Reactions of (Ph)tBuP-P(SiMe3)Li·3THF with [(PNP)TiCl2] and [MeNacNacTiCl2·THF]: synthesis of first PNP titanium(iv) complex with the phosphanylphosphinidene ligand [(PNP)Ti(Cl){η2-P-P(Ph)tBu}]

Abstract

Herein, the lithium derivative of diphosphane, (Ph)tBuP-P(SiMe₃)Li (1), is isolated for the first time and investigated in reactions with β-diketiminate (^MeNacnac⁻ = [Ar]NC(Me)CHC(Me)N[Ar]; Ar = 2,6-iPr₂C₆H₃) and PNP-pincer (PNP = N[2-PiPr₂-4-methylphenyl]₂) Ti(III) complexes. The β-diketiminate titanium(III) complex containing the phosphanylphosphido ligand [^MeNacNacTi(Cl){η²-P(SiMe₃)-P(Ph)tBu}] (2) is prepared via the reaction of [^MeNacNacTiCl₂·THF] with (Ph)tBuP-P(SiMe₃)Li in toluene solution with good yield and purity. The corresponding titanium(IV) complex involving the phosphanylphosphinidene ligand [^MeNacNacTi(Cl){η²-P-P(Ph)tBu}] (3) is synthesized via the oxidation of complex (2) with [iBu₃PAgCl]₄. Interestingly, an analogous PNP titanium(IV) complex, [(PNP)Ti(Cl){η²-P-P(Ph)tBu}] (4), is obtained in the reaction of [(PNP)TiCl₂] with (Ph)tBuP-P(SiMe₃)Li in toluene solution and a 1 : 1 molar ratio instead of the expected titanium(III) complex with the phosphanylphosphido ligand. The solid-state structures of (Ph)tBuP-P(SiMe₃)Li·3THF (1), [^MeNacNacTi(Cl){η²-P(SiMe₃)-P(Ph)tBu}] (2), [^MeNacNacTi(Cl){η²-P-P(Ph)tBu}] (3) and [(PNP)Ti(Cl){η²-P-P(Ph)tBu}] (4) are determined by single-crystal X-ray diffraction, which reveals that in all obtained complexes, both the phosphanylphosphinidene (Ph)tBuP-P and phosphanylphosphido (Ph)tBuP-P(SiMe₃) ligands are bidentate-coordinated to the metal center.