallographic studies.